Biology EOC Study Guide
Characteristics of Life and Nature of Science
All living things share six characteristics: - Made of Cells: The smallest unit of life. - Contain DNA: The genetic blueprint that codes for proteins. - Use Energy: Usually from food, which is broken down into ATP (adenosine triphosphate). - Maintain Homeostasis: A stable internal environment despite external changes. - Reproduce: Can be sexual or asexual. - Undergo Evolution: Populations change over generations.
Science Vocabulary Definitions
Hypothesis: A testable proposed explanation for an observation.
Theory: A well-supported explanation backed by substantial evidence (e.g., theory of evolution, cell theory). Theories are not converted to laws; they serve different roles in answering questions.
Law: Describes what happens in nature, often mathematically, but not why it occurs (e.g., law of gravity).
Fact: A confirmed observation.
The Scientific Method
Steps involve: 1. Observation 2. Question 3. Hypothesis 4. Prediction 5. Experiment 6. Results 7. Conclusion
Requirements for good experiments: - Independent Variable: What the experimenter changes. - Dependent Variable: What is measured. - Control Group: No treatment group for comparison. - Constants: All other variables kept the same. - Sample Size: The larger the sample size, the more reliable the results.
Properties of Water
Polarity: Water is polar, with a slightly negative oxygen end and slightly positive hydrogen ends due to oxygen's stronger pull on electrons.
This polarity leads to hydrogen bonds between water molecules.
Key properties include: - Cohesion: Water sticks to itself, leading to surface tension (e.g., water striders). - Adhesion: Water sticks to other surfaces, causing capillary action (e.g., water moving up plant xylem). - High Specific Heat: Water resists temperature changes, stabilizing cell and ocean temperatures. - Density of Ice: Solid water (ice) is less dense than liquid water, allowing ice to float and insulate lakes in winter. - Universal Solvent: Polar molecules and ions dissolve in water.
Macromolecules in Biology
Main Elements: Carbon, hydrogen, oxygen, and nitrogen (CHON)
Four main macromolecules: - Carbohydrates: - Monosaccharides (e.g., glucose) are the building blocks. - Functions: - Quick energy source. - Structural material in plants (e.g., cellulose, starch). - Polysaccharide: Cellulose (rigid plant cell walls, not digestible by humans). - Energy Storage: Starch in plants, glycogen in animals (liver/muscles). - Lipids: - Composed of glycerol and fatty acids. - Functions: - Long-term energy storage. - Structural components of cell membranes (phospholipids). - Hormones (steroids like testosterone). - Hydrophobic nature. - Proteins: - Made of amino acids linked by peptide bonds. - Functions include: - Enzymatic activity (speeding up reactions). - Structural roles (collagen, keratin). - Transport (hemoglobin). - Defense (antibodies). - Signaling (some hormones). - Nucleic Acids: - DNA and RNA, made of nucleotides (sugar, phosphate, nitrogen base). - DNA: Double-stranded; contains genetic information. - RNA: Single-stranded; involved in protein synthesis. - Types: - mRNA (messenger) - tRNA (transfer) - rRNA (ribosomal)
Enzymes
Enzymes are proteins that lower activation energy for faster reactions.
They operate via a specific active site that fits a substrate (lock-and-key or induced-fit model).
Denaturation: Can occur through heat or incorrect pH, causing the enzyme's 3D shape to unfold and cease function.
Prokaryotes vs. Eukaryotes
Prokaryotes (e.g., bacteria, archaea): - Lack a nucleus and membrane-bound organelles. - Contain a cell wall, plasma membrane, ribosomes, and DNA in a nucleoid region.
Eukaryotes (e.g., animals, plants, fungi, protists): - Contain a true nucleus and membrane-bound organelles. - Share plasma membrane, ribosomes, cytoplasm, and DNA with prokaryotes.
Antibiotics target prokaryotic features, thus not affecting fungal infections (eukaryotic) or viruses.
Key Cell Organelles
Nucleus: Stores DNA, controls cell activities.
Ribosomes: Synthesize proteins; located freely in cytoplasm or on rough ER.
Rough ER: Processes and transports proteins; studded with ribosomes.
Smooth ER: Synthesizes lipids, detoxifies poisons; lacks ribosomes.
Golgi Apparatus: Modifies and ships proteins from rough ER.
Mitochondria: Produce ATP through cellular respiration, possess their own DNA.
Chloroplasts (in plants): Site of photosynthesis, also with own DNA.
Lysosomes: Contain enzymes to break down waste, old organelles, and food particles.
Vesicles: Transport substances within the cell.
Vacuoles: Storage structures (e.g., large central vacuole in plants for turgor pressure).
Cell Membrane: Phospholipid bilayer, selectively permeable.
Cell Wall (in plants, fungi, bacteria): Rigid outer layer, made of cellulose in plants.
Cytoskeleton: Maintains cell shape, aids in cell movement.
Cell Membrane and Transport
Composed of a phospholipid bilayer with polar/hydrophilic heads and nonpolar/hydrophobic tails.
Fluid Mosaic Model: Proteins float within the bilayer.
Passive Transport: Uses no energy, moves with concentration gradient (high to low): - Simple Diffusion: Small/nonpolar molecules (e.g., O2, CO2). - Facilitated Diffusion: Larger/polar molecules use protein channels (e.g., glucose, ions). - Osmosis: Diffusion of water through a semipermeable membrane.
Active Transport: Requires ATP, moves against concentration gradient (low to high), e.g., sodium-potassium pump.
Endocytosis: Brings large substances into the cell via membrane vesicle. - Types: - Phagocytosis: Cell eating (solids). - Pinocytosis: Cell drinking (liquids). - Receptor-mediated endocytosis: Specific molecules.
Exocytosis: Releases materials from the cell via vesicles fusing with the membrane.
Osmosis Tonicity
Hypotonic Solution: Less solute outside than inside, causing cells to swell. (Red blood cells may burst, plant cells become turgid).
Hypertonic Solution: More solute outside, resulting in water rushing out (red blood cells shrivel, plant cells plasmolyze).
Isotonic Solution: Equal solute concentration, no net water movement, cells maintain normal state.
Photosynthesis and Cellular Respiration
Photosynthesis occurs in chloroplasts: - Converts sunlight, CO2, water into glucose and oxygen: - Occurs in two stages: - Light Reactions: In thylakoids, capture light energy, split water (releasing O2), and produce ATP/NADPH. - Calvin Cycle: In stroma, uses ATP/NADPH to fix CO2 into glucose.
Cellular Respiration occurs primarily in mitochondria: - Breaks down glucose to produce ATP: - Three stages: - Glycolysis (in cytoplasm): Splits glucose into 2 pyruvate, yielding 2 net ATP (anaerobic). - Krebs Cycle (mitochondrial matrix): Breaks down pyruvate, releasing CO2, producing 2 ATP, NADH, and FADH2. - Electron Transport Chain (inner mitochondrial membrane): Electrons from NADH/FADH2 drive the pumping of H⁺ through proteins, generating ~32-34 ATP.
Oxygen is the final electron acceptor, resulting in water formation.
Anaerobic Respiration: In humans, produces lactic acid, causing muscle cramps; in yeast, produces ethanol and CO2.
ATP and Plant Metabolism
ATP: Energy currency of the cell, like dollars; used for: - Muscle contractions - Active transport - Building molecules
Plants perform both photosynthesis and cellular respiration due to their mitochondria, especially at night.
Photosynthesis and respiration are nearly opposite processes; the byproducts of one serve as the reactants of the other.
Respiration is distinct from breathing (which pertains to gas exchange).
Mitosis, the Cell Cycle, and Cancer
Cell Cycle: Consists of Interphase (about 90% of the cycle) and Mitosis plus Cytokinesis (about 10%).
Interphase Phases: - G1: Cell growth. - S: DNA replication. - G2: Preparation for division.
Mitosis: Results in two genetically identical diploid cells; essential for growth, repair, asexual reproduction.
Phases of Mitosis: - Prophase: Chromosomes condense, nuclear membrane disintegrates, spindle fibers form. - Metaphase: Chromosomes align at the cell equator. - Anaphase: Sister chromatids separate towards opposite sides. - Telophase: Nuclear membranes reform, chromosomes decondense. - Cytokinesis: Cytoplasmic division occurs (different in plants and animals).
Humans have 46 chromosomes (23 pairs). Chromosomes consist of DNA and proteins.
Cancer: Arises from uncontrolled cell division due to mutations in genes regulating the cell cycle (e.g., p53 mutations). Causes include UV radiation, smoking, chemicals, viruses, and inherited mutations.
Meiosis and Genetic Diversity
Meiosis: Produces gametes with half chromosome count (haploid), involves two rounds of division (Meiosis I and II). - Starts with 1 diploid cell, ends with 4 haploid cells.
Key Sources of Genetic Diversity: - Crossing Over: Occurs during prophase I, homologous chromosomes swap DNA segments. - Independent Assortment: Chromosomes align randomly during metaphase I and II, leading to varied combinations (for 23 pairs, possibilities). - Random Fertilization: Further increases diversity.
Inheritance and Genetics
Genotypes: Genetic makeup (e.g., Bb).
Phenotypes: Physical traits (e.g., brown eyes).
Mendel's Laws: Dominant alleles mask recessive ones.
Punnett Squares: Tool for predicting offspring ratios.
Non-Mendelian Inheritance Examples: - Incomplete Dominance: Blending of traits (red x white = pink). - Codominance: Both traits expressed (black x white = speckled). - Multiple Alleles: More than two alleles exist (e.g., ABO blood types). - Polygenic Traits: Controlled by multiple genes (e.g., skin color). - Sex-linked Traits: Genes on X chromosome (color blindness, hemophilia), affecting males more due to XY composition.
DNA, RNA, and Protein Synthesis
DNA Structure: Double helix, composed of sugar (deoxyribose) and phosphate backbones with nitrogen base pairs (A, T, G, C). - Base pairing: A-T (2 hydrogen bonds), G-C (3 hydrogen bonds).
DNA Replication: Process involves helicase, DNA polymerase, & ligase; results in one old and one new strand (semiconservative).
RNA Types: Single-stranded, contains ribose sugar, and uracil instead of thymine.
Protein Synthesis Stages: - Transcription (in nucleus): DNA copied into mRNA by RNA polymerase. - Translation (at ribosome): mRNA codons read, tRNA brings amino acids matching the codons, forming polypeptides.
Eukaryotic mRNA Processing: Introns spliced out, exons joined, 5' cap and poly-A tail added.
Mutations
Mutation Types: - Point Mutation: Change in one base. - Substitution: Swapping one base for another, can be silent, missense, or nonsense. - Insertion: Addition of bases. - Deletion: Removal of bases. - Frameshift Mutation: Insertion/deletion causing shifts in reading frame; consequential. - Duplication: Copying a chromosome segment. - Translocation: A segment of chromosome moves. - Inversion: Segment flipped backward.
Effects of Mutations: - Body cell mutations affect the individual; gamete mutations can be inherited. Most mutations are neutral or harmful but occasionally beneficial, influencing evolution.
Endosymbiotic Theory
Proposes that eukaryotic cells originated when one prokaryotic cell engulfed another, resulting in symbiosis instead of digestion.
Evidence: 1. Mitochondria and chloroplasts have their own circular DNA. 2. They possess ribosomes resembling bacterial types. 3. They have double membranes (inner from engulfed bacteria, outer from host). 4. They replicate independently through binary fission.
Evolution and Natural Selection
Evolution: Change in genetic makeup over generations.
Natural Selection: Mechanism proposed by Darwin and Wallace: - Variation exists due to mutations and meiosis. - Favorable variations confer advantages for survival; those individuals reproduce more successfully.
Modern domestic dogs evolved from wolves via artificial selection.
Evidence for Evolution
Fossil Record: Evidence of gradual change over time.
Comparative Anatomy: Homologous structures indicate common ancestry; vestigial structures represent historical remnants; analogous structures suggest convergent evolution.
Embryology: Similar early development patterns among vertebrates.
Molecular Biology: Similar sequences in DNA and proteins indicate evolutionary relationships.
Biogeography: Geographic distribution of species supports evolutionary patterns.
Honors Content: Speciation and Hardy-Weinberg Principle
Speciation: Populations become separate enough to not interbreed (allopatric: geographic isolation, sympatric: other mechanisms).
Hardy-Weinberg Principle: Allele frequencies remain constant barring external influences (mutation, gene flow, genetic drift, natural selection, non-random mating).
Phylogeny and Taxonomy
Phylogeny: Evolutionary history, depicted through phylogenetic trees.
Taxonomy: Classification science, initiated by Linnaeus with binomial nomenclature.
Taxonomic Hierarchy: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
Dichotomous Key: Identification tool with stepwise questions.
Human Body Systems Overview
Nervous: Controls voluntary/involuntary actions.
Skeletal: Provides support, protects organs, makes blood cells.
Muscular: Facilitates movement through various tissue types.
Digestive: Breaks down food, absorbs nutrients.
Respiratory: Facilitates gas exchange (oxygen intake, carbon dioxide release).
Circulatory: Transports nutrients and removes waste.
Excretory: Eliminates bodily wastes.
Endocrine: Regulates hormone secretion.
Immune: Defends against foreign pathogens.
Integumentary: Protects body; largest organ system (skin).
Reproductive: Produces gametes (sperm in testes, eggs in ovaries), process of fertilization and development within the uterus.
Three trimesters of human pregnancy: - First: Organ formation, initial structures develop. - Second: Growth, determine sex, lung development. - Third: Weight gain, rapid brain development, organ maturation.
Biogeochemical Cycles
Nutrients (CHNOPS) cycle through ecosystems.
Water Cycle: Evaporation, condensation, precipitation, absorption by plants (transpiration), and groundwater movement.
Carbon Cycle: Photosynthesis by plants; respiration in animals; decomposition returns carbon to the atmosphere.
Nitrogen Cycle: Atmospheric nitrogen is unusable by most; nitrogen-fixing bacteria convert N₂ to forms usable by plants.
Phosphorus Cycle: Unique as it lacks an atmospheric phase; phosphorus in rocks weather into soil, cycles through ecosystems.
Ecological Succession
Gradual community changes: - Primary Succession: On bare rock; begins with pioneer species (e.g., lichens) that produce soil. - Secondary Succession: After a disturbance with soil present; faster due to existing soil.
Pioneer Species: Colonize barren land; set conditions for subsequent species.
Biodiversity, Biomagnification, and Human Impact
Biodiversity: Variety of life enhances ecosystem stability.
Biomagnification: Increase of toxins at higher trophic levels (e.g., mercury).
Human Impacts: Habitat destruction, pollution, climate change, and invasive species reduce biodiversity.
Ecological Footprint: Total resources utilized by an individual. Biocapacity: Earth's capacity to sustainably meet those needs.
The I = PAT equation: Impact = Population × Affluence × Technology evaluates environmental impact based on consumption.
Food Chains, Food Webs, and Energy Flow
Food Chain: Linear path of energy flow; Food Web: Complex interconnections. - Arrows indicate energy direction, ending at the eater.
Trophic Levels: - Producers: Most energy (plants). - Primary Consumers: Herbivores. - Secondary Consumers: Carnivores/omnivores. - Tertiary Consumers: Predators. - Decomposers: Recycle nutrients from dead matter.
10% Rule: Only about 10% of energy transfers between levels; 90% lost as heat.
Honors-Level Quick Hits and Common Test Mistakes
Mitosis yields 2 identical diploid cells; meiosis yields 4 diverse haploid cells.
Both plants and animals utilize cellular respiration, but only plants perform photosynthesis directly.
DNA resides in the nucleus while mRNA exits to ribosomes, and tRNA brings amino acids.
Codons and anticodons should not be confused.
Comprehend the distinctions regarding hypotonic, hypertonic, and isotonic solutions.
Ensure awareness of active versus passive transport energy requirements.
Distinguish between theory and mere speculation.
Mitosis:
- Type of cell division resulting in two genetically identical diploid cells.
- Essential for growth, repair, and asexual reproduction.
- Phases of Mitosis:
- Prophase: Chromosomes condense, nuclear membrane disintegrates, spindle fibers form.
- Metaphase: Chromosomes align at the cell equator.
- Anaphase: Sister chromatids separate towards opposite sides.
- Telophase: Nuclear membranes reform, chromosomes decondense.
- Cytokinesis: Cytoplasmic division occurs, resulting in two separate cells.Meiosis:
- Produces gametes (sperm and egg) with half the chromosome count (haploid), involves two rounds of division (Meiosis I and II).
- Starts with one diploid cell and ends with four haploid cells.
- Key Sources of Genetic Diversity:
- Crossing Over: Occurs during prophase I, homologous chromosomes swap DNA segments.
- Independent Assortment: Chromosomes align randomly during metaphase I and II, leading to varied combinations.
- Random Fertilization: Further increases diversity.