Biology Exam Study Guide: Nature of Science, Population, Community, and Ecosystem Ecology

Study Guide - Smart Notes

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Organization: Life is structured in a hierarchy, from molecules to the biosphere. Levels include: molecules, organelles, cells, tissues, organs, organisms, populations, communities, ecosystems, and the biosphere.
Information: Genetic information flows from DNA to RNA to Protein (the central dogma of molecular biology).
Energy & Matter: Energy flows through ecosystems (usually entering as sunlight and exiting as heat), while matter cycles among living and nonliving components.
Interactions: Organisms interact with each other and their environment, affecting survival and evolution.
Evolution: Explains both the unity and diversity of life; all organisms are related through descent with modification.

Steps: Observation → Hypothesis → Prediction → Experiment → Data → Revision
Hypothesis: A testable explanation for an observation.
Theory: A broad, well-supported explanation for a wide range of phenomena.
Variables: Independent variable is manipulated; dependent variable is measured.
Control group: Serves as a baseline for comparison.
Inductive reasoning: Deriving general principles from specific observations.
Deductive reasoning: Predicting specific results from general principles.

Descent with modification: Species change over generations, giving rise to new species.
Natural selection: The process by which individuals with advantageous traits survive and reproduce more successfully.
Requirements for natural selection:
- Variation in traits
- Heritability of traits
- Overproduction of offspring
- Differential survival and reproduction
Fitness: The reproductive success of an individual relative to others.

Density: Number of individuals per unit area or volume.
Dispersion: Pattern of spacing among individuals:
- Clumped: Individuals aggregate in patches.
- Uniform: Evenly spaced, often due to territoriality.
- Random: Unpredictable spacing, independent of others.
Survivorship curves:
- Type I: Low death rates early, high late (e.g., humans).
- Type II: Constant death rate (e.g., some birds).
- Type III: High death rates early, low later (e.g., oysters).

Exponential Growth: Population increases under ideal conditions; produces a J-shaped curve.
- Equation:
- N = population size, r = intrinsic rate of increase
Logistic Growth: Population growth slows as it approaches carrying capacity (K); produces an S-shaped curve.
- Equation:
- K = carrying capacity

Density-dependent factors: Effects increase with population density (e.g., competition, disease).
Density-independent factors: Affect populations regardless of density (e.g., weather, natural disasters).

Biomes are major life zones characterized by vegetation type (terrestrial) or physical environment (aquatic).

Biome	Climate	Key Features
Tropical forest	Warm, wet	High biodiversity, dense canopy
Desert	Dry	Low precipitation, extreme temperatures
Grassland	Seasonal rain	Fires, large herbivores
Temperate forest	Moderate	Deciduous trees, seasonal variation
Taiga (Boreal forest)	Cold	Coniferous trees, long winters
Tundra	Very cold, low precipitation	Permafrost, short growing season

Fundamental niche: The full range of conditions a species can use.
Realized niche: The actual conditions used, limited by competition.
Competitive exclusion principle: Two species competing for the same resource cannot coexist indefinitely.

Definition: Species with a disproportionate effect on community structure relative to abundance.
Example: Sea otters maintain kelp forest ecosystems by controlling sea urchin populations.

Primary succession: Occurs on newly exposed surfaces (e.g., after lava flow), starting with pioneer species.
Secondary succession: Follows disturbance in an area with existing soil (e.g., after fire).
Stages: Pioneer → Intermediate → Climax community

One-way flow: Energy enters as sunlight, flows through trophic levels, and exits as heat.
10% rule: Only about 10% of energy is transferred from one trophic level to the next; the rest is lost as heat.

Gross Primary Production (GPP): Total amount of energy captured by photosynthesis.
Net Primary Production (NPP): Energy available to consumers;
Net Ecosystem Production (NEP): Net accumulation of energy in an ecosystem;

Water cycle: Movement of water through evaporation, condensation, precipitation, and runoff.
Carbon cycle: Carbon moves between atmosphere, organisms, and earth via photosynthesis, respiration, and decomposition.
Nitrogen cycle: Nitrogen fixation, nitrification, assimilation, ammonification, and denitrification move nitrogen through the biosphere.
Phosphorus cycle: Phosphorus moves through rocks, soil, water, and organisms; no atmospheric component.

Fossil fuels: Burning increases atmospheric CO2, contributing to climate change.
Nutrient runoff: Excess fertilizers cause eutrophication and dead zones in aquatic systems.