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.