APBIO 22-24

Microevolution

Change in allele frequencies in a population over generations.

Macroevolution

Broad pattern of evolution above species level.

Speciation

Formation of a new species.

Biological species concept

A population that interbreeds producing fertile offspring but doesn’t interbreed with other populations.

Prezygotic barriers

Barriers that prevent fertilization, such as habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, and gametic isolation.

Postzygotic barriers

Barriers that occur after zygote formation, such as reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown.

Allopatric speciation

Speciation that occurs when a population forms new species while geographically isolated from the parent population.

Sympatric speciation

Speciation that occurs when a subset of the population forms new species without geographic separation, through polyploidy, sexual selection, or habitat differentiation.

Polyploidy

Organisms having more than two sets of chromosomes, either from the same species (autopolyploidy) or different species (allopolyploidy).

Allopolyploidy

Organisms containing two or more sets of chromosomes from different species.

Sexual selection

Process where a species self-propagates itself asexually, leading to changes in sterile hybrids into fertile polyploids.

Punctuated equilibrium

Theory that describes periods of apparent stasis punctuated by sudden change in speciation.

Evolution

Change in the genetic composition of a population from generation to generation.

Aristotle and Linnaeus

Viewed species as fixed and arranged on a ladder of increasing complexity.

Georges Cuvier

Explained the appearance of the record of life in rock strata as representing sudden catastrophic events and subsequent repopulation by different species.

James Hutton and Charles Lyell

Proposed gradual mechanisms to explain Earth's geologic features and processes.

Jean-Baptiste de Lamarck

Proposed the mechanism of use and disuse and inheritance of acquired characteristics to explain changes in life over time.

Adaptations

Inherited characteristics of organisms that enhance survival and reproduction in specific environments.

Natural selection

Process in which individuals with certain inherited traits tend to survive and reproduce at higher rates than others.

Individuals

Do not evolve. Species evolve.

Soapberry bugs

Demonstrated observable evolutionary change through natural selection in response to introduced food sources.

MRSA

Methicillin-resistant Staphylococcus aureus, a pathogenic organism that evolved resistance to antibiotics.

Homologous structures

Structures in different species with the same structure but different functions, supporting evolution.

Vestigial structures

Structures present in ancestors but not used in current species, supporting evolution.

Analogous structures

Structures in different species with different structures but the same function, not supporting evolution.

Evolutionary tree

A diagram that shows the relationships and evolutionary history of different species.

DNA

The genetic material that carries the instructions for the development and functioning of living organisms.

Homologs

Similar structures or genes that are inherited from a common ancestor.

Convergent evolution

The independent evolution of similar features in different lineages.

Analogous structures

Structures that have similar functions but do not share a common ancestry.

Sugar glider and flying squirrel

Two examples of convergent evolution where both species evolved the ability to glide through the air.

Natural selection

The process by which individuals with traits best suited to their environment tend to produce more offspring.

Genetic drift

Random, non-adaptive changes in allele frequency due to chance events.

Gene flow

The transfer of alleles into or out of a population due to the movement of individuals or gametes.

Adaptive evolution

Evolution that improves the match between organisms and their environment.

Either-or characters

Phenotypic characters determined by a single gene locus with different alleles producing distinct phenotypes.

Characters along a continuum

Phenotypic characters influenced by the influence of two or more genes on a single character.

Point mutation

A change of as little as one base in a gene.

Neutral variation

Point mutations in noncoding regions that do not result in phenotypic changes.

Gene duplication

The process by which a gene is duplicated during meiosis, leading to an increase in the number of genes in the genome.

Independent assortment

The random distribution of alleles during gamete formation.

Random fertilization

The random fusion of gametes during sexual reproduction.

Crossing over

The exchange of genetic material between homologous chromosomes during meiosis.

Population

A group of individuals of the same species living in the same area and interbreeding.

Gene pool

The collection of all copies of every type of allele at every locus in all members of a population.

Fixed allele

When only one allele exists for a particular locus in a population, resulting in all individuals being homozygous for that allele.

Hardy-Weinberg equilibrium

The condition in which the frequency of alleles in a population remains constant over generations.

p+q=1

p2+2pq+q2=1

Founder effect

When a few individuals become isolated from a larger population, establishing a new population with a different gene pool.

Bottleneck effect

A sudden reduction in the size of a population due to a natural disaster or other environmental change.

Adaptive evolution

Evolution that results in organisms becoming better suited to their environment through mutations.

Relative fitness

The contribution an individual makes to the gene pool of the next generation relative to other individuals.

Stabilizing selection

Selection that favors intermediate variants and reduces variation.

Directional selection

Selection that favors individuals exhibiting one extreme of a phenotypic range.

Disruptive selection

Selection that favors individuals at both extremes of a phenotypic range.

Sexual selection

Selection based on traits that increase an individual's chances of mating.

Intrasexual selection

Competition between individuals of the same sex for mates.

Intersexual selection

Mate choice by one sex based on the traits of the other sex.

Heterozygous advantage

Greater fitness of heterozygotes compared to both kinds of homozygotes.

Frequency-dependent selection

The fitness of a phenotype depends on its frequency in the population.

Natural selection

The only mechanism that consistently causes adaptive evolution.

Biogeography

The study of the geographic distribution of species.

Continental drift

The movement of Earth's continents over time.

Endemic species

Species that are found only in a specific geographic area.