Copy of Bio 150 questions.docx

UNIT 1

What are the characteristics that define a living organism?

Living organisms must exhibit several key characteristics: they grow, reproduce, respond to stimuli, metabolize, maintain homeostasis, adapt to their environment, and consist of one or more cells.

What are the six key elements in biology?

The six key elements are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), and sulfur (S).

What types of covalent bonds do the main elements form?

Carbon and hydrogen primarily form nonpolar covalent bonds, whereas oxygen, nitrogen, and sulfur tend to form polar covalent bonds due to their higher electronegativity.

What is a covalent bond, and how does it differ from non-covalent interactions?

A covalent bond is a chemical bond formed by the sharing of electrons between atoms. It differs from non-covalent interactions, which are weaker and include forces like hydrogen bonds, ionic interactions, van der Waals forces, and hydrophobic effects.

What is a polar covalent bond, and what makes a molecule polar?

A polar covalent bond occurs when electrons are shared unequally between atoms, resulting in partial charges. A polar molecule has regions of partial positive and negative charge due to uneven electron distribution.

What is a nonpolar covalent bond, and what makes a molecule nonpolar?

A nonpolar covalent bond occurs when electrons are shared equally between atoms, resulting in no partial charges. A nonpolar molecule lacks regions of charge separation.

Why is water essential for life?

Water is unique due to its polarity, high specific heat, cohesive and adhesive properties, ability to dissolve many substances, and role in temperature regulation, making it essential for life.

What are the four non-covalent interactions in biology?

The four non-covalent interactions in biology are hydrogen bonds, ionic interactions, van der Waals forces, and hydrophobic interactions.

How do functional groups contribute to non-covalent interactions in macromolecules?

Functional groups interact through different non-covalent interactions: hydroxyl groups form hydrogen bonds, charged groups participate in ionic interactions, nonpolar groups engage in van der Waals forces, and hydrophobic groups cause hydrophobic effects.

What is the difference between covalent bonds and non-covalent interactions in biomolecules?

Covalent bonds are key to the structural stability of biomolecules, while non-covalent interactions are crucial for functional dynamics, including molecular recognition and assembly.

How can non-covalent interactions strengthen biomolecular interactions?

Non-covalent interactions allow strength in biomolecular interactions through additive effects. Their reversible nature provides specificity, enabling selective binding and recognition.

What is a macromolecule, and what is a polymer?

A macromolecule is a large biological molecule like proteins, nucleic acids, carbohydrates, and lipids. A polymer is a chain of monomers, the smaller subunits that make up the macromolecule.

What are the four macromolecules, their monomers, and their functions?

The four macromolecules are proteins (amino acid monomers, functions include catalysis and structure), nucleic acids (nucleotide monomers, functions include information storage), carbohydrates (monosaccharide monomers, functions include energy storage and structure), and lipids (not true polymers, but include fatty acids, functioning in energy storage and membranes).

How are polymers formed and broken down?

Polymers form through dehydration synthesis (removal of water), creating covalent bonds. These bonds are broken by hydrolysis (addition of water).

What is polarity in a polymer, and how does it affect function?

Polarity in a polymer refers to directional asymmetry (e.g., 5' to 3' in nucleic acids). This affects function, like directional synthesis or molecular recognition.

How do nucleic acids utilize non-covalent interactions?

In nucleic acids, complementary bases (A-T/U, G-C) interact through hydrogen bonding, a critical non-covalent interaction.

What is templated synthesis?

Templated synthesis means a strand of nucleic acid serves as a guide for creating a complementary strand.

What is DNA replication, and how does DNA structure support it?

Replication is the process by which DNA is copied. DNA's double-helix structure, with complementary base pairing, provides a mechanism for accurate replication.

What is gene expression?

Gene expression refers to the process by which information in DNA is used to produce functional molecules, typically proteins.

What are transcription and translation?

In transcription, DNA is copied into RNA. In translation, RNA directs protein synthesis by specifying the sequence of amino acids.

What is the general structure of an amino acid?

Amino acids share a general structure: an amino group (-NH2), a carboxyl group (-COOH), and a unique R group (side chain). The R group varies, determining chemical properties and non-covalent interactions.

What are the four levels of protein structure?

Protein structure has four levels: primary (sequence of amino acids, stabilized by peptide bonds), secondary (alpha helices and beta sheets, stabilized by hydrogen bonds), tertiary (3D folding, stabilized by various non-covalent interactions and disulfide bonds), and quaternary (assembly of multiple polypeptides; not all proteins have this level).

How do proteins fold into their functional structures?

Protein folding involves the formation of secondary structures followed by tertiary and quaternary organization, driven by hydrophobic effects, hydrogen bonding, and other interactions.

What is secondary structure in proteins?

Secondary structure includes alpha helices and beta sheets, formed by hydrogen bonding within the backbone.

What is tertiary structure in proteins?

Tertiary structure is the 3D arrangement of a polypeptide, driven by hydrophobic interactions, hydrogen bonds, ionic bonds, and van der Waals forces.

What is quaternary structure in proteins?

Quaternary structure involves the arrangement of multiple polypeptides. Not all proteins have quaternary structures; some function as single polypeptides.

How does information flow from DNA to protein?

Information flows from DNA to protein via transcription (DNA to RNA) and translation (RNA to protein).

What is the general formula for carbohydrates?

The general formula for carbohydrates is (CH2O)n.

Why is the shape of a sugar molecule important?

Shape is crucial as it determines function. For example, the glycosidic bond shape differs in glycogen versus beta glucans, affecting properties and digestibility.

Why are sugars soluble in water?

Sugars like glucose form hydrogen bonds with water due to their hydroxyl groups, making them very soluble.

What gives polysaccharide ropes and jellies their properties?

Polysaccharide ropes (e.g., cellulose) are rigid due to extensive hydrogen bonding. Polysaccharide jellies (e.g., pectin) form gels by trapping water molecules.

What is the general formula of a hydrocarbon?

The general formula of a hydrocarbon is CxHy.

What are lipids, and how are they defined?

All lipids are hydrophobic or amphipathic molecules, with structures that do not mix well with water.

What is the structure of a fatty acid?

A fatty acid has a carboxyl group (-COOH) and a hydrocarbon chain, which can vary in length and saturation.

What is the structure and function of triacylglycerols?

Triacylglycerols consist of three fatty acids linked to a glycerol molecule, functioning as energy storage molecules.

What is a phospholipid, and how does it relate to membranes?

A membrane phospholipid has a hydrophilic head (phosphate group) and two hydrophobic tails (fatty acid chains), essential for bilayer formation.

What does amphipathic mean?

Amphipathic means having both hydrophilic and hydrophobic regions, crucial for membrane structure.

What is the hydrophobic effect?

The hydrophobic effect drives nonpolar molecules together in aqueous environments, enabling membrane self-assembly.

How do hydrocarbons interact?

Hydrocarbons can interact via van der Waals forces due to induced dipoles in nonpolar molecules.

What is potential energy, and how does it relate to chemical energy, entropy, and Gibbs free energy?

Potential energy is stored energy. Chemical energy is a form of potential energy stored in chemical bonds. Entropy is the degree of disorder in a system. Gibbs free energy (ΔG) predicts whether a reaction is spontaneous.

How does diffusion relate to entropy?

Diffusion is driven by entropy because systems tend toward higher disorder (lower energy states).

What is the difference between endergonic and exergonic reactions?

Free energy (ΔG) relates to work; endergonic reactions require energy input (positive ΔG), while exergonic reactions release energy (negative ΔG).

Why do cells maintain steady-state non-equilibrium?

Cells maintain steady-state non-equilibrium to drive processes away from equilibrium, enabling life-sustaining reactions.

What is chemical equilibrium?

Chemical equilibrium occurs when forward and reverse reaction rates are equal, with no net change in reactants or products.

What is steady-state non-equilibrium?

Steady-state non-equilibrium involves constant input and output of energy and matter, unlike chemical equilibrium.

What is a kinetically stable molecule?

A kinetically stable molecule, like glucose, resists reaction despite being thermodynamically favorable, due to high activation energy.

Why is ATP the cell's energy currency?

ATP is the cell's energy currency because its hydrolysis releases energy used to power other reactions.

What is energetic coupling?

Energetic coupling uses ATP's hydrolysis to make non-spontaneous reactions proceed by lowering their overall ΔG.

How do cells drive endergonic reactions forward?

Cells use enzymes, ATP, and other molecules to drive endergonic reactions forward.

What is the transition state, and what is activation energy?

Transition state is the high-energy intermediate during a reaction. Activation energy is the energy needed to reach it, affecting reaction rate.

How do enzymes catalyze reactions?

Enzymes catalyze reactions by lowering activation energy, often by stabilizing the transition state.

What is the active site of an enzyme?

The active site is where substrates bind and reactions occur. Proper binding orients substrates for efficient catalysis.

How do cells control enzyme activity?

Cells alter enzyme or substrate concentrations via gene expression, compartmentalization, or transport.

What is metabolism?

Metabolism encompasses all chemical reactions in a cell, including catabolism (breakdown) and anabolism (synthesis).

What is feedback inhibition?

Feedback inhibition prevents overproduction by using the end product to inhibit early steps. This maintains homeostasis.

What do kinases and phosphatases do?

Kinases add phosphate groups to molecules, while phosphatases remove them. Both regulate enzyme activity.

What is the basic structure of membrane lipids?

Membrane lipids have a hydrophilic head and hydrophobic tails, driving bilayer formation due to the hydrophobic effect.

What is the role of the hydrophobic effect in membranes and proteins?

The hydrophobic effect excludes nonpolar molecules from water, stabilizing membranes and protein folding.

What is the function of triacylglycerols?

Triacylglycerols do not participate in membranes but function as energy reserves.

What determines membrane fluidity?

Membrane fluidity depends on lipid composition (e.g., unsaturated fatty acids increase fluidity) and temperature.

How do cells regulate membrane fluidity?

Cells maintain fluidity by adjusting lipid composition, such as increasing unsaturated fatty acids at low temperatures.

What are the types of membrane proteins?

Membrane proteins are categorized as integral, peripheral, or lipid-anchored, differing in their interactions with the bilayer.

What is the function of alpha helices in transmembrane proteins?

Alpha helices in transmembrane proteins facilitate spanning the hydrophobic membrane, forming channels for transport.

How do proteins associate with membranes?

Proteins associate with membranes through hydrophobic regions or covalent attachment to lipids.

What role does the plasma membrane play in homeostasis?

The plasma membrane regulates homeostasis by controlling the exchange of substances with the environment.

What is selective permeability?

Selectively permeable membranes allow some molecules to pass while blocking others, crucial for cellular function.

What is diffusion, and how is it different from facilitated diffusion?

Diffusion is the passive movement of molecules from high to low concentration, whereas facilitated diffusion requires transport proteins.

What is the difference between channels and carriers in facilitated diffusion?

Channels provide a pore for molecules, while carriers undergo conformational changes to transport substances.

What is osmosis?

Osmosis is the diffusion of water across a selectively permeable membrane.

What is active transport?

Active transport moves molecules against their concentration gradient, using energy. Primary uses ATP directly; secondary uses energy from another gradient.

What is an example of facilitated diffusion?

GLUT is an example of facilitated diffusion, transporting glucose without energy input.

How do prokaryotes use transport systems?

Prokaryotes use transporters and pumps for nutrient uptake, powered by gradients or ATP.

UNIT 2

What is the basic structure of a prokaryotic cell?

• First life form, a simple cell, has cell membrane, cytoplasm, cell wall, a singular DNA chromosome in the nucleoid, and ribosomes located in the cytoplasm.

How can we classify organisms based on their energy source? On their carbon source?

• We can classify organisms as either phototrophs (energy from sun) or chemotrophs (energy from carbon compounds. Organisms can then be classified on their carbon source as either autotroph (carbon from inorganic sources) or heterotroph (carbon from organic compounds)

Start learning the inputs and outputs of the different stages of oxidative metabolism and of the different stages of photosynthesis.

• Oxidative metabolism equation : + 6 6C + 6.
  • Uses to extract energy
  • Produces ATP
• Photosynthesis equation : 6C + 6 O + 6.
  • Produces

ATP is a good energy currency because the phosphate bond that donates the energy is only intermediate in strength? Explain.

• Since the phosphate bond is only intermediate in strength, it can be broken down readily when energy is needed, but it is not weak to the point that it spontaneously breaks, allowing for a controlled process.

Be able to differentiate substrate-level and oxidative phosphorylation.

• Substrate level phosphorylation is when ADP or GDP is phosphorylated (introduced a phosphate group into) by a substrate to produce ATP or GTP. This one used readily available high-substrate energy.
• Oxidative phosphorylation is when ADP or GDP is phosphorylated using the available free energy from redox reactions in the electron transport chain. This one uses free energy (energy available in a system to do work) from electron transfer reactions.

What’s the purpose of fermentation, and why is it important?

• Fermentation is an anabolic (lack of oxygen) metabolic process in which nutrients like sugar, and alcohol are converted to ATP by recycling electron carriers needed for glycolysis. This is important because it allows organisms to survive without oxygen.

How does diffusion limit cell size in simple prokaryotes?

• Diffusion limits the size of prokaryotic cells, because only a limited volume of cytoplasm gets resources fast enough through diffusion. As the cell grows larger, the time needed to transport nutrients becomes longer, ultimately restricting the cell’s ability to function.

Compare the organization of prokaryotic and eukaryotic cells.

• Prokaryotic cells are unicellular, lack nucleus, and DNA is free floating.
• Eukaryotic cells are multicellular, have membrane bound organelles, DNA is in the nucleus, and they are larger.

What makes up the endomembrane system? What organelles are part of the endomembrane system?

• The endomembrane system is made up of the rough endoplasmic reticulum (Entry of new proteins for secretion), golgi apparatus (Processing of proteins) , plasma membrane (Site of secretion to extracellular space), lysosomes (Recycling of macromolecules), and vesicles (interconnect organelles by fission and fusion).

What organelles are NOT part of the endomembrane system?

• The organelles that are not part of the endomembrane system are mitochondria, chloroplasts, and peroxisomes.

What’s the general structure of the nuclear envelope?

• Nuclear envelope is a double biological membrane with 2 phospholipid bilayers. They also contain large membrane protein channels called nuclear pores.

What are the roles of rough and of smooth ER?

• The rough endoplasmic reticulum is involved in protein synthesis.
• The smooth endoplasmic reticulum is involved in lipid synthesis.

What are vesicles, and what organelles are they used to “connect”?

• Vesicles are small, membrane bound sacs that transport materials, store substances, and secrete molecules by fusing with the cell membranes. Vesicles also fuse with the golgi apparatus, and they are produced at the golgi.

What happens in the Golgi apparatus?

• The golgi apparatus modifies and sorts proteins and lipids as they move to their final destinations out of the cell (secretion).

What happens in the lysosome?

• Lysosomes contain enzymes that break down macromolecules such as proteins, nucleic acids, lipids, and carbohydrates.

Why are cells limited in size? How do organelles allow for larger cells?

• Diffusion limits the size of prokaryotic cells, because only a limited volume of cytoplasm get resources fast enough through diffusion. Organelles allow for larger cells due to the compartmentalizing of different cellular functions within the cell.

How do we think organelles evolved?

• Organelles evolved from free-living prokaryotic cells that were engulfed (absorbed/eating) by another cell, leading to the creation of organelles.

What is meant by "repurposed plasma membrane"?

• Repurposed plasma membrane refers to the plasma membrane from previous cells that were repurposed for the creation of new organelles.

What is endosymbiosis?

• Endosymbiosis is a theory that suggests that some of the organelles (like mitochondria and chloroplasts) inside these cells were once separate, simple bacteria that were engulfed by larger cells. These bacteria formed a symbiotic relationship with their host, providing energy or other benefits.

How does diffusion limit cell size in simple prokaryotes? How do organelles allow eukaryotic cells to overcome some limits on diffusion?

• Diffusion limits the size of prokaryotic cells, because only a limited volume of cytoplasm get resources fast enough through diffusion. Organelles allow for larger cells due to the compartmentalizing of different cellular functions within the cell.

What are the stages of "cellular respiration"? Respiration is defined as "Oxygen in, Carbon Dioxide out"!

• The stages of cellular respiration are glycolysis, pyruvate oxidation, the krebs cycle (citric acid cycle), and oxidative phosphorylation (electron transport chain).

What are the inputs and outputs of glycolysis, of pyruvate oxidation, of the citric acid cycle (carbon oxidation), of the electron transport chain, and of ATP synthase in oxidative metabolism?

• Glycolysis - Fuel molecules are partially broken down, producing ATP and electron carriers.
  • Glucose + 2 NAD+ + 2 ADP + 2 Pi + 2 ATP --> 2 Pyruvate + 2 NADH + 2 H+ 4 ATP + 2 H2O.
• Pyruvate oxidation - Oxidize pyruvate to create acetyl CoA for the citric acid cycle.
  • inputs - pyruvate, NAD+ and coenzyme A (CoA).
  • Outputs - acetyl CoA, carbon dioxide, and NADH.
• Citric acid cycle - Fuel molecules are fully broken down, producing ATP and electron carriers.
  • Input - Acetyl Coa
  • Output - CO2, NADH, FADH2, ATP.
• Electron transport chain - Electron carriers donate electrons to the electron transport chain, leading to the synthesis of ATP.
  • Inputs - NADH, FADH2, and oxygen (O2).
  • Outputs - ATP, water (H2O), NAD+, and FAD
• ATP synthase - an enzyme that catalyzes the formation of ATP from ADP, and Pi.
  • Input - ADP + Pi + 2H
  • Output - ATP + H2O + 2H.

What makes ATP a good energy currency? Why is it important that ATP be only intermediate in phosphate-bond strength?

• ATP is a good energy currency because the phosphate bond is only intermediate in strength, it can be broken down readily when energy is needed, but it is not weak to the point that it spontaneously breaks, allowing for a controlled process.

What is the difference between substrate-level and oxidative phosphorylation?

• Substrate level phosphorylation is when ADP is phosphorylated (introduced a phosphate group into) by a substrate to produce ATP. It uses readily available high-substrate energy.
• Oxidative phosphorylation is when ADP is phosphorylated using the available free energy from redox reactions in the electron transport chain. This one uses free energy (energy available in a system to do work) from electron transfer reactions.

What’s the purpose of anaerobic (glycolytic) fermentation?

• The purpose of fermentation is that organisms can undergo a metabolic process in which nutrients like sugar, and alcohol are converted to ATP by recycling electron carriers needed for glycolysis, without the need of oxygen.

What are oxidation-reduction reactions? How and why do NADH (and other electron carriers) carry electrons?

• Oxidation-reduction reactions are any form of reactions in which the oxidation number of a molecule, atom or ion changes by the gaining or losing of an electron.
• NADH (and other electron carriers) carry electrons through chemical change in which it accepts an electron from a donor molecule, becoming reduced to NADH, and then later donating the electron to another molecule and becoming oxidized to NAD+. This transfer is used to generate ATP.

What is endosymbiosis?

• Endosymbiosis is a theory that suggests that some of the organelles (like mitochondria and chloroplasts) inside these cells were once separate, simple bacteria that were engulfed by larger cells. These bacteria formed a symbiotic relationship with their host, providing energy or other benefits.

What are the spaces in the mitochondria, and what reactions happen in each space? What is produced by pyruvate oxidation? What are the inputs and outputs of the citric acid cycle (carbon oxidation)? How is the electron transport coupled to proton pumping?

• The spaces in the mitochondria are the intermembrane space, and the matrix. The intermembrane space involves protein activation related to apoptosis. In the matrix the citric acid cycle takes place, alongside oxidative phosphorylation which leads to ATP production.
• Pyruvate oxidation produces acetyl CoA, carbon dioxide, and NADH.
• The inputs and outputs of the citric acid cycle are Acetyl Coa for CO2, NADH, FADH2, ATP.
• The energy from the electron transport chain that arises from redox reactions is coupled to the conformational changes in the protein that facilitates proton pumping (a protein in the membrane of a cell that moves protons across the membrane).

What path do electrons take through the mitochondrial electron transport chain? What molecule donates the electrons; what molecule is the ultimate acceptor of electrons? How is this an example of energetic coupling? How does this lead to ATP synthesis?

• The path taken by electrons through the mitochondrial electron transport chain is NADH → NADH dehydrogenase complex → ubiquinone → cytochrome b-c1 complex → cytochrome c → cytochrome oxidase complex → molecular oxygen (O2).
• Electrons are donated by two primary molecules NADH, and FADH2. The ultimate acceptor of electrons is molecular oxygen (O2).
• This is an example of energetic coupling because of an exergonic process that drives an endergonic process (ATP synthesis). As electrons flow through the complexes, the energy released is used to pump protons (H⁺ ions) from the mitochondrial matrix into the intermembrane space, creating a proton gradient.

How is photosynthesis an example of redox (oxidation-reduction) chemistry?

• Photosynthesis is an example of redox reaction because H2O (water) loses electrons (oxidized) to produce oxygen gas, while CO2 (carbon dioxide) is reduced (gains electrons) to produce glucose, essentially transferring electrons, and creating a redox reaction.

What are the inputs and the outputs of photosynthesis (the light-harvesting reactions and Calvin cycle/carbon reduction).

• Photosynthesis equation : 6C + 6 O + 6.

What are the functions of pigments?

• Pigments absorb light and light energy.
  • It is very easy to generate compounds that have color.
• Retinol pigment has a similar role as an electron carrier.

Generally, how does the photosynthetic electron transport chain harvest energy from light?

• Photosynthetic electron transport chains harvest energy from light by using pigments like chlorophyll to absorb protons which energize electrons, releasing energy at each step to pump protons which create a proton gradient that generates ATP.

Compare electron transport in chloroplasts to electron transport in mitochondria

• In chloroplasts, the electrons come from water molecules that are split by light energy.
• In the mitochondria, electrons originate from the breakdown of organic molecules like glucose.

Compare and Contrast -- Mitochondria and Chloroplasts!

• Mitochondria produces energy from food molecules through cellular respiration.
• Chloroplasts capture light energy and produce sugar through photosynthesis. This is only available in plant cells.

What are the three types of cytoskeletal elements in animal cells? What types are found in plants, fungi and protists?

• The three types of cytoskeletal elements in animal cells are microtubules, actin filaments, and intermediate filaments.
• Microtubules, and actin are found in all eukaryotes.
• Intermediate filaments are just found in animals.

What protein makes up microtubules?

• Microtubules are made up of tubulin.

What’s the difference between plus and minus ends?

• The plus end is where β-tubulin faces into solution and grows more rapidly.
• The minus ends are anchored in structures called microtubule organizing centers, the α-tubulin is exposed, and they grow slower.

Why is it important that MTs and actin filaments are made from small, compact protein subunits? Why is it important that they’re held together by non-covalent interactions?

• It is important that microtubules and actin filaments are made up from small, and compact protein subunits because it allows for the rapid assembly, disassembly of the filaments, and it allows for a quick response to change.
• Non-covalent interactions allow for these structures to quickly respond to cellular signals by readily adding or removing subunits as needed.

What’s the general structure of a MT? What do we mean when we say it has polarity? Why is that polarity important?

• The general structure of a microtubule is a hollow cylindrical structure composed of 13 protofilaments which have dimers of α- and β-tubulin polymerize arranged around a central core, forming a rigid, tube-like structure.
• We say it has polarity because it has a distinct plus and minus end, each end is structurally different from the other which allows for directional growth and movement within the cell.

Why does the endomembrane system require MTs?

• The endomembrane system requires microtubules because they organize the cells organelles and cytoplasm.
• The vesicles going from the rough endoplasmic reticulum to the golgi use the minus end-directed motors from the microtubules.
• The vesicles going from the golgi to the plasma membrane use plus end-directed motors from the microtubules.
• The minus ends of the microtubules are also anchored to the centrosome near the golgi apparatus.

What protein makes up actin?

• The protein that makes up actin is actin. Actin makes up microfilaments.

How are the proteins that make up intermediate filaments different from actin monomers and tubulin?

• Intermediate filaments are made from a variety of proteins, compared to actin and tubulin are single distinct proteins. Additionally, intermediate filaments are made from elongated, fibrous proteins that assemble to form rope-like structures , while actin, and tubulin are made up from globular proteins that polymerize to form filaments.

What’s the general structure of an actin filament? What do we mean when we say it has polarity? Why is that polarity important?

• The general structure of an actin filament is two strands of globular molecules (G-actin) twisted into a helix.
• All the monomers are oriented in the same direction, causing a distinct polarity since it has one plus end, and one minus end.
• The polarity allows for directed movement of the filament.

Understand how kinesins and myosins are examples of ATPase-driven motors that use conformation change to do work. Not the tiny details, just the general principles.

• They are examples of ATPase-driven motors because they used the energy released from the hydrolysis-(using water to break down a compound)-of ATP to provide power for the conformational changes within their protein structure, which creates the force needed to move along cellular tracks like microtubules (kinesin), and actin filament (myosin).

Understand the roles of actin—how can it be used in vesicle transport and changing the membrane shape?

• Actin provides a dynamic track for movement and generating force which deform membranes, and allow vesicles to move throughout the cell, facilitating processes like endocytosis (the ingestion of large particles and the uptake of fluids or macromolecules in small vesicles) and exocytosis (a process for moving large molecules out of the cell to the cell exterior). It also contributes to changing cell membrane shape by polymerizing and depolymerizing, pushing against the membrane to create protrusions or pulling it inwards to form invaginations.

What’s the actin cortex? Why is it important?

• The actin cortex is a cage of actin supporting the phospholipid bilayer on the cytoplasmic side. It includes the myosin motors and other proteins. It is important because it plays a crucial role in controlling cell shape, movement, and maintaining cell structure.

How is actin important in making microvilli? In making an intact tube of cells?

• Actin helps in the formation of microvilli as it provides the structural core on the cell surface, essentially acting like the backbone that allows the microvilli to extend outward, and increase the cells surface area. Actin helps in maintaining cell shape and polarity by forming a network of filaments that connect cells together.
• Microvilli are projections of plasma membranes, based on the actin cortex.

How does a cell crawl? How are actin and myosin used?

• A cell crawls by a process in which actin filaments, and myosin, where the actin pushes the membrane forward, while the myosin contraction at the rear pulls the cell body along, allowing it to crawl.

What’s the general structure of an intermediate filament? Why are these non-polar in structure?

• The general structure of an intermediate filament is composed of elongated protein subunits with a central, conserved alpha-helical rod domain flanked by non-helical head and tail domains, which assemble in antiparallel fashion, resulting in non-polar structure with no distinct ends.

What does this sentence mean? "The signal passed in a cellular signal transduction pathway, from start to finish, is protein conformational change."

• This sentence means that in a cellular signal transduction pathway, the key event that happens throughout the process—from the moment the signal is received until the response is triggered—is the change in the shape or structure (conformation) of proteins. Signal transduction pathways involve a series of steps where proteins interact with one another, and these interactions often depend on the proteins changing their shapes. These conformational changes are critical because they alter the protein's function, allowing it to pass the signal along the pathway, ultimately leading to a cellular response.

Do ligands that bind cell-surface protein receptor enter the cytoplasm?

• The ligands that bind cell-surface protein receptors do not enter the cytoplasm, rather they remain on the extracellular side of the cell membrane, and signal the cell through the receptor protein which then triggers intracellular signaling pathways.

How do receptors recognize the correct signal?

• Receptors recognize the correct signal due to the short amino acid sequences present which send and accept the signals.

Kinases and phosphatases -- how are they involved in conformational change?

• Kinases and phosphatases are enzymes that regulate protein function through phosphorylation, and dephosphorylation. This is important in conformational change ( Information passed in cell communication, Signal passed in cell communication ) since it allows for the movement of proteins due to the repelling nature of phosphate.

Look for instances of signal amplification in the pathways we discuss.

• Signal amplification: The process of increasing the intensity of a signal or the use of specific techniques to increase the signal in a reaction

G-PROTEINS -- very important!

• G-Proteins are guanine nucleotide binding proteins.
• G-proteins assumes two conformations, Conformation regulated by GTP and GDP, GTP-bound: “active” conformation, GDP-bound: inactive conformation
• G protein: Conformation changed by binding of GTP or GDP

Why is it important that second messengers be able to be rapidly degraded or removed?

• Enzymes in the cytosol specifically degrade cAMP, which stops the phosphorylation and activation of target proteins by PKA (protein kinase a).
• It allows cells to quickly respond to changing environmental signals by ensuring the signal is not sustained for too long.

How can different cell types have different responses to the same signal molecule?

• Different cell types have different responses to the same signal molecule because they express different sets of receptors on their cell surface, and the set of genes that the receptor regulates is different in each cell type.

How is a GPCR activated? What does it do once active?

• The GPCR is activated by various stimuli such as hormones, neurotransmitters, chemokines, odorants, and others. GPCRs influence broad physiological processes such as neurotransmission, cellular metabolism, secretion, cell growth, and immune responses.

How is a G-protein activated? What does it do once active? How is it inactivated?

• G-proteins are activated by G-protein coupled receptors. Once activated they can regulate the activity of target proteins in the plasma membrane. It is inactivated by reversibly binding to Guanosine diphosphate (GDP).

Receptor kinases (RTKs). How do the proteins in the receptor activate themselves when ligand binds? Look at the conformation changes. Look for the G-protein!

• RTKs are generally activated by receptor-specific ligands. Growth factor ligands bind to extracellular regions of RTKs, and the receptor is activated by ligand-induced receptor dimerization

What’s meant by the MAP kinase pathway

• The MAP Kinase pathway are a major components of pathways controlling embryogenesis, cell differentiation, cell proliferation, and cell death.
• They are also a series of protein kinases that transmit signals from cell surface receptors to the DNA in the nucleus

How is a receptor kinase activated? Why does it phosphorylate itself?

• Cross-linking activates the tyrosine kinase activity in these RTKs through phosphorylation — specifically, each RTK in the dimer phosphorylates multiple tyrosines on the other RTK.

What is RAS, how is it activated, and what does it activate? How is it inactivated?

• RAS is activated by GDP/GTP exchange stimulated by GEFs and inactivated by GTP hydrolysis stimulated by GAPs.
• Ras is activated by guanine nucleotide exchange factors (GEFs) that release guanosine diphosphate (GDP) and allow GTP binding.

What’s a phosphorylation cascade?

• A series of events in a signaling pathway that involves one enzyme phosphorylating another, which leads to a chain reaction that phosphorylates thousands of proteins.

How is a signaling event turned off?

• A signaling event can be turned off by degrading or removing the ligand so it can no longer access its receptor.
• Additionally, enzymes called phosphatases remove phosphate groups from proteins, which can turn off the signaling cascade.

UNIT 3

What are the stages of mitosis? Focus on what happens to the DNA and chromosomes, the nuclear envelope and organelles, and the microtubules!

Prophase: Chromosomes condense; nuclear envelope begins to disassemble; spindle fibers form from centrosomes.

Metaphase: Chromosomes align at the metaphase plate; spindle fibers attach to kinetochores.

Anaphase: Sister chromatids separate and are pulled to opposite poles; microtubules shorten.

Telophase: Nuclear envelope reforms around chromosomes; chromosomes decondense; spindle fibers disassemble.

What’s cytokinesis? How does it differ in animals, plants and fungi?

Cytokinesis is the process of cytoplasm division, resulting in two daughter cells.

Animals: A cleavage furrow forms via actin and myosin, pinching the cell in two.

Plants: A cell plate forms from vesicles, eventually becoming a cell wall.

Fungi: Similar to plants, but division often involves the formation of septa.

What is the difference between mitosis and cytokinesis?

Mitosis involves division of the nucleus and chromosomes, while cytokinesis involves division of the cytoplasm and the formation of two separate cells.

Describe the process of mitosis the way we considered it in class.

Mitosis begins with prophase, where chromosomes condense, and the spindle fibers form. In metaphase, chromosomes align at the equator of the cell. During anaphase, sister chromatids are pulled apart to opposite poles. Finally, in telophase, nuclear envelopes reform, and chromosomes decondense.

How is the cell cycle set up to be "free-wheeling," that is, to continue without pause?

The cell cycle operates via a series of regulatory checkpoints and feedback mechanisms that ensure smooth progression from one phase to the next without unnecessary delays, unless a problem (e.g., DNA damage) is detected.

What are cyclins? What are cyclin-dependent kinases? What's the difference?

Cyclins are regulatory proteins whose levels fluctuate during the cell cycle, and they activate cyclin-dependent kinases (CDKs). CDKs are enzymes that, when activated by cyclins, phosphorylate target proteins to drive cell cycle progression.

What is the metaphase-anaphase transition, why is it important, and why is it different from the other control points in mitosis?

The metaphase-anaphase transition ensures that all chromosomes are properly aligned and attached to spindle fibers before sister chromatids separate. It is unique because it involves the destruction of specific proteins (e.g., securin) to trigger an irreversible process.

What happens if a cell can’t fix mutated DNA?

If DNA damage cannot be repaired, the cell may undergo apoptosis (programmed cell death) to prevent the propagation of mutations, or it may become cancerous if checkpoint mechanisms fail.

Why is it important that the cell cycle regulation system have checkpoints?

Checkpoints ensure that key processes, such as DNA replication and chromosome alignment, are completed correctly before progression, preventing errors that could lead to mutations or cell death.

What are the three key checkpoints—where are they in the cell cycle and what do they check for?

G1 checkpoint: Assesses cell size, nutrients, and DNA integrity before entering S phase.

G2 checkpoint: Verifies DNA replication and repairs damage before mitosis.

Metaphase checkpoint: Ensures all chromosomes are aligned and attached to spindle fibers before anaphase.

What is the key regulator of cell cycle progression?

Cyclin-CDK complexes are the main regulators. Cyclin levels must increase to activate CDKs at specific times and decrease to allow progression to the next phase.

How are G0 and G1 different? What kinds of cells might enter a permanent G0? Why?

G1 is a phase of cell growth and preparation for DNA synthesis, while G0 is a quiescent phase where cells exit the cycle and stop dividing. Differentiated cells, such as neurons and muscle cells, often enter permanent G0 because they no longer need to divide.

What’s a mitogen and how does it lead cell division?

A mitogen is a signaling molecule that stimulates cell division by activating pathways, such as MAPK, leading to increased cyclin expression and CDK activity.

What is endosymbiosis?

Endosymbiosis is a symbiotic relationship where one organism lives inside another. In the context of eukaryotic evolution, it refers to the origin of organelles like mitochondria and chloroplasts, which were once free-living prokaryotes engulfed by a host cell.

What properties do all multicellular eukaryotes share?

All multicellular eukaryotes have:

Adhesion between cells.

Communication mechanisms (e.g., signaling pathways).

Cellular differentiation for specialized functions.

What exactly is diffusion and why is it limiting?

Diffusion is the passive movement of molecules from high to low concentration. It limits cell size because it becomes inefficient over long distances, restricting nutrient and waste transport in large organisms.

How does the ability to perform bulk transport allow more complex body organization?

Bulk transport moves substances over long distances via systems like blood vessels or xylem, enabling the development of larger, more complex organisms by overcoming diffusion limits.

Think about the importance of adhesion, communication and differentiation to multicellularity.

Adhesion allows cells to stick together to form tissues, communication coordinates activities across cells, and differentiation enables specialized functions, all of which are essential for multicellular life.

What role did the great oxygenation event have on eukaryotic evolution?

The great oxygenation event increased atmospheric oxygen, allowing for aerobic respiration, which produces more ATP, enabling the evolution of larger and more complex eukaryotes.

How did eukaryotic diversity arise, and why is predation thought to be important?

Eukaryotic diversity arose through adaptations to different environments and interactions like predation. Predation drove the evolution of cytoskeletal changes, motility, and phagocytosis.

Why are flexible membranes and an adaptable cytoskeleton key developments in the evolution of eukaryotes?

Flexible membranes allow phagocytosis and compartmentalization, while an adaptable cytoskeleton enables shape changes, intracellular transport, and motility.

Why are cells small, and prokaryotes smallest?

Cells are small to maintain a high surface area-to-volume ratio for efficient nutrient and waste exchange. Prokaryotes are smallest because they rely entirely on diffusion for molecular transport.

What’s bulk transport and how does it apply in the context of a single-celled eukaryote? A multicellular eukaryote?

Bulk transport moves large quantities of materials. In single-celled eukaryotes, it involves vacuoles and vesicles. In multicellular organisms, it includes systems like circulatory and vascular tissues.

What is simple multicellularity and what advantages does it provide over unicellularity? What features do simple multicellular organisms have?

Simple multicellularity involves groups of cells sticking together with minimal specialization. Advantages include protection, increased resource access, and group functionality. Features include adhesion and limited differentiation.

What do we mean by differentiation? How can prokaryotes provide an example of differentiation in time? How is that different from differentiation in space?

Differentiation is the specialization of cells for specific functions. Prokaryotes can show temporal differentiation, like spore formation during stress. Eukaryotic differentiation occurs spatially, with distinct cell types in tissues.

Compare and contrast common features to all multicellular organisms across animals, plants, and fungi.

All multicellular organisms have:

Adhesion molecules.

Communication systems (e.g., hormones, signals).

Differentiated cells organized into tissues.

Differences lie in structural components like collagen in animals, cellulose in plants, and chitin in fungi.

How does the ability to perform bulk flow allow more complex body organization?

Bulk flow systems, like circulatory or vascular systems, enable efficient transport of nutrients and waste over large distances, supporting the development of larger, more complex bodies.

What’s a tissue? What is an organ?

A tissue is a group of cells with a specific function, such as muscle or epidermis. An organ is a structure made of multiple tissues working together, like a heart or leaf.

What are the functions of connective tissue?

Connective tissue provides structural support, connects tissues, stores energy (adipose), and transports substances (blood).

What is collagen? What can you build with collagen? How does its structure relate to its function?

Collagen is a structural protein that provides tensile strength. It forms tendons, ligaments, and skin. Its triple-helix structure resists stretching, making it strong and flexible.

What are GAGs? What can you build with them? How does their structure relate to their function?

Glycosaminoglycans (GAGs) are long polysaccharides that retain water and provide cushioning. They form components of cartilage and extracellular matrices, where their hydrophilic nature aids in shock absorption.

How can extracellular matrices be different from one another structurally and functionally?

Extracellular matrices (ECMs) vary based on their protein and polysaccharide composition. For example, bone ECM is rigid due to calcium phosphate, while cartilage ECM is flexible and absorbs shock.

Why is ECM "metabolically inexpensive?"

The ECM is metabolically inexpensive because its components, like collagen and GAGs, are synthesized once and persist without continuous metabolic input.

• Inside cell needs lots of ATP, ECM does not because it has many resources

What are cell adhesion molecules? How do cadherins and integrins differ, and where are each used?

Cell adhesion molecules mediate cell-cell or cell-ECM adhesion. Cadherins are used in cell-cell junctions, relying on calcium, while integrins connect cells to the ECM and mediate signaling.

What are anchoring junctions, and where are they used? Compare/contrast adherens junctions, desmosomes, and hemidesmosomes.

Anchoring junctions are cellular connections that mechanically attach cells to one another or to the extracellular matrix, providing structural support.

Adherens junctions connect cells via cadherins and link to actin filaments, playing a role in cell shape and tension.

Desmosomes use cadherins to connect intermediate filaments, providing strong adhesion for mechanical stress.

Hemidesmosomes connect cells to the extracellular matrix using integrins and anchor intermediate filaments, supporting cell-matrix adhesion.

What are tight junctions, and where are they critical?

Tight junctions form a seal between adjacent cells, preventing leakage of molecules between them. They are critical in epithelial tissues, such as the intestinal lining and blood-brain barrier, to maintain compartmentalization.

Compare and contrast gap junctions, plasmodesmata, and fungal septa pores. Why are each necessary?

Gap junctions in animal cells connect cytoplasm between cells via connexin proteins, enabling communication.

Plasmodesmata in plants are membrane-lined channels allowing cytoplasmic exchange, including organelles.

Fungal septa pores allow cytoplasmic flow between hyphal compartments. Each is necessary for nutrient sharing, signaling, and maintaining functional syncytia.

What are some roles of connective tissue? How do their matrices differ, and how does that provide their different functions?

Connective tissues provide support, protection, and nutrient transport.

Bone has a mineralized matrix for rigidity.

Cartilage has a gel-like matrix for flexibility.

Blood has a liquid matrix for nutrient transport.

What role does the basal lamina play in skin?

The basal lamina anchors the epidermis to the dermis, provides structural support, and regulates cell behavior via signaling.

What are some of the functions of epithelial tissue?

Epithelial tissue protects surfaces, facilitates absorption, secretion, and filtration, and forms sensory structures like taste buds.

For all the junctions, compare and contrast.

Tight junctions form a seal, preventing leakage.

Adherens junctions connect cells via actin filaments.

Desmosomes and hemidesmosomes anchor cells to each other or the ECM using intermediate filaments.

Gap junctions enable cytoplasmic exchange and communication. Tight junctions regulate transport but do not allow communication.

Relate tight junctions back to transcellular glucose transport—why are tight junctions critical?

Tight junctions prevent paracellular leakage of glucose, forcing it to be transported through cells, maintaining directional glucose movement.

Consider the evolution of nervous systems, from nerve nets to ganglia to brains.

Nerve nets in simple animals enable diffuse signaling.

Ganglia provide localized processing in invertebrates.

Brains centralize control for complex processing and behavior in vertebrates.

What’s membrane potential? What do we mean by the resting membrane potential of a neuron?

Membrane potential is the voltage difference across a cell membrane. Resting membrane potential is the steady-state voltage (typically ~-70mV in neurons) maintained by ion pumps and channels.

What’s depolarization? What happens when threshold potential is reached?

Depolarization is the membrane potential becoming less negative due to Na+ influx. When the threshold is reached, an action potential is triggered.

What happens during an action potential? What triggers one? What happens to voltage-gated ion channels?

An action potential is triggered by depolarization to the threshold, causing voltage-gated Na+ channels to open, followed by K+ channels, restoring the resting potential.

What triggers neurotransmitter release at a synapse? What happens in the post-synaptic cell as a result?

Neurotransmitter release is triggered by Ca2+ influx due to an action potential. The neurotransmitter binds to receptors on the post-synaptic cell, initiating a response like depolarization.

Describe the parts of a neuron, and know what happens in each.

Cell body: Contains the nucleus, integrates inputs.

Axon: Transmits action potentials.

Dendrites: Receive signals.

Synapse: Communication point.

What’s a nerve net, and what is it capable of? What are ganglia, and why were they an evolutionary advantage? What are brains, and why are they a major evolutionary advantage?

A nerve net is a decentralized system capable of basic reflexes.

Ganglia allow local processing, improving efficiency.

Brains centralize complex decision-making and learning.

Review ion channels!

What controls the gate in voltage-gated channels? Ligand-gated channels?

Voltage-gated channels are controlled by membrane potential changes. Ligand-gated channels are controlled by the binding of specific molecules.

Be able to describe the process from neurotransmitter binding to receptors on a dendrite of a cell through its release of neurotransmitters from its axon.

Neurotransmitter binding to receptors on a dendrite triggers ion channel openings, causing depolarization. This depolarization generates an action potential that travels down the axon, where voltage-gated calcium channels open at the axon terminal. Calcium influx prompts vesicles to release neurotransmitters into the synaptic cleft.

Know your terminology: Muscle fiber, myofibril, actin/myosin, Z disks, sarcomere, troponin/tropomyosin.

Muscle fiber: A single muscle cell containing many myofibrils.

Myofibril: The structural unit of a muscle fiber, containing repeating sarcomeres.

Actin/Myosin: Proteins forming thin and thick filaments, respectively, responsible for contraction.

Z disks: Boundaries of a sarcomere, anchoring actin filaments.

Sarcomere: The functional unit of muscle contraction.

Troponin/Tropomyosin: Regulatory proteins controlling the interaction of actin and myosin.

How do muscle fibers transduce energy?

Muscle fibers use ATP hydrolysis to energize myosin heads, enabling them to bind to actin and pull, converting chemical energy into mechanical force.

Describe the organization of a sarcomere.

A sarcomere is bounded by Z disks. Thin actin filaments extend from Z disks, overlapping with thick myosin filaments in the center. The central H zone lacks actin, while the A band spans the entire length of myosin.

What is the sliding filament model, and how does it explain muscle contraction?

The sliding filament model describes muscle contraction as thin actin filaments sliding over thick myosin filaments, shortening the sarcomere. Myosin heads attach to actin, perform a power stroke, and release, repeating this cycle to generate force.

Review the cycle of myosin (We covered it with the cytoskeleton.)

The myosin cycle includes ATP binding, causing detachment from actin; ATP hydrolysis, cocking the myosin head; actin binding; and the power stroke as ADP is released, pulling the actin filament.

What’s the sarcoplasmic reticulum, and what role does it play in a muscle cell?

The sarcoplasmic reticulum (SR) stores and releases calcium ions, which are crucial for muscle contraction. Calcium release from the SR triggers troponin to move tropomyosin, exposing binding sites on actin for myosin.

Terminology: twitch, tetanus, motor unit (Some will be used more in lab than lecture.)

Twitch: A single contraction in response to a stimulus.

Tetanus: A sustained contraction from rapid, repeated stimuli.

Motor unit: A single motor neuron and all the muscle fibers it innervates.

What is force summation?

Force summation occurs when multiple twitches overlap due to rapid stimuli, increasing overall tension and contraction strength.

Describe the structure of a muscle.

Muscle is composed of bundles of muscle fibers (fascicles), each containing myofibrils. Myofibrils are organized into repeating sarcomeres, the structural units of contraction.

What is a sarcomere? How does it shorten? How does the sliding actin filament model explain muscle contractions?

A sarcomere is the functional unit of muscle contraction. It shortens as actin filaments slide over myosin filaments, reducing the distance between Z disks. This sliding generates muscle contraction.

How does myosin “walk”?

Myosin "walks" along actin by using ATP. The myosin head binds ATP, hydrolyzes it to cock, binds actin, and performs a power stroke during the release of ADP and phosphate.

Compare and contrast a synapse and a neuromuscular junction.

A synapse is a communication point between two neurons, while a neuromuscular junction (NMJ) connects a motor neuron to a muscle fiber.

Both involve neurotransmitter release (e.g., acetylcholine in NMJs) but differ in targets and responses.

The NMJ triggers muscle contraction, while synapses propagate neural signals.

Be able to describe the process from neurotransmitter binding to receptors on a dendrite of a motor neuron through the contraction of a muscle cell. What roles do troponin and tropomyosin play? How is calcium released into the cytosol of a muscle cell?

When a neurotransmitter (acetylcholine) binds to receptors on the dendrite of a motor neuron, it generates an action potential that travels down the axon. The action potential reaches the neuromuscular junction, causing calcium ion channels to open. Calcium enters the neuron, triggering the release of acetylcholine into the synaptic cleft. Acetylcholine binds to receptors on the muscle cell membrane (sarcolemma), leading to depolarization and the propagation of an action potential across the muscle fiber. The action potential travels along the T-tubules to the sarcoplasmic reticulum (SR), which releases calcium ions into the cytosol. Calcium binds to troponin, which causes a conformational change in tropomyosin, exposing the binding sites on actin for myosin heads to attach. This results in muscle contraction.

What is turgor pressure and what are the roles of cell walls and vacuoles?

Turgor pressure is the pressure exerted by the cell membrane against the cell wall due to water intake. The cell wall provides structural support and prevents the cell from bursting under pressure. The vacuole stores water and contributes to maintaining turgor pressure, helping the plant maintain rigidity and shape.

Review diffusion and osmosis.

- Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration, driven by the concentration gradient.

- Osmosis is the diffusion of water across a selectively permeable membrane, moving from an area of low solute concentration to an area of high solute concentration, until equilibrium is reached.

What problems do land plants have that aquatic photosynthetic organisms don’t? How does that impact the way land plants have evolved?

Land plants face challenges like water loss through evaporation and the need for a more complex support system to stand upright. Unlike aquatic plants, they must develop structures for water and nutrient transport (xylem and phloem), and mechanisms to reduce water loss (e.g., cuticle, stomata). Over time, land plants have evolved adaptations like vascular tissues, stomatal regulation, and water storage systems to cope with these challenges.

What are the three tissues in plants and what do they do?

- Dermal tissue : Protects the plant and controls water and nutrient exchange (e.g., epidermis, cuticle).

- Ground tissue : Involved in photosynthesis, storage, and support (e.g., parenchyma, collenchyma, sclerenchyma).

- Vascular tissue : Transports water, nutrients, and sugars (e.g., xylem, phloem).

What organs are found in vascular plants? What are three tissues?

Vascular plants have organs like roots, stems, and leaves. The three primary tissues in vascular plants are dermal tissue, ground tissue, and vascular tissue.

What’s the general structure of a leaf? Why have a cuticle? What role do stomata and guard cells play? How does this relate to transpiration (and generally what is transpiration?)

A leaf typically consists of a flat blade, petiole (stem attachment), and veins. The cuticle is a waxy layer that reduces water loss. Stomata are openings on the leaf surface, and guard cells regulate their size to control gas exchange and water loss. Transpiration is the loss of water vapor through stomata, helping draw water up through the plant and cool the leaf.

What’s the general structure of a stem? What are the two types of vascular tissue, and what do they transport, and from where to where in the plant? In general, how do they differ in structure?

A stem consists of nodes, internodes, and vascular bundles. The two types of vascular tissue are xylem (transports water and minerals from roots to leaves) and phloem (transports sugars from leaves to other parts of the plant). Xylem typically consists of dead, hollow cells, while phloem consists of living cells and includes sieve tubes for nutrient transport.

How do plant cells elongate? What two plant cellular components control expansion?

Plant cells elongate by increasing the size of the central vacuole, which causes the cell to expand. Cellulose in the cell wall and turgor pressure are key components that facilitate expansion by allowing the cell wall to stretch as water is absorbed into the vacuole.

What did plants need to overcome to perform photosynthesis in air?

Plants needed to overcome the challenge of water loss and the ability to efficiently capture carbon dioxide in the dry environment. This led to the evolution of structures like stomata for gas exchange, waxy cuticles to reduce water loss, and vascular systems to transport water and nutrients.

What role(s) does the epidermis play in a leaf? A cuticle? Ground tissue like mesophyll cells?

The epidermis acts as a protective layer, preventing water loss and pathogen entry. The cuticle reduces water loss through evaporation. Mesophyll cells in the ground tissue carry out photosynthesis due to their high chloroplast content.

How do plants regulate gas flow into leaves?

Plants regulate gas flow into leaves through stomata , which open and close based on environmental conditions. Guard cells control the size of the stomatal pores to balance gas exchange with water conservation.

What’s the structure of xylem, and what does it carry? In general, what’s transpiration?

Xylem is made up of vessels and tracheids that are hollow and dead at maturity. It carries water and minerals from the roots to the rest of the plant. Transpiration is the process by which water evaporates from the leaves, creating a negative pressure that helps pull water up through the plant.

What’s the structure of phloem, and what does it carry?

Phloem consists of living cells like sieve tubes, companion cells, and phloem fibers. It carries sugars (produced during photosynthesis) from the leaves to other parts of the plant for growth and storage.

What role do fungi play in the ecosystem? How are they limited in finding resources?

Fungi decompose organic material, recycling nutrients in the ecosystem. They are limited in finding resources by their need for organic matter to break down, which may not be evenly distributed in the environment.

How are cells connected in a filamentous fungus?

Cells in filamentous fungi are connected by septa , which are cross-walls that divide the hyphae into cells but allow for the flow of cytoplasm and nutrients between cells.

What restrictions do fungi have on nutrient acquisition?

Fungi rely on external digestion, secreting enzymes to break down organic matter before absorbing nutrients. This limits them to environments where organic material is available for decomposition.

What are hyphae? Mycelia? How do hyphae explore for resources? How do they share resources through the mycelium?

Hyphae are long, branching filaments that make up the body of a fungus. Mycelia is the network of hyphae. Hyphae explore resources by growing through substrates and secreting enzymes to break down organic matter. They share resources by transferring nutrients and energy between interconnected hyphae in the mycelium.

How do yeast differ from other filamentous fungi?

Yeasts are unicellular fungi that typically grow as individual cells or in short chains, while filamentous fungi grow in long, branched hyphal networks.

Why do fungi need spores?

Fungi need spores for reproduction. Spores can disperse over large distances, allowing fungi to colonize new environments and continue their lifecycle.

UNIT 4

What is the body plan of a filamentous fungi? What is a hypha; what is a mycelium?

- A filamentous fungi consists of a network of hyphae, which are long, thread-like structures that absorb nutrients and form the basic structural unit of the fungus. The mycelium is the dense network of hyphae that spreads through the substrate.

How do fungi digest and acquire nutrients like reduced carbon?

- Fungi digest food externally by secreting enzymes that break down organic matter into smaller molecules. They primarily acquire nutrients through saprotrophy, where they decompose dead organic material, or through symbiosis with other organisms.

What does the fungal resource environment look like?

- Fungi thrive in environments rich in organic matter, such as decaying plant material, soil, and wood, where they can break down complex molecules to acquire nutrients.

What is a meristem? How do meristem cells differ from non-meristem cells?

- A meristem is a region of plant tissue where active cell division occurs, allowing for growth. Meristem cells are undifferentiated and capable of dividing, whereas non-meristem cells are differentiated and no longer divide.

Review the general structures of shoots, roots, leaves, and stems, and of xylem and phloem.

- Shoots consist of stems, leaves, and flowers. Roots anchor the plant and absorb water and nutrients. Xylem transports water and minerals from the roots to the rest of the plant, while phloem carries sugars and other organic compounds from the leaves to other parts of the plant.

How do stems grow? What roles does the shoot apical meristem play in the shape of the stem/positions of leaves and branches?

- Stems grow through the activity of the shoot apical meristem, which is responsible for elongating the stem and producing leaves and branches. The shoot apical meristem influences the overall shape of the stem and the arrangement of leaves.

How do leaves form?

- Leaves form from the shoot apical meristem, where cells divide and differentiate to form the various structures of the leaf, including the blade, petiole, and veins.

What are hormones and (in general) what do they do? We’ll mainly consider auxin, so focus on its role in leaf development and apical dominance. Understand polar transport of auxin, a kind of bulk transport.

- Hormones are signaling molecules that regulate various physiological processes. Auxin, a plant hormone, plays a role in leaf development by promoting cell elongation. It also controls apical dominance by inhibiting the growth of lateral buds and directing growth toward the apical bud.

What are lateral or secondary meristems, and what are they responsible for?

- Lateral or secondary meristems are regions of growth in plants that produce new tissues in thickness. They are responsible for secondary growth, such as the formation of bark and the widening of stems and roots.

What is the root apical meristem, and what role does it play in root growth and development?

- The root apical meristem is a region of active cell division at the tip of the root. It is responsible for the growth and elongation of roots and the formation of root cap cells that protect the growing tip.

What is tropism? How does auxin regulate phototropism and gravitropism in shoots and in roots?

- Tropism is a plant's growth response to environmental stimuli. Auxin regulates phototropism (growth towards light) by accumulating on the shaded side of the shoot, causing cells to elongate and the shoot to bend towards light. In roots, auxin regulates gravitropism (growth in response to gravity) by redistributing towards the lower side, causing the root to grow downward.

What impact do environmental signals have on the shape of plants?

- Environmental signals, such as light, gravity, and touch, influence plant growth and shape by triggering specific hormone responses like auxin distribution, which affects processes such as phototropism, gravitropism, and thigmotropism.

What are hormones and (in general) what do they do?

- Hormones are chemical signals that regulate growth, development, and various physiological processes in plants and animals.

From Chapter 33: What is an animal, and what features are unique to animals? Tissues vs. organs vs. organ systems. Review types of animal tissue. Do all animals have organs and organ systems?

- Animals are multicellular organisms that are heterotrophic, typically having specialized tissues, organs, and organ systems. Not all animals have organs or organ systems; simpler animals may rely on specialized cells or tissues for basic functions.

What is molting, and why must insects do it? How does it differ from metamorphosis?

- Molting is the process of shedding an old exoskeleton to grow a new, larger one. Insects must molt to accommodate growth. Metamorphosis is a developmental process in which an insect undergoes a series of stages, often including a dramatic change in form, like from larva to adult.

How were experiments with Rhodnius used to understand the role of hormones on changes in body plan?

- Experiments with the insect Rhodnius showed that hormones regulate the process of molting and metamorphosis, influencing changes in the body plan during development.

What is homeostasis?

- Homeostasis is the maintenance of a stable internal environment within an organism, despite external fluctuations.

What is tropism? What are phototropism and gravitropism? How do roots and shoots differ in these responses? What role does auxin play?

- Tropism is a plant's directional growth response to environmental stimuli. Phototropism is the growth of plants towards light, while gravitropism is the response to gravity. Shoots exhibit positive phototropism (grow towards light) and negative gravitropism (grow away from gravity), while roots exhibit negative phototropism and positive gravitropism.

What is gravitropism? How do positive and negative gravitropism differ?

- Gravitropism is a plant's response to gravity. Positive gravitropism is the growth of plant parts toward gravity (roots), while negative gravitropism is the growth away from gravity (shoots).

How can a plant shoot cell determine which way is “up”?

- A plant shoot cell determines the direction of growth by sensing gravity, often through the movement of statoliths (dense particles) in specialized cells.

How do cells elongate? How does auxin facilitate elongation? How does elongation cause changes in shoot structure?

- Cells elongate by absorbing water and expanding, a process regulated by auxin. Auxin promotes cell wall loosening, allowing cells to elongate. This process contributes to the bending of shoots toward light (phototropism).

What’s a statolith, and what does it do?

- A statolith is a dense particle found in plant cells that helps detect gravity. It settles at the bottom of the cell, aiding in the plant's ability to sense and respond to gravitational changes.

How does this process differ in roots?

- In roots, auxin regulates gravitropism by redistributing toward the lower side of the root, causing elongation on the upper side, thus making the root grow downward in response to gravity.

Why do fungi care about gravity? How do they detect which way is “up” and how do they respond to changes?

- Fungi use gravity to orient their growth, especially in relation to the direction of resource acquisition. They detect gravity through specialized structures and grow accordingly to maximize nutrient absorption.

What are sensory receptor cells? Sensory organs?

- Sensory receptor cells are specialized cells that detect environmental stimuli. Sensory organs are structures composed of receptor cells that help organisms sense and respond to their environment.

What is sensory transduction?

- Sensory transduction is the process by which sensory receptor cells convert external stimuli (such as light or pressure) into electrical signals that can be processed by the nervous system.

We’ll mainly focus on gravity, so understand things like statocysts and, in general, the vestibular system.

- Statocysts are sensory organs in invertebrates that help detect gravity. The vestibular system in vertebrates is responsible for maintaining balance and detecting changes in head position and movement, including gravity.

How can hair cells transduce pressure or mechanical movement into an electrical signal?

- Hair cells in the ear or other sensory organs detect pressure or mechanical movement by bending in response to stimuli. This bending opens ion channels, leading to changes in electrical potential and initiating a neural response.

What is a statocyst, and how does it allow invertebrates to sense gravity changes?

- A statocyst is an organ found in some invertebrates that detects gravity. It contains statoliths that move in response to gravity, triggering sensory cells to send signals to the nervous system.

How does the vestibular system allow mammals to detect both movement and gravity? What roles do the semicircular canals and otolith organs play in this?

- The vestibular system in mammals detects movement and gravity. The semicircular canals sense rotational movement, while the otolith organs detect linear movement and gravity by responding to the position of crystals within the fluid of the inner ear.

What type of receptors are used to detect sound?

- Sound is detected by mechanoreceptors known as hair cells. These hair cells are located in the cochlea of the inner ear. When sound waves cause vibrations in the fluid-filled cochlea, the movement bends the hair cells, which then convert mechanical energy into electrical signals that are transmitted to the brain.

What type of receptors are used to detect chemicals (e.g. odor and taste)?

- Chemicals are detected by chemoreceptors. Olfactory receptors detect airborne chemicals (odorants) and are located in the nose. Gustatory receptors detect dissolved chemicals (taste) and are located on the tongue and other parts of the mouth.

What is special about the membrane protein used to detect light?

- The membrane proteins used to detect light are called photopigments. These proteins, such as rhodopsin in the retina, undergo a conformational change when they absorb light, initiating a signaling cascade that ultimately leads to visual perception. Photopigments are unique because they are sensitive to specific wavelengths of light, enabling organisms to detect and respond to different colors.

What is phototropism? What triggers it? How is the response to light similar to the response to gravity?

- Phototropism is the growth of a plant in response to light. It is triggered by the plant’s ability to sense light and directs growth towards the light source (positive phototropism). The response to light is similar to gravitropism in that both are directional growth responses, but while phototropism is driven by light and gravitropism is driven by gravity, both involve auxin regulation that influences cell elongation.

How does soil moisture affect root elongation and branching?

- Soil moisture plays a crucial role in root growth. In moist conditions, roots tend to elongate more rapidly and branch more frequently, as the plant seeks out more water. In dry conditions, roots may grow deeper in search of water or reduce branching to conserve energy and resources.

What drives fungal growth through the environment?

- Fungal growth is driven by the need to find and absorb nutrients, such as organic matter, which fungi decompose. The growth of hyphae spreads through the environment in search of food sources. Fungi also respond to environmental conditions like moisture, temperature, and pH.

Saprotrophs vs. necrotrophs

- Saprotrophs are fungi that obtain nutrients by decomposing dead organic matter, breaking down complex organic compounds. Necrotrophs, on the other hand, kill living hosts to obtain nutrients, often through the secretion of toxins or enzymes that break down the host’s tissues.

In shoots, does light override gravity or vice versa? Why?

- Light generally overrides gravity in shoots because phototropism (growth towards light) is a stronger signal than gravitropism (growth in response to gravity) in shoots. This is because plants need light for photosynthesis, and growth toward light maximizes their exposure to it.

How do molecules enter fungal cells? How are they moved by bulk transport through the mycelium?

- Molecules enter fungal cells through various transport mechanisms, including passive diffusion and active transport. Bulk transport of nutrients through the mycelium is facilitated by the cytoplasmic streaming, which moves nutrients and molecules across the hyphae to the growing tips, ensuring that the fungus has access to the resources it needs.

Why are fungi especially good at breaking down woody plants?

- Fungi are equipped with enzymes like lignin peroxidase and cellulase that break down complex polymers found in wood, such as lignin and cellulose. These enzymes enable fungi to decompose wood and recycle nutrients, making them vital in ecosystems.

Why does CO2 uptake cause water loss? How do plants reduce water loss?

- CO2 uptake in plants requires the opening of stomata (tiny pores in leaves), and as these pores open to allow CO2 in for photosynthesis, water vapor also escapes (transpiration). To reduce water loss, plants can close their stomata, alter leaf structure, or develop waxy coatings that reduce evaporation.

What is transpiration?

- Transpiration is the process by which water is absorbed by plant roots, moves through the plant, and is then released as vapor through stomata in the leaves. It is crucial for nutrient transport and cooling the plant.

What is xylem? How is its structure key to its function? How is water pulled through xylem?

- Xylem is the vascular tissue responsible for transporting water and minerals from the roots to the rest of the plant. Its structure, with hollow cells called vessels and tracheids, allows for efficient water transport. Water is pulled through xylem by capillary action and transpiration, which creates a negative pressure that draws water upwards.

What is phloem? How is its structure key to its function?

- Phloem is the vascular tissue that transports sugars and other nutrients from sources (like leaves) to sinks (such as roots or fruits). Phloem contains sieve tube elements and companion cells, which help in the transport of phloem sap through pressure-flow mechanisms.

How are sugars pushed through phloem? What role does xylem play in this process?

- Sugars are pushed through phloem by pressure-flow mechanisms, where pressure builds up in the source cells (typically in leaves) and drives the flow toward the sink cells (such as roots or fruits). Xylem plays a role in supplying water to the phloem to maintain pressure.

What types of nutrients do roots obtain from soil?

- Roots obtain a variety of nutrients from the soil, including macronutrients like nitrogen, phosphorus, potassium, sulfur, calcium, and magnesium, as well as micronutrients like iron, manganese, and zinc.

What are the endodermis and the Casparian strip? How are they key to selective uptake of minerals and water?

- The endodermis is a layer of cells that surrounds the vascular tissue in roots. The Casparian strip is a band of suberin (a waxy substance) that blocks the passive flow of water and dissolved substances through the cell walls. This structure ensures selective uptake of minerals and water into the plant’s vascular system.

How do fungi acquire and take up the various resources? How do they distribute the various resources through the cell and mycelium?

- Fungi acquire resources like organic matter by secreting enzymes that break down complex molecules. The resulting smaller molecules are absorbed into the hyphal cells. These resources are then distributed via the mycelium through cytoplasmic streaming.

Where and how do root branches form? What happens when a root grows through a nutrient-rich patch of soil?

- Root branches form in the root apical meristem and lateral roots, where cells divide and elongate. When a root encounters a nutrient-rich patch of soil, it may increase branching to maximize nutrient uptake in that area.

How do plants regulate what can enter into the xylem from the roots?

- Plants regulate what enters the xylem by selective uptake in the root cortex, where the Casparian strip forces water and minerals to pass through the plasma membrane of cells before entering the xylem. This ensures that harmful substances are filtered out.

What’s the structure of xylem?

- Xylem consists of tracheids and vessel elements, which are hollow cells that transport water. The walls of these cells are reinforced with lignin, which gives xylem strength and helps resist collapse under pressure.

What is transpiration? Why is it dependent on the odd physical properties of water? How does water (and minerals) move from roots through shoots?

- Transpiration is the evaporation of water from plant leaves, creating a negative pressure that pulls water from roots through the xylem. This process is dependent on the cohesion of water molecules (due to hydrogen bonding) and adhesion to cell walls, allowing water to be moved efficiently through the plant.

How and where do plants acquire carbon? What are the carbon sources and sinks?

- Plants acquire carbon dioxide (CO2) from the air through stomata in the leaves. Carbon is used in photosynthesis to produce sugars. Carbon sources are areas where carbon is actively produced (like leaves), and carbon sinks are areas where carbon is stored (like roots, fruits, and seeds).

What’s the structure of phloem?

- Phloem consists of sieve tube elements, companion cells, phloem fibers, and phloem parenchyma. Sieve tube elements are responsible for transporting sugars, and companion cells assist in the loading and unloading of the sieve tubes.

How are sugars moved from sources to sinks?

- Sugars are moved from sources (typically the leaves) to sinks (roots, fruits) through phloem by a pressure-flow mechanism, where high pressure at the source pushes the phloem sap toward areas of lower pressure at the sink.

Thinking question—it can be said that evolution in movement, evolution in sensation and neural integration, evolution of digestion, and changes in predatory behavior all influenced one another. Explain.

- The evolution of movement, sensation, and neural integration is interdependent. For example, as animals evolved better sensory systems (sight, hearing), they could detect and respond to prey or predators more efficiently, which required more complex neural integration. These developments influenced predatory behaviors, such as hunting strategies, and required changes in digestive systems to handle different types of food.

How do molecules enter fungal cells? How are they moved by bulk transport through the mycelium?

- Molecules enter fungal cells through active and passive transport mechanisms, including facilitated diffusion and endocytosis. Once inside, nutrients and molecules are moved by bulk transport, primarily through the mycelium, using cytoplasmic streaming or vesicular transport.

Why are fungi especially good at breaking down woody plants?

- Fungi are equipped with powerful enzymes like lignin peroxidases and cellulases that break down lignin and cellulose, the key components of woody plants. This makes them efficient decomposers of plant material, especially in forest ecosystems.

Why does CO2 uptake cause water loss? How do plants reduce water loss?

- CO2 uptake occurs through stomata, which open to allow gas exchange. However, when stomata are open, water vapor can also escape, causing water loss. Plants reduce water loss by closing stomata, particularly in dry conditions, and by having adaptations like waxy cuticles or smaller stomatal openings.

What is transpiration?

- Transpiration is the process by which water is absorbed by plant roots, moves through the plant, and evaporates into the atmosphere through stomata, primarily in leaves. It is a key part of water and nutrient transport in plants.

What is xylem? How is its structure key to its function? How is water pulled through xylem?

- Xylem is vascular tissue in plants responsible for transporting water and dissolved minerals from roots to other parts of the plant. It consists of hollow tubes (vessels and tracheids) that allow water to move efficiently. Water is pulled through xylem by capillary action, root pressure, and the cohesion-tension mechanism driven by transpiration.

What is phloem? How is its structure key to its function?

- Phloem is vascular tissue responsible for transporting sugars and other organic compounds throughout the plant. Its structure includes sieve tube elements and companion cells, which facilitate the movement of food and nutrients in the form of sap.

How are sugars pushed through phloem? What role does xylem play in this process?

- Sugars are pushed through phloem by pressure flow, where high pressure at the source (like leaves) forces the sap through the sieve tubes to areas of lower pressure (sinks). Xylem provides water to the phloem, ensuring that the flow of sap remains efficient and supporting the process with water and nutrients.

What types of nutrients do roots obtain from soil?

- Roots absorb water and various minerals from the soil, including nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and trace elements like iron, manganese, and zinc.

What are the endodermis and the Casparian strip? How are they key to selective uptake of minerals and water?

- The endodermis is a layer of cells surrounding the vascular tissue in roots, and the Casparian strip is a band of suberin (a waxy substance) in the endodermal cell walls. These structures regulate the selective uptake of water and minerals by controlling their passage into the vascular system.

How do fungi acquire and take up the various resources? How do they distribute the various resources through the cell and mycelium?

- Fungi acquire resources through external digestion, secreting enzymes that break down organic matter, which they then absorb. The mycelium distributes nutrients by cytoplasmic streaming, where nutrients are transported through the hyphal network.

Where and how do root branches form? What happens when a root grows through a nutrient-rich patch of soil?

- Root branches form at sites called root primordia, typically near the root tip. When a root grows through a nutrient-rich patch, it may increase branching to maximize nutrient absorption.

How do plants regulate what can enter into the xylem from the roots?

- The endodermis and Casparian strip regulate what enters the xylem by controlling the movement of water and minerals through selective barriers, ensuring only necessary nutrients pass into the vascular system.

What’s the structure of xylem?

- Xylem consists of vessels, tracheids, fibers, and parenchyma cells. Vessels are long, hollow tubes that transport water, while tracheids are elongated cells with tapered ends that also conduct water. The fibers provide structural support, and parenchyma cells aid in storage.

What is transpiration? Why is it dependent on the odd physical properties of water? How does water (and minerals) move from roots through shoots?

- Transpiration is the evaporation of water from plant leaves. It is dependent on water's high cohesion and adhesion properties, allowing it to form a continuous column in xylem vessels. As water evaporates from stomata, it creates a vacuum that pulls more water from the roots through the plant.

How and where do plants acquire carbon? What are the carbon sources and sinks?

- Plants acquire carbon through photosynthesis by absorbing CO2 from the atmosphere via stomata in the leaves. The carbon is used in the production of sugars and other organic compounds. Carbon sinks include the plant tissues themselves, where carbon is stored, and soil, where organic matter can be buried.

What’s the structure of phloem?

- Phloem is made up of sieve tube elements, companion cells, phloem fibers, and phloem parenchyma. Sieve tube elements are the main conducting cells, while companion cells assist in the loading and unloading of sugars into the sieve tubes.

How are sugars moved from sources to sinks?

- Sugars are moved from sources (where they are produced, like leaves) to sinks (where they are used or stored, like roots or fruits) by pressure flow. Water from xylem helps create the pressure gradient that drives the movement of sugars.

What is a hydrostatic skeleton? Why are GAGs important? How can muscles interact with a hydrostatic skeleton to produce movement?

- A hydrostatic skeleton is a type of skeleton where fluid-filled cavities maintain shape and support movement. GAGs (glycosaminoglycans) are important for their role in maintaining the structure and elasticity of the skeleton. Muscles contract against the hydrostatic skeleton to produce movement, creating changes in pressure and shape.

What is an exoskeleton? What are the advantages and disadvantages of one? How do muscles interact with an exoskeleton to produce movement?

- An exoskeleton is a rigid external covering that provides support and protection. Advantages include protection from predators and environmental stress, while disadvantages include limiting growth and flexibility. Muscles attach to the inside of the exoskeleton and contract to produce movement.

What is an endoskeleton? What are the advantages and disadvantages of one? How do muscles interact with an endoskeleton to produce movement?

- An endoskeleton is an internal skeleton found in vertebrates and some invertebrates. Advantages include growth potential and flexibility, while disadvantages include vulnerability to external injury. Muscles contract against the bones of the endoskeleton, enabling movement through leverage.

Chapter 38: Review metabolism! We’ll return to temperature regulation.

What are essential nutrients? What are some of the adaptations made to animal feeding structures?

- Essential nutrients are substances that an organism cannot synthesize on its own and must obtain from its diet, including amino acids, fatty acids, vitamins, and minerals. Adaptations in animal feeding structures include specialized teeth for grinding (herbivores), sharp teeth for tearing (carnivores), and the presence of beaks or proboscises in some species for extracting specific types of food.

What organs are in the foregut, midgut, and hindgut? What happens in each region?

- Foregut : Includes the mouth, esophagus, and stomach. In this region, food is ingested and begins to be broken down mechanically and chemically.

- Midgut : Includes the small intestine, where most digestion and nutrient absorption occurs.

- Hindgut : Includes the large intestine, where water and minerals are reabsorbed, and waste is compacted for elimination.

What are the layers of tissue in the digestive organs, and how does that relate to the process of digestion?

- The digestive organs have four main tissue layers:

1. Mucosa : The innermost layer, which secretes enzymes and absorbs nutrients.

2. Submucosa : Contains blood vessels and lymphatic tissue to transport nutrients.

3. Muscularis : Smooth muscle responsible for peristalsis and movement of food through the digestive tract.

4. Serosa : The outermost layer, which provides structure and protection.

What is a hydrostatic skeleton? How do muscles interact with them to generate movement? How can hydrostatic elements interact with endoskeletons?

- A hydrostatic skeleton is a structure found in some animals, consisting of a fluid-filled cavity (like a coelom) that maintains body shape. Muscles contract around the cavity to generate movement by altering the pressure of the fluid. Hydrostatic elements can interact with endoskeletons, like in some invertebrates, where the exoskeleton provides protection and the hydrostatic skeleton helps with flexibility and movement.

What is an exoskeleton? Advantages/disadvantages? How do mollusks and arthropods make skeletons?

- An exoskeleton is an external skeleton that provides support and protection.

- Advantages : Protection from predators, environmental stress, and desiccation; provides leverage for movement.

- Disadvantages : Limits growth, requires molting to increase size.

- Mollusks produce a calcium carbonate shell, and arthropods produce a chitin-based exoskeleton.

What is an endoskeleton? What makes it stiff? Advantages/disadvantages? How is bone tissue formed and remodeled/repaired?

- An endoskeleton is an internal skeleton made of bone or cartilage.

- Stiffness : Bone tissue is stiff due to the mineralization of collagen fibers with hydroxyapatite, a calcium phosphate compound.

- Advantages : Supports growth, provides flexibility, and can be repaired.

- Disadvantages : Vulnerability to injury.

- Bone tissue is formed through ossification and remodeled/repaired through osteoblasts (bone-forming cells) and osteoclasts (bone-resorbing cells).

How do animals adjust their metabolism when they sprint?

- When animals sprint, they increase their metabolic rate to provide energy for muscle contraction, typically by relying more on anaerobic metabolism (glycolysis) for rapid energy production. Oxygen delivery to tissues also increases, and stored glycogen is broken down for quick access to glucose.

What are some ways animals can feed? Why are jaws important?

- Animals can feed through filter feeding, grazing, scavenging, or predation. Jaws are important because they allow for the manipulation, capture, and consumption of food, making it possible to process a wide range of food types, from plant material to other animals.

What’s the overall process of digestion?

- The process of digestion begins with ingestion, where food enters the mouth. Mechanical and chemical breakdown occurs in the mouth and stomach. In the small intestine, enzymes break down macromolecules, and nutrients are absorbed. The remaining material moves to the large intestine, where water is absorbed, and waste is excreted.

What are the regions of the digestive tract? What organs make up each of them?

- The digestive tract is divided into three main regions:

- Foregut : Mouth, esophagus, stomach.

- Midgut : Small intestine (duodenum, jejunum, ileum).

- Hindgut : Large intestine (cecum, colon, rectum, anus).

What happens in the mouth? The stomach? The small and large intestines?

- In the mouth , food is ingested, chewed, and mixed with saliva (containing enzymes like amylase) to begin breaking down starches. In the stomach , food is mixed with gastric juices, including hydrochloric acid and pepsin, to break down proteins. In the small intestine , digestion continues with the help of enzymes, and nutrients are absorbed through villi. In the large intestine , water and electrolytes are absorbed, and waste is compacted for elimination.

What’s peristalsis, and how is it controlled?

- Peristalsis is the rhythmic contraction of smooth muscles in the digestive tract that moves food along. It is controlled by the enteric nervous system, which is regulated by neural and hormonal signals.

Understand glucose absorption!!

- Glucose is absorbed in the small intestine through active transport by sodium-glucose co-transporters (SGLTs) in the epithelial cells lining the villi. Once inside the cells, glucose enters the bloodstream via facilitated diffusion through GLUT transporters.

Think big picture—what happens where? How are each of the classes of macromolecules broken?

- Proteins are broken down in the stomach (via pepsin) and small intestine (via pancreatic proteases). Carbohydrates are broken down in the mouth (via amylase) and small intestine (via pancreatic amylase). Lipids are broken down in the small intestine via bile (emulsification) and lipases. Nucleic acids are broken down by nucleases in the small intestine.

How must an organism body plan be designed to rely on simple diffusion to meet gas exchange needs?

- Organisms that rely on simple diffusion for gas exchange typically have small body sizes, large surface-area-to-volume ratios, or specialized, thin-walled structures like skin or gills that allow gases to diffuse efficiently.

How do the structures of gills and insect tracheae allow for gas exchange?

- Gills are made up of thin filaments with a large surface area and are surrounded by water, allowing oxygen to diffuse into the bloodstream and carbon dioxide to diffuse out. Insects use tracheae, a system of tubes that directly deliver oxygen to tissues and remove carbon dioxide, with spiracles regulating airflow.

How do countercurrent flow & countercurrent exchange allow for optimal gas exchange?

- In countercurrent flow, water and blood flow in opposite directions across the gills, maximizing the diffusion gradient for oxygen exchange. This allows for the maximum possible oxygen uptake from the water as blood absorbs oxygen at every point along the gill.

How are lungs of terrestrial mammals structured? What are the advantages and disadvantages?

The lungs of terrestrial mammals are composed of a network of airways, including the trachea, bronchi, bronchioles, and alveoli. The alveoli are small air sacs where gas exchange occurs, providing a large surface area for efficient oxygen and carbon dioxide exchange.

Advantages: The large surface area provided by alveoli allows for efficient gas exchange. The structure is well-adapted to extracting oxygen from air.

Disadvantages: The lungs are vulnerable to infections, pollutants, and environmental damage. Additionally, the moist surfaces of the alveoli can lead to water loss in terrestrial environments.

What’s an open circulatory system?

An open circulatory system is one in which blood or hemolymph is not contained in blood vessels but instead flows freely through cavities in the body. This system is commonly found in arthropods and most mollusks, where the blood bathes the organs directly.

How do animals with closed systems make use of varying the diameter of vessels?

Animals with closed circulatory systems use vasodilation (widening of blood vessels) and vasoconstriction (narrowing of blood vessels) to regulate blood flow. This helps control blood pressure, direct blood to specific organs or tissues based on demand, and maintain homeostasis, especially in response to changes in activity levels or environmental conditions.

How has the structure of the heart changed with evolution? What solution are the changes providing?

Over time, the heart structure has evolved from a simple two-chambered heart in fish to a more complex three-chambered heart in amphibians, and a four-chambered heart in birds and mammals. These changes allow for better separation of oxygenated and deoxygenated blood, providing a more efficient system for oxygenating blood and supporting high metabolic demands.

Can any animals rely on just diffusion for oxygen uptake? If so, how?

Yes, certain small or thin-bodied animals, such as flatworms or some amphibians, can rely on diffusion for oxygen uptake because their large surface-area-to-volume ratio allows oxygen to diffuse directly into their cells. The absence of specialized respiratory organs works because the distances are small enough for diffusion to meet their needs.

How do insects exchange gases and nutrients?

Insects use a system of tracheae, a network of tubes that deliver oxygen directly to tissues and remove carbon dioxide. The tracheae open to the exterior through small pores called spiracles. Nutrients are circulated through hemolymph, which is not confined to blood vessels like in closed circulatory systems.

What are the advantages and disadvantages of an open circulatory system?

Advantages: The open circulatory system is energetically less demanding and simpler than a closed circulatory system. It works well for smaller or less metabolically active animals.

Disadvantages: The lack of pressure control and mixing of oxygenated and deoxygenated blood make the system less efficient at transporting oxygen and nutrients compared to closed systems.

What problems do aquatic organisms have that terrestrial organisms don’t? How do fish gills help solve some of those problems? Why is countercurrent flow more efficient than concurrent flow?

Aquatic organisms face challenges related to oxygen scarcity in water. Fish gills address this by providing a large surface area and utilizing countercurrent flow.

Countercurrent flow: Water flows in the opposite direction to the blood in the gills, maintaining a gradient that allows for continuous oxygen transfer from the water to the blood. This is more efficient than concurrent flow, where water and blood flow in the same direction, causing the oxygen gradient to equalize and limiting further oxygen exchange.

How do human lungs create a large and efficient gas exchange surface?

Human lungs are structured with millions of alveoli, tiny sacs that provide a vast surface area for gas exchange. This allows oxygen to diffuse into the blood while carbon dioxide diffuses out efficiently.

How are lungs ventilated?

Lungs are ventilated through the process of inhalation and exhalation. Inhalation occurs when the diaphragm and intercostal muscles contract, expanding the chest cavity and lowering pressure in the lungs, allowing air to flow in. Exhalation occurs when these muscles relax, compressing the chest cavity and pushing air out.

How do capillaries and alveoli allow rapid, efficient diffusion of gases?

Capillaries surrounding the alveoli are extremely thin, only one cell thick, facilitating rapid gas exchange. The close proximity of capillaries and alveoli ensures that oxygen and carbon dioxide can diffuse efficiently between the air and the bloodstream.

What advantages and disadvantages come with different numbers of heart chambers?

Advantages: A greater number of heart chambers (e.g., four chambers in mammals and birds) enables more effective separation of oxygenated and deoxygenated blood, supporting higher metabolic activity.

Disadvantages: More heart chambers result in a more complex heart structure and energy cost.

How do the structures of arteries and veins correlate to their functions?

Arteries: Have thick, muscular walls that can withstand and maintain high pressure, allowing them to carry oxygenated blood from the heart to the body.

Veins: Have thinner walls and larger lumens, designed to carry deoxygenated blood back to the heart. Veins have valves to prevent backflow.

How must an organism body plan be designed to rely on simple diffusion to meet gas exchange needs?

Organisms relying on diffusion for gas exchange must have a small, flat body structure with a high surface-area-to-volume ratio. This allows gases to diffuse efficiently across the body surface without the need for specialized respiratory organs.

How do the structures of gills and insect tracheae allow for gas exchange?

Gills: Have thin, flattened filaments with a large surface area that facilitate oxygen uptake from water.

Insect tracheae: Are a network of tubes that allow oxygen to diffuse directly to tissues, bypassing the need for blood to transport oxygen.

How are lungs of terrestrial mammals structured? What are the advantages and disadvantages?

- Mammalian lungs consist of branching tubes, including the trachea, bronchi, bronchioles, and alveoli. The alveoli provide a large surface area for gas exchange with a high concentration of capillaries.

- Advantages : High surface area for efficient gas exchange, specialized for extracting oxygen from air.

- Disadvantages : Vulnerable to damage, particularly from environmental toxins or pathogens. The need to maintain moisture in the alveoli can lead to water loss.

What’s an open circulatory system?

- An open circulatory system is one in which the blood or hemolymph is not confined to blood vessels but instead flows freely through the body cavity, bathing organs directly. Found in many invertebrates like arthropods and most mollusks.

How do animals with closed systems make use of varying the diameter of vessels?

- Animals with closed circulatory systems regulate blood flow by adjusting the diameter of blood vessels. Vasodilation (widening of vessels) increases blood flow and lowers pressure, while vasoconstriction (narrowing of vessels) reduces blood flow and increases pressure. This helps control blood distribution and blood pressure.

How has the structure of the heart changed with evolution? What solution are the changes providing?

- Heart structures have evolved from a two-chambered heart in fish to a three-chambered heart in amphibians and reptiles, and a four-chambered heart in birds and mammals. The four-chambered heart fully separates oxygenated and deoxygenated blood, providing more efficient circulation for high metabolic needs.

Can any animals rely on just diffusion for oxygen uptake? If so, how?

- Yes, small or thin animals like flatworms or amphibians can rely on diffusion for oxygen uptake. Their small size or large surface-area-to-volume ratio allows gases to diffuse directly into the body without needing specialized respiratory organs.

How do insects exchange gases and nutrients?

- Insects use a system of tracheae, which are tubes that deliver oxygen directly to cells. Air enters through small openings called spiracles, and nutrients are transported through the hemolymph (a fluid analogous to blood in open circulatory systems).

What are the advantages and disadvantages to an open circulatory system?

- Advantages : Simpler and less energy-intensive than closed circulatory systems, efficient in smaller or less metabolically active organisms.

- Disadvantages : Less control over blood flow, and less efficient in delivering oxygen to tissues since hemolymph is not confined to vessels.

What problems do aquatic organisms have that terrestrial organisms don’t? How do fish gills help solve some of those problems? Why is countercurrent flow more efficient than concurrent flow?

- Aquatic organisms face challenges with lower oxygen concentration in water. Fish gills help by extracting oxygen from water through a large surface area and countercurrent flow, where water flows opposite to blood, maintaining a concentration gradient for efficient oxygen exchange.

- Countercurrent flow is more efficient than concurrent flow because it maintains the concentration gradient across the entire gill filament, ensuring more oxygen transfer.

How do human lungs create a large and efficient gas exchange surface?

- The human lungs have millions of alveoli, tiny sacs with thin walls surrounded by capillaries, providing an immense surface area for gas exchange between the air and blood.

How are lungs ventilated?

- Lungs are ventilated through a process of inhalation and exhalation. During inhalation, the diaphragm contracts, expanding the thoracic cavity and creating a vacuum that pulls air in. During exhalation, the diaphragm relaxes, and the chest cavity compresses, pushing air out.

How do capillaries and alveoli allow rapid, efficient diffusion of gases?

- Capillaries around the alveoli are extremely thin (one cell thick), allowing gases to diffuse rapidly. The close proximity of capillaries and alveoli ensures efficient exchange of oxygen and carbon dioxide between the blood and air.

What advantages and disadvantages come with different numbers of heart chambers?

- Advantages : More chambers allow for better separation of oxygenated and deoxygenated blood (e.g., four-chambered hearts in birds and mammals), improving efficiency in oxygen delivery.

- Disadvantages : More chambers require more complex structure and energy to maintain.

How do the structures of arteries and veins correlate to their functions?

- Arteries : Thick, muscular walls to handle high-pressure blood from the heart and distribute it throughout the body.

- Veins : Thinner walls and larger lumens, with valves to prevent backflow and carry blood back to the heart under lower pressure.

Why does the oxygen binding curve of hemoglobin differ from that of myoglobin? How does that make each well-suited for its function?

- Hemoglobin’s curve is sigmoidal, indicating cooperative binding: as one oxygen molecule binds, it makes it easier for others to bind. This helps hemoglobin efficiently pick up oxygen in the lungs and release it in tissues.

- Myoglobin has a hyperbolic curve, indicating it binds oxygen more tightly and is better at storing oxygen in muscles.

What is meant by cooperative binding?

- Cooperative binding refers to the phenomenon where the binding of one molecule (e.g., oxygen) to a protein (e.g., hemoglobin) increases the affinity of the protein for subsequent molecules, improving the efficiency of oxygen loading and unloading.

Why is hemoglobin great at oxygen transport? How does cooperativity allow it to be responsive to the needs of tissue?

- Hemoglobin’s cooperative binding allows it to pick up oxygen efficiently in the lungs and release it in tissues where it’s needed. When oxygen concentration is low, hemoglobin releases oxygen, and when the concentration is high, it binds oxygen more readily.

How does the heart ensure that cardiac cells in each chamber contract in unison?

- The heart’s pacemaker cells, located in the sinoatrial (SA) node, send electrical impulses that spread throughout the heart muscle, ensuring coordinated contraction. The atrioventricular (AV) node further ensures the ventricles contract after the atria.

Understand osmosis!

- Osmosis is the passive movement of water across a semipermeable membrane, from an area of low solute concentration to an area of high solute concentration.

Why do animals need an excretory system?

- Animals need an excretory system to remove metabolic wastes, maintain homeostasis, regulate fluid and electrolyte balance, and eliminate excess nitrogenous waste.

What does a kidney do? How does its design help it remove wastes without losing molecules like glucose? How can the kidney control the amount of water that is lost during excretion?

- The kidney filters blood to remove waste products, excess ions, and water. Its design, with structures like the nephron, allows for selective reabsorption of useful molecules (like glucose) and regulation of water and electrolyte balance via processes like osmosis and active transport.

What’s interstitial fluid?

- Interstitial fluid is the fluid that surrounds cells, filling the spaces between them. It plays a role in nutrient and waste exchange between blood and cells.

How do you build a kidney? What happens in each of the parts we discussed?

- The kidney consists of nephrons, which include the renal corpuscle (where blood is filtered) and the renal tubule (where reabsorption and secretion occur). The glomerulus filters the blood, and the tubules reabsorb useful substances and secrete wastes.

What role does the kidney play in water and salt balance?

- The kidney regulates water and salt balance through filtration, reabsorption, and secretion. The nephron’s loop of Henle is particularly important in creating a concentration gradient that allows the kidney to conserve water and control salt levels.

What role does ADH play in water balance?

- Antidiuretic hormone (ADH) regulates water balance by increasing water reabsorption in the kidneys, particularly in the collecting ducts. This helps conserve water when the body is dehydrated.

Why was the ability to make highly concentrated urine important to animal diversity?

- The ability to produce concentrated urine allows animals to conserve water in arid environments, facilitating survival and reproduction in diverse habitats.

What role does the kidney play in regulating blood pressure?

- The kidneys help regulate blood pressure by adjusting the volume of blood and the amount of sodium in the blood. The renin-angiotensin-aldosterone system (RAAS) plays a key role in this process.

What is homeostasis? Why is it not just like chemical equilibrium?

- Homeostasis is the maintenance of stable internal conditions despite external fluctuations. It differs from chemical equilibrium because it involves dynamic regulation and constant adjustments to keep the body functioning within optimal parameters.

Compare and contrast cellular homeostasis and organismal homeostasis.

- Cellular homeostasis refers to the maintenance of a stable internal environment at the cellular level, such as maintaining ion concentrations or pH.

- Organismal homeostasis involves the regulation of entire body functions, such as temperature, blood pressure, and fluid balance, often involving complex systems.

How does an organism detect and respond to changes? What is a set point and why is it important?

- Organisms detect changes through receptors and sensors that send signals to the brain or nervous system. A set point is the desired value for a regulated variable (e.g., body temperature), and it’s important for maintaining stable internal conditions.

Generally, how do animals regulate body temperature?

- Animals regulate body temperature through mechanisms like behavioral adjustments (seeking shade or sun), physiological responses (sweating, shivering, vasodilation, or vasoconstriction), and metabolic changes.

Review hormones and signaling pathways.

- Hormones are chemical messengers that regulate various physiological processes. They are released by endocrine glands and act on target cells via specific receptors

How does the hypothalamus-pituitary axis tie nervous and endocrine system responses together?

- The hypothalamus-pituitary axis connects the nervous and endocrine systems by integrating neural signals from the brain with hormonal signals from the pituitary gland. The hypothalamus produces releasing and inhibiting hormones that control the release of hormones from the pituitary. These pituitary hormones then regulate other endocrine glands, allowing the body to respond to internal and external stimuli.

Compare and contrast water balance: (plants! fungi!) aquatic and land animals.

- Aquatic animals : Water balance is less of an issue since they are surrounded by water. However, they must manage ions and salts through specialized structures like gills.

- Land animals : Water balance is critical because they lose water to the environment through evaporation and excretion. They have specialized kidneys, skin, and behavior to conserve water.

- Plants and fungi : In plants, water balance is regulated through transpiration, stomatal opening, and root absorption. Fungi also manage water through their hyphal networks, but they tend to thrive in environments with consistent moisture.

What is homeostasis? Why is negative feedback important in maintaining homeostasis?

- Homeostasis is the maintenance of a stable internal environment despite external fluctuations. Negative feedback is crucial because it counteracts changes, bringing the system back to a set point. For example, regulating body temperature (through sweating or shivering) prevents extreme deviations that could harm the body.

What are the CNS and PNS? What role does the autonomic nerve system play in regulating body functions? Sympathetic vs. parasympathetic?

- CNS (Central Nervous System) : Consists of the brain and spinal cord, processing and interpreting information.

- PNS (Peripheral Nervous System) : Includes nerves outside the CNS, transmitting sensory information to the CNS and motor commands to muscles.

- The autonomic nervous system regulates involuntary functions like heart rate and digestion. The sympathetic nervous system prepares the body for action (fight or flight), while the parasympathetic nervous system calms the body (rest and digest).

What’s the endocrine system? What are hormones?

- The endocrine system is a network of glands that produce and release hormones into the bloodstream. Hormones are chemical messengers that regulate processes such as metabolism, growth, mood, and reproduction.

Why is the endocrine system important to homeostasis?

- The endocrine system maintains homeostasis by controlling long-term changes in the body, like regulating growth, metabolism, and reproduction, in response to signals from the nervous system or external stimuli.

What are positive and negative feedback and how can they regulate body functions?

- Negative feedback : A process where a change triggers a response that counteracts the original change, helping to stabilize conditions (e.g., temperature regulation).

- Positive feedback : A process where a change triggers a response that amplifies the original change (e.g., childbirth contractions). Both mechanisms regulate vital functions, with negative feedback maintaining stability and positive feedback promoting rapid change.

How do insulin and glucagon work to regulate blood glucose levels?

- Insulin lowers blood glucose levels by promoting glucose uptake into cells and storage as glycogen in the liver.

- Glucagon raises blood glucose levels by stimulating the liver to break down glycogen into glucose and release it into the bloodstream.

What are the chemical types of hormones, and how does that determine the way they interact with target cells? How can the signal be amplified? (What’s a releasing hormone?)

- Hormones can be peptides , steroids , or amines .

- Peptide hormones bind to receptors on the cell surface, activating a signal transduction pathway.

- Steroid hormones pass through the cell membrane and bind to intracellular receptors, affecting gene expression.

- Releasing hormones are produced by the hypothalamus and stimulate the pituitary gland to release specific hormones, amplifying the signal throughout the body.

What’s meant by hypothalamus-pituitary axis and how does it regulate body functions?

- The hypothalamus-pituitary axis involves the hypothalamus sending signals to the pituitary gland, which then regulates other endocrine glands. This axis controls vital functions like growth, stress responses, and reproduction through hormonal signals.

What are tropic hormones?

- Tropic hormones are hormones that target other endocrine glands to stimulate the release of additional hormones. Examples include thyroid-stimulating hormone (TSH) and adrenocorticotropic hormone (ACTH).

What are the modes of chemical signaling?

- Endocrine signaling : Hormones are released into the bloodstream and act on distant target cells.

- Paracrine signaling : Signals affect nearby cells.

- Autocrine signaling : Signals affect the same cell that released them.

- Juxtacrine signaling : Direct contact between neighboring cells influences signaling.

How are concentrations of O2, CO2, and H+ sensed and regulated?

- Chemoreceptors in the brain and arteries sense changes in oxygen, carbon dioxide, and pH levels. In response, they trigger adjustments in respiration and blood circulation to maintain homeostasis.

What are vasoconstriction and vasodilation, and how can they be used to regulate blood pressure?

- Vasoconstriction is the narrowing of blood vessels, which increases blood pressure.

- Vasodilation is the widening of blood vessels, which decreases blood pressure. These processes are regulated by the autonomic nervous system to maintain optimal blood pressure.

How do plants that live in dry environments conserve water?

- Plants in dry environments (xerophytes) conserve water by developing thick cuticles, reducing stomatal openings, and using specialized structures like spines or modified leaves to reduce water loss. They may also store water in specialized tissues.

How do plants get minerals and nitrogen?

- Plants absorb minerals and nitrogen from the soil through their roots. Nitrogen is typically obtained in the form of nitrates or ammonium, and the process of nitrogen fixation involves symbiotic relationships with bacteria in root nodules for some plants, like legumes.

What is special about the soil environment in terms of water and temperature?

- The soil environment acts as a reservoir for water and a buffer against temperature fluctuations. It also provides nutrients and minerals for plant growth. Soil temperature can affect root metabolism and water availability.

How do fungi get minerals and nitrogen?

- Fungi obtain minerals and nitrogen by decomposing organic material in the soil or through symbiotic relationships with plants (mycorrhizae), which allow for nutrient exchange.

Why is a seed amazing?

- Seeds are remarkable because they contain an embryo with stored nutrients, allowing for delayed germination. This enables plants to wait for optimal environmental conditions before beginning to grow, improving survival chances.

How did animals drive the diversity of flowers and fruits?

- Animals, particularly pollinators like bees, birds, and bats, have driven the evolution of diverse flowers and fruits by influencing plant reproduction. Flowers have evolved to attract specific pollinators, and fruits have evolved to aid in seed dispersal by animals.

Compare and contrast asexual and sexual reproduction.

- Asexual reproduction involves a single parent and produces genetically identical offspring, allowing for rapid population growth.

- Sexual reproduction involves two parents and produces genetically diverse offspring, which enhances adaptability and survival in changing environments.

r-strategists vs. K-strategists

- r-strategists produce many offspring with little parental care and thrive in unstable environments (e.g., insects).

- K-strategists produce fewer offspring with significant parental investment and are adapted to stable environments (e.g., mammals).

Compare and contrast reproduction (fertilization) and dispersal across life.

- Fertilization can be internal (e.g., mammals) or external (e.g., fish), with different strategies for ensuring successful reproduction.

- Dispersal involves the movement of offspring or seeds to new locations to reduce competition and spread the species. Methods include wind, water, and animal transport.

Compare and contrast asexual and sexual reproduction---advantages and disadvantages of each?

- Asexual reproduction : Advantages include rapid population growth and no need for a mate. Disadvantages include a lack of genetic diversity, making the species more vulnerable to diseases or environmental changes.

- Sexual reproduction : Advantages include genetic diversity, which enhances adaptability. Disadvantages include the need for a mate and slower reproduction rates.

Compare and contrast r-strategists and K-strategists—advantages and disadvantages of each.

- r-strategists : Advantages include rapid reproduction and colonization of new environments. Disadvantages include high mortality rates and lack of parental care.

- K-strategists : Advantages include stable populations and greater care for offspring. Disadvantages include slower reproduction and vulnerability to environmental changes.