Midterm 4:

Comprehensive Study Guide for Ecology, Behavioral Ecology, and Population Ecology

Chapter 49: Introduction to Ecology

Levels of Ecological Study

1. Organismal Ecology - Study of morphological, physiological, and behavioral adaptations that help organisms survive.

2. Population Ecology - Examines changes in population size and distribution over time.

3. Community Ecology - Investigates species interactions, including predation, parasitism, and competition.

4. Ecosystem Ecology - Studies how nutrients and energy move through organisms and the environment.

5. Global Ecology - Examines large-scale effects of human activities on the biosphere.

Abiotic and Biotic Factors

• Abiotic factors: Non-living environmental factors (temperature, moisture, sunlight, wind).

• Biotic factors: Interactions with other organisms (competition, predation, parasitism).

• Niche: The range of conditions a species can tolerate and the resources it utilizes.

• Dispersal: Movement of organisms from their birth site to another location.

Climate and Biomes

• Weather vs. Climate: Weather is short-term atmospheric conditions, while climate is long-term patterns.

• Earth’s Tilt and Seasonality: The Earth's tilt (23.5°) causes seasonal variation in temperature and daylight hours.

• Hadley Cells: Global air circulation patterns that create tropical rainforests and deserts.

• Coriolis Effect: The deflection of wind and ocean currents due to Earth’s rotation, causing clockwise circulation in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

• Gyres: Large-scale ocean current systems that redistribute heat across the globe.

• Rain Shadows: Dry areas on the leeward side of mountains due to moisture loss from ascending air.

• Oceanic Zones:

  • Intertidal Zone: Area between high and low tide.

  • Neritic Zone: Coastal waters, often rich in nutrients and biodiversity.

  • Oceanic Zone: Open ocean, divided into photic and aphotic zones.

  • Benthic Zone: Ocean floor, home to detritus-feeding organisms.

• Lake Zones:

  • Littoral Zone: Shallow waters near the shore, supporting rooted plants.

  • Limnetic Zone: Open water receiving enough sunlight for photosynthesis.

  • Photic Zone: Sunlit layer where photosynthesis occurs.

  • Aphotic Zone: Deeper water lacking sufficient light for photosynthesis.

  • Benthic Zone: Bottom of the lake, home to decomposers.

Climate Change and Its Study

• Human Impact: CO₂ emissions and deforestation contribute to global climate change.

• Methods to Study Climate Change:

  1. Simulation Studies: Computer models predicting climate patterns.

  2. Observational Studies: Long-term monitoring of climate variables.

  3. Historical Studies: Examining climate patterns from past geological records.

  4. Experimental Studies: Manipulating environmental conditions to observe responses.

• Effects of Climate Change:

  • Rising temperatures and shifting weather patterns.

  • Changes in species distributions and ecosystem functions.

  • Increased frequency of extreme weather events.

Chapter 50: Behavioral Ecology

Proximate vs. Ultimate Causes

• Proximate (Mechanistic) Causes: How a behavior occurs (e.g., hormones, neural activity).

• Ultimate (Evolutionary) Causes: Why a behavior exists (e.g., evolutionary advantage).

Optimal Foraging

• Organisms maximize food intake while minimizing effort and risk.

• Example: Cuttlefish choose prey based on number, size, and quality.

Mating Systems & Sexual Selection

• Monogamy: One mate per lifetime (e.g., bald eagles).

• Polygamy: One individual has multiple mates (e.g., some bird and mammal species).

• Promiscuity: Multiple mates with no long-term bonds (e.g., cuttlefish).

• Sexual Selection:

  • Intersexual selection: Choosing a mate based on traits.

  • Intrasexual selection: Competition among individuals for mates.

Communication

• Signal: Any information-transmitting behavior.

• Example: Honeybee waggle dance to indicate food sources.

• Deceptive Communication: Some species evolve to deceive others (e.g., hognose snakes playing dead).

Altruism and Cooperation

• Hamilton's Rule: Altruistic behavior is favored when Br > C.

• Kin Selection: Altruism benefits relatives, increasing indirect fitness.

• Reciprocal Altruism: Helping others with the expectation of future benefits.

Chapter 51: Population Ecology

Population Characteristics

• Population: Group of the same species in the same area.

• Population Ecology: Study of population changes and factors influencing them.

• Density and Distribution:

  • Clumped: Grouped around resources.

  • Uniform: Evenly spaced due to territorial behavior.

  • Random: No predictable pattern.

• Metapopulation: A network of populations linked by migration.

Demography & Life History

• Demography: Study of population size and structure over time.

• Life Tables: Summarize survival and reproduction across age classes.

• Survivorship Curves:

  1. Type I: High survival until old age (e.g., humans).

  2. Type II: Steady death rate (e.g., birds).

  3. Type III: High early mortality (e.g., fish, plants).

Population Growth Models

• Exponential Growth:

  • Formula:

  • = population size, = per capita rate of increase, = time interval

  • Occurs when resources are unlimited (J-shaped curve).

• Logistic Growth:

  • Formula:

  • = carrying capacity, = population size

  • Growth slows as population nears (S-shaped curve).

Population Dynamics & Human Impact

• Overshoot & Crash: Populations may exceed carrying capacity, leading to decline.

• Population Cycles: Predator-prey relationships can cause fluctuations.

• Age Pyramids: Show population structure and predict growth trends.

• Human Population Growth: Exponential growth but slowing due to lower birth rates.

Key Takeaways

1. Ecology operates at multiple levels, from organisms to the biosphere.

2. Behavioral ecology explains how and why organisms act in certain ways.

3. Population ecology focuses on changes in population size and structure over time.

4. Human activity significantly impacts ecosystems and global biodiversity.

Ecosystems and Global Ecology Study Guide

I. Global Cycles of Energy and Nutrients

Key Points:

• The biosphere is the global ecological system integrating all living beings and their relationships with the environment.

• Humans now drive changes in global cycles.

• Human activities:

  • Accelerate energy use

  • Alter habitats

  • Disrupt nutrient cycles

II. Energy Flow in Ecosystems

A. Efficiency of Autotrophs

• Autotrophs (primary producers): Organisms that synthesize their own food using sunlight or chemical energy.

• Only 0.8% of sunlight is used by plants (vs. 22% in solar panels).

• 45% of GPP is used for new biomass; the rest is lost.

• Efficiency limits:

  • Photopigments absorb only some wavelengths.

  • Photosynthesis slows in winter.

  • Dry conditions halt photosynthesis.

B. Primary Productivity

• Gross Primary Productivity (GPP): Total chemical energy produced by autotrophs.

• Net Primary Productivity (NPP): Energy available for growth and reproduction.

  • Formula: NPP = GPP - Respiration (R)

• Biomass: Stored energy in organic material.

C. NPP Across Biomes

• Biome: A large naturally occurring community of flora and fauna occupying a major habitat.

• Low NPP: Deserts, poles, open oceans.

• High NPP: Tropical forests, coral reefs.

• Largest contributors:

  • Tropical forests → High productivity, moderate area.

  • Oceans → Low productivity, vast area.

  • Coral reefs → Very high productivity, small area.

III. Trophic Levels and Food Chains/Webs

A. Food Chains

• Food chain: A linear sequence of organisms through which nutrients and energy pass as one organism eats another.

• Energy transfer:

  • Primary producers → Primary consumers → Secondary consumers → Tertiary consumers

• Types:

  • Grazing food chain: Herbivores & their predators.

  • Decomposer food chain: Organisms feeding on detritus.

B. Food Webs

• Food web: A network of interconnected food chains showing complex feeding relationships.

• More realistic than food chains.

• Food webs summarize how energy moves through an ecosystem by illustrating complex feeding interactions among organisms.

IV. Energy and Nutrient Cycling

A. Energy Flow vs. Nutrient Cycling

• Energy flow: The transfer of energy from one organism to another, eventually dissipating as heat.

• Nutrient cycling: The movement of chemical elements through the ecosystem.

• Trophic levels:

  • Primary consumers → Secondary consumers → Tertiary consumers → Decomposers

B. Energy Transfer Efficiency

• Pyramid of productivity: A graphical representation of energy transfer through trophic levels.

  • Only ~10% energy transfer per level.

  • Larger mammals more efficient than small mammals.

  • Ectotherms more efficient than endotherms.

C. Human Dietary Efficiency

• Eating at lower trophic levels is more efficient:

  • Primary consumer (vegan diet): 10% efficiency.

  • Secondary consumer (chicken diet): 1% efficiency.

  • Tertiary consumer (fish diet): 0.1% efficiency.

V. Nutrient Cycles and Biogeochemistry

A. General Nutrient Cycle

• Nutrient cycle: The movement and exchange of organic and inorganic matter back into the production of living matter.

• Nutrients cycle between:

  • Organisms at different trophic levels.

  • Detritus (dead organic material).

  • Abiotic reservoirs (atmosphere, rocks, soil, water).

• Processes: Consumption, decomposition, nutrient fixation.

B. Global Cycles

1. Water Cycle

• Water cycle: The continuous movement of water within the Earth and atmosphere.

• Water evaporates → Precipitates → Returns via streams/groundwater.

• Human impacts:

  • Concrete reduces aquifer recharge.

  • Deforestation increases runoff.

  • Over-extraction threatens water supply.

2. Nitrogen Cycle

• Nitrogen cycle: The movement of nitrogen through the biosphere, atmosphere, and geosphere.

• Nitrogen fixation: Converts N₂ into usable ammonium.

• Sources: Lightning, bacterial enzymes.

• Human impacts:

  • Fossil fuel combustion → Acid rain, ozone depletion.

  • Fertilizer overuse → Eutrophication, dead zones.

3. Carbon Cycle

• Carbon cycle: The movement of carbon among the atmosphere, land, and oceans.

• Photosynthesis stores carbon; respiration releases CO₂.

• Human impacts:

  • Deforestation and agriculture release excess CO₂.

  • Fossil fuel burning moves carbon into the atmosphere.

VI. Climate Change and Human Impacts

A. CO₂ Increase & Greenhouse Effect

• Greenhouse effect: The trapping of the sun’s warmth in the planet’s lower atmosphere due to greenhouse gases.

• Major contributors:

  • Fossil fuel combustion.

  • Deforestation.

  • Agriculture & industry.

• Greenhouse gases trap heat: CO₂, CH₄, H₂O vapor, N₂O.

• Data shows CO₂ levels rising, causing global warming.

B. Climate Projections

• Expected temperature increases:

  • 1.5–2.0°C by 2100.

  • 0.5–7.0°C by 2300.

• Polar regions will warm more than tropics.

• More extreme weather events expected.

C. Mitigation Strategies

• Mitigation: Actions taken to reduce or prevent the effects of climate change.

• Reduce fossil fuel use.

• Reforestation & conservation.

• Sustainable water & nitrogen management.

Study Guide: Biodiversity and Conservation Ecology

How We Measure Biodiversity

Biodiversity is assessed at multiple levels: populations, species, and ecosystems.

1. Populations

• A population is a group of individuals of the same species in a specific area.

• Genetic diversity within populations enables adaptation through natural selection.

2. Species Diversity

• Species diversity refers to the variety of species within an ecosystem or region and includes:

  1. Species richness – The total number of species in an area.

  2. Species evenness – A measure of how equal the populations of different species are within an ecosystem.

• Measuring Species Diversity

  • Species counting – Directly observing and cataloging species.

  • DNA barcoding – Uses genetic sequences to identify species accurately.

• Why Species Diversity Matters

  • Increases ecosystem productivity – Diverse ecosystems tend to have higher net primary productivity (NPP).

  • Enhances ecosystem stability – Greater species diversity leads to stronger resistance and resilience to disturbances.

  • Supports ecosystem services – More species contribute to key functions like nutrient cycling, pollination, and carbon storage.

3. Ecosystem Diversity

• Ecosystem diversity refers to the variety of ecosystems within a region and includes:

  • Horizontal diversity – The number of species at each trophic level.

  • Vertical diversity – The number of trophic levels in an ecosystem.

  • Abiotic interactions – The influence of non-living factors like climate, water availability, and soil composition.

• Ecosystem function – The sum of biological and chemical processes within an ecosystem, including:

  • Primary production – The conversion of sunlight into energy by producers.

  • Nutrient cycling – Movement of elements like nitrogen and carbon through the ecosystem.

  • Decomposition – Breakdown of organic matter, returning nutrients to the environment.

• Diversity Increases Ecosystem Stability

  • Resistance – The ability of an ecosystem to remain unchanged when disturbed.

  • Resilience – The speed at which an ecosystem recovers after a disturbance.

  • Higher biodiversity leads to stronger resistance and resilience.

Conservation

Why Does Biodiversity Matter?

Biodiversity enhances:

• Ecosystem productivity – More diverse ecosystems produce more biomass (higher NPP).

• Ecosystem stability – Increases:

  • Resistance – How much an ecosystem is affected by a disturbance.

  • Resilience – How quickly an ecosystem recovers after a disturbance.

  • Higher biodiversity = greater resistance and resilience.

• Ecosystem services – Essential benefits provided by ecosystems:

  • Provisioning services – Food, water, fuel, medicine.

  • Regulating services – Climate regulation, air purification, water filtration.

  • Cultural services – Recreation, aesthetics, education.

  • Supporting services – Pollination, nutrient cycling, soil formation.

What Is Happening to Biodiversity?

Biodiversity is declining due to:

1. Habitat destruction – Deforestation, agriculture, urbanization.

2. Overexploitation – Overfishing, poaching, unsustainable hunting.

3. Invasive species – Non-native species disrupting ecosystems.

4. Pollution – Air, water, and soil contamination.

5. Climate change – Rising temperatures, shifting precipitation patterns, habitat loss.

Can We Conserve Biodiversity?

Yes! Conservation strategies include:

• Protecting habitats – Establishing national parks and reserves.

• Sustainable resource management – Reducing overharvesting, enforcing regulations.

• Combating climate change – Reducing carbon emissions, transitioning to renewable energy.

• Restoring ecosystems – Reforestation, wetland restoration, species reintroduction.

• Legislation and education – Strengthening conservation laws, raising awareness.

Key Takeaways

• Biodiversity is measured at genetic, species, and ecosystem levels.

• Ecosystem diversity includes species variety, trophic levels, and abiotic interactions.

• Higher biodiversity improves ecosystem function, stability, resistance, and resilience.

• Human activities are the main drivers of biodiversity loss.

• Conservation focuses on habitat protection, resource sustainability, and restoration.