BioFinal PDF - Biology Notes

Chapter 1: Introduction to Biology 1. Properties of Living Things Order: Organized structures like cells. Reproduction: Ability to produce offspring. Growth and Development: DNA-guided growth. Energy Processing: Metabolism for energy use. Regulation: Maintaining homeo...

Chapter 1: Introduction to Biology 1. Properties of Living Things Order: Organized structures like cells. Reproduction: Ability to produce offspring. Growth and Development: DNA-guided growth. Energy Processing: Metabolism for energy use. Regulation: Maintaining homeostasis. Response to Environment: Reacting to stimuli. Evolutionary Adaptation: Traits evolving over time. 2. Biological Organization Examples Atoms: Carbon (C). Molecules: Water (H₂O). Organelles: Nucleus in cells. Cells: Muscle cells. Tissues: Muscle tissue. Organs: Heart. Organ Systems: Circulatory system. Organisms: Humans. Populations: Herd of deer. Communities: Deer, trees, and predators in a forest. Ecosystems: Rainforest. Biosphere: Earth. 3. Hierarchical Taxonomy Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species. 4. Discovery vs. Hypothesis Science Discovery Science: Observational; e.g., cataloging species. Hypothesis Science: Experimental; e.g., testing a drug's effect. 5. Hypothesis vs. Theory Hypothesis: Testable explanation. Theory: Broad, supported by evidence. Chapter 2: Chemistry of Life 1. Structure of Atoms Protons: Positive, in nucleus. Neutrons: Neutral, in nucleus. Electrons: Negative, orbit around nucleus. 2. Definitions Atomic Number: Number of protons. Mass Number: Protons + Neutrons. Isotope: Atoms with the same protons but different neutrons. Ion: Charged atom (lost/gained electrons). 3. Electron Configurations Sodium (Na): 2, 8, 1 (valence: 1). Potassium (K): 2, 8, 8, 1 (valence: 1). Oxygen (O): 2, 6 (valence: 6). Carbon (C): 2, 4 (valence: 4). 4. Bond Types Bond Type Description Example Ionic Transfer of electrons NaCl Covalent Sharing of electrons H₂O Hydrogen Weak attraction between Water molecules molecules 5. Water's Molecular Structure Polar: Oxygen is slightly negative, hydrogen is slightly positive. 6. Water’s Properties Cohesion, adhesion, high heat capacity, solvent abilities. 7. pH Scale Measures H⁺ concentration. Lemon juice ([H⁺] 10x soda). Pure water ([H⁺] 1000x tomato juice). 8. pH Definitions  Acid: pH < 7 (e.g., lemon juice). Base: pH > 7 (e.g., bleach). Neutral: pH = 7 (e.g., water). 9. Macromolecules Macromolecule Monomer Function Example Carbohydrate Monosaccharide Energy Glucose Lipid Fatty acid Storage Oil Protein Amino acid Enzymes Hemoglobin Nucleic Acid Nucleotide Genetic Info DNA 10. Saturated vs. Unsaturated Fats Saturated: No double bonds, solid. Unsaturated: Double bonds, liquid. Chapter 3: Cell Structure and Function 1. Prokaryotic vs. Eukaryotic Cells Prokaryotes: No nucleus, smaller (bacteria). Eukaryotes: Nucleus, organelles (plants, animals). 2. Endosymbiotic Theory Evidence: Mitochondria/chloroplasts have DNA, double membranes, similar to prokaryotes. 3. Plasma Membrane Structure: Phospholipid bilayer with proteins. Function: Regulates transport. 4. Organelle Functions Cytoplasm: Jelly-like, holds organelles. Cytoskeleton: Support and movement. Nucleus: Stores DNA. Rough ER: Protein synthesis. Smooth ER: Lipid production.  Golgi Apparatus: Packaging proteins. Lysosomes: Digestive enzymes. Vesicles/Vacuoles: Storage/transport. Ribosomes: Protein synthesis. Mitochondria: Energy (ATP). Chloroplast: Photosynthesis. Cell Wall: Structural support (plants). Central Vacuole: Storage (plants). 5. Cilia vs. Flagella Cilia: Short, numerous, move fluid. Flagella: Long, few, move cells. 6. Endomembrane System Includes: ER, Golgi, vesicles. Function: Protein/lipid transport. 7. Plant vs. Animal Cells Plant: Cell wall, chloroplast, central vacuole. 8. Solutions Hypertonic: Water leaves cell. Isotonic: No net movement. Hypotonic: Water enters cell. 9. Transport Types Process Description Active? Direction Energy? Diffusion High → low, no Passive High → low No protein Facilitated High → low, Passive High → low No Diffusion protein Osmosis Water diffusion Passive High → low No Phagocytosis "Cell eating" Active Low → high Yes Pinocytosis "Cell drinking" Active Low → high Yes Receptor-mediat Selective uptake Active Low → high Yes ed endocytosis  Exocytosis Expels materials Active Low → high Yes Osmosis Diagram 1. Fig A: Hypertonic, shrivel. 2. Fig B: Hypotonic, swell. 3. Fig C: Isotonic, stay same. Chapter 4: How Cells Obtain Energy 1. Kinetic, Potential, and Chemical Energy ○ Kinetic Energy: Energy due to motion. Example: A moving car. ○ Potential Energy: Stored energy due to position or state. Example: A rock at the top of a hill. ○ Chemical Energy: Energy stored in chemical bonds. Example: Glucose stores energy released during cellular respiration. 2. How Enzymes Speed Up Reactions Enzymes lower the activation energy required for chemical reactions. They bind substrates at their active sites, facilitating the reaction without being consumed. 3. Effects of Inhibitors on Enzyme Activity ○ Competitive Inhibition: Inhibitor competes with the substrate for the active site. ○ Non-competitive Inhibition: Inhibitor binds elsewhere, altering enzyme shape and reducing activity. ○ Uncompetitive Inhibition: Inhibitor binds only to the enzyme-substrate complex, preventing product release. 4. How ATP Powers Cellular Work ATP transfers a phosphate group to other molecules (phosphorylation), releasing energy for cellular activities like muscle contraction and active transport. 5. Overall Equation for Cellular Respiration C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP) (Glucose + Oxygen → Carbon Dioxide + Water + Energy) 6. Stages of Cellular Respiration Stage Location Reactants Products Glycolysis Cytoplasm Glucose, 2 ATP, 2 Pyruvate, 4 ATP, NAD⁺ NADH Acetyl-CoA Mitochondrial matrix Pyruvate, NAD⁺ Acetyl-CoA, NADH, Production CO₂ Citric Acid Cycle Mitochondrial matrix Acetyl-CoA, NAD⁺, CO₂, NADH, FADH₂, FAD ATP Oxidative Inner mitochondrial NADH, FADH₂, O₂ ATP, H₂O Phosphorylation membrane 7. Anaerobic vs. Aerobic Respiration ○ Alcohol Fermentation: Yeast converts glucose to ethanol, CO₂, and a small amount of ATP without oxygen. ○ Lactic Acid Fermentation: Muscle cells convert glucose to lactic acid and ATP in low oxygen. ○ Aerobic Respiration: Uses oxygen, producing more ATP (up to 38 per glucose molecule). Chapter 5: Photosynthesis 1. Autotrophs and Heterotrophs ○ Autotrophs: Produce their own food. Example: Plants perform photosynthesis. ○ Heterotrophs: Rely on consuming other organisms. Example: Animals and fungi. 2. Overall Equation for Photosynthesis 6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂ (Carbon Dioxide + Water + Light → Glucose + Oxygen) 3. Light Absorption by Pigments ○ Chlorophyll a: Absorbs blue-violet and red light. ○ Chlorophyll b: Absorbs blue and red-orange light. ○ Carotene: Absorbs blue and green light; reflects yellow, orange, and red. 4. How Light Powers Photosynthesis Light excites electrons in chlorophyll, driving the light-dependent reactions. This generates ATP and NADPH used in the Calvin cycle to fix carbon into glucose. 5. Stages of Photosynthesis Stage Location Reactants Products Light Reaction Thylakoid Water, Light, NADP⁺, Oxygen, ATP, membranes ADP NADPH Calvin Cycle Stroma CO₂, ATP, NADPH Glucose, ADP, NADP⁺ 6. Types of Photosynthesis ○ C3 Photosynthesis: Direct CO₂ fixation into a 3-carbon compound. Example: Wheat. ○ C4 Photosynthesis: CO₂ fixed into a 4-carbon compound, reducing photorespiration. Example: Corn.  ○ CAM Photosynthesis: CO₂ fixed at night to conserve water. Example: Cactus. Chapter 12: Diversity of Life 1. Domains of Life ○ Bacteria ○ Archaea ○ Eukarya 2. Taxonomic Groups ○ Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species 3. Binomial Nomenclature Example: Homo sapiens (Genus capitalized, species lowercase, italicized). 4. Homologous vs. Analogous Structures ○ Homologous: Shared ancestry but different functions. Example: Human arm and bat wing. ○ Analogous: Similar functions but no shared ancestry. Example: Bird and insect wings. 5. Ancestral vs. Derived Traits ○ Shared Ancestral Trait: Found in all descendants. Example: Vertebral columns in vertebrates. ○ Shared Derived Trait: Unique to a group. Example: Feathers in birds. 6. Interpreting Phylogenetic Trees ○ Nodes represent common ancestors. Organisms sharing recent ancestors are closely related. Chapter 13: Microbes, Fungi, and Protists 1. Characteristics of Bacteria and Archaea ○ Bacteria: Peptidoglycan in cell walls, diverse habitats. ○ Archaea: Unique lipids, often extremophiles. 2. Prokaryote Interactions with Humans ○ Harmful: Pathogens like Salmonella. ○ Beneficial: Gut flora, antibiotics, bioremediation. 3. Characteristics of Protists ○ Nutrition: Autotrophic, heterotrophic, mixotrophic. ○ Structure: Mostly unicellular, some multicellular. ○ Reproduction: Asexual or sexual. 4. Characteristics of Fungi ○ Nutrition: Absorptive heterotrophs. ○ Structure: Hyphae, chitin in cell walls. ○ Reproduction: Sexual and asexual spores.  5. Roles and Uses of Fungi ○ Ecological: Decomposers, mutualistic with plants. ○ Commercial: Antibiotics, food (bread, beer). 6. Mycorrhizae and Lichens ○ Mycorrhizae: Fungi assist plants in nutrient absorption. ○ Lichens: Symbiosis of fungi with algae/cyanobacteria; aid in soil formation. 7. Lichen Growth Forms ○ Crustose: Flat. ○ Foliose: Leafy. ○ Fruticose: Branching. Chapter 6: Reproduction at the Cellular Level 1. Describe the difference between sister chromatids and homologous chromosomes. Sister Chromatids: Identical copies of a chromosome connected by a centromere, formed during DNA replication. They are produced during the S phase of the cell cycle and are separated during mitosis. Homologous Chromosomes: Pairs of chromosomes (one from each parent) that have the same genes but may have different alleles. They are similar in size, shape, and genetic content, and are involved in meiosis. 2. Describe the differences between haploid and diploid cells. Haploid Cells: Contain one set of chromosomes (n). Examples include gametes (sperm and egg cells). Diploid Cells: Contain two sets of chromosomes (2n), one set from each parent. Examples include somatic (body) cells. 3. Compare the types of cell division in prokaryotic and eukaryotic cells. Prokaryotic Cell Division: Occurs through binary fission, a simpler process where the DNA is replicated and the cell divides into two identical cells without the complex stages of mitosis. Eukaryotic Cell Division: Involves mitosis (for somatic cells) and meiosis (for gametes), which include complex stages (prophase, metaphase, anaphase, telophase) and the formation of a mitotic spindle. 4. Describe the key events that occur during each phase of the cell cycle and mitosis. Interphase: G1 Phase: Cell growth, normal metabolic functions, and preparation for DNA synthesis. S Phase: DNA replication occurs, resulting in sister chromatids. G2 Phase: Further growth and preparation for mitosis, including the synthesis of proteins and organelles. Mitotic Phase a. Prophase: Chromatin condenses into visible chromosomes, the mitotic spindle forms, and the nuclear envelope breaks down. b. Metaphase: Chromosomes align at the metaphase plate, and spindle fibers attach to the centromeres of the chromosomes. c. Anaphase: Sister chromatids are pulled apart to opposite poles of the cell. d. Telophase: Chromosomes decondense, nuclear envelopes reform around the two sets of chromosomes, and the mitotic spindle disassembles. e. Cytokinesis: The cytoplasm divides, resulting in two separate daughter cells. Chapter 7: Cellular Basis of Inheritance 1. Describe the differences between gametes and somatic cells. Gametes: Haploid reproductive cells (sperm and eggs) that fuse during fertilization to form a diploid zygote. Somatic Cells: Diploid cells that make up most of the body's tissues and organs, not involved in reproduction. 2. Describe the key events that occur during each phase of meiosis I and meiosis II. Interphase I: Chromosomes replicate, forming sister chromatids. Interphase II: Similar to interphase but without DNA replication. Meiosis I 1. Prophase I: Homologous chromosomes pair and exchange genetic material through crossing over. 2. Metaphase I: Homologous chromosomes align at the metaphase plate. 3. Anaphase I: Homologous chromosomes are pulled apart to opposite poles.  4. Telophase I: Chromosomes may decondense and nuclear envelopes may reform. 5. Cytokinesis: Cytoplasm divides, resulting in two haploid cells. Meiosis II 1. Prophase II: Chromosomes condense again, and a new spindle apparatus forms. 2. Metaphase II: Chromosomes align at the metaphase plate. 3. Anaphase II: Sister chromatids are pulled apart to opposite poles. 4. Telophase II: Nuclear envelopes reform, and chromosomes decondense. 5. Cytokinesis: Cytoplasm divides, resulting in four haploid daughter cells. 3. Describe how independent assortment of chromosomes and crossing over contribute to genetic diversity in offspring during meiosis. Independent Assortment: During meiosis, the orientation of homologous chromosome pairs at the metaphase plate is random, leading to a mix of maternal and paternal chromosomes in gametes. Crossing Over: During prophase I, homologous chromosomes exchange segments of DNA, resulting in new combinations of alleles and increasing genetic variation. 4. Compare the overall similarities and differences between meiosis and mitosis. Aspect Mitosis Meiosis # of daughter cells produced Two (2n) Four (n) Are daughter cells identical to Yes No parent? Which cells carry out the Somatic cells Gametes process Are the daughter cells diploid Diploid (2n) Haploid (n) or haploid? Chapter 8: Patterns of Inheritance 1. Explain the following terms: Gene (Characteristic): A segment of DNA that codes for a specific trait or characteristic. Allele (Trait): A variant form of a gene that can produce different traits.  Dominant Allele: An allele that expresses its trait even in the presence of a recessive allele. Recessive Allele: An allele that only expresses its trait when two copies are present (homozygous). Phenotype: The observable traits or characteristics of an organism. Genotype: The genetic makeup of an organism, represented by alleles. Homozygous: Having two identical alleles for a specific gene (e.g., AA or aa). Heterozygous: Having two different alleles for a specific gene (e.g., Aa). 2. Explain the following inheritance patterns and provide an example of each one: Complete Dominance: The dominant allele completely masks the effect of the recessive allele. (Example: AA or Aa = purple flowers in pea plants). Incomplete Dominance: The phenotype is a blend of the dominant and recessive traits. (Example: Red flower (RR) crossed with white flower (WW) results in pink flowers (RW)). Codominance: Both alleles are fully expressed in the phenotype. (Example: AB blood type where both A and B alleles are expressed). Polygenic Inheritance: Multiple genes influence a trait. (Example: Skin color in humans). Epistasis: One gene's effect masks or modifies the effect of another gene. (Example: Coat color in Labrador retrievers, where one gene determines pigment and another gene determines if the pigment is expressed). Multiple Alleles: More than two alleles exist for a gene. (Example: ABO blood groups). 3. Describe how the inheritance of sex-linked genes differs from non-sex-linked genes. Sex-Linked Genes: Genes located on sex chromosomes (X or Y). Inheritance is often related to the sex of the offspring; males are more likely to express recessive traits linked to the X chromosome due to having only one X chromosome. Non-Sex-Linked Genes: Genes located on autosomes (non-sex chromosomes) that do not show a difference in inheritance patterns based on the sex of the individual. 4. Be able to solve genetics problems for non-sex-linked genes, sex-linked genes, and blood types. a) In pea plants, the allele for tall (T) is dominant over the allele for short (t). i. List the possible genotypes for a tall plant. TT, Tt ii. List the possible genotype for a short plant.  tt iii. A Tt plant is crossed with a Tt plant (Tt x Tt). What are the genotype and phenotype ratios of this cross? Genotype Ratio: 1 TT : 2 Tt : 1 tt (1:2:1) Phenotype Ratio: 3 Tall : 1 Short (3:1) b) Red-green color blindness is a sex-linked recessive trait on the X chromosome. A woman with normal vision whose father was colorblind marries a man who is colorblind. What is the probability that they would have a color-blind child? (N - normal vision, n – color blind) The woman has one normal vision allele (X^N) from her mother and one colorblind allele (X^n) from her father, making her genotype X^N X^n. The man is colorblind (X^n Y). The possible offspring genotypes are: ○ X^N X^n (normal vision female) ○ X^n X^n (color-blind female) ○ X^N Y (normal vision male) ○ X^n Y (color-blind male) Probability of color-blind child: 1/4 (X^n X^n) + 1/4 (X^n Y) = 1/2. c) A child has blood type B and the mother has type O. What is the genotype of the child’s blood type? The child’s genotype must be BO (I^B i). d) Both parents are blood type A. Is it possible for these parents to have a child with blood type O? What must the parents’ genotypes be? Yes, it is possible if both parents are heterozygous (I^A i). The potential offspring ratios include 1/4 O (ii) when both parents contribute an i allele. Chapter 9: Molecular Biology 1. Describe the process of DNA replication. DNA replication is semi-conservative, involving the unwinding of the double helix by helicase, followed by the synthesis of new complementary strands by DNA polymerase. Each original strand serves as a template, resulting in two DNA molecules, each containing one original strand and one newly synthesized strand. 2. What is the Central Dogma?  The Central Dogma of molecular biology states that genetic information flows from DNA to RNA to protein. It describes the processes of transcription (DNA to RNA) and translation (RNA to protein). 3. a) What is transcription? Transcription is the process by which the genetic information in DNA is copied into messenger RNA (mRNA). 3. b) Where does transcription occur in a eukaryotic cell? In the nucleus. 3. c) List and explain the steps of transcription. Steps of Transcription Description 1. Initiation RNA polymerase binds to the promoter region of DNA and unwinds the DNA strands. 2. Elongation RNA polymerase synthesizes a complementary RNA strand by adding RNA nucleotides. 3. Termination RNA polymerase reaches a terminator sequence, causing it to detach from the DNA and release the mRNA strand. 4. a) What is translation? Translation is the process by which the mRNA sequence is read by ribosomes to synthesize a polypeptide (protein). 4. b) Where does translation occur in a eukaryotic cell? In the cytoplasm (at ribosomes). 4. c) List and explain the steps of translation. Steps of Translation Description 1. Initiation Ribosome assembles around the start codon of the mRNA, with the initiator tRNA attached. 2. Elongation Ribosome moves along the mRNA, adding amino acids as tRNA brings them to the ribosome. 3. Termination Ribosome reaches a stop codon, releasing the completed polypeptide chain and disassembling. 5. Distinguish between insertion, deletion, and substitution mutations. Explain how mutations can affect organisms. Insertion Mutation: Addition of one or more nucleotide pairs, potentially shifting the reading frame and altering the protein produced. Deletion Mutation: Removal of one or more nucleotide pairs, which can also shift the reading frame and disrupt protein function. Substitution Mutation: Replacement of one nucleotide with another, which may result in a silent mutation (no change), missense mutation (different amino acid), or nonsense mutation (stop codon). Mutations can lead to changes in protein function, which can be beneficial, harmful, or neutral to the organism. 6. Describe the characteristics of viruses and how they replicate. Viruses are acellular entities composed of genetic material (DNA or RNA) surrounded by a protein coat (capsid). They cannot reproduce independently and must infect a host cell to replicate. Upon infection, a virus injects its genetic material into the host, hijacking the host's cellular machinery to produce new viral particles. 7. Describe what bacteriophages are and the differences between the lytic cycle and lysogenic cycle of bacteriophages. Bacteriophages: Viruses that specifically infect bacteria. Lytic Cycle: The bacteriophage attaches to a host, injects its DNA, uses the host's machinery to produce new phages, and ultimately causes the host cell to lyse (burst), releasing new viruses. Lysogenic Cycle: The bacteriophage integrates its DNA into the host's genome (prophage) and replicates along with the host's DNA without immediately killing the host. The virus can later enter the lytic cycle under certain conditions. 8. Explain how the COVID-19 virus can infect and affect humans. COVID-19, caused by the SARS-CoV-2 virus, infects human cells primarily through the respiratory route. The virus uses its spike protein to bind to the ACE2 receptor on human cells, allowing entry. Once inside, it hijacks the host's cellular machinery to replicate, leading to cell damage and an immune response. Symptoms range from mild respiratory issues to severe complications, including pneumonia and acute respiratory distress syndrome. Transcription/Translation Practice Problems  9. a) Write the sequence of amino acids that would be coded by translation from the following sequence of mRNA: AAA---AUG---GCA---AGU---AUA---ACA---UGC---GCC---CCC---UAA The sequence starts with AUG (start codon), leading to the following amino acids: ○ Methionine (Met) ○ Alanine (Ala) ○ Serine (Ser) ○ Isoleucine (Ile) ○ Threonine (Thr) ○ Cysteine (Cys) ○ Alanine (Ala) ○ Proline (Pro) ○ Stop codon (UAA) 9. b) What is the total number of amino acids that the translated protein will have? Total amino acids: 8 (from AUG to UAA, not including the stop codon). 10. Identify whether each of the mutations in (b) – (d) are neutral/silent, missense, or nonsense. DNA RNA Amino Acid a. ACA UGU Cysteine (original) b. ACG UGC Cysteine (neutral/silent) c. ATT UAA Stop codon (nonsense) d. ATA UAU Tyrosine (missense) Chapter 11: Evolution and Its Processes 1. Types of Evidence for Evolution ○ Fossil Evidence: Shows transitions between species over time (e.g., Archaeopteryx links dinosaurs to birds). ○ Anatomy: Homologous structures indicate shared ancestry; analogous structures result from convergent evolution. ○ Embryology: Similar early developmental stages in different species suggest common ancestry. ○ Biogeography: Geographic distribution of species reflects evolutionary history (e.g., Darwin's finches). ○ Molecular Biology: DNA and protein similarities show relationships among species (e.g., human and chimpanzee genomes). 2. Mechanisms of Evolution  ○ Natural Selection: Traits improving survival/reproduction increase in frequency (e.g., peppered moths). ○ Mutation: Random DNA changes introduce new traits (e.g., antibiotic resistance in bacteria). ○ Genetic Drift: Random changes in allele frequencies, especially in small populations. Bottleneck Effect: Drastic population reduction (e.g., cheetahs). Founder Effect: New population established by a few individuals (e.g., island birds). ○ Gene Flow: Movement of alleles between populations (e.g., migration). 3. Selection Types ○ Natural Selection: Traits that improve fitness prevail (e.g., camouflage in prey). ○ Artificial Selection: Human-driven selection (e.g., breeding dogs). ○ Sexual Selection: Traits that improve mating success (e.g., peacock feathers). 4. Species Concepts ○ Biological Species Concept: Groups of interbreeding populations producing fertile offspring. Cannot classify asexual organisms or fossils. ○ Morphological Species Concept: Classifies species based on physical traits. 5. Speciation ○ Allopatric Speciation: Geographic barriers separate populations (e.g., river divides squirrel populations). ○ Sympatric Speciation: Reproductive barriers within the same area (e.g., polyploidy in plants). 6. Reproductive Barriers ○ Prezygotic Barriers: Prevent fertilization (e.g., temporal isolation in frogs). ○ Postzygotic Barriers: Hybrid offspring are inviable or sterile (e.g., mule). 7. Modes of Selection ○ Directional Selection: Favors one extreme (e.g., antibiotic resistance). ○ Stabilizing Selection: Favors intermediate traits (e.g., human birth weight). ○ Disruptive Selection: Favors extremes (e.g., light and dark mice on varied terrain). Chapter 16: The Body’s Systems 1. Four Tissue Types ○ Epithelial: Covers body surfaces and lines organs (e.g., skin). ○ Connective: Supports and connects tissues (e.g., bone, blood). ○ Muscle: Facilitates movement (e.g., skeletal muscle). ○ Nervous: Processes and transmits information (e.g., neurons). 2. Homeostasis Maintenance of internal balance (e.g., body temperature regulation, blood sugar control).  3. Negative Feedback Loops Reverse deviations from set points (e.g., sweating to cool the body when overheated). 4. Action Potential Electrical signal triggered when a neuron depolarizes, transmitting information along the axon. Chapter 17: The Immune System 1. Innate vs. Adaptive Immunity ○ Innate: Nonspecific, immediate response (e.g., skin, phagocytes). ○ Adaptive: Specific, slower response involving memory (e.g., antibodies). 2. Immune Cells ○ Phagocytic Cells: Engulf pathogens (e.g., macrophages). ○ T Cells: Attack infected cells or help other immune responses. ○ B Cells: Produce antibodies. ○ Dendritic Cells: Present antigens to T cells. 3. Antigens and Antibodies ○ Antigens: Molecules that provoke an immune response. ○ Antibodies: Proteins produced by B cells to neutralize antigens. Chapter 19: Population and Community Ecology 1. Population Size vs. Density ○ Size: Total number of individuals. ○ Density: Number of individuals per unit area. 2. Species Distribution Patterns ○ Random: No pattern (e.g., dandelions). ○ Clumped: Grouped in patches (e.g., herds). ○ Uniform: Evenly spaced (e.g., penguins). 3. Population Growth ○ Exponential: Rapid growth without limits (J-curve). ○ Logistic: Growth with carrying capacity limits (S-curve). 4. Density-Dependent vs. Density-Independent Factors ○ Density-Dependent: Impact depends on population size (e.g., disease). ○ Density-Independent: Affects population regardless of size (e.g., natural disasters). 5. Interspecific Interactions ○ Competition: Compete for resources (e.g., lions and hyenas). ○ Predation: Predator-prey (e.g., hawk and mouse). ○ Herbivory: Plants consumed by herbivores (e.g., deer eating leaves). ○ Commensalism: One benefits, other unaffected (e.g., barnacles on whales).  ○ Mutualism: Both benefit (e.g., bees and flowers). ○ Parasitism: One benefits, one harmed (e.g., ticks on dogs). 6. Defenses Against Predation and Herbivory ○ Plants: Thorns, toxins (e.g., poison ivy). ○ Animals: Camouflage, mimicry, physical defenses (e.g., porcupine quills).