BIOL 122 Exam 4

🌿 Ecology Notes: Lectures 16–18

📌 1. Introduction to Ecology

➤ What is Ecology?

  • Study of interactions between organisms and their environment.

  • Goal: Understand distribution and abundance of organisms.

  • Critical for conservation efforts.

📚 2. Levels of Ecological Study

  1. Organismal Ecology: Adaptations (behavioral, morphological, physiological).

  2. Population Ecology: How populations change over time.

  3. Community Ecology: Species interactions within an area.

  4. Ecosystem Ecology: Energy/nutrient flow between biotic & abiotic components.

🏞 3. Terrestrial Biomes

Biomes = Ecosystem types defined by climate & vegetation.

Biome

Climate & Features

Tropical Wet Forest

Warm, rainy, high biodiversity/productivity.

Subtropical Desert

Hot, dry; low productivity; species adapted for drought.

Temperate Grassland

Moderate rainfall; dominated by grasses; fertile soils.

Temperate Forest

Deciduous trees; consistent rainfall; seasonal.

Boreal Forest (Taiga)

Cold-tolerant conifers; low diversity; high biomass.

Arctic Tundra

Cold, permafrost soils, low biomass/diversity.

Mountains (Elevation)

Varies with altitude; can include tundra conditions.

🌊 4. Aquatic Ecosystems

  • Defined by water depth and movement.

  • Light and nutrient availability are key.

Habitat Type

Characteristics

Lakes & Ponds

Standing freshwater, stratified by depth.

Wetlands

Shallow, water-saturated soils; high productivity.

Streams & Rivers

Flowing water; stream order (1st–12th).

Estuaries

Where rivers meet oceans; very productive.

Oceanic Zones

Vary in light & pressure; open ocean relies on phytoplankton productivity.

Deep-Sea Vents

Energy via chemosynthesis from bacteria.

👥 5. Community Ecology

➤ Types of Species Interactions

Type

Effect

Example

Competition

(–/–)

Plants competing for sunlight.

Predation

(+/–)

Lion hunting antelope.

Parasitism

(+/–)

Tapeworm in intestine.

Commensalism

(+/0)

Barnacles on whale skin.

Mutualism

(+/+)

Pollination; corals & algae; mycorrhizae.

Amensalism?

(0/–)

Penicillium killing bacteria.

➤ Niche Concepts

  • Fundamental Niche: Potential resources used.

  • Realized Niche: Actual resources used under competition.

  • Competitive Exclusion Principle: No two species can occupy the same niche indefinitely.

➤ Mimicry

  • Müllerian: Harmful species mimic each other.

  • Batesian: Harmless species mimics harmful one.

  • Aposematism: Bright coloring = warning sign.

➤ Keystone Species

  • Have disproportionate impact on community structure.

    • E.g., Sea otters, gopher tortoises, sea stars.

➤ Succession

  • Change in community structure over time after disturbance.

📊 6. Population Ecology

➤ Key Concepts

  • Population: Individuals of a species in a defined area.

  • Demography: Study of birth, death, immigration, emigration.

  • Distributions: Uniform, clumped, or random.

  • Age Structures: Indicate growth trends (age pyramids).

  • Survivorship Curves:

    • Type I: Low early death (humans).

    • Type II: Constant mortality (birds).

    • Type III: High early death (turtles).

➤ Growth Models

  • Exponential: Rapid growth (ideal conditions).

  • Logistic: Growth slows near carrying capacity (K).

  • Regulation:

    • Density-dependent: Biotic (predation, disease).

    • Density-independent: Abiotic (weather).

➤ Life Histories

  • Trade-offs in growth, survival, reproduction (e.g., garter snake activity patterns).

🔄 7. Ecosystem Ecology

➤ Energy Flow

  • Energy enters via photosynthesis → transferred through trophic levels.

  • Trophic Levels:

    1. Producers

    2. Primary Consumers (herbivores)

    3. Secondary Consumers

    4. Tertiary Consumers

    5. Decomposers

➤ Food Chains & Webs

  • Food chain: Linear path.

  • Food web: Interconnected chains.

  • Energy Pyramid: Energy decreases at each level due to heat loss, metabolism, etc.

➤ Open Ocean Anomaly

  • Low producer biomass, high productivity → fast phytoplankton turnover.

☠ 8. Biomagnification

  • Toxins (e.g., mercury, DDT) accumulate up trophic levels.

♻ 9. Nutrient Cycling & Biogeochemical Cycles

➤ Controlled by decomposition

  • Depends on climate and detritus quality.

  • Slower in cold/dry areas (e.g., tundra) vs. warm/wet (rainforest).

➤ Carbon Cycle

  • Driven by respiration, photosynthesis, and fossil fuel burning.

  • Climate change linked to increased atmospheric CO₂.

  • International efforts: Kyoto Protocol, Paris Agreement.

➤ Nitrogen Cycle

  • Essential for proteins/nucleic acids.

  • Human impact: fertilizer use → pollution, eutrophication.

➤ Phosphorus Cycle

  • Excess leads to eutrophication in aquatic systems.

    • More snails → trematodes → deformed frogs.

➤ Acid Precipitation

  • From industrial pollution; lowers lake pH, affects fish, increases algal blooms.

🌐 Summary

  • Ecology connects living organisms with their environment through interactions, energy transfer, and nutrient cycles.

  • Human activities increasingly influence ecosystem dynamics.