Lecture 5 - Mechanisms of Evolution

University:
Cornell University
Course:
BIOG 1140 | Foundations of Biology
Academic year:

2021
Views:

315

Pages:

7
Author:

Aishani Madassu

Unit 5 Lecture 5 - Mechanisms of Evolution 5 Main Mechanisms that cause Evolution (allelic frequency change) ● Natural Selection ● Mutation ● Genetic Drift ● Gene Flow ● Sexual Selection Genetic Drift (ex. Bottleneck Theory) • Populations isolated into smaller groups, preventing from breeding with other groups • Causes changes in the gene pool rapidly (e.g. mutations are felt more significantly in the population) Effects of Genetic Drift • Genetic drift is significant in small populations • Genetic drift can cause allele frequencies to change at random • Genetic drift can lead to a loss of genetic variation within populations • Genetic drift can cause harmful alleles to become fixed Gene flow Gene Flow – transfer of alleles into or out of a population due to the movement of fertile individuals (immigration/emigration). Human migration is leading to the merging of races…creating a large central gene pool. Sexual selection: individuals with certain traits are more likely to get a mate Sexual Dimorphism- differences in appearances of males/females Evolution cannot and does not produce perfection! • Selection can only edit existing variation, limited by historical constraints • Adaptations are often compromises (ie – human pelvis)