AP Bio Unit 7 Vocabulary

Biogeography

geographic distribution of species

Evolution

descent with modification; the idea that living species are descendants of ancestral species that were different from the present-day ones; also defined more narrowly as the change in the genetic composition of a population from generation to generation

Descent With Modification

darwin’s way of referring to evolution. principle that each living species has descended, with changes, from other species over time

Natural Selection

the process by which individuals that are better suited to their environment survive and reproduce most successfully; also called survival of the fittest

Fitness

organisms ability to survive and reproduce

Competition

struggle between organisms to survive in a habitat with limited resources

Biotic Factors

living factors in an enviroment

Abiotic Factors

non-living factors in an enviroment

Selective Pressures

environmental conditions that select for certain characteristics of individuals and select against other characteristics

Adaptations

characteristic that improves an individual’s ability to survive and reproduce in a particular environment

Phenotype

physical expression of a gene

Genotype

genetic makeup or allele combination

Artificial Selection

selection by humans for breeding of useful traits from the natural variation among different organisms

Mutation

change in the nucleotide sequence that affects genetic information

Population

a group of individuals that belong to the same species and live in the same area

Gene Pool

combined genetic information of all the members of a particular population

Fixed

refers to an allele for which all members of a population are homozygous

Genetic Drift

gradual changes in gene frequencies in a population due to random events

Bottleneck Effect

genetic drift that occurs when the size of a population is reduced, as by a natural disaster or human actions. typically, the surviving population is no longer genetically representative of the original population

Founder Effect

change in allele frequencies as a result of a small subgroup of a population

Gene Flow

form of natural selection where the center of the curve remains in its current position; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end

Directional Selection

where individuals at one end of the curve have a higher fitness than individuals in the middle or at the other end

Stabilizing Selection

selection against extreme values, large or small, in a continuous trait

Disruptive Selection

also called diversifying selection, describes changes in population genetics in which extreme values for a trait are favored over intermediate values

Sexual Selection

form of natural selection in which individuals with certain inherited characteristics are more likely than others to obatin mates

Hardy Weinberg Equilibrium

condition that occurs when the frequency of alleles in a particular gene pool remain constant over time

Comparative Morphology

analysis of the structures of living and extinct organisms

Analogous Structures

structures that do not have a common evolutionary origin but are similar in function

Embryonic Homology

describes the similarities in the pre-birth development in different species

Vestigial Structure

structure that is present in an organism but no longer serves its original purpose

Molecular Homology

a type of homology that compares similarities/differences in DNA; one of the strongest ways to determine the relatedness or lack thereof between two organisms

Homologous Structures

similar structures that related species have inherited from a common ancestor

Common Ancestor

ancestral species from which a later species evolved

Convergent Evolution

evolution toward similar characteristics in unrelated species

Homology

similarity of characteristics due to common ancestry

Fossil

preserved remanant/impression of a past organism

Node

the points at the ends of branches which represent sequences or hypothetical sequences at various points in evolutionary history

Cladogram

diagram that shows the evolutionary relationships among a group of organisms

Phylogenetic Tree

diagram showing evolutionary relationships of organisms with a common ancestor; resembles a tree

Systemics

scientific discipline focused on classifying organisms and determining their evolutionary relationships

Basal Taxon

diverges early in the history of a group and originates near the common ancestor of the group

Sister Taxa

groups that share an immediate common ancestor

Monophyletic Group

a taxonomic grouping that includes an ancestral species and all of its descendants

Derived Characteristics

characteristic that appears in recent parts of a lineage, but not in its older members

Ancestral Characteristics

characteristics that have arisen in organisms as a result of common evolutionary descent

Synapomorphy

shared derived characteristics

Paraphyletic Group

group of taxa that consists of a common ancestor and some of its descendants, but not all

Polyphyletic Group

a taxonomic grouping consisting of several species that lack a common ancestor (more work is needed to uncover species that tie them together into a monophyletic clade

Taxonomy

scientific study of how living things are classified

Phylogenetics

study of evolutionary relationships among species

Root

the oldest point in the tree and corresponds to the theoretical last common ancestor of all taxonomic units included in the tree

Outgroup

generally, any group that one does not belong to

Parsimony

choose simplest scientific explanation that fits evidence

Species

group of similar organisms that can breed and produce fertile offspring

Speciation

the formation of new species as a result of change over time

Geography

study of the earth’s physical and cultural features

Temporal Isolation

form of reproductive isolation in which 2 populations reproduce at different times

Prezygotic Barrier

reproductive barrier - impedes mating between species or hinders fertilization if interspecies mating is attempted

Postzygotic Barrier

reproductive barrier - prevents hybrid zygotes being produced by 2 different species from developing into viable, fertile adults

Sympatric Speciation

formation of new species in populations that live in the same geographic areas

Behavioral Isolation

form of reproductive isolation in which 2 populations have differences in courtship rituals or other types of behavior that prevent them from breeding

Mechanical Isolation

mating is attempted, but morphological differences prevent its successful completion

Reduced Hybrid Viabilty

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

Reduced Hybrid Fertility

even if hybrids are vigorous, they may be sterile

Punctuated Equillibrium

the hypothesis that evolutionary development is marked by isolated episodes of rapid speciation between long periods of little or no change

Macroevolution

evolution on a large scale extending over geologic era and resulting in the formation of new taxonomic groups

Hybrid Breakdown

hybrid is fertile, but when they breed the next generation is sterile

Gradualism

proposed explanation in evolutionary biology stating that new species arise from the result of slight modifications (mutations and resulting phenotypic changes) over many generationsdi

Divergent Evolution

when 2 or more species sharing a common ancestor become more different over time

Convergent Evolution

process by which unrelated organisms independently evolve similarities when adapting to similar enviroments

Allopatric Speciation

formation of new species in populations that are geographically isolated from one another

Gametic Isolation

a prezygotic reproductive barrier where the sperm of one species may not be able to fertilize the eggs of another species−65.7

Microevolution

evolutionary change within a species or small group of organisms, especially over a short period

Adaptive Radiation

an evolutionary pattern in which many species evolve from a single ancestral species

Habitat Isolation

2 species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers

Extinction

typically describes a species that no longer has any known living individuals

RNA World Hypothesis

hypothesis that RNA was the first nucleic acid to evolve and that early life was based on RNA, rather than DNA or protein