Chp 14 Speciation & Extinction

Species

distinct groups of organisms

Microevolution

small evolutionary changes that accumulate in a population

Macroevolution

large-scale evolutionary change

Carolus Linnaeus

classified species based on appearnce

Biological species concept

defines species by reproduction

The biological species concept is difficult/cannot be applied to which organsims?

asexual/extinct organisms

DNA analysis

helps to define species based on the nucleotide sequence of genes

If DNA of 2 organisms is more than ___% identical, they are considered the same species

97

Reproductive barriers

barriers that maintain reproductive isolation

Prezygotic reproductive barriers

prevent fertilization

Postzygotic reproductive barriers

prevent development of fertile offspring

Speciation

formation of a new species

Gradualism

slow and steady speciation

Punctuated equilibrium

short, irregular bursts of speciation

Extinction

disappearance of a species

Background extinction rate

steady, ongoing losses of species

Mass extinction

disappearance of many species over relatively short expanses of time

Taxonomy

science of describing, naming, and classifying species

Cladistics

defines groups based on ancestral and derived traits

Ancestral traits

inherited from an ancestor

Derived traits

NOT inherited from an ancestor

Cladograms

diagrams showing evolutionary relationships

Clades

groups of organisms that consist of a common ancestor and all its descendants

Common ancestors indicate evolutionary _______

relationships

Phylogenetics

study of evolutionary relationships among species