Accumulative Final

bio 2

microevolution

small scale rapid genetic changes within a population or species

macroevolution

large scale changes over geological time, leading to new species or higher taxonomic groups

natural selection

lead to change in allele frequencies; frequencies of alleles of a gene from generation to generation

disruptive selection

favors extreme phenotypes over intermediate ones; leading to formation of two or more distinct species

directional selection

individuals with an extreme phenotype at one end of the spectrum are favored over intermediate or opposite extremes; populations trait distribution to shift consistently toward that extreme over time; driven by environmental changes

stabilizing selection

favors average phenotypes rather than extreme variations, reducing genetic diversity and maintaining the status quo within a population

what is the biological species concept

a species is a group of organisms that can interbreed in nature and produce viable fertile offspring and are reproductively isolated from other such groups

1. mutation

random DNA changes introduce new alleles into a population

2. variation

mutations create heritable differences among individuals

3. selection

natural selection favors individuals with traits that increase survival or reproduction

4. reproductive isolation

populations become genetically separated stopping gene flow; geographically, behaviorally, temporally

5. speciation

once isolated long enough, populations diverge so much that they become distinct species

mass extinctions

5 have occurred; 96% of all species have perished in a given extinction; 6th underway

adaptive radiation

closely related species that have recently evolved from a common ancestor by adapting to different parts of the environment