ap bio chapter 11

evolution

The Fossil Record

The history of life on Earth as shown by fossils, showing how organisms have changed over time.

Analogous Structures

Body parts that perform a similar function in different species but do not come from a common ancestor (e.g., bird wing vs. insect wing).

Homologous Structures

Similar body structures in different species that show a common ancestor, even if they have different functions (e.g., human arm and whale flipper).

Vestigial Structures

Structures that have lost most or all of their original function through evolution (e.g., human appendix, whale pelvis).

Founder Effect

A type of genetic drift where a new population is started by a small group of individuals, leading to reduced genetic diversity.

Polymorphic Effect

The presence of two or more distinct traits (forms) within a population due to genetic variation (e.g., different blood types in humans).

Hardy-Weinberg Effect (Equilibrium)

A condition where a population's allele frequencies remain constant unless acted on by outside forces, used to study whether evolution is occurring.

Disruptive Selection

A type of natural selection where individuals with extreme traits are favored over average traits.

Stabilizing Selection

A type of natural selection where average traits are favored, reducing variation in a population.

Directional Selection

A type of natural selection where one extreme trait is favored, shifting the population in that direction.

Gene Flow

The movement of genes between populations through migration, increasing genetic variation.

Convergent Evolution

When unrelated species evolve similar traits due to similar environments.

Divergent Evolution

when a species splits into multiple species over time, each adapted to different environments or lifestyles

Genetic Drift

Random changes in allele frequencies, especially in small populations, reducing genetic variation.

Mechanical Isolation

A prezygotic barrier where species can't mate due to incompatible reproductive structures.

Gametic Isolation

A prezygotic barrier where sperm and egg from different species can't fuse.

Habitat Isolation

A prezygotic barrier where species live in the same area but different habitats and don't meet to mate.

Temporal Isolation

A prezygotic barrier where species reproduce at different times.

Sympatric Speciation

New species form in the same area due to genetic or behavioral changes, not physical separation.

Fitness

An organism’s ability to survive and reproduce in its environment.

Allopatric Speciation

New species form due to geographic separation of populations.

Polygenic Inheritance

A trait controlled by multiple genes, resulting in a range of phenotypes (e.g., skin color, height).

Microevolution

Small evolutionary changes within a population over a short time (e.g., allele frequency changes).

Macroevolution

Large-scale evolutionary changes over long time periods, such as new species forming.

Biological Species Concept

Defines species as groups that can interbreed and produce fertile offspring, but are reproductively isolated from others.

Prezygotic Barrier

Reproductive barrier that prevents mating or fertilization.

Postzygotic Barrier

Reproductive barrier that occurs after fertilization, affecting hybrid survival or fertility.

Behavioral Isolation

Prezygotic barrier where differences in mating behavior prevent reproduction.

Reduced Hybrid Viability

Postzygotic barrier where the hybrid fails to develop or dies early.

Reduced Hybrid Fertility

Postzygotic barrier where hybrids are healthy but sterile (e.g., mule).

Hybrid Breakdown

Postzygotic barrier where the hybrid is fertile, but future generations are weak or infertile.

Punctuated Equilibrium

Evolution occurs in short, rapid bursts followed by long periods of little change.

Gradualism

Evolution occurs slowly and steadily over long periods.

Gene Pool

The total collection of genes and alleles in a population at a given time.

Intrasexual Selection

A type of sexual selection where members of the same sex (usually males) compete for mates.

Intersexual Selection

A type of sexual selection where one sex (usually females) chooses mates based on certain traits.

Competition

The struggle between organisms to survive in a habitat with limited resources.

Mate Choice

The process by which individuals select partners for reproduction based on preferred traits.

Descent with Modification

The passing of traits from parent to offspring, with changes occurring over generations.

Natural Selection

The process by which individuals with traits best suited to their environment survive and reproduce more successfully.