Bio 1B - Lab 4 - Macroevolution of the Horse

Macroevolution

large-scale evolutionary changes that take place over long periods of time

Microevolution

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

Speciation

the formation of new and distinct species in the course of evolution.

adaptive radiation

the rapid increase in the number of species with a common ancestor

cladogram

a branching diagram showing the cladistic relationship between a number of species.

Phylogeny

Evolutionary history of a species or group of species.

fossils

describe macroevolutionary patterns

evolutionary radiation

a clade undergoes a high rate of speciation in a relatively short period of geological time

when does a non-adaptive evolutionary radiation occur

when a large population is broken into many isolated habitat types than existed previously

Why does adaptive radiation happen?

as a response to the opening of new geological niches

niche

the role an organism plays in the community

what two scenarios can cause a new niche to form

adaptive radiation occurs in response to the evolution of a new beneficial phenotype

when the environment changes and creates new niches that had not previously existed in a location

beneficial phenotype

refers to a new character that results in higher fitness in a particular environment for those organisms that possess the character -- organisms are able to outcompete other species that were already in that environment, filling all ecological niches previously occupied

hypsodonty

high crowned teeth

mammals that eat soft foods have (high/low) crowned teeth

low

what is the benefit of having high crowned teeth

slows the damage that results from a diet of high grasses

hypsodonty index

crown height / crown length

grazers

animals that feed on grasses and other monocots

browsers

animals that feed on trees and bushes

grazers have a (flat/round) muzzle

flat -- enables grazers to crop grass at ground level

browsers have a (flat/round) muzzle

round -- can pull leaves off tress and bushes

postorbital bar

the bone that closes the back of the eye socket

a complete postorbital bar indicates a (grazer/browser)

grazer -- strong temporalis muscles needed to chew repeatedly