Unit 7: Natural Selection

Natural Selection

The process where organisms better adapted to their environment tend to survive and produce more offspring.

Adaptation

A trait or characteristic that increases an organism's chances of survival and reproduction in a specific environment.

Homologous Structures

Body parts in different species that have a similar structure due to common evolutionary origin, even if they serve different functions.

Analogous Structures

Body parts in different species that serve similar functions but do not have a common evolutionary origin.

Genetic Drift

A random change in allele frequencies in a population, often more noticeable in small populations.

Directional Selection

A form of natural selection where one extreme phenotype is favored over others, shifting the population's traits in that direction.

Stabilizing Selection

A type of natural selection where intermediate phenotypes are favored, reducing variability in a population.

Disruptive Selection

A type of natural selection that favors both extreme phenotypes at the expense of intermediate phenotypes.

Hardy-Weinberg Law

A principle stating that allele frequencies in a population will remain constant from generation to generation in the absence of evolutionary forces.

Speciation

The formation of new and distinct species in the course of evolution.

Divergent Evolution

The process by which two or more related species become more dissimilar over time, often due to different environmental pressures.

Punctuated Equilibrium

A theory suggesting that evolution occurs in rapid bursts, followed by long periods of stability or little change.

Gametes

The body cells that include copies of the regular old genome, which do not change based on experiences in life.

Phylogenetic Tree

A branching diagram showing the evolutionary relationships between different species based on shared characteristics.

Bottleneck (Founder Effect)

A sharp reduction in the size of a population due to environmental events, leading to a loss of genetic diversity.

Environmental Pressure

External factors such as predators, climate, or food sources that influence the survival and reproduction of organisms.

Genetic Variability

The diversity in gene frequencies within a population, which provides the raw material for evolution.

Sexual Selection

A form of natural selection where certain traits increase an individual's chances of attracting mates, even if those traits do not enhance survival.

Random Mutation

A spontaneous change in an organism's DNA that can lead to new traits and genetic variation.

Evolutionary Fitness

The ability of an organism to survive, reproduce, and pass on its genes to the next generation.

Pre-zygotic Barriers

Reproductive barriers that prevent fertilization from occurring, such as differences in mating behaviors or timing.

Post-zygotic Barriers

Reproductive barriers that occur after fertilization, leading to reduced hybrid viability or fertility.

Morphological Homologies

Similarities in the structure or form of organisms due to shared ancestry, indicating common origin.

Homologous Structures

Body parts in different species that have a similar structure due to common evolutionary origin, even if they serve different functions.

Analogous Structures

Body parts in different species that serve similar functions but do not have a common evolutionary origin.

Adaptation

A trait or characteristic that increases an organism's chances of survival and reproduction in a specific environment.

Evolutionary Fitness

The ability of an organism to survive, reproduce, and pass on its genes to the next generation.

Peppered Moths

A classic example of natural selection, where the frequency of dark-colored moths increased due to industrial pollution and predation by birds.

Genetic Drift

A random change in allele frequencies in a population, often more noticeable in small populations.

Directional Selection

A form of natural selection where one extreme phenotype is favored over others, shifting the population's traits in that direction.

Speciation

The formation of new and distinct species in the course of evolution.