AP Biology: Evolution & Natural Selection

What is the modern biological definition of evolution?

Evolution is defined as a change in the allele frequencies in a population over generations.

Describe the process of natural selection.

Natural selection is a process where individuals with heritable traits better suited to their environment tend to survive and reproduce more successfully than others, leading to an increase in the frequency of those advantageous traits in the population over time.

What are the three essential conditions for natural selection to occur?

Natural selection requires genetic variation within a population, heritability of traits, and differential reproductive success based on those traits.

How do homologous structures provide evidence for evolution?

Homologous structures are similar anatomical features found in different species that share a common ancestor, indicating divergent evolution from a shared basic design despite different functions.

Differentiate between convergent and divergent evolution.

Convergent evolution occurs when unrelated species independently evolve similar traits due to similar environmental pressures, while divergent evolution describes species with a common ancestor evolving different traits over time.

Explain the concept of genetic drift and name two types.

Genetic drift is a random change in allele frequencies in a population due to chance events, especially significant in small populations. The bottleneck effect and the founder effect are two types.

What are the five conditions required for a population to be in Hardy-Weinberg equilibrium?

The five conditions are no mutation, random mating, no natural selection, extremely large population size (no genetic drift), and no gene flow (migration).

Define speciation and distinguish between allopatric and sympatric speciation.

Speciation is the process by which one species splits into two or more distinct species. Allopatric speciation occurs due to geographic isolation, while sympatric speciation occurs within the same geographic area without physical barriers.

Give two examples of prezygotic reproductive barriers.

Prezygotic barriers prevent mating or fertilization, such as habitat isolation (species live in different areas) and temporal isolation (species breed at different times).

What is the difference between an adaptation and an acclimatization?

An adaptation is a heritable trait that increases an organism's fitness in its environment, evolving over generations, while acclimatization is a short-term physiological adjustment an individual makes to cope with environmental changes.

How does fossil evidence support the theory of evolution?

Fossils provide a historical record of life, showing changes in organisms over time, the existence of extinct species, and transitional forms that link ancestral species to modern ones.

What is the main idea conveyed by a phylogenetic tree or cladogram?

A phylogenetic tree illustrates the evolutionary relationships among various biological species or other entities, showing patterns of descent with modification from common ancestors.

Explain the role of mutation in evolution.

Mutation is the ultimate source of new genetic variation in a population. While often neutral or harmful, beneficial mutations can arise and be acted upon by natural selection, driving evolutionary change.

Describe sexual selection and its two main forms.

Sexual selection is a form of natural selection where individuals with certain inherited characteristics are more likely to obtain mates. It can be intrasexual (competition among one sex) or intersexual (mate choice by the opposite sex).

What is gene flow and how does it affect population genetics?

Gene flow is the transfer of alleles or genes from one population to another. It can reduce genetic differences between populations and introduce new alleles, potentially increasing genetic variation within a population.