Ecology, Ecosystems, and Conservation Biology: Study Notes for BIOL 107 Exam 1

Ecology: Introduction and Scope

Definition and Significance of Ecology

• Ecology is the scientific study of the interactions between organisms and their environment, encompassing both biotic (living) and abiotic (non-living) components.

• Significance: Ecology helps us understand the distribution and abundance of organisms, the functioning of ecosystems, and the impact of human activities on the natural world.

• Applications include endangered species recovery, ecosystem management, and building sustainable societies.

Levels of Ecological Study

• Organismal Ecology: Focuses on individual organisms' adaptations to their environment.

• Population Ecology: Examines groups of individuals of the same species and factors affecting their size and distribution.

• Community Ecology: Studies interactions among species in a community.

• Ecosystem Ecology: Investigates energy flow and nutrient cycling among biotic and abiotic components.

• Landscape and Global Ecology: Explores patterns and processes across large spatial scales.

Factors Limiting Species Distribution

• Dispersal: Movement of individuals away from their origin or from high population density areas.

• Biotic Factors: Interactions with other organisms (e.g., predation, competition, disease).

• Abiotic Factors: Physical and chemical factors (e.g., temperature, water, sunlight, soil, climate).

Population Ecology

Population Characteristics

• Population: A group of individuals of the same species living in the same area at the same time.

• Population Size: Determined by direct counts, sampling, or mark-recapture methods.

• Density: Number of individuals per unit area or volume.

• Dispersion Patterns:

  • Clumped: Individuals aggregate in patches (e.g., resource availability).

  • Uniform: Evenly spaced, often due to territoriality.

  • Random: Unpredictable spacing, not strongly influenced by interactions.

Demographics and Life Tables

• Life Table: Summarizes survival and reproductive rates of individuals in specific age groups.

• Cohort: A group of individuals of the same age, followed through their lifespans.

• Life tables often focus on females, as they determine reproductive output.

• Reproductive Output: Average number of female offspring produced per female in each age group.

• Survivorship Curves:

  • Type I: High survival early/midlife, steep decline in old age (e.g., humans).

  • Type II: Constant death rate (e.g., squirrels).

  • Type III: High death rates for young, survivors live long (e.g., oysters).

Population Growth Models

• Exponential Growth: Population increases under ideal conditions.

  • Equation: $\frac{dN}{dt} = rN$

  • N = population size, r = intrinsic rate of increase

• Logistic Growth: Population growth slows as it approaches carrying capacity (K).

  • Equation: $\frac{dN}{dt} = rN \left(1 - \frac{N}{K}\right)$

  • K = carrying capacity (maximum population size environment can support)

• Population growth is greatest at intermediate population sizes (N ≈ K/2).

• Deviations: Overshoot, boom-bust cycles (e.g., Daphnia, moose and wolves).

Population Regulation

• Density-Dependent Factors: Intensify as population increases (e.g., competition, predation, disease).

• Density-Independent Factors: Affect populations regardless of size (e.g., weather, natural disasters).

• Biotic and abiotic factors often interact to regulate populations.

Life History Strategies

• Life History: Traits affecting an organism's schedule of reproduction and survival.

• r-selection: High reproductive rate, many small offspring, little parental care (e.g., insects, weeds).

• K-selection: Few large offspring, high parental care, stable environments (e.g., elephants, humans).

• Trade-offs: Number vs. size of offspring, parental survival, reproductive timing.

Metapopulations

• Metapopulation: A group of spatially separated populations linked by dispersal.

• Local populations may go extinct and be recolonized, maintaining overall persistence.

Community Ecology

Community Structure and Diversity

• Community: An assemblage of populations of different species living close enough for interaction.

• Key characteristics:

  • Species Diversity: Includes species richness (number of species) and relative abundance (proportion of each species).

  • Measured using the Shannon Diversity Index: $H' = -\sum (p_i \ln p_i)$, where $p_i$ is the proportion of species i.

  • Higher diversity often leads to greater community stability.

• Trophic Structure: Feeding relationships among organisms (food chains and food webs).

Species Interactions

• Competition:

  • Interspecific (between species) vs. intraspecific (within species).

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

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

  • Resource Partitioning: Differentiation of niches to reduce competition.

  • Fundamental vs. realized niche: Potential vs. actual conditions used.

  • Character Displacement: Tendency for characteristics to diverge in sympatric populations (living together) but not in allopatric (separate) populations.

• Exploitation:

  • Predation: Adaptations include camouflage, warning coloration, mimicry (Batesian and Müllerian).

  • Herbivory: Plant defenses and herbivore adaptations.

  • Parasitism: Parasite adaptations for exploiting hosts.

• Positive Interactions:

  • Mutualism: Both species benefit.

  • Commensalism: One benefits, other unaffected.

Species with Large Impacts

• Foundation/Dominant Species: High abundance or biomass, strong influence on community structure.

• Keystone Species: Exert strong control despite low abundance (e.g., sea otters).

• Ecosystem Engineers: Modify the environment (e.g., beavers).

• Invasive Species: Non-native, often disrupt community structure.

Community Dynamics

• Bottom-up Control: Influence of lower trophic levels on higher ones.

• Top-down Control (Trophic Cascades): Predators control community structure.

• Biomanipulation: Altering community structure by adding/removing species.

• Disturbance: Events that change communities (e.g., fire, storms).

• Intermediate Disturbance Hypothesis: Moderate disturbance fosters highest diversity.

• Succession:

  • Primary: Begins in lifeless areas (e.g., after lava flow).

  • Secondary: Occurs where soil remains (e.g., after fire).

Biogeographic Factors

• Latitudinal Gradients: Species richness increases toward the equator due to evolutionary history and climate.

• Species-Area Curve: Larger areas support more species.

• Island Equilibrium Model: Species richness on islands depends on island size and distance from mainland.

Ecosystem Ecology

Energy and Mass Flow in Ecosystems

• Ecosystem: All organisms in a community plus the abiotic factors with which they interact.

• Autotrophs (producers) convert solar energy to chemical energy; heterotrophs (consumers) depend on autotrophs.

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.

• Second Law of Thermodynamics: Every energy transfer increases entropy; energy conversions are inefficient.

• Law of Conservation of Mass: Matter cannot be created or destroyed.

• Energy flows through ecosystems (not recycled); nutrients cycle.

Primary Production

• Gross Primary Production (GPP): Total primary energy assimilated by producers.

• Net Primary Production (NPP): GPP minus energy used by producers for respiration.

  • Equation: $NPP = GPP - R_a$

• NPP varies among ecosystems; limited by light and nutrients in aquatic systems, and by temperature, moisture, and nutrients in terrestrial systems.

Secondary Production and Energy Transfer

• Secondary Production: Amount of chemical energy in consumers' food converted to new biomass.

• Production Efficiency: Fraction of energy stored in food not used for respiration.

• Trophic Efficiency: Percentage of production transferred from one trophic level to the next (typically 10%).

• Energy Pyramid: Shows energy loss at each trophic level.

• Biomass Pyramid: Depicts the amount of living organic matter at each trophic level.

• Implication: More energy is available at lower trophic levels; vegetarian diets are more energy-efficient.

Biogeochemical Cycles

• Water Cycle: Driven by evaporation, condensation, precipitation, and runoff.

• Carbon Cycle: Involves photosynthesis, respiration, decomposition, and fossil fuel combustion.

• Nitrogen Cycle: Key processes include nitrogen fixation, nitrification, assimilation, ammonification, and denitrification.

• Phosphorus Cycle: Involves weathering of rocks, uptake by organisms, and return via decomposition.

• Decomposition rates affect nutrient cycling; influenced by temperature and moisture.

Human Impacts and Restoration Ecology

• Human activities (e.g., deforestation, pollution) disrupt chemical cycles.

• Restoration ecology aims to restore degraded ecosystems through habitat restoration, bioremediation (using organisms to detoxify), and biological augmentation (adding essential materials).

Conservation Biology and Global Change

Biodiversity and Its Importance

• Biodiversity includes:

  • Species diversity (variety of species)

  • Genetic diversity (variation within species)

  • Ecosystem diversity (variety of ecosystems)

• Biodiversity provides ecosystem services (medicine, pollination, food) and is vital for human welfare.

Threats to Biodiversity

• Major threats: Habitat loss, introduced species, overharvesting, climate change.

• Examples: Deforestation, invasive zebra mussels, overfishing, global warming.

Conservation Strategies

• Small-Population Approach: Focuses on populations at risk of extinction due to small size (e.g., extinction vortex).

• Declining-Population Approach: Identifies and addresses causes of population decline.

• Effective Population Size: Number of individuals contributing genes to the next generation; important for genetic diversity.

• Conservation efforts include protecting habitat, creating corridors, and managing reserves (e.g., biodiversity hotspots, zoned reserves).

Landscape and Ecosystem Conservation

• Landscape features (edges, corridors) influence biodiversity.

• Natural reserves must be integrated into larger landscapes to be effective.

Global Change and Sustainable Development

• Greenhouse Effect: Warming of Earth due to atmospheric gases trapping heat.

• Global Warming: Long-term rise in Earth's average temperature; evidence includes melting ice, rising sea levels.

• Human population growth and ecological footprint affect Earth's carrying capacity.

• Sustainable Development: Using resources in ways that do not compromise future generations' ability to meet their needs.

Table: Comparison of r- and K-Selected Species

Characteristic	r-Selected Species	K-Selected Species
Offspring Number	Many	Few
Offspring Size	Small	Large
Parental Care	Little/None	Extensive
Survivorship Curve	Type III	Type I
Environment	Unstable	Stable
Examples	Weeds, insects	Humans, elephants

Table: Major Biogeochemical Cycles

Cycle	Main Processes	Major Reservoirs
Water	Evaporation, precipitation, runoff	Oceans, atmosphere, groundwater
Carbon	Photosynthesis, respiration, combustion	Atmosphere, fossil fuels, biomass
Nitrogen	Fixation, nitrification, denitrification	Atmosphere, soil, biomass
Phosphorus	Weathering, uptake, decomposition	Rocks, soil, biomass

Additional info: These notes synthesize and expand upon the provided outlines and study guide, integrating key definitions, examples, and equations for exam preparation in college-level ecology and conservation biology.