Cells passing through the more posterior portions of the primitive streak give rise to the majority of mesodermal tissues.

TLS Online TPP Program

#Id: 9206

#Unit 11. Evolution and Behavior

Genetic drift 

Genetic drift is an evolutionary force, in which allelic frequency change over generation Just by chance (sampling error). 

The deviations from the expected ratios are random, the direction of change is unpredictable.

TLS Online TPP Program

#Id: 9207

#Unit 11. Evolution and Behavior

TLS Online TPP Program

#Id: 9208

#Unit 11. Evolution and Behavior

CAUSES OF GENETIC DRIFT

Genetic drift in a small population over multiple generations can significantly affect the composition of a population’s gene pool. 

TLS Online TPP Program

#Id: 9209

#Unit 11. Evolution and Behavior

Founder effect

A few individuals form a population start a new population with a different allele frequency than the original population.

Sampling error can arise is through the founder effect, which results from the establishment of a population by a small number of individuals.

TLS Online TPP Program

#Id: 9210

#Unit 11. Evolution and Behavior

Genetic bottleneck

Genetic drift arises is through a genetic bottleneck, which develops when a population undergoes a drastic reduction in size

TLS Online TPP Program

#Id: 9211

#Unit 11. Evolution and Behavior

THE MAGNITUDE OF GENETIC DRIFT

n  = population size

pq=allelic frequency

sp2=variance in allelic frequency among the populations