Principles of Ecology Final

Exam 1:

1. Foundations of Ecology

  • Definition: Ecology = study of relationships between organisms and their environment.

    • Biology: the study of life

    • Economics: the study of how individuals and groups interact to make choices about the use and exchange of scarce resources

Key Influencers:

  • Ernst Haeckel: coined "ecology" from Greek oikos (house).

  • Rachel Carson: Silent Spring, ecological effects of pesticides.

  • Wangari Maathai: Greenbelt Movement, reforestation in Kenya.

  • Akira Miyawaki: microforests, high density of native plants in small area

Foundations:

  • Evolution and natural selection form foundation

  • Evolution: change in gene frequencies over time

Core Concepts:

  • Multidisciplinary fields involving biology, physics, chemistry, statistics, genetics, etc.

  • Human impacts (biodiversity loss, climate change) are now inseparable from ecological systems.

  • Systems: interconnected sets of elements that are coherently organized in a way that achieves something; digestive system, football team, etc.

  • Feedback loops:

    • Balancing (Negative): keeps a stock at a given value or within a range of values; opposes whatever direction of change is imposed on the system; an example is body temp, sweating to cool when it's hot and shivering to warm up when it's cold

    • Reinforcing (Positive): generates more input to a stock with increasing amounts (and less input with decreasing amounts); snowballing

  • Dynamic equilibrium: forward and reverse processes occur at the same rate, so the overall levels remain constant over time

2. Scientific Method in Ecology

  • Observe → Ask Questions → Hypothesize → Experiment → Collect Data → Analyze → Revise Hypothesis

  • Use of models: simplified systems to explain/predict ecological phenomena (e.g., niche models).

3. Levels of Ecological Organization

  • Organism: How it interacts with the environment.

  • Population: Size, structure, dynamics.

  • Community: Species interactions.

  • Ecosystem: Energy/nutrient flow.

  • Landscape: Spatial patterns.

  • Biosphere: Global processes.

4. Evolution as a Basis for Ecology

  • Ecology is medium we use to study environmental forces that drive evolution

  • Darwin & Wallace: Natural Selection — traits favorable to survival become more common.

    • Darwin: competition drives evolution; descent with modification

    • Wallace: environmental pressures drive evolution

  • Lamarck: individuals changed to meet environmental needs and passed acquired characteristics to offspring

  • Mendel: Inheritance patterns → Modern Synthesis = Evolution + Genetics.

    • Law of segregation – each individual has two alleles for each gene; a parent passes on one of these two alleles to their offspring.
      Law of independent assortment – alleles are transmitted independently to the gametes, i.e., having Y doesn’t mean have S

  • Hardy-Weinberg Equilibrium:

    • Predicts allele frequencies under no evolution.

    • Assumptions: random mating, no mutation, no migration, no natural selection, large population

5. Evolutionary Mechanisms

  • Special creationism: living things created to exactly suit particular niche

  • Blending Hypothesis

    • Offspring would have some intermediate level of a trait found in both parents. Tall parent + short parent = medium height offspring

  • Drives of Evolution: natural selection, genetic drift, gene flow, mutation

  • Natural Selection:

    • Adaptation to the environment.

      • Disruptive: Average phenotype less successful than the extremes; extremes more common

      • Stabilizing: Extreme phenotypes less successful than the average; average more common

      • Directional: Exceptional phenotype has greater survival and reproduction; population shifts in that direction

  • Genetic Drift: random change in allele frequency

    • Bottleneck: chance event kills/prevents reproduction in large amount of  population; loss of diversity

    • Founder effect: establishment of new population; loss of diversity

  • Gene Flow: movement of alleles between populations.

  • Mutation: new genetic variation.

  • Sexual Selection: traits for mating success.

  • Darwin’s postulates:

    • Variability: Individuals within a species vary

    • Heritability: Some variations passed to offspring

    • Adaptation: individuals vary in their ability to survive and reproduce

    • Selection: Most favorable traits in the environment are more likely to survive

  • Speciation:

    • Allopatric: split by vicariance and subject to selection

    • Sympatric: sub-population arises within parent population; genetically distinct species

  • Heritability: increases with increased VG

    • Equation: h2 = VG / (VG + VE)

    • If VG = 0, not heritable

6. Biogeography

  • Species Range:
    Fundamental: where it can live.

    • Realized: where it does live.

  • Factors: microclimate, dispersal, competition, barriers (e.g., Grand Canyon, Isthmus of Panama).

    • Dispersal: a process that can maintain gene flow between populations; permanent, one way movement of individuals from parent habitat somewhere else

    • Migration: regular, cyclical movement of a species through its environment

  • Vicariance: geographic separation → speciation; a process that disrupts gene flow

7. Island Biogeography (MacArthur & Wilson)

  • Equilibrium between immigration and extinction rates.

  • Influenced by island size (target effect) and distance (rescue effect).

  • Species-Area Curve: S=cAz

    • S = number of species, A = area, c = constant, z = slope of the line

8. Ecosystem Services

  • Ecosystem Services: Benefits ecosystems provide to humans.

    • Regulating (climate), provisioning (water), cultural, and supporting services.

  • Valuation Controversies: ethics of monetizing nature.

  • Term Project: With U.S. State Dept. — assign economic value to wildlife & wild spaces.

9. Population Genetics & Heritability

  • Phenotype = Genotype + Environment + Random Noise.

  • Heritability (h²) = genetic variance / total phenotypic variance.

    • High h² = strong genetic basis, low h² = more environmental influence.

  • Heritable traits:

    • Discrete: trait received as one of two distinct forms

    • Quantitative: trait has continuous distribution

10. Climate & Abiotic Factors

  • Milankovitch Cycles: affect long-term climate (eccentricity, precession, tilt)

    • Changes in earth’s movement on climate

    • Eccentricity - orbital shape (around sun)

    • Precession - axial rotation (towards sun)

    • Obliquity - axial tilt (towards sun)

  • Coriolis Effect & Ekman Transport: drive global wind/water patterns → gyres, upwelling.

    • Ekman Transport: water deflected 45° from wind direction; Each water layer transfers energy and is deflected 90° from wind’s direction

      • Gyres: circular motion in oceans

      • Upwelling: surface water pushed offshore, deeper water takes its place

    • Northern hemisphere deflects right

    • Southern hemisphere deflects left

  • Wind Pattern: heating warms air, air rises, air moves to poles, cooler air moves in, cooler air sinks, repeat

  • Soil formation = rock + rain + vegetation interactions.

11. Biomes

  • Defined by climate, soil, vegetation, and animal life

    • Climate: physical/chemical features of an environment

  • Terrestrial Biomes: tundra, taiga, temperate forest, grassland, desert, tropical rainforest, etc.

  • Marine Biomes: coral reefs, intertidal zones, pelagic and benthic zones.

12. Extinction

  • Background Extinction: normal rate (1-10 species/year).

  • Mass Extinction: 5 historical, humans driving a potential sixth.

  • Biodiversity Hotspots: areas with high endemism + high threat (e.g., California Floristic Province).

Exam 2:

13. Trade-offs, Homeostasis, and Metabolism

Trade-offs in Organismal Performance

  • Organisms face trade-offs between:

    • Fecundity (number and investment in offspring)

    • Growth (size, defense)

    • Longevity (lifespan)

  • Example: Eastern Fence Lizards show differences in energy intake (MEI) based on temperature and population origin.

Temperature and Performance

  • All organisms have a narrow temperature range where performance peaks.

  • Acclimation: short-term physiological adjustments.

  • Adaptation: long-term physiological/genetic changes.

  • Evolution: changes in allele frequencies over generations.

Homeostasis

  • The ability to maintain stable internal conditions.

  • Key concepts:

    • Ectotherm: heat from environment.

    • Endotherm: heat from internal metabolism.

    • Poikilotherm: variable body temperature.

    • Homeotherm: constant internal temperature.

    • Stenotherm: narrow thermal tolerance.

Heat Balance Equation:

HS = Hm ± Hcd ± Hcv ± Hr - He

  • Metabolism, conduction, convection, radiation, evaporation.

Mechanisms of Temperature Regulation

  1. Anatomy:

    • Insulation (fur, feathers, blubber)

    • Coloration

    • Counter-current heat exchange (rete mirabile)

    • Thermal inertia (whales)

  2. Physiology:

    • Bradycardia (diving reflex)

    • Vasoconstriction

    • Sweating / Evaporative cooling

  3. Behavior:

    • Basking, migration, hibernation

14. Water Balance and Temperature Trade-offs

Water Balance in Animals

  • Equation: Water = Wd + Wf + Wa – We – Ws

    • Ingestion, food metabolism, absorption vs. evaporation and secretion.

  • Adaptations include behavior, physiology, and habitat use.

Water Balance in Plants

  • Transpiration: water loss through stomata.

  • Evapotranspiration: balance between water gain and environmental loss.

  • Trade-off: water conservation vs. photosynthesis efficiency.

  • Potential Evapotranspiration (PET): atmospheric demand for water.

15. Metabolism and Energy Use

Photosynthesis

  • CO₂ + H₂O → CH₂O + O₂ (uses light energy)

  • Reduces carbon; stores energy in chemical bonds.

Respiration

  • Opposite of photosynthesis.

  • Oxidizes sugars to release stored energy.

Metabolic Strategies

  • Photosynthetic autotrophs (e.g., plants, cyanobacteria)

  • Chemosynthetic autotrophs (e.g., sulfur bacteria)

  • Heterotrophs (e.g., animals, fungi)

Photosynthetic Pathways

  • C3: common, less efficient in hot/dry areas.

  • C4: spatial separation of fixation and synthesis (e.g., corn).

  • CAM: temporal separation (e.g., cacti), open stomata at night.

16. Energy Limitation and Optimal Foraging

Energy Trade-offs

  • Even abundant resources can’t be fully utilized due to physiological constraints.

  • Pmax: max photosynthesis rate.

  • Isat: light level needed to reach Pmax.

Animal Functional Response

  • Type I: linear increase then plateau (e.g., filter feeders)

  • Type II: decelerating intake (common)

  • Type III: sigmoidal curve; low response at low prey density.

Optimal Foraging Theory (OFT)

  • Predicts how organisms maximize net energy gain.

  • Trade-offs: foraging time vs. handling time.

  • Applied to both animals and plants (e.g., root/shoot allocation).

17. Life History Strategies

Life Cycles

  • Asexual vs. Sexual reproduction.

  • Types: Gametic (humans), Zygotic (fungi), Sporic (ferns).

Key Traits

  • Age at maturity, number/size of offspring, lifespan.

  • Trade-offs: investing in current vs. future reproduction.

r/K Selection

Trait

r-selected

K-selected

Development

Fast

Slow

Reproduction

Early

Delayed

Offspring size

Small

Large

Quantity

Many

Few

Environment

Unpredictable

Stable

Plant Life Strategies (Grime’s Model)

  • Ruderals: tolerate disturbance.

  • Stress-tolerators: conserve in poor conditions.

  • Competitors: thrive in resource-rich, stable areas.

18. Population Ecology

Population Growth Models

  • Geometric growth: pulsed reproduction.

  • Exponential growth: continuous reproduction.

  • Nt = N₀λᵗ (geometric), dN/dt = rN (exponential)

  • Logistic growth: includes carrying capacity K.

    • dN/dt = rN(1 - N/K)

Density Factors

  • Density-dependent: effects intensify as population grows (e.g., disease, competition).

  • Density-independent: unrelated to density (e.g., weather).

19. Distribution and Abundance

Factors Influencing Distribution

  • Direct environment (light, temp)

  • Indirect effects (predators, symbiosis)

  • Microclimate

  • Biotic interactions (competition)

Fundamental vs. Realized Niche

  • Fundamental: potential range.

  • Realized: actual due to competition, predation.

Patterns of Distribution

  • Random, Regular, Clumped

    • Random: organisms indifferent to other individuals and environment

    • Regular: organisms antagonistic with other individuals and resources are depleted

    • Clumped: organisms attracted to other individuals or individuals attracted to a common resource

  • Small-scale vs. large-scale patterns.

Abundance

  • Inverse relationship between body size and population density.

20. Dispersal and Metapopulations

Dispersal Types

  • Range expansion (e.g., invasive species)

  • Within-range movement

  • Metapopulation dispersal: multiple subpopulations connected by migration.

Source-Sink Dynamics

  • Source: high-quality habitat, exports individuals.

  • Sink: poor-quality, needs immigration to persist.

21. Competition

Types

  • Intraspecific: within the same species.

  • Interspecific: between different species.

Lotka-Volterra Competition Model

  • Adds competition coefficients (α) to logistic growth.

  • Predicts outcomes: coexistence or competitive exclusion.

Niche Partitioning

  • Species evolve to use different resources to reduce overlap.

  • Examples: warblers, barnacles, Anolis lizards.

22. Consumer-Resource Interactions

Types of Exploitation

  • Herbivory, Predation, Parasitism, Amensalism

Predator-Prey Cycles

  • Modeled using Lotka-Volterra:

    • dNh/dt = rhNh – pNhNp (prey)

    • dNp/dt = cpNhNp – dpNp (predator)

Stabilizing Factors

  • Refuges, alternative prey, time lags, predator inefficiency.

Refuges

  • Space, numbers, morphology, size, behavior.

23. Community Ecology

Community Diversity

  • Species richness: number of species.

  • Evenness: relative abundance of each.

Diversity Indices

  • Shannon-Wiener Index: accounts for richness & evenness.

  • Simpson’s Index: probability two individuals are same species.

Rank-Abundance Curves

  • Visualize abundance and evenness.

  • Flat slope = high evenness, steep = dominance by few species.

Environmental Complexity

  • More complex environments → more niches → greater diversity.

Exam 3/Final:

24. Ecological Disturbance

  • Definition: Short-term intense event causing major ecosystem changes (e.g., fire, storms).

  • Levels Affected: Primarily communities.

  • Types:

    • Natural (e.g., wildfires)

    • Anthropogenic (e.g., pollution, habitat destruction)

    • Scale varies from small to large.

25. Intermediate Disturbance Hypothesis

  • Joseph Connell (1975): Species diversity is highest at intermediate levels of disturbance.

    • High disturbance → fast-growing “weedy” (r-selected) species dominate.

    • Low disturbance → competitively dominant (K-selected) species take over.

    • Intermediate → balance of colonizers and competitors.

  • Sousa (1979): Supported this with marine boulder algae/invertebrate studies.

26. Succession

  • Definition: Gradual change in community composition over time following disturbance.

  • Types:

    • Primary: Development on new substrate (e.g., lava, glacier retreat).

    • Secondary: After disturbance but soil remains (e.g., fire).

  • Pioneer species: first species to colonize open area; r-selected, fast-growing, nitrogen-fixing.

  • Climax species: K-selected, slow-growing, stable competitors.

  • Intermediate species: Blend of traits.

27. Successional Models

  • Facilitation: Early species prepare habitat for others.

  • Inhibition: Early species prevent others until they die.

  • Tolerance: Any species that can survive conditions may dominate.

  • Autogenic succession: driven by organisms.

  • Allogenic succession: driven by abiotic factors.

28. Stability & Disturbance Response

  • Resistance: Ability to withstand disturbance.

  • Resilience: Ability to recover after disturbance; a measure of a system’s ability to survive and persist within a variable environment

  • Phase Shift: Permanent change due to long-term pressure (e.g., Kaneohe Bay algae replacing coral); underlying conditions change community composition

  • Altered Stable State: Community changes after keystone species removal; may return if conditions reverse.

29. Ecosystem Ecology

  • Focus: Energy flow & nutrient cycling in systems of interacting biotic and abiotic components.

  • Systems Approach: Understand the system as a whole via studying its parts.

30. Ecosystem Energetics

  • GPP (Gross Primary Productivity): Total energy captured.

  • R (Respiration): Energy used by producers.

  • NPP (Net Primary Productivity): Energy available to herbivores.
    NPP=GPP−R

  • Energy Pyramids: Visualize energy loss at each trophic level.

    • Inverted pyramids in oceans (fast turnover of phytoplankton).

31. Symbiosis and Interactions

  • Symbiosis: Long-term close interactions between species.

  • Commensalism: One benefits, the other unaffected.

    • Types:

      • Phoresy (transport): shark and remora or dog and spiked seed pods

      • Inquilinism (housing): squirrel in tree or plants growing on tree

      • Metabiosis (afterlife resource use): crab uses sea snail shell

  • Mutualism: Both benefit.

    • Resource–Resource (e.g., mycorrhizae, coral-zooxanthellae)

    • Resource–Service (e.g., pollination)

    • Service–Service (e.g., clownfish & anemone)

    • Can be obligate (required) or facultative (optional)

      • Dispersive: one disperses the other

      • Defensive: one protects the other

      • Trophic: one provides food

32. Sustainability

  • Definition: Meeting current needs without compromising future generations.

  • Renewable Resources: Replenishable on human time scale.

  • Nonrenewable: Finite, slow to replenish.

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

33. Urban Reforestation & Restoration Ecology

  • Restoration Ecology: Active human effort to restore degraded habitats.

  • Urban Reforestation: Planting trees in urban areas for:

    • Air quality

    • Urban heat island mitigation

    • Noise reduction

    • Wildlife habitat

    • Food and aesthetics

  • Challenges:

    • Land competition

    • Maintenance

    • “Lollipop trees”: trap ozone beneath trees

    • Native vs. non-native plants

34. Innovative Solutions:

  • Miyawaki Method / Microforests:

    • Dense native planting in small urban plots.

    • 200 years of forest growth simulated in 20 years.

35. Ecosystem Services

  • Definition: Benefits humans gain from ecosystems.

    • Provisioning: Food, water

    • Regulating: Climate, air

    • Cultural: Recreation, aesthetics

    • Supporting: Nutrient cycling, soil formation

  • Case Study – Ascot Hills Park:

    • Value: $110,664–$2.9M/year

    • Used for reforestation and restoration studies.

36. Global Conservation Efforts

  • IPBES (Intergovernmental Platform on Biodiversity and Ecosystem Services):

    • Established 2012 to link science and policy.

    • Provides: Assessments, policy support, capacity building, outreach.