I

Evolution and Biodiversity

I. Types and Origins of Life

  • Cells:
    • Prokaryotic: No nucleus, primitive (e.g., bacteria, archaea).
    • Eukaryotic: Nucleus and internal structures.
  • Classification (Taxonomy):
    • Order: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Specific name.
    • Most inclusive is Domain, least inclusive is Specific name.
    • Scientific names (Genus species) are written with Genus capitalized and specific name lowercase.
  • Species: Organisms with the potential to produce fertile offspring.
  • Emergence of Life:
    • Chemical Evolution: Formation of small organic molecules, then large organic molecules, then protocells.
    • Biological Evolution: Unicellular prokaryotes \rightarrow Photosynthetic bacteria ( \text{cyanobacteria} ) producing \text{O}_2 (oxygen revolution) \rightarrow Unicellular eukaryotes \rightarrow Multicellular eukaryotes; colonization of land.
  • Evidence of Past Life: Fossil record, radioactive dating, DNA, ice and mud cores.

II. Evolution and Adaptation

  • Evolution: A change in the genetic makeup of a population through successive generations.
  • How Evolution Works:
    • Genetic information in DNA, genes code for heritable traits. A population's gene pool is its collection of genes.
    • Alleles are different forms of a gene, shuffled during sexual reproduction.
    • Variation/variability is the key ingredient for evolution.
  • Key Evolutionary Factors:
    • Mutation: Random, rare changes in an individual's DNA structure, often lethal, caused by mutagens.
    • Gene Flow: Genes moving between populations.
    • Natural Selection: Occurs when traits enable some individuals to survive and produce more offspring. Requires heritability, variability, and reproductive advantage (differential reproduction), leading to increased frequency of advantageous alleles.
    • Selective Pressure: Environmental conditions that make a mutation beneficial, resulting in an adaptation/adaptive trait.
  • Types of Natural Selection:
    • Directional: Favors one extreme end of the variability range.
    • Stabilizing: Eliminates individuals at the extremes, favoring the average.
    • Diversifying/Disruptive: Favors both extremes, eliminating the average.
  • Coevolution: Different species evolve based on each other's adaptations.
  • Adaptive Radiation: Rapid evolution of numerous new species to fill niches after mass extinctions/depletions.

III. Adaptation and the Niche

  • Niche: An organism's functional role or "job"; habitat is "where you live."
    • Fundamental Niche: Potential niche.
    • Realized Niche: Actual niche.
  • Generalists: Occupy broad niches (e.g., raccoons).
  • Specialists: Occupy narrow, specific niches.
  • Convergent Evolution: Similar selective pressures in similar ecosystems lead to similar adaptations in different taxonomic groups.
  • Limits to Adaptation: Adaptations rely on existing gene pool traits, are often compromises, reproductive capacity is limited, and other individuals without the trait also reproduce.

IV. Speciation, Extinction, and Biodiversity

  • Speciation: Development of two species from one, driven by natural selection.
    • Typically involves geographic isolation followed by reproductive isolation. = divergent evolution.
  • Extinction: Permanent loss of a species.
    • Approximately 99.9\% of all species that ever lived are extinct.
    • Types: background extinction (normal rate), mass depletion, mass extinction.
    • Extinction creates opportunities for adaptive radiation.
  • Large-Scale Factors Impacting Speciation/Extinction: Climate change, continental drift, meteor impacts.

V. Island Biogeography

  • Island species are often unique and specialized.
  • Highly vulnerable to extinction due to limited resources (food, territory) and the introduction of non-native species.

VI. The Future of Evolution: Human Impact

  • Artificial Selection: Humans selectively breed organisms for desired traits (e.g., poodles, purple tomatoes); alters/reduces gene pool and biodiversity.
  • Genetic Engineering (Genetic Modification): Inserting genes from one organism into another (producing GMOs/transgenic organisms); a faster process than artificial selection, controversially alters the gene pool permanently.

VII. Biodiversity and its Importance

  • Biodiversity: Variety of genes in a population, species richness, variety of ecosystems, and variety of roles within an ecosystem.
  • Importance:
    • Stability: Generally, more biodiversity leads to greater ecosystem resistance to disturbance or catastrophe.
    • Resources: Provides essential goods and services like food, wood, fiber, energy, medicines, clean air and water, fertile soils, and pest control.

VIII. Loss of Biodiversity and Protecting Biodiversity

  • Anthropogenic Causes (HIPPCO):
    • Habitat Loss (especially specialized habitat, fragmentation).
    • Invasive Species.
    • Population growth (human).
    • Pollution.
    • Climate Change.
    • Overhunting/Overexploitation.
  • Habitat Fragmentation: Division of large habitats into smaller, isolated areas, increasing "edge habitat" (often populated by weedy species) and impacting species needing large areas (e.g., apex predators). Caused by roads, agriculture, logging.
  • Ways to Reduce Biodiversity Loss:
    • Criminalize poaching.
    • Sustainable land management.
    • Habitat restoration.
    • Protect land and create wildlife corridors.
    • CITES Treaty (1975): International agreement banning the hunting, capturing, and selling of endangered species (ES) or their products.
    • Endangered Species Act (ESA, 1973): Makes it illegal to hunt, kill, injure, sell/buy products from, or damage the habitat of endangered species.