Unit 2 APES Test

Chapter 5: Evolution of Biodiversity 

5.1: The Biodiversity of Earth

Definition of Biodiversity

  • Biodiversity encompasses three levels:

    • Genetic diversity: Variation within species.

      • Example: Some populations have genetic traits for disease resistance.

    • Species diversity: Variety of species in a habitat.

      • Species richness: Number of species in a given area.

      • Species evenness: Relative abundance of species in a community.

    • Ecosystem diversity: Variety of ecosystems within a region.

  • Importance of Biodiversity in Ecosystems:

    • Enhances stability, resilience, and productivity.

5.2: Evolution Creates Biodiversity

Definition of Evolution

  • Change in the genetic composition of a population over time.

    • Microevolution: Changes within a species (e.g., antibiotic resistance in bacteria).

    • Macroevolution: Evolution resulting in new species, genera, families, etc.

Mechanisms of Evolution

  1. Mutation: Random changes in DNA that introduce new traits.

  2. Gene Flow: Movement of genes between populations.

  3. Genetic Drift: Random changes in allele frequencies, more pronounced in small populations.

    • Founder Effect: Small group starts a new population with limited genetic variation.

    • Bottleneck Effect: Population size is drastically reduced, decreasing genetic diversity.

  4. Natural Selection: Based on variation, heritability, and differential reproduction.

    • Types of selection:

      • Directional: Favors one extreme trait.

      • Stabilizing: Favors the average trait.

      • Disruptive: Favors both extremes.

    • Results in fitness (ability to survive and reproduce) and adaptations (traits enhancing survival).

  5. Artificial Selection: Human-driven selection of traits (e.g., dog breeding, agriculture).

Speciation

  • Allopatric Speciation: Geographic isolation leads to reproductive isolation and new species.

  • Sympatric Speciation: Speciation without geographic isolation, often via polyploidy in plants.

5.3: Pace of Evolution

Factors Influencing Evolution

  1. Rate of Environmental Change: Rapid changes challenge species adaptation.

  2. Genetic Variation: Higher variation increases adaptability.

  3. Population Size: Smaller populations evolve faster but are at higher risk of extinction.

  4. Generation Time: Shorter generation times lead to faster evolution.

Extinction

  • Natural extinction occurs at a baseline rate.

  • Mass Extinctions: Widespread, rapid biodiversity loss (e.g., dinosaur extinction).

5.4: Ecological Niches and Species Distributions

Niche Concept

  1. Fundamental Niche: Full range of conditions a species can survive in.

  2. Realized Niche: Conditions where a species actually lives, considering competition and predators.

Niche Generalists vs. Niche Specialists

  • Generalists: Broad tolerance for conditions (e.g., raccoons).

  • Specialists: Narrow tolerance for specific conditions (e.g., pandas).

Distribution of Species

  • Determined by abiotic (temperature, soil) and biotic (predators, competitors) factors.

  • Range of Tolerance: Range of environmental conditions where a species can survive.

  • Species Dispersal: Movement across geographic ranges.

5.5: How Environmental Change Can Alter Species Distributions

Environmental Change and Species Movement

  • Climate change, natural disasters, and human activities lead to shifts in species distributions.

    • Example: Glacial retreat creates new habitats.

Species Extinction Risks

  • Limited Range or Small Population Size: Increases vulnerability to environmental changes.

  • Lack of Adaptability: Failure to adapt to changing conditions can lead to extinction.

Conservation Importance

  • Preserving habitats is critical for preventing species loss.