AP Bio Unit 7 (Natural Selection) Vocab

Biogeography

The geographic distribution of species

Evolution

Change in the genetic makeup of a population over time; descent with modification

Descent with modification

Heritable traits change from generation to generation

Natural selection

A process in which individuals that have certain traits tend to survive and reproduce at higher rates than other individuals because of those traits

Fitness

The ability to survive and reproduce

Competition

When more offspring are produced than can survive due to limited resources, leading to differential survival

Biotic factors

The living components of an ecosystem that directly/indirectly affect other organisms and the environment

Abiotic factors

The non-living components of an ecosystem that affect the organisms and environment

Selective pressures

Any environmental factor that influences which organisms in a population survive and reproduce

Adaptations

Inherited characteristics of organisms that enhance their survival and reproduction

Phenotype

An organism’s observed traits

Genotype

An organism’s unique set of genes (specific alleles that dictate the organism’s traits)

Artificial selection

The selective breeding of domestic plants and animals to encourage the occurrence of desirable traits

Mutation

A random change to one’s DNA that can result in changes to one’s phenotype

Population

A group of individuals of the same species that live in the same area and interbreed to produce fertile offspring

Gene pool

A population’s genetic makeup

Fixed

When there is only one allele present for a particular locus in the population

Genetic drift

Chance events that cause a change in allele frequency from one generation to the next

Bottleneck effect

When a large population is drastically reduced by a non-selective disaster

Founder effect

When a few individuals become isolated from a large population and establish a new small population with a gene pool that differs from the large population

Gene flow

The transfer of alleles into or out of a population due to fertile individuals or gametes

Directional selection

Selection towards one extreme phenotype

Stabilizing selection

Selection towards the mean and against the extreme phenotypes

Disruptive selection

Selection against the mean. Both phenotypic extremes have the highest relative fitness

Sexual selection

A type of natural selection that explains why many species have unique/showy traits

Hardy-Weinberg Equilibrium

The frequencies of alleles and genotypes in a population will remain constant from generation to generation, provided that only mendelian segregation and recombination of alleles are at work.

Comparative morphology

Analysis of the structures of living and extinct organisms

Analogous structures

Structures that are similar but have separate evolutionary origins

Embryonic homology

Many species have similar embryonic development

Vestigial structure

Structures that are conserved even though they no longer have a use

Molecular homology

Many species share similar DNA and amino acid sequences

Homologous structures

Characteristics that are similar in two species because they share a common ancestor

Common Ancestor

An earlier organism from which two or more species have evolved

Convergent evolution

Similar adaptations that have evolved in distantly related organisms due to similar environments

Homology

Characteristics in related species that have similarities even if the functions differ

Fossils

Remains or traces of past organisms

Nodes

Represent common ancestors

Cladogram

Diagrams that represent the evolutionary history of a group of organisms

Phylogenetic tree

Diagrams that represent the evolutionary history of a group of organisms. Similar to cladograms except they show the amount of change over time measured by the fossils

Systemics

Classification of organisms and determining their evolutionary relationships

Basal taxon

A lineage that evolved from the root and remains unbranched

Sister taxa

Two classes that emerge from the same node

Monophyletic group

Includes the most recent common ancestor of the group and all of its descendants (clade)

Derived characteristic

Similarity derived from the most recent common ancestor of an entire group

Ancestral characteristic

Similarity that arose prior to the common ancestor

Synapomorphy

A derived characteristic shared by clade members

Paraphyletic group

Includes the most recent common ancestor of the group, but not all its descendants

Polyphyletic group

Does not include the most recent common ancestor of all members of the group

Taxonomy

Naming and classifying species

Phylogenetics

Hypothesis of evolutionary history

Root

The common ancestor of all species

Outgroup

A lineage that is the least closely related to the rest of the organisms

Parsimony

If there are conflicts among characters, use the hypothesis that requires the fewest assumptions (DNA changes)

Species

A group able to interbreed and produce viable, fertile offspring

Speciation

Formation of new species

Geography

Spacial distribution and physical barriers that isolate populations, limiting gene flow and contributing to speciation

Temporal isolation

Species breed at different times of the day, year, or season

Prezygotic barrier

Prevent mating or hinder fertilization

Postzygotic barrier

Prevent a hybrid zygote from developing into a viable, fertile adult

Sympatric speciation

A new species evolves while still inhabiting the same geographic region as the ancestral species

Behavioral isolation

Unique behavioral patterns and rituals separate species

Mechanical isolation

The reproductive anatomy of one species does not fit with the anatomy of another species

Reduced hybrid viability

The genes of different parent species may interact in ways that impair the hybrid’s development or survival

Reduced hybrid fertility

A hybrid can develop into a healthy adult, but it is sterile

Punctuated equilibrium

When evolution occurs rapidly after a long period stasis

Macroevolution

Large evolutionary patterns (ie - mass extinction)

Hybrid breakdown

The hybrid of the first generation may be fertile, but when they mate with a parent species or one another, their offspring will be sterile

Gradualism

When evolution occurs slowly over hundreds, thousands, or millions of years

Divergent evolution

Groups with the same common ancestor evolve and accumulate differences resulting in the formation of new species

Convergent evolution

Two different species develop similar traits despite having different ancestors

Allopatric speciation

Physical barrier divides population OR a small population is separated from the main population (ie - Founder Effect)

Gametic isolation

Proteins on the surface of gametes do not allow for the egg and sperm to fuse

Microevolution

Changes in allele frequencies within a single species or population (Natural and sexual selection, genetic drift, gene flow)

Adaptive radiation

If a new habitat or niche becomes available, species can diversify rapidly

Habitat isolation

Species live in different areas or they occupy different habitats within the same area

Extinction

The termination of a species

RNA World Hypothesis

Proposes that RNA could have been the earliest genetic material