Ecology: Introduction, Population, and Community Study Guide

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Ecology: Introduction, Population, and Community Study Guide

Ch.49 - Introduction to Ecology

Ecology is the scientific study of how organisms interact with each other and with their environment. It encompasses multiple levels of biological organization, from individuals to ecosystems, and aims to understand the distribution and abundance of organisms.

Goals of Ecology: To describe, explain, and predict patterns of distribution and abundance of organisms.
Approaches: Observational studies, experiments, and modeling.

Key Ecological Terms

Range: The geographic area where a species is found.
Niche: The sum of a species' use of biotic and abiotic resources in its environment.
Biotic Factors: Living components (e.g., plants, animals, microbes).
Abiotic Factors: Non-living components (e.g., temperature, water, sunlight, soil).

Exotic vs. Invasive Species

Exotic Species: Species introduced to an area where they are not native.
Invasive Species: Exotic species that spread rapidly and negatively impact native species and ecosystems.
Example: Zebra mussels in North America are invasive, outcompeting native mussels.

Climate vs. Weather

Climate: Long-term average of weather patterns in a region.
Weather: Short-term atmospheric conditions.
Seasons: Caused by the tilt of Earth's axis, affecting the angle of sunlight incidence.

Sunlight and Earth's Climate

Angle of Incidence: Sunlight strikes the equator more directly, leading to warmer temperatures; at higher latitudes, sunlight is spread over a larger area, causing cooler temperatures.
Atmospheric Circulation: Hadley, mid-latitude (Ferrel), and polar cells distribute heat and moisture.
Coriolis Effect: Causes moving air and water to turn due to Earth's rotation, influencing wind and ocean currents.
Land Masses and Oceans: Land heats and cools faster than water, affecting local climates; oceans moderate coastal climates.

Biomes

Biome: A major ecological community type defined by climate and dominant vegetation.
Importance: Biomes help classify regions of the world based on ecological similarities.

Tropical Rain Forest: High rainfall, high biodiversity.
Subtropical Desert: Low rainfall, extreme temperatures.
Temperate Grassland: Moderate rainfall, dominated by grasses.
Temperate Forest: Moderate climate, deciduous trees.
Boreal Forest (Taiga): Cold, coniferous trees.
Arctic Tundra: Very cold, low biodiversity, permafrost.

Net Primary Productivity (NPP)

Definition: The rate at which plants and other producers convert solar energy to chemical energy, minus the energy used for respiration.
Formula: where GPP = Gross Primary Productivity, R = Respiration

Determinants of Biomes

Terrestrial Biomes: Determined by temperature, precipitation, and seasonality.
Aquatic Biomes: Determined by salinity, water depth, flow, and nutrient availability.

Zonation in Aquatic Environments

Photic Zone: Sunlit region where photosynthesis occurs.
Aphotic Zone: Region with little or no sunlight.
Benthic Zone: Bottom of a body of water.
Intertidal Zone: Area between high and low tide.

Water Flow and Nutrient Availability

Coastal Runoff: Brings nutrients from land to aquatic systems.
Ocean Upwelling: Deep, nutrient-rich water rises to the surface.
Lake Cycling: Seasonal turnover mixes nutrients in lakes.

Ch.51 - Population Ecology

Population ecology studies the dynamics of species populations and how these populations interact with the environment.

Population Thinking

Focuses on variation among individuals in a population and how this affects population dynamics.

Population Distribution

Range and Scale: The spatial extent and density of a population.
Distribution Patterns:
- Clumped: Individuals aggregate in patches (e.g., schools of fish).
- Random: Position of each individual is independent (e.g., wind-dispersed plants).
- Uniform: Evenly spaced due to competition (e.g., territorial birds).

Sampling Techniques

Quadrat Sampling: For immobile or slow-moving organisms (plants, corals).
Mark-Recapture: For mobile animals (birds, mammals).

Demographics

Age Structure: Proportion of individuals in different age groups.
Life Table: Summarizes survival and reproductive rates.
Survivorship Curves: Graphs showing the number of survivors at each age.

Fitness Trade-Offs and Population Dynamics

Fecundity: Number of offspring produced by an individual.
Life History: Traits that affect survival and reproduction.
Exponential Growth: Population increases under ideal conditions. where = population at time t, = initial population, = intrinsic rate of increase.

Density-Dependent and Independent Factors

Density-Dependent: Effects increase with population density (e.g., competition, disease).
Density-Independent: Effects not related to density (e.g., weather, natural disasters).

Carrying Capacity

Definition: Maximum population size an environment can sustain.
Overshoot: If population exceeds carrying capacity, resources become depleted, leading to population decline.

Interspecific vs. Intraspecific Interactions

Intraspecific: Interactions within a species (e.g., competition for mates).
Interspecific: Interactions between species (e.g., predation, competition).

Bottom-Up and Top-Down Control

Bottom-Up: Population size is controlled by resource availability.
Top-Down: Population size is controlled by predators or consumers.

Metapopulations

Definition: A group of spatially separated populations connected by dispersal.
Importance: Increases persistence of species in fragmented habitats.

Human Population Growth

Problems: Resource depletion, habitat loss, pollution.
Replacement Rate: Number of offspring needed per female to maintain population size (usually about 2.1).

Habitat Corridors

Example: Christmas Island corridors help maintain gene flow between populations.
Importance: Facilitate movement and reduce effects of habitat fragmentation.

Ch.52 - Community Ecology

Community ecology examines how populations of different species interact and form functional communities.

Community vs. Population

Community: All populations of different species in an area.
Population: Individuals of a single species in an area.

Fitness

Definition: The ability of an organism to survive and reproduce in its environment.

Species Interactions

Commensalism (+/0): One benefits, other unaffected.
Consumption (+/-): One benefits, other harmed (includes predation, herbivory, parasitism).
Competition (-/-): Both species are harmed by shared resource use.
Mutualism (+/+): Both species benefit.

Altruism

Definition: Behavior that benefits another at a cost to oneself.
Debate: True altruism is rare; often explained by kin selection or reciprocal benefits.

Effects of Competition and Niche

Symmetric Competition: Both species are equally affected.
Asymmetric Competition: One species is more negatively affected.
Fundamental Niche: Full range of conditions a species can use.
Realized Niche: Actual conditions used due to competition.
Example: Barnacle species with overlapping but distinct niches.
Character Displacement: Evolution of differences to reduce competition.

Categories of Consumption

Herbivory: Animals eat plants.
Predation: One organism kills and eats another.
Parasitism: Parasite lives on or in host, harming it.
Endoparasite: Lives inside host (e.g., tapeworm).
Ectoparasite: Lives on host surface (e.g., tick).
Parasitoid: Lays eggs in host; larvae consume host (e.g., wasps).

Survival Strategies

Constitutive Defenses: Always present (e.g., thorns, toxins).
Inducible Defenses: Produced in response to predators (e.g., chemical defenses in plants).
Mimicry:
- Müllerian: Two harmful species resemble each other.
- Batesian: Harmless species mimics harmful one.

Cheaters in Mutualisms

Definition: Organisms that exploit mutualistic relationships without reciprocating.
Example: Nectar robbers in plant-pollinator systems.

Community Attributes and Food Webs

Food Web: Network of feeding relationships.
Keystone Species: Species with disproportionate impact on community structure.
Trophic Cascade: Effects that cascade down through trophic levels.

Clements vs. Gleason Debate

Clements: Communities are stable, integrated units (climax community).
Gleason: Communities are loose assemblages of species with individual responses.

Disturbance and Succession

Disturbance: Event that changes community structure (e.g., fire, storm).
Disturbance Regime: Pattern and frequency of disturbances.
Succession: Sequence of community changes after disturbance.
Primary Succession: Occurs on newly formed surfaces (no soil).
Secondary Succession: Occurs where soil remains after disturbance.
Pioneering Species: First to colonize disturbed areas.
Facilitator: Species that make environment more suitable for others.
Inhibitor: Species that hinder establishment of others.
Tolerant: Species unaffected by presence of others.

Shannon Diversity Index

Definition: Measures species diversity in a community.
Formula: where = proportion of species i, S = total number of species.
Richness: Number of species.
Evenness: Relative abundance of species.
Pros: Accounts for both richness and evenness.
Cons: Sensitive to sample size and rare species.

Island Biogeography

Concept: Species richness on islands depends on island size and distance from mainland.
Key Points: Larger and closer islands have more species due to higher immigration and lower extinction rates.

Behavioral Ecology

Innate Behaviors: Genetically programmed, present at birth.
Learned Behaviors: Acquired through experience (e.g., Pavlov's dogs).
Intelligence: Measured by problem-solving, learning, and adaptability.

Summary Table: Types of Species Interactions

Interaction	Effect on Species 1	Effect on Species 2	Example
Commensalism	+	0	Barnacles on whales
Mutualism	+	+	Bees and flowers
Competition	-	-	Plants competing for light
Consumption	+	-	Wolf and deer

Additional info: Some explanations and examples have been expanded for clarity and completeness, and formulas have been provided for key ecological concepts.