Forces of Evolutionary Change Reading Guide

Evolution

Descent w/ modification; Change in allele frequencies in a population over time.

Gene

A DNA sequence that encodes a protein; in part, an organism's proteins determine its traits.

Population

Members of the same species occupying the same interbreeding region.

Gene pool

The collection of alleles in a population.

Microevolution

Short term changes in allele frequencies within a population.

Macroevolution

Large-scale evolutionary change or species.

Natural selection

Differential reproduction of organisms based on inherited traits; individuals with certain genotypes that are best suited to the environment have greater reproductive success than others.

Descent with modification

The idea that species change over time, giving rise to new species, and sharing a common ancestor.

Allele frequencies

The relative frequency of an allele (variant of a gene) at a genetic locus in a population.

Galapagos island finches

A group of finches that exemplify the concept of descent with modification as observed by Charles Darwin.

Diversity of species

The variety of different species within a given ecosystem or environment.

Reproductive success

The passing on of genes to the next generation in a way that they can also reproduce.

Environmental adaptation

Changes in traits that enhance an organism's ability to survive and reproduce in its environment.

Allele

A variant form of a gene.

Genotype

The genetic constitution of an individual organism.

Phenotype

The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences.

Extinction

The end of an organism or a group of organisms, typically due to environmental changes or loss of habitat.

Speciation

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

Adaptive radiation

The rapid evolution of diversely adapted species from a common ancestor.

Fitness

The ability of an organism to survive and reproduce in its environment.

Genetic drift

A mechanism of evolution that refers to random changes in allele frequencies in a population.

Mutation

A change in the DNA sequence that can lead to new traits in a population.

Gene flow

The transfer of genetic variation from one population to another.

Heritable variation

Variation within a species where no two individuals are identical.

Limited resources

Every habitat contains limited supplies of the resources required for survival.

Overproduction of offspring

More individuals are born than survive to reproduce.

Struggle for existence

Individuals compete for limited resources that enable them to survive.

Unequal reproductive success

The inherited characteristics of some individuals make them more likely to obtain resources and reproduce.

Descent with modification

Over many generations, a population's characteristics can change by natural selection, potentially giving rise to new species.

Modern evolutionary synthesis (MES)

The idea that genetic mutation creates the variation upon which selection acts.

Natural selection

The process where individuals with traits best suited to prevailing conditions tend to leave more surviving, fertile offspring.

Adaptation

An inherited trait that permits an organism to survive and reproduce.

Fitness (evolutionary sense)

An organism's contribution to the next generation's gene pool.

Natural selection and extinction

If none of the plants can reproduce without water, the population might go extinct.

Natural selection's influence on alleles

Natural selection changes the genetic makeup of a population by favoring alleles that contribute to reproductive success.

Phenotype

The observable characteristics of an organism that result from the interaction of its genotype with the environment.

Environmental conditions

Conditions that constantly change, affecting the adaptation and evolution of populations.

Survival of the fittest

A phrase often used to describe natural selection, emphasizing the survival of individuals best suited to their environment.

Genetic diversity

The variety of genetic characteristics within a population, crucial for natural selection.

Reproductive success

The ability of an organism to pass its genes to the next generation.

Natural selection modes

Natural selection can shape populations in three main ways, affecting phenotypes.

Phenotypic variation

Differences in physical traits among individuals in a population.

Selection against alleles

Natural selection indirectly influences a population's alleles by favoring those that enhance survival and reproduction.

Population adaptation

Natural selection leads to populations that are better adapted to their environments.

Evolutionary theory foundation

Darwin laid a foundation for evolutionary theory, emphasizing variation but not understanding its genetic basis.

Inherited trait

A characteristic that permits an organism to survive and reproduce.

Natural selection

The process by which environmental conditions favor certain traits over others, leading to changes in the genetic makeup of a population.

Prolonged drought effect on plant population

If none of the plants can reproduce without water, the population might go extinct; those that can will pass on their alleles.

Directional selection

A form of natural selection in which one extreme phenotype is favored by the environment.

Disruptive selection

A form of natural selection in which both extreme phenotypes are favored over the intermediate phenotype.

Stabilizing selection

A form of natural selection in which the intermediate phenotype is favored over the extremes.

Sexual selection

A type of natural selection resulting from the ability to obtain mates.

Forms of sexual selection

Fighting to mate and attracting females.

Spine number in cacti

Average of 4 spines/cm² with a range of 2-7 spines/cm²; after predation, the average increases to 6 spines/cm².

Mutation

A change in an organism's DNA sequence that introduces a new allele to a population.

Genetic drift

Changes in allele frequencies due to chance events, which can eliminate alleles from a population.

Founder effect

Genetic drift that occurs when a small, non-representative group of individuals leaves their ancestral population to begin a new settlement.

Bottleneck effect

Genetic drift that occurs as a result of a sudden reduction in the size of a population.

Migration (gene flow)

Movement of individuals into or out of a population that can transfer alleles between populations.

Natural selection (adaptation)

Results in populations that are better adapted to their environment.

Gene flow/migration

Tends to minimize genetic differences between different populations.

Genetic variation reduction

Tends to be caused by genetic drift and natural selection.

Effect of small population size

Genetic drift has more of an effect when population size is small.

Mutation (genetic diversity)

Increases genetic diversity by creating completely new alleles.

Zombie apocalypse scenario

Describes genetic drift due to the founder effect as a result of a small surviving population.

Current population genetic variation

The current population exhibits less genetic variation than the pre-zombie apocalypse population.

Green eyes trait introduction

The introduction of a new trait (green eyes) to a population is an example of gene flow.