Evolution

Define evolution. Use the words population, genetic variation and time in your definition.

Evolution is the change in the genetic composition of a population over time due to changes in allele frequencies. It depends on existing genetic variation and occurs across generations, not within individuals.

Explain why genetic variation within a population is a prerequisite for evolution.

Without genetic variation, all individuals would be identical, and natural selection would have no traits to favor or disfavor. Variation provides the raw material for evolutionary change as different traits increase or decrease survival and reproduction.

What factors can produce genetic variation among populations?

Genetic variation arises from mutation, sexual reproduction (recombination and independent assortment), and gene flow between populations. Environmental differences can also cause distinct selective pressures that shape variation.

Explain why genetic drift and gene flow are considered mechanisms of evolution.

Both processes change allele frequencies over time. Genetic drift is random change due to chance events, while gene flow occurs when individuals migrate between populations, introducing or removing alleles.

Provide examples of genetic drift and gene flow.

Genetic drift: a hurricane randomly kills most of a beetle population, changing allele frequencies. Gene flow: pollen from one population fertilizes plants in another, introducing new genetic traits.

Describe the mechanism of natural selection, using examples.

Natural selection is the process where individuals with advantageous traits survive and reproduce more successfully, passing those traits on. Example: peppered moths in polluted areas evolved darker coloration for camouflage against predators.

Discuss why natural selection is the only mechanism that causes adaptive evolution.

Natural selection increases the frequency of beneficial traits that improve fitness. Other mechanisms (like genetic drift or mutation) change allele frequencies but do not necessarily lead to adaptations that improve survival or reproduction.

Provide examples of direct observations of evolutionary change.

Examples include the evolution of antibiotic resistance in bacteria, pesticide resistance in insects, and changes in beak size in Darwin's finches in response to food availability.

Explain why the development of drug resistance supports the theory of evolution.

Drug resistance demonstrates natural selection in action: bacteria with mutations that confer resistance survive antibiotic exposure and reproduce, leading to a population adapted to the drug.

Illustrate with an example how fossils document the occurrence of evolutionary changes.

Fossils show transitional forms, such as the evolution of whales from land-dwelling mammals (with species like Ambulocetus showing intermediate features), documenting gradual change over time.

Describe and contrast homology and analogy, and provide an example of each.

Homology refers to shared traits due to common ancestry (e.g., the forelimbs of humans, cats, and whales). Analogy refers to traits with similar function but different evolutionary origins (e.g., wings of bats and insects).

Explain how the field of embryology contributed to our discovery of homologies between species.

Embryology revealed that many species share similar developmental stages and structures (e.g., pharyngeal pouches in fish and human embryos), suggesting descent from a common ancestor.

Biogeography has shown that islands with similar environments, but located in different parts of the world, are not populated by closely related species, but by species similar to the closest continental mass. Discuss how this observation has supported the theory of evolution.

This pattern supports evolution by showing that species evolve from local ancestors, not by independent creation. Organisms adapt to their environment through natural selection, leading to similar ecological forms (convergent evolution) in separate regions.