Lesson 11 Definitions

Question 1

species

Answer 1

groups of interbreeding populations that are reproductively isolated from each other

Question 2

speciation

Answer 2

a process whereby over time one species evolves into a different species (anagenesis) or whereby one species diverges to become two or more species (cladogenesis)

Question 3

clade

Answer 3

“branch”: a group consisting of a single common ancestor and all its descendants

Question 4

Cambrian explosion

Answer 4

a point in the fossil record where all modern phyla appear

Question 5

stasis

Answer 5

periods without evolutionary change

Question 6

punctuated equilibrium

Answer 6

long periods of stasis, followed by rapid speciation events

Question 7

peripatric speciation

Answer 7

a mode of speciation in which a new species is formed from an isolated peripheral population

Question 8

mosaic evolution

Answer 8

evolution occurring in stages, unevenly paced

Question 9

adaptive radiation

Answer 9

an event in which a lineage rapidly diversifies, with the newly formed lineages evolving different adaptations

Question 10

divergent evolution

Answer 10

accumulation of differences which can lead to formation of different species from a common ancestor (adaptive radiation on a smaller scale) species will have homologous structures

Question 11

convergent evolution

Answer 11

different species with similar phenotypes, or analogous structures

Question 12

balanced polymorphism

Answer 12

a situation in which two different versions of a gene are maintained in a population of organisms because individuals carrying both versions are better able to survive than those who have two copies of either version alone.

Question 13

orthologs

Answer 13

genes in different species that evolved from a common ancestral gene by speciation, usually retaining the same function

Question 14

molecular clocks

Answer 14

the use of genetic information together with fossil data to determine the time of divergence of two species