Ecology and Conservation Biology: Study Guide for BIO 311D (Module 4)

Big Idea IV – Ecology

Introduction to Ecology and Its Subdisciplines

Ecology is the scientific study of the interactions between organisms and their environment. It encompasses multiple levels of biological organization and investigates how these interactions shape the distribution, abundance, and adaptations of organisms.

• Physiological Ecology: Examines how organisms adapt physiologically to environmental conditions (e.g., temperature, water, salinity).

• Population Ecology: Focuses on populations of a single species, analyzing factors that affect population size, density, and growth.

• Community Ecology: Studies interactions among different species living in the same area and how these interactions influence community structure and diversity.

• Ecosystem Ecology: Investigates energy flow and nutrient cycling among biotic (living) and abiotic (nonliving) components of ecosystems.

Levels of Ecological Organization:

• Organismal: Individual adaptations to the environment.

• Population: Groups of individuals of the same species.

• Community: Assemblages of different species.

• Ecosystem: Communities plus their physical environment.

• Biosphere: All ecosystems on Earth.

Physical Factors and Climate

Physical processes such as solar radiation, Earth's tilt, and atmospheric circulation create variations in climate at global and local scales. These variations drive the formation of different biomes and influence the adaptations of organisms.

• Edge Effects: Changes in population or community structures at the boundary of two habitats.

• Key Climate Factors: Latitude, altitude, ocean currents, and topography.

• Biomes: Major life zones characterized by vegetation type (terrestrial) or physical environment (aquatic). Examples include tropical rainforests, deserts, tundra, and aquatic biomes like lakes and oceans.

• Photic vs. Aphotic Zones: In aquatic systems, the photic zone receives sufficient light for photosynthesis, while the aphotic zone does not.

Species Distribution and Adaptations

• Limiting Factors: Both biotic (e.g., competition, predation) and abiotic (e.g., temperature, water) factors can restrict species distributions.

• Physiological Adaptations: Examples include antifreeze proteins in polar fish or water conservation in desert plants.

• Climographs: Graphical representations of climate data (temperature and precipitation) used to compare biomes.

Population Ecology

Population Dynamics and Growth Models

Populations are groups of individuals of the same species living in a defined area. Their size and distribution change over time due to births, deaths, immigration, and emigration.

• Population Characteristics: Density (number per unit area), dispersion (pattern of spacing), and demographics (age structure, sex ratio).

• Estimating Population Size: Methods include direct counts, mark-recapture, and sampling plots.

• Dispersion Patterns: Clumped, uniform, or random, often reflecting resource distribution or social interactions.

Population Growth Models

• Exponential Growth: Occurs under ideal conditions; population increases by a constant proportion. Equation: $\frac{dN}{dt} = rN$

• Logistic Growth: Incorporates carrying capacity (K), the maximum population size the environment can support. Equation: $\frac{dN}{dt} = rN \left(1 - \frac{N}{K}\right)$

• Carrying Capacity (K): Can be exceeded temporarily, but leads to resource depletion and population decline.

Regulation of Population Size

• 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).

• Survivorship Curves: Graphs showing the proportion of individuals surviving at each age (Type I, II, III).

• Life History Strategies: r-selected species (high reproduction, low survival) vs. K-selected species (low reproduction, high survival).

• Ecological Footprint: Measure of human demand on Earth's ecosystems.

Community Ecology

Species Interactions and Community Structure

Communities are shaped by interactions among species, which influence population dynamics and community composition.

• Types of Interspecific Interactions:

  • Predation: One species kills and eats another (e.g., lion and zebra).

  • Parasitism: One benefits, one is harmed (e.g., tapeworm in mammals).

  • Competition: Both species are harmed by shared resource use.

  • Mutualism: Both benefit (e.g., bees and flowers).

  • Commensalism: One benefits, other unaffected (e.g., barnacles on whales).

• Competitive Exclusion Principle: Two species competing for the same resource cannot coexist indefinitely.

• Ecological Niche: The sum of a species' use of biotic and abiotic resources.

• Fundamental vs. Realized Niche: Fundamental is the potential niche; realized is the actual niche occupied.

• Character Displacement & Resource Partitioning: Evolutionary changes that reduce competition, allowing coexistence.

• Food Chains vs. Food Webs: Food chains are linear; food webs are interconnected networks of feeding relationships.

• Trophic Levels: Producers, primary consumers, secondary consumers, etc.

• 10% Rule: Only about 10% of energy is transferred from one trophic level to the next.

Species Role	Description	Example
Foundation Species	Have large effects by virtue of their abundance or biomass	Coral in coral reefs
Keystone Species	Exert strong control despite low abundance	Sea otters in kelp forests
Ecosystem Engineers	Modify the environment	Beavers building dams

• Bottom-Up vs. Top-Down Control: Bottom-up: resources control community structure; top-down: predators control structure. Both models can apply depending on the ecosystem.

• Disturbance and Succession: Disturbances (e.g., fire, storms) can reset communities, leading to primary succession (on new substrates) or secondary succession (after disturbance in existing communities). Pioneer species are the first to colonize disturbed areas.

Ecosystem Ecology

Energy Flow and Nutrient Cycling

Energy flows through ecosystems in one direction, while nutrients cycle between biotic and abiotic components.

• Energy Flow: Sunlight → Producers → Consumers → Decomposers. Energy is lost as heat at each step.

• Why Constant Input is Needed: Energy cannot be recycled; ecosystems require continuous energy input.

• Biomass Pyramids: Show the decrease in biomass at higher trophic levels due to energy loss.

• Limiting Factors: Light, nutrients (e.g., nitrogen, phosphorus) in aquatic and terrestrial systems.

• Decomposers and Detritivores: Break down dead organic matter, recycling nutrients.

Term	Definition
Gross Primary Production (GPP)	Total energy captured by producers
Net Primary Production (NPP)	GPP minus energy used by producers for respiration
Net Ecosystem Production (NEP)	Net accumulation of energy in an ecosystem

• Biogeochemical Cycles: Movement of elements like water, carbon, and nitrogen through ecosystems.

Cycle	Main Processes
Water	Evaporation, condensation, precipitation, runoff
Carbon	Photosynthesis, respiration, combustion
Nitrogen	Nitrogen fixation, nitrification, assimilation, denitrification

• Human Impacts: Eutrophication (nutrient enrichment), dead zones, biological magnification (toxin accumulation in food chains).

Conservation Biology and Global Change

Threats to Biodiversity and Conservation Strategies

Human activities have accelerated species extinction and disrupted ecosystems. Conservation biology seeks to understand and counteract these threats.

• Major Threats: Habitat destruction, fragmentation, pollution, overexploitation, invasive species, climate change.

• Biodiversity: Includes genetic, species, and ecosystem diversity.

• Minimum Viable Population (MVP): The smallest population size needed for a species to survive long-term.

• Extinction Vortex: A downward spiral of population decline due to inbreeding and genetic drift.

• Biological Magnification: Increase in concentration of toxins at higher trophic levels (e.g., DDT in birds of prey).

• Movement Corridors: Strips of habitat connecting isolated populations; can aid gene flow but also spread disease.

• Biodiversity Hotspots: Areas with high species richness and endemism, prioritized for conservation.

• Conservation Success: Example: Recovery of the American bald eagle through habitat protection and banning DDT.

• Global Climate Change: Increased atmospheric CO2 leads to higher global temperatures, affecting species distributions, phenology, and ecosystem function.

Summary Table: Levels of Biodiversity

Level	Description	Example
Genetic	Variation within and between populations	Different alleles in cheetah populations
Species	Number of species in an area	Bird species diversity in the Amazon
Ecosystem	Variety of ecosystems in a region	Forests, wetlands, grasslands in a landscape

Conservation Biology: The integrated study of ecology, genetics, evolution, and social sciences to protect and restore biodiversity.

Application: Conservation biology applies ecological principles to real-world problems, such as designing reserves, restoring habitats, and mitigating climate change impacts.

Additional info: This guide covers core concepts in ecology and conservation biology, including population and community dynamics, energy flow, nutrient cycling, and human impacts on ecosystems. Students should be able to apply these concepts to analyze ecological data, interpret graphs (e.g., climographs, survivorship curves), and evaluate conservation strategies.