Comprehensive Biology and Evolution: Cell Theory, Microorganisms, Plant and Animal Diversity

What is the endosymbiotic theory?

The theory that eukaryotic cells originated from a symbiotic relationship where a larger host cell engulfed smaller prokaryotic cells (like mitochondria and chloroplasts) that eventually became organelles.

Distinguish between heterotrophic and autotrophic organisms.

Autotrophs produce their own organic food using energy from sunlight or inorganic chemicals, while heterotrophs must consume other organisms to obtain organic carbon.

What distinguishes prokaryotes from eukaryotes?

Prokaryotes lack a membrane-bound nucleus and membrane-bound organelles, and their DNA is typically circular and located in a nucleoid region.

What is unique about the membrane phospholipids in archaea?

Archaea possess ether-linked lipids with branched hydrocarbon chains, which provide greater stability in extreme environments compared to the ester-linked lipids found in bacteria and eukaryotes.

What is the difference between Gram-positive and Gram-negative bacteria?

Gram-positive bacteria have a thick peptidoglycan cell wall that retains crystal violet stain, while Gram-negative bacteria have a thinner peptidoglycan layer and an outer lipopolysaccharide membrane.

Define horizontal gene transfer in prokaryotes.

The movement of genetic material between unicellular and/or multicellular organisms other than by the transmission of DNA from parent to offspring, occurring via transformation, transduction, or conjugation.

What are protists?

A diverse group of mostly unicellular eukaryotic organisms that do not fit into the kingdom Fungi, Plantae, or Animalia.

Why are fungi more closely related to animals than to plants?

Fungi and animals share a common ancestor, are heterotrophic, and both use chitin as a structural component (in fungal cell walls and arthropod exoskeletons).

What are hyphae, mycelia, and chitin?

Hyphae are the thread-like filaments of fungi, mycelia are the collective network of hyphae, and chitin is the tough polysaccharide used in fungal cell walls.

What are mycorrhizae?

A symbiotic association between fungal hyphae and plant roots that enhances nutrient and water uptake for the plant while providing the fungus with carbohydrates.

What is the alternation of generations in plants?

A life cycle involving two multicellular stages: a haploid gametophyte that produces gametes and a diploid sporophyte that produces spores via meiosis.

What are the derived traits of land plants?

Key traits include alternation of generations, walled spores produced in sporangia, multicellular gametangia, and apical meristems.

What distinguishes sponges from other animals?

Sponges lack true tissues and organs, possessing a simple body plan organized around a water-filtering system.

What is the Cambrian explosion?

A relatively short evolutionary period approximately 541 million years ago marked by a rapid diversification of animal body plans and the appearance of most major animal phyla.

What are the key features of chordates?

A notochord, a dorsal hollow nerve cord, pharyngeal slits or clefts, and a post-anal tail.

What are the defining features of amniotes?

Amniotes are tetrapods that produce an amniotic egg, which contains specialized membranes to protect and nourish the embryo, allowing for reproduction on land.

What differentiates humans from other great apes?

Humans are distinguished by bipedal locomotion, larger brain size relative to body size, complex language, and symbolic thought.

What is nitrogen fixation?

The process by which certain bacteria convert atmospheric nitrogen (N2) into ammonia (NH3), making nitrogen accessible for biological use by other organisms.

What is the function of vascular tissue in plants?

Vascular tissue (xylem and phloem) allows for the transport of water, minerals, and nutrients throughout the plant, enabling growth to larger sizes and colonization of drier environments.

What is the significance of radial symmetry in Cnidarians?

Radial symmetry allows these organisms to encounter their environment equally from all sides, which is advantageous for sessile or drifting lifestyles.

Describe the relationship between human populations and evolution.

Human populations continue to evolve through natural selection (e.g., lactase persistence, high-altitude adaptation) and genetic drift in response to environmental pressures and cultural changes.

What are the four types of tissues in the animal body?

Epithelial, connective, muscle, and nervous tissue.

Define homeostasis.

The process by which living organisms maintain a relatively stable internal environment despite changes in external conditions.

What are the four components of a homeostatic control system?

Set point (target value), sensor (detects change), integrator (compares to set point), and effector (restores balance).

Negative vs. Positive Feedback

Negative feedback counteracts a change to return to a set point, while positive feedback amplifies a change away from a set point.

Osmoregulators vs. Osmoconformers

Osmoregulators actively maintain internal osmolarity regardless of the environment, whereas osmoconformers allow their internal osmolarity to match the environment.

Fick's Law of Diffusion

Measures the rate of diffusion across a membrane; it is affected by surface area, concentration gradient, membrane thickness, and permeability.

Primary vs. Secondary Active Transport

Primary active transport uses ATP directly to move solutes against a gradient, while secondary active transport uses the energy stored in an existing electrochemical gradient.

What is the Na+/K+-ATPase pump mechanism?

It pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell using ATP, maintaining the resting membrane potential.

What does 'electrogenic' mean in the context of the Na+/K+-ATPase pump?

It means the pump creates a net charge difference across the membrane because it moves an unequal number of positive charges (3 Na+ out vs 2 K+ in).

What are the main types of glial cells?

Astrocytes, microglia, oligodendrocytes (CNS myelin), and Schwann cells (PNS myelin).

Resting Membrane Potential

The electrical potential difference across the plasma membrane of a resting neuron, typically around -70mV, maintained by the Na+/K+ pump and K+ leak channels.

Graded Potentials vs. Action Potentials

Graded potentials are small, variable-strength changes in membrane potential that decay over distance; action potentials are all-or-none, self-propagating electrical signals.

What happens at the synapse when an action potential arrives?

Voltage-gated Ca2+ channels open, Ca2+ enters the terminal, triggering the fusion of neurotransmitter vesicles with the membrane and release into the synaptic cleft.

EPSP vs. IPSP

An Excitatory Postsynaptic Potential (EPSP) depolarizes the membrane toward threshold; an Inhibitory Postsynaptic Potential (IPSP) hyperpolarizes the membrane away from threshold.

Temporal vs. Spatial Summation

Temporal summation is the integration of multiple signals from one source over time; spatial summation is the integration of signals from multiple different sources simultaneously.

Ionotropic vs. Metabotropic Receptors

Ionotropic receptors are ligand-gated ion channels that open directly upon binding; metabotropic receptors are G-protein coupled receptors that trigger intracellular signaling cascades.

Structural organization of skeletal muscle

Muscle -> Fascicle -> Muscle fiber (cell) -> Myofibril -> Sarcomere -> Myofilaments (actin and myosin).

What is the sliding filament model of muscle contraction?

The theory that muscle contraction occurs as actin and myosin filaments slide past each other, shortening the sarcomere without the filaments themselves changing length.

What is the role of Ca2+ in muscle contraction?

Ca2+ binds to troponin, causing a conformational change in tropomyosin that exposes the myosin-binding sites on the actin filament.

What are the four steps in food processing?

Ingestion, digestion, absorption, and elimination.

What is the function of the pancreas in digestion?

It secretes digestive enzymes into the small intestine and produces bicarbonate to neutralize stomach acid.

Vitamins vs. Minerals

Vitamins are organic compounds required in small amounts for metabolism; minerals are inorganic elements required for various physiological functions.

Open vs. Closed Circulatory System

In an open system, hemolymph bathes organs directly in a body cavity. In a closed system, blood is confined to vessels, separating it from interstitial fluid.

Structure and Function of Arteries, Capillaries, and Veins

Arteries have thick, elastic walls to handle high pressure; capillaries have thin, single-cell walls for gas/nutrient exchange; veins have thinner walls and valves to prevent backflow under low pressure.

Cardiac Cycle Steps

1. Atrial and ventricular diastole (filling), 2. Atrial systole (atria contract), 3. Ventricular systole (ventricles contract and pump blood).

Role of the SA Node

The sinoatrial (SA) node acts as the heart's pacemaker, initiating electrical impulses that trigger atrial contraction and coordinate the cardiac cycle.

ECG Peaks Representation

P wave represents atrial depolarization, QRS complex represents ventricular depolarization, and T wave represents ventricular repolarization.

Alveoli Structure and Function

Alveoli are tiny, thin-walled air sacs that provide a large surface area for efficient gas exchange via diffusion between air and blood.

Tidal Volume

The volume of air inhaled or exhaled in a single normal breath.

Surfactant Function

A substance that reduces surface tension in the alveoli, preventing them from collapsing during exhalation.

Four Steps of Excretion

1. Filtration (filtering body fluids), 2. Reabsorption (reclaiming valuable solutes), 3. Secretion (adding nonessential solutes/wastes), 4. Excretion (releasing processed filtrate as urine).

Nitrogenous Wastes in Humans

Humans excrete urea. We do not excrete ammonia because it is highly toxic and requires large amounts of water to dilute.

Nephron Components Order

Glomerulus/Bowman's capsule, proximal tubule, loop of Henle (descending then ascending), distal tubule, and collecting duct.

Role of ADH and Aldosterone

ADH increases water reabsorption in the collecting ducts; aldosterone promotes sodium reabsorption, which increases water retention and blood pressure.

Three Classes of Hormones

Peptide hormones (water-soluble, surface receptors), steroid hormones (lipid-soluble, intracellular receptors), and amine hormones (derived from amino acids).

Trophic Hormone

A hormone that regulates the secretion of other endocrine glands.

Negative vs. Positive Feedback

Negative feedback inhibits a process to maintain homeostasis; positive feedback amplifies a response until a specific outcome is reached.

Blood Glucose Regulation

Insulin lowers blood glucose by promoting uptake into cells; glucagon raises blood glucose by stimulating glycogen breakdown in the liver.

Innate vs. Adaptive Immunity

Innate immunity is non-specific, rapid, and present at birth; adaptive immunity is specific, slower, and involves memory cells.

T-cells vs. B-cells

B-cells produce antibodies for humoral immunity; T-cells (helper or cytotoxic) coordinate immune responses and kill infected host cells.

Antibodies

Y-shaped proteins produced by B-cells that bind to specific antigens to neutralize pathogens or mark them for destruction.

Memory Cells

Long-lived immune cells that 'remember' a specific pathogen, allowing for a faster and stronger response upon re-exposure.

How Vaccines Work

Vaccines introduce harmless antigens to the body, stimulating the immune system to create memory cells without causing the actual disease.

Autoimmune Disease

A condition where the immune system fails to distinguish 'self' from 'non-self' and attacks the body's own healthy tissues.

What is the difference between external and internal fertilization?

External fertilization occurs when eggs and sperm are released into the environment, while internal fertilization occurs when sperm is deposited within the female reproductive tract.

What is the fast block to polyspermy?

The fast block involves a rapid change in the egg cell membrane potential (depolarization) upon sperm contact, preventing other sperm from fusing.

What is the slow block to polyspermy?

The slow block, or cortical reaction, involves the release of cortical granules that harden the fertilization envelope, physically blocking additional sperm.

What are the roles of FSH and LH in male reproduction?

FSH stimulates spermatogenesis in the testes, while LH stimulates the Leydig cells to produce testosterone.

What is the function of the corpus luteum?

The corpus luteum secretes progesterone and estrogen to maintain the uterine lining during the early stages of pregnancy.

What is the function of hCG?

Human chorionic gonadotropin (hCG) is released by the embryo to maintain the corpus luteum, ensuring continued progesterone production to prevent menstruation.

What is the positive feedback loop of oxytocin during childbirth?

Oxytocin stimulates uterine contractions, which push the fetus against the cervix, triggering more oxytocin release until the baby is delivered.

What are apical meristems?

Apical meristems are regions of cell division located at the tips of roots and shoots, responsible for primary growth (lengthening).

What is the function of stomata and guard cells?

Stomata are pores that allow gas exchange; guard cells regulate the opening and closing of these pores to balance photosynthesis and water loss.

What is nitrogen fixation?

The process by which certain bacteria convert atmospheric nitrogen (N2) into ammonia (NH3) that plants can use for growth.

What are mycorrhizae?

A symbiotic association between fungi and plant roots where the fungi increase surface area for nutrient absorption in exchange for carbohydrates from the plant.

Where do the light-dependent reactions of photosynthesis occur?

They occur within the thylakoid membranes of the chloroplast.

What is the purpose of water splitting in photosynthesis?

Water splitting provides electrons to replace those lost by Photosystem II and releases oxygen as a byproduct.

What are the three phases of the Calvin cycle?

The three phases are carbon fixation, reduction, and regeneration of the CO2 acceptor (RuBP).

What is water potential?

Water potential is the potential energy of water in a system compared to pure water, determining the direction of water movement via osmosis.

What is transpiration?

The process of water movement through a plant and its evaporation from aerial parts, primarily leaves, which pulls xylem sap upward.

How do guard cells regulate stomatal opening?

Guard cells accumulate potassium ions, lowering their water potential, which causes water to enter via osmosis, making them turgid and opening the stoma.

What are the unique features of angiosperms?

Angiosperms are characterized by the production of flowers and the development of seeds within fruits.

What is double fertilization in angiosperms?

A process where one sperm fertilizes the egg to form a zygote, and a second sperm fuses with two polar nuclei to form the triploid endosperm.

What is the difference between apoplastic and symplastic transport?

Apoplastic transport occurs through cell walls and extracellular spaces, while symplastic transport occurs through the cytoplasm connected by plasmodesmata.

What is apical dominance?

The phenomenon where the main central stem of a plant grows more strongly than the side branches due to hormones produced in the apical bud.

Why is coitus interruptus not an effective form of birth control?

It is unreliable because pre-ejaculate fluid can contain sperm, and it requires perfect timing and self-control, which are difficult to maintain.

What are the levels of biological organization in ecology?

Individual, population, community, ecosystem, biome, and biosphere.

How does the tilt of the Earth generate seasons?

The Earth's axial tilt causes different hemispheres to receive varying intensities of sunlight throughout the year as the planet orbits the sun.

What is a Fixed Action Pattern (FAP)?

A sequence of unlearned, innate behaviors that is essentially unchangeable and, once initiated, usually carried to completion.

What is optimality theory in behavioral ecology?

A model that predicts an animal's behavior will maximize the net energy gain or reproductive success relative to the costs of that behavior.

What are the three main dispersion patterns in populations?

Clumped (individuals aggregate in patches), uniform (individuals are evenly spaced), and random (position of each individual is independent of others).

What is the difference between K-selected and r-selected species?

K-selected species are adapted to stable environments with high parental investment and lower birth rates; r-selected species are adapted to unstable environments with high reproductive rates and minimal parental investment.

What is the Intermediate Disturbance Hypothesis?

The theory that moderate levels of disturbance foster greater species diversity than low or high levels of disturbance by preventing competitive exclusion.

What is the rule of 10 in energy flow?

The principle that only about 10% of the energy at one trophic level is transferred to the next, with the rest lost primarily as heat.

What is the difference between weather and climate?

Weather refers to short-term atmospheric conditions, while climate refers to the long-term average of weather patterns in a specific region.

What is the greenhouse effect?

The process by which certain atmospheric gases trap heat radiated from the Earth's surface, keeping the planet warmer than it would be otherwise.

What is an ecological footprint?

A measure of the total land and water area required to provide the resources an individual or population consumes and to absorb their waste.

What are the three levels of biodiversity?

Genetic diversity, species diversity, and ecosystem diversity.

What is primary succession?

The process of biological community change that occurs in an area where no soil exists, such as on a new volcanic island or a retreating glacier.