Units 1-15 Biology

Unit 1: The Scientific Method, Data Analysis, and Fields of Biology

1. The Scientific Method

A systematic approach to research, consisting of:

1. Observation – Identifying a phenomenon.

2. Question – Formulating a research question.

3. Hypothesis – A testable prediction.

4. Experiment – Conducting tests with controlled variables.

5. Data Collection – Recording observations and measurements.

6. Analysis – Interpreting data, often using statistics.

7. Conclusion – Accepting, rejecting, or modifying the hypothesis.

8. Communication – Sharing findings with the scientific community.

2. Hypotheses vs. Theories

• Hypothesis: A tentative explanation based on prior knowledge. Example: Increasing sunlight increases plant growth.

• Theory: A well-tested explanation with strong supporting evidence. Example: Cell Theory states all living things are made of cells.

3. Data Accuracy & Statistical Analysis

• Accuracy: How close a measurement is to the true value.

• Precision: Consistency of repeated measurements.

• Statistical Analysis: Determines reliability of results (mean, median, standard deviation, significance testing).

4. Fields of Biology & Their Specialties

• Botany – Study of plants.

• Zoology – Study of animals.

• Microbiology – Study of microscopic organisms.

• Genetics – Study of heredity and DNA.

• Ecology – Study of organisms and their environment.

• Physiology – Study of bodily functions.

• Biotechnology – Application of biological processes in technology.

Unit 2: Characteristics of Life & Cell Structure

1. Characteristics of Living Things

All living organisms share these key traits:

• Cells – The basic unit of life (unicellular or multicellular).

• Organization – Structured in an orderly way (cells → tissues → organs → systems).

• Growth & Development – Increase in size and complexity over time.

• Energy Use – Metabolism converts energy for survival.

• Homeostasis – Maintaining internal balance (e.g., body temperature).

• Response to Stimuli – Reacting to environmental changes (e.g., pupils dilating in dim light).

• Reproduction – Producing offspring (sexual or asexual).

• Evolution & Adaptation – Genetic changes over generations for survival.

2. Cell Types, Structures, and Functions

• Prokaryotic Cells – Simple, no nucleus (e.g., bacteria).

• Eukaryotic Cells – Complex, with a nucleus and organelles (e.g., plant & animal cells).

• Organelles & Their Functions:

  • Nucleus – Stores genetic material (DNA).

  • Mitochondria – Produces energy (ATP) via cellular respiration.

  • Ribosomes – Synthesizes proteins.

  • Endoplasmic Reticulum (ER) – Processes and transports proteins/lipids.

    • Smooth ER - Makes and changes proteins

    • Rough ER - makes lipids and helps clean out harmful substances from the cell.

  • Golgi Apparatus – Modifies and packages proteins.

  • Lysosomes – Breaks down waste.

  • Cell Membrane – Controls what enters and exits the cell.

  • Cell Wall (plants) – Provides structure and protection.

  • Vacuoles – Stores water, nutrients, and waste.

3. Solutions & Their Effects on Cells

• Hypotonic Solution – Water enters the cell, causing it to swell.

• Isotonic Solution – Water movement is balanced, maintaining cell shape.

• Hypertonic Solution – Water leaves the cell, causing it to shrink.

4. Chloroplasts & Endosymbiosis

• Chloroplasts – Organelles in plant cells that perform photosynthesis.

• Endosymbiotic Theory – States that mitochondria and chloroplasts evolved from ancient prokaryotic cells that were engulfed by larger cells, forming a symbiotic relationship. Evidence includes:

  • Both have their own DNA.

  • Both replicate independently.

  • Both have double membranes.

Connections Between Concepts

• Cells are the foundation of life, and all living things share fundamental characteristics.

• Cell structure determines function—organelles work together to keep the cell alive.

• Osmosis and solutions affect cell survival, impacting water balance.

• Chloroplasts and mitochondria show how cells evolved, supporting the idea of symbiosis in early life forms.

Unit 3: DNA Structure, Replication, and RNA

1. History & Structure of DNA

• Discovery: James Watson & Francis Crick identified DNA’s double-helix structure, building on Rosalind Franklin’s X-ray crystallography.

  Structure:

  • Double Helix – Two strands twisted around each other.

  • Nucleotides – The building blocks of DNA, composed of:

    • Sugar (deoxyribose)

    • Phosphate group

    • Nitrogenous bases:

      • Adenine (A) pairs with Thymine (T)

      • Cytosine (C) pairs with Guanine (G)

2. DNA Replication

A semi-conservative process ensuring genetic continuity. Steps:

1. Unwinding – Helicase enzyme separates DNA strands.

2. Base Pairing – DNA polymerase adds complementary nucleotides.

3. Joining – Ligase seals gaps, forming two identical DNA molecules

   • Ligase Function: DNA ligase is an enzyme that seals breaks (nicks) in the DNA backbone by forming bonds between nucleotides.

     Role in DNA Replication:

     • After DNA polymerase adds nucleotides, gaps remain between fragments of newly synthesized DNA.

     • Ligase "glues" these fragments together, ensuring the DNA strand is continuous and complete..

3. Types & Functions of RNA

RNA helps convert genetic information into proteins.

• mRNA (Messenger RNA) – Carries genetic code from DNA to ribosomes.

• tRNA (Transfer RNA) – Brings amino acids to ribosomes for protein synthesis.

• rRNA (Ribosomal RNA) – Forms ribosomes, where proteins are assembled.

4. Coding vs. Non-Coding DNA

• Coding DNA – Contains genes that are transcribed into proteins.

• Non-Coding DNA – Regulates gene expression and includes elements like introns and enhancers.

Connections Between Concepts

• DNA carries genetic information, ensuring traits are passed to the next generation.

• DNA replication is vital for cell division, ensuring each new cell gets an exact copy of genetic material.

• RNA acts as the bridge between DNA and protein synthesis, translating genetic instructions into functional proteins.

• Not all DNA codes for proteins, but non-coding DNA plays essential regulatory roles in gene expression.

Unit 4: Carbon, Biomolecules, and Energy Processes

1. Importance of Carbon

• Carbon is the backbone of life because it forms stable bonds with many elements, allowing complex molecules to exist.

• Can form four covalent bonds, leading to diverse organic compounds.

2. Monomers vs. Polymers

• Monomers – Small, basic molecular units (e.g., amino acids, monosaccharides).

• Polymers – Large molecules made from monomers (e.g., proteins, carbohydrates).

3. Major Biomolecules & Their Functions

• Proteins: Serve as enzymes, structural components, and transport molecules in cells.

• Carbohydrates: Provide energy and serve as structural support in plant cell walls.

• Lipids: Store energy, form cell membranes, and act as signaling molecules.

• Nucleic Acids: Store and transmit genetic information (e.g., DNA and RNA).

4. Enzymes & Chemical Bonds

• Enzymes: Proteins that speed up chemical reactions by lowering activation energy.

• Active site: The specific region where a substrate binds.

• Chemical Bonds:

  • Covalent bonds – Strong, share electrons (e.g., carbon-carbon bonds).

  • Ionic bonds – Transfer electrons, weaker in water (e.g., NaCl).

  • Hydrogen bonds – Weak attractions, crucial for DNA & proteins.

5. Cellular Respiration vs. Chemosynthesis

Cellular Respiration Steps:

1. Glycolysis – Breaks glucose into pyruvate (occurs in cytoplasm).

2. Krebs Cycle – Produces electron carriers (mitochondria).

3. Electron Transport Chain (ETC) – Produces most ATP using oxygen.

Connections Between Concepts

• Carbon is fundamental to biomolecules, which are essential for life.

• Monomers link to form polymers, which make up proteins, carbohydrates, and nucleic acids.

• Enzymes control biochemical reactions, affecting metabolism and energy production.

• Cellular respiration provides ATP, powering biological functions, while chemosynthesis allows life in extreme environments.

Unit 5: Biological Organization and Homeostasis

1. Hierarchy of an Organism

Life is organized into increasing levels of complexity, from atoms to whole organisms:

1. Atoms & Molecules → Basic chemical components.

2. Cells → The fundamental unit of life.

3. Tissues → Groups of similar cells performing a function.

4. Organs → Structures made of tissues working together.

5. Organ Systems → Groups of organs coordinating functions.

6. Organism → A complete living being.

2. Major Organ Systems & Their Functions

3. Homeostasis: Maintaining Balance

• Definition: The process by which organisms maintain a stable internal environment despite external changes.

• Examples:

  • Body Temperature Regulation (Sweating when hot, shivering when cold).

  • Blood Sugar Control (Insulin lowers, glucagon raises glucose levels).

  • Osmoregulation (Kidneys maintain water balance).

4. Stimulus and Response

• Stimulus: A change in the environment (e.g., temperature drop).

• Response: The reaction to the stimulus (e.g., shivering to generate heat).

• Feedback Mechanisms:

  • Negative Feedback: Stabilizes conditions (e.g., body temperature control).

  • Positive Feedback: Amplifies changes (e.g., contractions during childbirth).

Connections Between Concepts

• The body's organization enables specialized functions—cells form tissues, which form organs, ensuring efficiency.

• Organ systems work together (e.g., the circulatory system delivers oxygen from the respiratory system to muscles).

• Homeostasis relies on feedback mechanisms to regulate processes, keeping the body stable despite external fluctuations.

Unit 6: Environmental Cycles and Biomes

1. Biogeochemical Cycles: The Movement of Essential Elements

Matter cycles through ecosystems, ensuring the availability of essential nutrients.

A. Carbon Cycle

• Importance: Carbon is the backbone of organic molecules (carbohydrates, proteins, lipids, nucleic acids).

• Main Processes:

  • Photosynthesis: Plants absorb CO₂ and convert it into glucose.

  • Respiration: Organisms release CO₂ back into the atmosphere.

  • Decomposition: Dead organisms break down, returning carbon to the soil.

  • Combustion: Burning fossil fuels releases stored carbon as CO₂.

• Human Impact: Excessive CO₂ from burning fossil fuels contributes to climate change.

B. Nitrogen Cycle

• Importance: Nitrogen is essential for amino acids (proteins) and DNA.

• Main Processes:

  • Nitrogen Fixation: Bacteria convert atmospheric nitrogen (N₂) into usable forms (ammonia, NH₃).

  • Nitrification: Ammonia is converted into nitrates (NO₃⁻) by bacteria.

  • Assimilation: Plants absorb nitrates and incorporate nitrogen into organic molecules.

  • Denitrification: Bacteria return nitrogen gas to the atmosphere.

• Human Impact: Overuse of fertilizers leads to nitrogen runoff, causing water pollution and algal blooms.

C. Water Cycle (Hydrologic Cycle)

• Main Processes:

  • Evaporation: Water from oceans, lakes, and plants (transpiration) turns into vapor.

  • Condensation: Water vapor cools and forms clouds.

  • Precipitation: Water falls as rain, snow, sleet, or hail.

  • Runoff & Infiltration: Water moves into rivers, lakes, and groundwater.

• Human Impact: Deforestation reduces transpiration, and pollution affects water quality.

2. Biomes: The Major Ecosystems of Earth

Biomes are classified based on climate, vegetation, and animal life.

A. Terrestrial Biomes

B. Aquatic Biomes

3. Earth's Atmosphere and Climate

• Layers of the Atmosphere:

  • Troposphere: Weather occurs here.

  • Stratosphere: Contains the ozone layer.

  • Mesosphere: Meteors burn up.

  • Thermosphere: Satellites orbit here.

• Climate vs. Weather:

  • Climate: Long-term atmospheric conditions (temperature, precipitation).

  • Weather: Short-term atmospheric changes.

• Factors Affecting Climate:

  • Latitude, ocean currents, wind patterns, and elevation.

Connections Between Concepts

• Biogeochemical cycles sustain life by recycling essential nutrients.

• Biomes are shaped by climate—temperature and precipitation determine which organisms can survive.

• Human activities impact cycles and climate—pollution, deforestation, and fossil fuel use disrupt natural processes.

Unit 7: Photosynthesis and Plant Biology

1. Photosynthesis: Converting Light into Energy

Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy (glucose).

A. Overall Equation

6CO2+6H2O+light→C6H12O6+6O26CO_2 + 6H_2O + light → C_6H_{12}O_6 + 6O_26CO2​+6H2​O+light→C6​H12​O6​+6O2​

(Carbon dioxide + Water + Light → Glucose + Oxygen)

• Carbon Balance:

  • Glucose (C₆H₁₂O₆) has 6 carbon atoms, so we need 6 CO₂ molecules to provide the 6 carbon atoms.

• Hydrogen Balance:

  • Water (H₂O) provides hydrogen atoms.

  • Glucose has 12 hydrogen atoms, and since each water molecule has 2 hydrogen atoms, we need 6 H₂O molecules to provide 12 hydrogens.

• Oxygen Balance:

  • On the left, we have 6 CO₂ molecules (12 oxygen atoms) and 6 H₂O molecules (6 oxygen atoms) → total 18 oxygen atoms.

  • On the right, glucose (C₆H₁₂O₆) contains 6 oxygen atoms, and the 6 O₂ molecules contribute another 12 oxygen atoms → total 18 oxygen atoms.

B. Stages of Photosynthesis

1. Light-Dependent Reactions (Thylakoid Membrane)

   • Occur in the chloroplasts’ thylakoids.

   • Input: Light & water

   • Output: ATP, NADPH, and O₂ (oxygen released as a byproduct).

   • Uses Photosystem I & II to capture light energy.

2. Light-Independent Reactions (Calvin Cycle) (Stroma)

   • Does not require light, occurs in the stroma.

   • Input: CO₂, ATP, NADPH

   • Output: Glucose (C₆H₁₂O₆)

   • Uses RuBisCO enzyme to fix carbon.

2. Plant Structure and Function

Plants have specialized structures that support growth, reproduction, and nutrient transport.

A. Plant Tissues

1. Dermal Tissue: Protective outer layer (epidermis, cuticle).

2. Vascular Tissue:

   • Xylem: Transports water & minerals upward.

   • Phloem: Transports sugars from leaves to other parts.

3. Ground Tissue: Provides storage, support, and photosynthesis.

B. Monocots vs. Dicots

3. Plant Reproduction and Growth

A. Flower Structure

B. Pollination & Fertilization

• Pollination: Transfer of pollen to stigma (by wind, insects, birds).

• Fertilization: Pollen fertilizes the ovule, forming a seed.

4. Seedless Plants, Fungi, and Protists

A. Seedless Plants

• Bryophytes (Mosses): No vascular tissue, depend on water for reproduction.

• Ferns: Have vascular tissue but reproduce using spores.

B. Fungi

• Heterotrophic decomposers (absorb nutrients).

• Structures:

  • Hyphae: Thread-like structures forming the mycelium.

  • Spores: Reproductive units.

• Types:

  • Molds (bread mold)

  • Yeasts (unicellular)

  • Mushrooms (multicellular).

C. Protists

• Diverse group including: Algae, amoebas, and slime molds.

• Can be plant-like (photosynthetic), animal-like (heterotrophic), or fungus-like.

Connections Between Concepts

• Photosynthesis powers ecosystems, providing oxygen and glucose for cellular respiration.

• Xylem and phloem transport nutrients, linking photosynthesis and plant growth.

• Reproductive adaptations (seeds, flowers) allow plants to spread across diverse environments.

• Fungi & protists play key ecological roles, as decomposers and in symbiotic relationships.

Unit 8: Energy Flow and Ecosystem Dynamics

1. Energy Flow in Ecosystems

• Energy transfer follows the 10% rule—only about 10% of energy is passed to the next trophic level, while the rest is lost as heat.

• Trophic levels:

  • Producers (Autotrophs) – Convert sunlight into chemical energy via photosynthesis (e.g., plants, algae).

  • Primary Consumers (Herbivores) – Eat producers (e.g., rabbits, deer).

  • Secondary Consumers (Carnivores/Omnivores) – Eat herbivores (e.g., snakes, foxes).

  • Tertiary Consumers (Apex Predators) – Eat secondary consumers (e.g., hawks, wolves).

2. Energy Pyramids

• Show the relative amount of energy at each trophic level.

• Types:

  • Energy pyramid – Displays energy flow (measured in kcal or joules).

  • Biomass pyramid – Shows the mass of organisms at each level.

  • Numbers pyramid – Shows the number of individuals at each level.

3. Invasive Species

• Definition: Non-native species that disrupt ecosystems by outcompeting native species.

• Examples:

  • Kudzu vine (USA) – Overgrows and smothers native plants.

  • Zebra mussels – Outcompete native aquatic species.

• Impact: Can cause biodiversity loss, habitat destruction, and economic damage.

4. Ecological Succession

• The gradual change in ecosystems over time.

• Two types:

  • Primary Succession – Starts from barren land with no soil (e.g., volcanic islands, glaciers retreating).

  • Secondary Succession – Occurs after a disturbance (e.g., fire, flood) but soil remains intact.

• Pioneer species: First organisms to colonize (e.g., lichens, mosses).

5. Limiting Factors in Ecosystems

• Factors that restrict population growth.

• Types:

  • Density-dependent factors – Affected by population size (e.g., competition, disease, predation).

  • Density-independent factors – Affect populations regardless of size (e.g., natural disasters, climate change).

Connections to Previous Units:

• Trophic levels relate to photosynthesis (Unit 7) since producers rely on sunlight to create energy.

• Invasive species can disrupt biodiversity (Unit 9) by altering population dynamics.

• Ecological succession is influenced by environmental cycles (Unit 6) such as carbon and nitrogen cycles.

Unit 9: Biodiversity, Populations, and Ecosystems

1. Biodiversity and Its Importance

• Definition: The variety of life in an ecosystem, including species, genetic, and ecosystem diversity.

• Higher biodiversity = greater ecosystem stability and resilience.

• Threats to biodiversity:

  • Habitat destruction

  • Pollution

  • Climate change

  • Overexploitation (e.g., overfishing, deforestation)

2. Resource Partitioning

• Occurs when species divide resources to reduce competition.

• Example: Different bird species feeding in separate areas of the same tree.

3. Ecosystem Components

• Biotic factors – Living parts of an ecosystem (e.g., plants, animals, bacteria).

• Abiotic factors – Non-living elements (e.g., temperature, sunlight, water).

• Interactions between these factors shape ecosystems.

4. Population Ecology

• Communities vs. Populations:

  • Population – A group of the same species in one area.

  • Community – Multiple populations living together.

• Population characteristics:

  • Population size – Total number of individuals.

  • Density – How many individuals per unit area.

  • Dispersion – How individuals are spaced (clumped, uniform, random).

5. Population Growth and Regulation

• Exponential Growth (J-Curve) – Rapid growth without limiting factors.

• Logistic Growth (S-Curve) – Growth slows as population reaches carrying capacity.

• Carrying Capacity (K): Maximum population an environment can support.

6. Symbiotic Relationships

• Mutualism (+/+) – Both species benefit (e.g., bees and flowers).

• Commensalism (+/0) – One benefits, the other is unaffected (e.g., barnacles on whales).

• Parasitism (+/-) – One benefits, the other is harmed (e.g., ticks on dogs).

7. Overpopulation and Its Consequences

• Leads to resource depletion, habitat destruction, and increased pollution.

• Can cause population crashes if resources become too scarce.

8. Environmental Issues & Conservation

• Pollution: Harmful substances released into air, water, and land.

• Habitat destruction: Deforestation, urbanization, and agriculture reduce natural habitats.

• Conservation efforts:

  • Protected areas (e.g., national parks, wildlife reserves).

  • Sustainable resource management (e.g., fishing quotas, reforestation).

Connections to Previous Units:

• Ecosystem components tie into the carbon, nitrogen, and water cycles (Unit 6).

• Symbiotic relationships influence energy flow (Unit 8).

• Overpopulation links to natural selection and competition (Unit 13).

Unit 10: Atoms, Compounds, and Microbiology

1. Basic Chemistry in Biology

• Atoms: Smallest unit of matter, made up of protons (+), neutrons (0), and electrons (-).

• Elements: Pure substances consisting of only one type of atom (e.g., Carbon, Oxygen).

• Compounds: Two or more elements chemically combined (e.g., H₂O, CO₂).

2. Chemical Reactions in Biology

• Reactants → Products (Substances change in a reaction).

• Types of reactions important in biology:

  • Synthesis: Small molecules → Larger molecules (e.g., protein formation).

  • Decomposition: Large molecules → Smaller molecules (e.g., digestion).

  • Oxidation-Reduction: Transfer of electrons (e.g., cellular respiration).

3. Water and pH

• Water’s Properties:

  • Cohesion (sticks to itself) and adhesion (sticks to other substances).

  • High heat capacity (regulates temperature).

  • Universal solvent (dissolves many substances).

• pH Scale:

  • Measures how acidic/basic a substance is (0-14).

  • Acids (0-6.9): High H⁺ concentration (e.g., stomach acid).

  • Bases (7.1-14): High OH⁻ concentration (e.g., soap).

  • Neutral (7.0): Pure water.

4. Pathogens and Bacterial Growth

• Pathogens: Microorganisms that cause disease (e.g., bacteria, viruses, fungi).

• Bacterial Growth:

  • Binary fission: Bacteria reproduce by splitting into two identical cells.

  • Growth is exponential but limited by resources, competition, and antibiotics.

5. Microbiomes and Their Role in Health

• Microbiome: Community of microorganisms living in a specific environment (e.g., gut, skin).

• Importance of microbiomes:

  • Aid in digestion and vitamin production.

  • Protect against harmful pathogens.

  • Influence immune system function.

• Disruptions (e.g., antibiotics) can lead to imbalances, causing infections or digestive issues.

6. Food Microbiology

• Role of Microorganisms in Food Production:

  • Fermentation (e.g., yogurt, cheese, bread).

  • Preservation (e.g., pickling, curing).

• Foodborne Illnesses:

  • Caused by bacteria (e.g., Salmonella, E. coli), viruses, or fungi.

  • Prevention: Proper cooking, hygiene, and refrigeration.

Connections to Previous Units:

• Chemical reactions (Unit 4) are essential for metabolism and energy production.

• Water’s role ties into environmental cycles (Unit 6).

• Microbiomes influence human homeostasis (Unit 5).

Unit 11: Cell Division and Reproduction

1. Why Do Cells Divide?

• Growth: Multicellular organisms grow by increasing their number of cells.

• Repair & Replacement: Damaged or dead cells are replaced (e.g., skin healing).

• Reproduction: Organisms reproduce using cell division.

2. The Cell Cycle

• Interphase (90% of the cycle):

  • G1 Phase: Cell grows and carries out normal functions.

  • S Phase: DNA is replicated.

  • G2 Phase: Cell prepares for division.

• Mitotic Phase (M Phase):

  • Mitosis (nuclear division).

  • Cytokinesis (cytoplasm divides, creating two cells).

3. Asexual vs. Sexual Reproduction

• Asexual Reproduction:

  • Produces genetically identical offspring.

  • Methods: Binary fission (bacteria), budding (yeast), fragmentation (starfish).

• Sexual Reproduction:

  • Involves two parents, offspring inherit genetic variation.

  • Requires meiosis (specialized cell division).

4. Mitosis vs. Meiosis

• Mitosis Stages:

  1. Prophase: Chromosomes condense, spindle fibers form.

  2. Metaphase: Chromosomes align in the center.

  3. Anaphase: Sister chromatids separate.

  4. Telophase: Two nuclei form.

  5. Cytokinesis: Cytoplasm splits, forming two identical cells.

• Meiosis Stages (Differences from Mitosis):

  • Two rounds of division (Meiosis I & II).

  • Crossing Over (Prophase I): Homologous chromosomes swap DNA, increasing genetic diversity.

  • Independent Assortment: Random separation of chromosomes.

5. Cancer: Uncontrolled Cell Division

• Caused by:

  • Mutations in oncogenes (promote division) or tumor suppressor genes (stop division).

  • Environmental factors (radiation, chemicals, viruses).

• Cancer Cells:

  • Ignore signals to stop dividing.

  • Form tumors that invade tissues.

  • Can metastasize (spread to other parts of the body).

6. Chromosomes vs. Chromatin

• Chromatin: Loosely packed DNA, present in non-dividing cells.

• Chromosomes: Tightly coiled DNA, visible during cell division.

• Humans have 46 chromosomes (23 pairs), with one set from each parent.

Connections to Previous Units:

• DNA replication (Unit 3) is essential before cell division.

• Mutations in DNA (Unit 12) can lead to cancer (Unit 11).

• Sexual reproduction and genetic diversity link to evolution (Unit 13).

Unit 12: Genetics and Inheritance

1. Gregor Mendel and the Foundation of Genetics

• Mendel’s Experiments:

  • Studied pea plants and identified patterns of inheritance.

  • Developed laws of inheritance based on dominant and recessive traits.

• Key Terms:

  • Gene: A segment of DNA that codes for a trait.

  • Allele: Different versions of a gene (e.g., dominant or recessive).

  • Genotype: Genetic makeup (e.g., AA, Aa, or aa).

  • Phenotype: Physical expression of a trait (e.g., purple or white flowers).

  • Homozygous: Two identical alleles (AA or aa).

  • Heterozygous: One dominant, one recessive allele (Aa).

2. Mendelian Laws of Inheritance

1. Law of Dominance:

   • A dominant allele masks a recessive allele (e.g., Aa = dominant trait expressed).

2. Law of Segregation:

   • During gamete formation, alleles separate so each gamete gets one allele.

3. Law of Independent Assortment:

   • Genes for different traits are inherited separately (if they are on different chromosomes).

3. Non-Mendelian Genetics

• Incomplete Dominance: Blended traits (e.g., red + white flowers = pink).

• Codominance: Both alleles are fully expressed (e.g., AB blood type).

• Multiple Alleles: More than two allele options (e.g., blood type: A, B, O).

• Polygenic Traits: Traits controlled by multiple genes (e.g., skin color, height).

• Sex-Linked Traits: Traits carried on X or Y chromosomes (e.g., color blindness, hemophilia).

4. Genetic Disorders and Mutations

• Types of Mutations:

  • Point Mutation: Single nucleotide change.

  • Frameshift Mutation: Insertion or deletion shifts the reading frame.

  • Chromosomal Mutation: Large-scale changes (e.g., deletion, duplication).

• Genetic Disorders:

  • Autosomal Disorders: Cystic fibrosis, sickle cell anemia, Huntington’s disease.

  • Sex-Linked Disorders: Hemophilia, Duchenne muscular dystrophy.

  • Chromosomal Abnormalities: Down syndrome (trisomy 21), Turner syndrome (XO).

• Environmental Factors: Can influence gene expression (e.g., temperature affects fur color in rabbits).

5. Genetic Inheritance and Pedigrees

• Pedigree Charts:

  • Used to trace inheritance of traits in families.

  • Circles = females, Squares = males.

  • Shaded = affected individuals.

6. Patterns of Inheritance Laws

• Hardy-Weinberg Equilibrium (links to Unit 14): Describes a non-evolving population if five conditions are met:

  1. Large population

  2. No mutations

  3. Random mating

  4. No natural selection

  5. No gene flow

Connections to Previous Units:

• Mutations (Unit 3) impact DNA and can lead to genetic disorders (Unit 12).

• Mitosis (Unit 11) produces identical cells, while meiosis (Unit 11) contributes to genetic diversity.

• Genetic variation (Unit 12) is crucial for evolution (Unit 13).

Unit 13: Evolution and Natural Selection

1. Charles Darwin and the Theory of Evolution

• Voyage on the HMS Beagle:

  • Observed variations in species, particularly finches in the Galápagos Islands.

  • Developed the theory of natural selection to explain adaptation and speciation.

• Key Influences on Darwin:

  • Geologists Lyell & Hutton: Earth is old and changes gradually.

  • Thomas Malthus: Populations grow faster than resources, leading to competition.

2. Principles of Natural Selection

1. Variation: Differences exist within populations.

2. Overproduction: More offspring are produced than can survive.

3. Competition: Organisms compete for resources.

4. Survival of the Fittest: Individuals with beneficial traits are more likely to survive and reproduce.

5. Descent with Modification: Favorable traits become more common over generations.

3. Evidence Supporting Evolution

• Fossil Record: Shows gradual changes in organisms over time.

• Comparative Anatomy:

  • Homologous Structures: Same structure, different function (e.g., human arm, bat wing).

  • Analogous Structures: Different structure, same function (e.g., bird wings vs. insect wings).

  • Vestigial Structures: Reduced or non-functional remnants of ancestors (e.g., human tailbone).

• Embryology: Similar embryos suggest common ancestry.

• Biogeography: Species in similar environments evolve similarly (convergent evolution).

• Molecular Biology: Similar DNA and proteins indicate evolutionary relationships.

4. Mechanisms of Evolution

• Genetic Drift: Random changes in allele frequency, especially in small populations.

• Gene Flow: Movement of genes between populations through migration.

• Mutations: Source of new genetic variations.

• Natural Selection: Differential survival and reproduction of individuals with advantageous traits.

5. Adaptations and Survival of the Fittest

• Structural Adaptations: Physical traits (e.g., camouflage, mimicry).

• Behavioral Adaptations: Actions that improve survival (e.g., migration, hibernation).

• Physiological Adaptations: Internal body processes (e.g., venom production, antibiotic resistance).

6. Heritable Variation and Evolutionary Fitness

• Heritable Traits: Passed down through generations, contributing to evolutionary change.

• Fitness: The ability of an organism to survive and reproduce.

• Artificial Selection: Human-driven breeding for desired traits (e.g., dog breeds, crop modifications).

Connections to Other Units:

• Genetic mutations (Unit 12) create variations that drive evolution.

• Population genetics (Unit 12) and evolutionary forces (Unit 14) shape species over time.

• Environmental pressures (Unit 6) influence survival and adaptation.

Unit 14: Evolutionary Patterns and Speciation

1. Hardy-Weinberg Equilibrium

• A mathematical model that predicts allele frequencies in a non-evolving population.

• Five conditions must be met for equilibrium (no evolution):

  1. No mutations (no new alleles introduced).

  2. No natural selection (all individuals have equal survival chances).

  3. No gene flow (no migration in or out of the population).

  4. Large population size (to minimize genetic drift).

  5. Random mating (no preference for certain traits).

• Equation:

  • p² + 2pq + q² = 1 (Genotype frequencies)

  • p + q = 1 (Allele frequencies)

  • p = dominant allele frequency, q = recessive allele frequency

2. Speciation: How New Species Arise

• Definition: The formation of new species due to reproductive isolation.

• Types of Speciation:

  • Allopatric Speciation: Physical barrier (e.g., mountains, rivers) separates populations.

  • Sympatric Speciation: No physical barrier, but differences in behavior or genetics cause separation.

3. Reproductive Barriers

• Prezygotic Barriers (Before Fertilization):

  • Temporal Isolation: Different breeding times.

  • Behavioral Isolation: Different mating rituals.

  • Mechanical Isolation: Physical differences prevent mating.

  • Gametic Isolation: Sperm and egg cannot fuse.

• Postzygotic Barriers (After Fertilization):

  • Hybrid Inviability: Offspring don’t develop properly.

  • Hybrid Sterility: Offspring are sterile (e.g., mule).

  • Hybrid Breakdown: Future generations weaken and die out.

4. Types of Natural Selection

• Directional Selection: One extreme trait is favored (e.g., taller giraffes survive better).

• Stabilizing Selection: Average traits are favored (e.g., human birth weight).

• Disruptive Selection: Both extreme traits are favored (e.g., small and large beak sizes, but not medium).

5. Bottleneck Effect & Founder Effect

• Bottleneck Effect: A large population is drastically reduced, leading to loss of genetic diversity (e.g., natural disasters, hunting).

• Founder Effect: A small group migrates and establishes a new population with limited genetic diversity (e.g., island colonization).

6. Patterns of Evolution

• Adaptive Radiation: A single species evolves into multiple distinct species (e.g., Darwin’s finches).

• Convergent Evolution: Different species evolve similar traits due to similar environments (e.g., dolphins and sharks).

• Divergent Evolution: Closely related species evolve different traits due to different environments (e.g., wolves and domesticated dogs).

• Coevolution: Two species evolve in response to each other (e.g., flowers and pollinators, predator-prey relationships).

• Extinction:

  • Background Extinction: Slow and natural extinction rate.

  • Mass Extinction: Sudden and widespread extinction due to catastrophic events.

Connections to Other Units:

• Mutations (Unit 12) and genetic variation drive speciation.

• Environmental pressures (Unit 6) influence species survival.

• Evolutionary evidence (Unit 13) supports patterns of diversification.

Unit 15: Classification and Taxonomy

1. Binomial Nomenclature

• Developed by Carl Linnaeus to give every organism a two-part scientific name.

• Format: Genus species (italicized; genus is capitalized, species is lowercase).

  • Example: Homo sapiens (humans), Canis lupus (wolves).

• This system ensures universal naming and avoids confusion caused by common names.

2. The Three Domains of Life

• Bacteria: Prokaryotic, unicellular, found everywhere (e.g., E. coli).

• Archaea: Prokaryotic, extremophiles, live in extreme environments (e.g., hot springs).

• Eukarya: Eukaryotic, includes all plants, animals, fungi, and protists.

3. Taxonomic Hierarchy (From Broadest to Most Specific)

Mnemonic: Dear King Philip Came Over For Good Soup

• Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species

• Organisms in the same genus are more closely related than those in the same family.

4. The Six Kingdoms

1. Eubacteria: Common bacteria, unicellular, prokaryotic.

2. Archaebacteria: Ancient bacteria, extremophiles.

3. Protista: Mostly unicellular eukaryotes (e.g., amoeba, algae).

4. Fungi: Heterotrophic decomposers, cell walls made of chitin (e.g., mushrooms).

5. Plantae: Autotrophic, photosynthetic, cell walls made of cellulose.

6. Animalia: Multicellular, heterotrophic, no cell walls.

5. Major Animal Phyla

• Porifera: Sponges, no true tissues.

• Cnidaria: Jellyfish, corals, stinging cells.

• Platyhelminthes: Flatworms, simple body structure.

• Nematoda: Roundworms, parasitic species.

• Annelida: Segmented worms (earthworms, leeches).

• Mollusca: Soft-bodied, often with shells (snails, octopuses).

• Arthropoda: Exoskeleton, jointed legs (insects, spiders, crabs).

• Echinodermata: Spiny skin, radial symmetry (starfish, sea urchins).

• Chordata: Vertebrates with a backbone (fish, birds, mammals).

6. Evolutionary Relationships & Cladistics

• Phylogenetic Trees: Show evolutionary relationships based on common ancestry.

• Cladograms: Show shared derived characteristics among species.

• Molecular Evidence: DNA and protein similarities provide more accurate classification than physical traits alone.

Connections to Other Units:

• Evolution (Unit 13 & 14) explains how species diverged over time.

• Cell types (Unit 11) distinguish domains and kingdoms.

• Ecological roles (Unit 9) determine interactions between different organisms.