a group of interbreeding organisms that can breed and produce offspring.
includes all alleles present in a gene pool
The number of times the allele occurs in a gene pool.
defined as changes in gene frequencines witha population over time. Microevolution results in evolutionary change within a population.
all members of a single species occuping specific region sharing a common genepool
Hardy Weinberg conditions
1) random : individuals are free to pair with any other member of a population. Individuals will pair by chance and not according to their genotypes or phenotypes.
2) Large Population: the population must be very large so that genetic drift is insignificant. Genetic drift: in small populations, an allele can become more or less common by chance.
3) There can be no movement, or gene flow, into or out of a population.
4) There can be no mutations in alleles.
5) There can be no natural selection where on genotype is favored over another.
*UNDER THESE CONDITIONS, NO EVOLUTION IS TAKING PLACE.
What are the four requirements of natural selections?`
Variation - the members of a population differ from one another.
Inheritance - different traits can be inherited.
Differential Adaptiveness - difference affect how well an individual is adapted to the environment.
Differential Reproduction - individuals who are better adapted to the environment are more likely to reproduce.
Give the 3 types of Natural selection.
1) Directional selectional:
-occurs when an extreme phenotype is favoted
-distribution curve in one direction.
Example: Body size of a horse overtime.
2) Stabilizing selection:
- Intermediete phenotype is favored
- environment remains constant.
Example: in human population, intermediete birthweight (not to fat, not to skinny) = better survival.
Example 2: Birds are better off laying 5-6 eggs for survival.
3) Disruptive selection:
- 2 or more extreme phenotypes are favored over intermediate phenotype.
Example: Sanils have a wide range of habitat.
-any evolutionary change at or above the level of species
-large scale of evolutionary change
- splitting of 1 species into 2 or more new species.
- origin of a new specie is due to changes in the gene pool and alllele frequencies over time
As more species evolve, populations become reproductively isolated from eachother from one another. Define and give examples of 5 Prezygotic Isolating Mechanisms.
-Species in the same location occupy different habitat
-Animals in rainforest occupy particular levels of forest canopy caused isolation from similar species.
- Species reproduce at different times
- 5 similar species of frogs in Ithica, New York remain seperate because they have different mating times.
- Species are capable of breeding but have differences in courtship patterns
-fireflies find other fireflies of the same type by the specific light pattern
-animal genetalia or plant reporductive structures are incompatilble (dragonflies have clasps that let them hold a female of the same type)
- even if gametes meet, they may not be able to produce a zygote.
- sperm may not be able to survieve in reproductive track
-eggs may have receptors for the same speciies.
Define and give examples of 3 postzygotic Isolating mechanisms.
1) Zygotes cannot survive due to different sets of chromosome.
2) Hybrid Sterality:
- Offsping may be born, but the adults are stearlity
- Cross a horse and a donkey, result is a mule which is usually sterile.
- complications during meiosis - cannot produble viable gametes
3) F2 fitness : hybrids reproduce, but their offsping are unable to reproduce (the F2 generation). In some cases, mules are fertile, but their offspring are not.
Define and give examples of the 2 modes of Speciation.
-orgin of a new species when population are geographically seperated.
-salamanders is (a-7 species (seperated by mountain ranges).
-Geographic seperation may not result in a new species.
-orgin of a new species in region that overlap geographically.
Addaptive Radiation is a form of allopatric radiation. Define adaptive radiation, and give an example.
Adaptive radiation is considered a type of allopatric speciation. The result of adaptiv radiation is the evolution of several species from a common ancestor in new geographic regions. The new species have adapted to different environments.
Darwin's finches are examples.
Sources of Microevolution (mating types)
-mating between relatives
In mating between relatives, allele frequencies do not change. The population is affected by mating between relatives by:
-decreases heterzygous pop.
-doesnt change allele frequencies
- increase frequencies of recessive abnormalities.
- random changes in allele frequencies due to chance.
-has large impact on small populations.
-a type of genetic drift is the bottleneck effect. The majority of genotypes are prevented from participating in the productocion of the next generation due to natural disaster or human interfernce. Alleles can be lost from a population.
Bottleneck effect - rare alleles occur at a higher frequency in a population that is isolated from the general population.