final Flashcards
(50 cards)
Population?
a group of organisms of a single species occupying a particular area at the same time.
What causes the variation in a genotype?
Population genetics is the study of this diversity in terms of allele differences. It evaluates the diversity of a population by studying genotype and phenotype frequencies over time.
The Hardy-Weinberg Equilibrium states that:
5
Allele frequencies in a population will remain constant assuming
- No Mutations
- No Gene Flow
- Random Mating
- No Genetic Drift
- No Selection
Hardy-Weinberg Equilibrium:
- Required conditions are rarely (if ever) met.
- Deviations from a Hardy-Weinberg equilibrium indicate that evolution has taken place.
- Analysis of allele changes in populations over time determines the extent to which evolution has occurred.
Homozygous dominant/recessive?
TT/tt
Heterozygous dominant?
Tt
Natural selection?
+Natural selection causes imperfect adaptations.
- it depends on evolutionary history
- Imperfections are common
Natural selection and adaptation:
5
- Members of a population have inheritable variations.
- More individuals are produced in each generation than the environment can support.
- Organisms compete for available resources.
- Some individuals have adaptive characteristics.
- Favorable traits that result in increased survival and reproduction which causes organisms within a population to differ in their reproductive success.
Darwin used _____ principles to formulate his idea of natural selection.
Malthus’
Darwin’s natural selection hypothesis was based on:
Observation of tortoises and finches on the Galápagos Islands
Geneflow?
(Gene migration) Movement of alleles between populations when:
- Gametes or seeds (in plants) are carried into another population
- Breeding individuals migrate into or out of population
Continual _______ reduces genetic divergence between populations
gene flow
Nonrandom Mating?
When individuals do not choose mates randomly
Assortative mating: (3)
- They select mates with the same phenotype with respect to a certain characteristic.
- They reject mates with different phenotype
- It can play an important role in the evolution of a population
Allele frequency?
It is the proportion of each allele within a populations genepool.
the gene pool of a population can be described in terms of ________ and ________.
Genotype frequencies and Allele frequencies
________ in a population will remain constant assuming- no mutations, no gene flow, random mating, no genetic drift, and no selection
Allele frequencies
Genetic drift?
+Changes in the allele frequencies of a population due to change rather than selection by the environment
- Does not necessarily lead to adaptation to the environment
- Occurs by disproportionate random sampling from population
- Stronger effect in small populations
- Likely to occur: after a bottleneck, when severe inbreeding occurs, or when founders start a new population
What are the three types of natural selection?
Directional, Stabilizing, and disruptive.
Directional selection?(4)
- An extreme phenotype is favored.
- The curve shifts in one direction.
- Bacteria become resistant to antibiotics.
- Body size increases in horse evolution
Stabilizing selection?(2)
-An intermediate phenotype is the most adaptive for the given environmental conditions. -The peak of the curve increases and tails decrease.
Ex. Human babies with low or high birth weight are less likely to survive
Disruptive selection?(
- Two or more extreme phenotypes are favored over the intermediate phenotype.
-The curve has two peaks
Ex. British land snails vary because a wide geographic range causes selection to vary
Stabilizing selection?
An intermediate phenotype is the most adaptive for the given environmental conditions. -The peak of the curve increases and tails decrease.
Ex. Human babies with low or high birth weight are less likely to survive
Tell what most birds male dominant appearance look like?
Flamboyant and colorful
