Evolution of Populations Flashcards
Chapter 23
Do species evolve?
No, populations evolve.
Microevolution
Chane in allele frequencies in a population over generations
3 mechanisms that causes allele frequency change.
- Natural Selection
- Genetic Drift
- Gene flow
Only natural selection causes adaptive evolution.
How can genetic variation be measured?
As gene variability or nucleotide variability.
How can new genes and alleles arise?
Mutations or crossing-over/gene duplication.
What is a mutation?
A change in dsDNA - genome
In what cells do mutations get passed down to offspring?
Cells that produce gametes, since somatic mutations cannot be passed to offspring.
Effects of point mutations:
-Mutations in noncoding regions of DNA are often harmless
-Mutations in genes can be neutral because of redundancy in the genetic code
-Mutations that result in a change in protein production are OFTEN harmful
-Mutations that result in a change in protein production can SOMETIMES be beneficial
Population definition
A localized group of individuals capable of interbreeding and producing fertile offspring.
Hardy-Weinberg equation
Frequency of all alleles in a population: p + q = 1
-Only applies a population that is not evolving. In a population remaining constant from generation to generation.
p^2 + 2pq + q^2 = 1.
Conditions for Hardy-Weinberg Equlibrium
- No mutations
- Random mating
- No natural selection
- Extremely large population
- No gene flow
Natural Selection
Differential success in reproduction results in certain alleles being passed to the next gen. in greater proportions.
Genetic Drift
Smaller sample = greater chance of deviation from predicted result.
Genetic drift describes how allele frequencies fluctuate unpredictably from one generation to the next. Genetic drift tends to REDUCE genetic variation through losses of alleles.
The Founder Effect
Occurs when a few individuals become isolated from a larger population. Allele frequencies of isolated population can be different from those in the larger parent population.
The Bottleneck Effect
A sudden reduction in population size due to a change in the environment. The resulting gene pool may no longer be reflective of the original population’s gene pool. If population remains small, may be further affected by genetic drift.
