Overview
This lecture reviews key concepts in Biology 20, including ecological organization, energy flow, cycles in nature, major organ systems, and biological processes relevant for the final exam.
Ecology & Biological Organization
- The biosphere includes all areas on Earth inhabited by life (air, water, land).
- Producers (autotrophs) make their own food; consumers (heterotrophs) eat others; decomposers break down dead matter.
- A niche is a species' role; a habitat is where it lives; its range is its geographic area.
- Biome: a large ecological area defined by climate and dominant flora.
- Ecosystems consist of communities and their abiotic (non-living) environment.
- Homeostasis maintains internal stability via feedback systems.
- The three domains: Archaea, Bacteria, Eukarya.
Hierarchy of Life & Taxonomy
- Organization: atoms β molecules β organelles β cells β tissues β organs β organ systems β organism β population β community β ecosystem β biosphere.
- Taxonomic hierarchy: Domain β Kingdom β Phylum β Class β Order β Family β Genus β Species.
- Classical Kingdoms: Monera, Protista, Fungi, Plantae, Animalia.
Energy Flow & Cycles
- Energy decreases by ~90% at each trophic level; limits food chains to 5 or fewer levels.
- Food chain: direct energy flow; food web: interconnected chains.
- Pyramid of energy: shows energy transfer; pyramid of biomass: shows organism mass at each level.
- Photosynthesis: plants convert COβ and sunlight to glucose; chemosynthesis: bacteria use chemical energy.
- Biomagnification: toxins increase in organisms higher up the food chain.
Major Nutrient Cycles
- Nitrogen cycle: nitrogen fixed by bacteria or lightning, assimilated by plants, returned by decomposition or denitrification.
- Water: unique because of surface tension, cohesion, adhesion, and capillary action.
Evolution & Adaptation
- Evolution: change in populations' inherited traits over time.
- Lamarck's theory: traits acquired by use/disuse are inherited.
- Darwin's theory: natural selection, descent with modification; populations evolve, not individuals.
Human Biology: Systems & Functions
Digestive System
- Digestion starts in the mouth (amylase), continues in stomach (HCl, pepsin), and completes in the small intestine (enzymes from pancreas, liver, gallbladder).
- Accessory organs: pancreas (digestive enzymes, neutralizes acid), liver (produces bile, detoxifies), gallbladder (stores bile).
- Large intestine absorbs water, forms feces, and houses bacteria.
Circulatory System
- Blood flow: body β vena cava β right heart β lungs β left heart β aorta β body.
- Blood: plasma (fluid), red cells (Oβ transport), white cells (immunity), platelets (clotting).
- Antibodies recognize antigens for immune defense.
- ABO and Rh blood group systems determine compatibility.
Urinary System
- Kidneys filter blood through nephrons: filtration, reabsorption, secretion.
- Aldosterone increases NaβΊ reabsorption, regulating blood pressure by blood volume.
Respiratory System
- Air travels: nose β trachea β bronchi β bronchioles β alveoli.
- Gas exchange in alveoli via diffusion; Oβ carried mainly by hemoglobin.
- Breathing regulated by medulla (brain) and chemoreceptors sensing COβ/Oβ.
Muscular System
- Three muscle types: smooth, cardiac, skeletal.
- Skeletal muscles work in pairs; contraction via sliding filament model (actin, myosin, ATP, CaΒ²βΊ).
- ATP powers muscles; requires energy from respiration.
Chemical & Cellular Processes
- Fermentation produces 2 ATP/glucose; aerobic respiration yields 36 ATP/glucose.
- Enzymes speed reactions, affected by temperature and pH.
- Dehydration synthesis: joins molecules, releases water; hydrolysis: splits molecules, uses water.
- Lipids: glycerol + 3 fatty acids; proteins: amino acids linked by peptide bonds.
Other Key Topics
- Biomagnification increases toxins up food chains.
- Physical barriers (like skin) defend against pathogens.
- Sexual vs asexual reproduction: pros and cons for each.
Key Terms & Definitions
- Biosphere β all life-supporting regions of Earth.
- Producer/Autotroph β organism that produces its own food.
- Consumer/Heterotroph β organism that eats other organisms.
- Decomposer β breaks down dead organic matter.
- Niche β ecological role of an organism.
- Biome β large ecological area with characteristic climate and species.
- Biomagnification β increase in toxin concentration up the food chain.
- Photosynthesis β conversion of solar energy to chemical energy by plants.
- Fermentation β anaerobic breakdown of glucose to ATP.
- Homeostasis β stable internal conditions.
- Enzyme β protein catalyst for biochemical reactions.
Action Items / Next Steps
- Review diagrams for energy pyramids, digestive, circulatory, urinary, respiratory, and muscular systems.
- Memorize key definitions and processes (nitrogen cycle, photosynthesis, respiration).
- Practice identifying organ structures and their functions.
- Study the effects of temperature/pH on enzyme activity.
- Prepare for questions on reproduction, biomagnification, and major organ systems.