Chapter 16,17- Micro evolution Flashcards
Biogeography
Discovery of species in isolated locations
The Great Chain in Being
Developed in the 14th century. Belief that all species were created at one time and in one place
Comparative morphology
Similarities between animals and their parts with no function
Fossils
Deep layers with simple fossils, overlying layers with increasing complexity
Microevolution
A change in an allele’s frequency from one generation to the next in a population
Polymorphism
Traits come in two or more distinct forms
Gene pool
All genes found in one population
Genetic Equilibrium
Theoretical state in which a population is not evolving
When does genetic equilibrium occur?
- No mutations
- No selections
- Random mating
- No migration
- Population is very large
Lethal Mutation
An expression of a gene that results in death
Neutral Mutation
Has no effect on survival and reproduction
Beneficial Mutation
Those that bestow survival advantages
Directional Selection
Shift in allele frequency in a consistent direction caused by environmental pressures or adaptive mutation
Example of Directional Selection
The Peppered Moth:
- Pollution darkened tree trunks
- Camouflage of black moths increased their survival from predators
- DS caused a shift away from light-gray towards dark gray moths
Stabilizing Selection
Intermediate forms of a trait is favored over the extreme trait, which are than eliminated from the population
Example of Stabilizing Selection
Eurosta Solidaginis(Fly)
- the size of the gall determines what it’s going to be eaten by.
- Small galls: Beetles
- Large galls: Birds
- Medium galls: Nothing
Disruptive Selection
Both forms at extreme ends are favored, thus the intermediate forms are eliminated
Detailed example of Disruptive Selection
African Finches:
- The bill of a finch that measures 12 millimeters wide are able to feed on soft seeds.
- the bill of a finch that measures wider than 15 millimeters are able to feed on hard seeds
- Leaving the intermediate forms of the finch to compete with both finches and end up starving.
Sexual Selection
Based on any trait that gives the individual a competitive edge in mating and producing offspring
Balancing Selection
Multiple alleles are maintained in a population with high frequency against homozygotes
Example of Balancing Selection
Sickle Cell Anemia:
- AA (normal blood) vulnerable to death from malaria
- aa (sickled blood) immune to malaria but still die at a young age
- Aa (carrier of sickle cell) immune to malaria and won’t die from sickle cell anemia
Gene flow
Physical flow (immigration/emigration) of alleles between populations
Genetic Drift
Random change in allele frequencies over generations brought about by chance
*Magnitude of drift is greatest in small populations
Bottleneck Effect
A drastic reduction in population size brought about by severe pressure
Founder Effect
Genetic drift is pronounced when a few individuals start a new population
Inbreeding
Breeding or mating between close relatives who share a large number of alleles
