AP Bio Exam Review - Ecology Unit

Ecology Definition

• Ecology: The scientific study of interactions between organisms and their environment
  • Involves both biotic (living) and abiotic (nonliving) influences
  • Biotic factors include other organisms, abiotic factors include temperature, water, salinity, sunlight, soil.

Hierarchy of Ecology

• Organisms: Individual living entities.
• Population: Group of individuals of the same species living in a particular area.
• Community: All organisms of different species inhabiting a particular area.
• Ecosystem: Includes both abiotic factors and communities of species in a given area.
• Biosphere: The global ecosystem comprising all ecosystems.

Biomes

• Different types of biomes can be identified based on vegetation and climate:
  • Desert
  • Temperate grassland
  • Tropical forest
  • Temperate broadleaf forest
  • Coniferous forest
  • Arctic and alpine tundra

Learning in Organisms

• Learning: A change in behavior resulting from experience.
  • Ranges from simple behavioral changes to complex problem-solving.
  • Social learning: Changes in behavior through observation and imitation (e.g. Vervet alarm calls).
• Innate behavior: Fixed, unlearned behavior associated with a particular species.
  • Fixed Action Patterns (FAPs): Innate behaviors that are unchangeable sequences completed once triggered by a sign stimulus.

Types of Learning

1. Habituation: Loss of responsiveness to unimportant stimuli.
2. Imprinting: Learning associated with innate components limited to sensitive periods (e.g. Lorenz's work on greylag geese).
3. Associative Learning: Associating one stimulus with another (e.g. classical conditioning in fruit flies).
4. Operant Conditioning: Associative learning through rewards and punishments (trial-and-error).
5. Cognition: The nervous system's ability to perceive, store, process, and use information (involves problem-solving).

Territorial Behavior

• Territorial behavior serves to parcel space and resources among individuals (e.g. animals marking and defending territories).

Patterns of Dispersal

• Clumped dispersion: Most common; groups near resources.
• Uniform dispersion: Even spacing often due to antagonistic interactions.
• Random dispersion: Uncommon; occurs in factors that influence growth like wind.

Population Dynamics

• Population changes due to births and deaths:
  • Life table: Age-specific summary of survival patterns.
  • Survivorship curves:
  • Type I: Low early-life mortality (e.g. humans).
  • Type II: Constant mortality rate (e.g. squirrels).
  • Type III: High early-life mortality (e.g. oysters).
• Zero Population Growth: Birth rate equals death rate.
• Exponential Growth: Population increases rapidly in ideal conditions.
• Logistic Model: Includes carrying capacity (K) to reflect environmental limits.

Population Strategies

• K-selection: Populations that are close to the carrying capacity.
• r-selection: Maximize reproductive success.
  • Characteristics:
  • K-selection: high prenatal care, low birth numbers, good survival of young.
  • r-selection: low care, high birth rates, poor survival of young.

Growth Limiting Factors

• Density-dependent factors: Actions that are influenced by population size (e.g. disease, competition).
• Density-independent factors: Unrelated to population size (e.g. natural disasters).

Interspecific Interactions

• Relationships can be positive, negative, or neutral.
• Examples include:
  • Competition (-/-): Both species are harmed.
  • Predation (+/-): One species benefits, the other is harmed.
  • Mutualism (+/+): Both species benefit.

Ecological Niche

• Ecological Niche: Total resources utilized by an organism; includes fundamental and realized niches.
• Competitive Exclusion Principle: Two species cannot occupy the same niche if they have identical requirements.

Community Structure

• Species diversity: Defined by species richness and relative abundance.
• Dominant species: Most abundant or largest biomass in a community.
• Keystone species: Critical for maintaining community structure (e.g. sea otters controlling sea urchin populations).

Disturbances and Succession

• Disturbance: Changes in community composition due to events (fire, storms).
• Primary Succession: Development in lifeless areas (e.g. volcanic islands).
• Secondary Succession: Recovery where soil remains after disturbance (e.g. after a forest fire).

Ecosystems

• Ecosystem: Sum of organisms and their abiotic environment. Key processes include energy flow and chemical cycling.
• Trophic Structures: Represent feeding relationships; categorized into trophic levels.
• Food webs: Interconnected food chains representing multiple trophic interactions.

Primary Production

• Gross Primary Production (GPP): Total light energy converted into chemical energy.
• Net Primary Production (NPP): GPP minus energy used by producers for respiration (NPP = GPP - R).

Factors Affecting Production

• Influenced by light availability, nutrient availability, temperature, and moisture.
• Eutrophication: Nutrient-rich environments supporting algae growth.

Energy Transfer Efficiency

• Around 10% of energy is transferred between trophic levels.
• Energy dissipates through heat during each level of consumption.

Nutrient Cycling

• Involves biogeochemical cycles, which connect biotic and abiotic parts.
• Key cycles include water, carbon, nitrogen, and phosphorus cycles.

Environmental Issues

• Acid Precipitation: Caused by human activity leading to environmental damage.
• Biological Magnification: Increasing concentration of toxins (e.g. mercury) through trophic levels.
• Greenhouse Effect: Absorption of heat due to greenhouse gases.
• Rising CO2 Levels: Industrial activities contributing to global warming.
• Threats to Biodiversity:
  1. Habitat destruction
  2. Introduction of invasive species
  3. Overexploitation
  4. Disruption of food chains through species extinction.