Chapter 18

Objective of field biologists: - Discover new, unrecorded species. - Expand understanding of the natural world. - Lead to innovations in medicine and agriculture.
Importance of plant and microbial species: - Reveal medicinal and nutritive knowledge. - Key roles in ecosystems or protection if rare.
Evidence for environmental regulations and laws: - Discovered species used as evidence.

Natural selection requires: - Variation among individuals in a population. - Genetic basis for differences.
Nongenetic variations do not contribute to evolutionary change.
Main mechanisms generating genetic diversity: - Mutation: - Change in DNA; source of new alleles. - Outcomes of mutations: - Reduced fitness. - Beneficial effect on fitness. - Neutral effect on fitness. - Sexual reproduction: - Unique combinations of alleles from parents.
Heritable traits aiding survival: - Defined as adaptations. - Examples of adaptations: - Platypus's webbed feet for swimming. - Snow leopard's thick fur for cold climates. - Cheetah's speed for catching prey.
Environmental condition dependency: - Traits’ favorability may vary based on the environment. - Example: - Plants with large leaves favored in moist conditions but not in dry ones.

Divergent Evolution: - Groups evolve in diverse directions from a common ancestor. - Example: - Reproductive organs of flowering plants vary while sharing a basic anatomy.
Convergent Evolution: - Distantly related species evolve similar traits independently. - Example: - Wings of bats and insects for flight.

Fossils indicate: - Organisms from the past differ from present ones. - Show gradual evolutionary changes. - Case study examples: - Evolution of humans and horses. - Whale flippers resemble bird and mammal appendages, indicating common ancestry.