Community Ecology, Population Dynamics, and Environmental Factors

Chapter 5: Community Ecology & Population Dynamics

  • Case Study: Kelp Forests/Otters/Urchins

  • Kelp Forests: Essential habitats for marine life.

  • Sea Otters: Apex predators that regulate sea urchin populations.

  • Impact of urchins: Without otters, urchins over-consume kelp, leading to ecosystem collapse.

Five Major Types of Community Interactions

  • Competition (−/−): Both species are negatively affected (e.g., lions and hyenas compete for prey).

  • Predation (+/−): One species benefits at the expense of another (e.g., wolves prey on deer).

  • Parasitism (+/−): The parasite benefits while the host suffers (e.g., ticks feed on dogs).

  • Mutualism (+/+): Both species benefit from the interaction (e.g., bees pollinating flowers).

  • Commensalism (+/0): One species benefits without affecting the other (e.g., barnacles on whales).

Resource Partitioning

  • Species minimize competition by dividing resources (e.g., different bird species feeding at various tree heights).

  • Population: A group of individuals of the same species inhabiting a specific area.

Distribution Patterns:

  • Clumped: Groups in patches (e.g., wolves).

  • Uniform: Evenly spaced (e.g., penguins).

  • Random: No specific pattern (e.g., dandelions).

  • Factors Affecting Population Size

  • Influenced by birth rate, death rate, immigration, and emigration.

Age Structure

  • Proportion of individuals in different age categories; crucial for predicting future population growth.

Limiting Factors & Ranges of Tolerance

  • Conditions affecting population viability (e.g., water, food, temperature).

R- vs K-Selected Species

  • R-Selected: Rapid reproduction, high offspring quantity (e.g., insects).

  • K-Selected: Fewer offspring, increased parental care (e.g., elephants).

Population Growth Models

  • Exponential Growth (J-shaped): Unchecked growth; population skyrockets.

  • Logistic Growth (S-shaped): Growth stabilizes at carrying capacity due to environmental constraints.

Population Crashes & Control Factors

  • Density-Dependent Factors: Impact populations based on density (e.g., competition, disease).

  • Density-Independent Factors: Influential regardless of population density (e.g., natural disasters, climate change).

Primary vs Secondary Succession

  • Primary Succession: Starts on barren lifeless terrain (e.g., after a volcanic eruption).

  • Secondary Succession: Recovery following a disturbance (e.g., after a wildfire).

Inertia vs Resilience in Ecosystems

  • Inertia: The ability to resist change.

  • Resilience: Capacity to recover after disturbances.

Chapter 6: Human Population & Demographics

  • World population exceeds 8 billion and continues to grow.

  • Major populations in China, India, and the US; growth mainly in developing nations.

  • Factors Affecting Birth & Death Rates

  • Influenced by healthcare systems, educational access, and economic conditions.

Demographic Transition Model

  • Stage 1: High birth and death rates; population remains stable.

  • Stage 2: Death rates decline, leading to rapid population growth.

  • Stage 3: Birth rates decline as society advances.

  • Stage 4: Both birth and death rates are low, population stabilizes.

Population Pyramids

  • Visual representations that depict age distribution, useful for predicting future population trends.

Immigration & Emigration Factors

  • Driven by economic opportunities, social conflict, environmental conditions.

  • Slowing Population Growth

  • Strategies include promoting education, implementing family planning, and empowering women.

China’s One-Child Policy & Effects

  • Intended to limit population growth; led to an aging population and gender imbalance issues.

Chapter 7: Climate & Biomes

  • Climate: Long-term atmospheric patterns, averaged over time.

  • Weather: Short-term atmospheric conditions experienced at a given time.

Key Abiotic Climate Factors

  • Solar energy, atmospheric compositions, Earth’s rotation, ocean currents, and geographical features.

Major Biomes & Their Traits

  • Tundra: Cold, low biodiversity, predominantly permafrost.

  • Desert: Very dry, extreme temperature variations.

  • Rainforest: High biodiversity, warm and moist conditions.

Rain Shadow Effect

  • Phenomenon where mountains block rainfall, resulting in dry leeward sides.

Urban Heat Island Effect

  • Cities maintain higher temperatures than surrounding areas due to concrete surfaces and decreased vegetation.

Chapter 8: Aquatic Ecosystems

Importance of Coral Reefs

  • Serve as biodiversity hotspots and protect coastal areas from erosion.

Freshwater vs Saltwater Ecosystems

  • Freshwater: Includes rivers, lakes, and wetlands.

  • Saltwater: Comprises oceans, estuaries, and mangroves.

Marine Food Web Basics

  • Producers: Algae and phytoplankton serve as the base.

  • Consumers: Include fish and whales.

  • Decomposers: Such as bacteria and fungi recycle nutrients.

Ocean Life Zones

  • Coastal: Shallow areas rich in biodiversity.

  • Open Ocean: Nutrient-poor, inhabited by larger predators.

  • Deep Ocean: Characterized by cold, darkness, and high pressure.

Estuaries & Wetlands Importance

  • Act as natural filters for pollutants and provide habitats for various species.

Human Impacts on Oceans

  • Issues include overfishing, pollution, and the effects of climate change.

Lake Life Zones & Eutrophication

  • Oligotrophic: Clear water with low nutrient levels.

  • Eutrophic: High nutrient concentrations leading to murky water.

  • Cultural Eutrophication: Human-induced process causing nutrient overload.

River Changes from Source to Mouth

  • Rivers start fast-flowing with clear waters at the source but slow down and may form deltas as they reach their mouths.