lecture 19 Flashcards
what is a population
All the individuals of the same species that live
in a particular place at the same time - variations in traits (ex. size, color….)
- some variation due to environment, and some due to heredity
what did Darwin’s theory and Mendel’s discovery create
population genetics: Science that studies the process of microevolution (how populations change genetically over time)
what is microevolution
Is change in the genetic makeup of a population from generation to generation
– evolutionary change below the species level
what can microevolution lead to
macroevolution (new species, new groups)
what is a gene pool
all the alleles for all the loci present in the population
* Diploid organisms have 2 alleles at each genetic locus (gene location)
* each individual only has a small fraction of the alleles present in the population’s gene pool
what is a genotype frequency
The proportion of a particular genotype in the population
what is allele frequency
proportion of a specific allele in a population
what is genetic equilibrium
Frequencies of alleles do not change from generation to generation unless influenced by outside factors
- A population whose allele and genotype freq. do not change from one generation to the next = equilibrium
what is the Hardy Weinberg principle
Allele and genotype frequencies do not change from generation to generation * no evolution is occurring in a population at genetic equilibrium.
what are the conditions for genetic equilibrium
- Random mating
- No mutation
- No natural selection
- Extremely large population size
- No Migration (no gene flow – transfer of alleles from another pop.)
what does the Hardy Weingerg principle give us? why is it useful
tells us what to expect when a sexually reproducing population is NOT EVOLVING
does genetic equilibrium really happen
no
what does the degree of departure between observed allele frequency and those expected by HW principle indicate
amount of evolutionary change
what factors cause microevolution
- Mutations
- Sexual Recombination
- Natural Selection
- Genetic Drift
- Gene Flow
in what types of cells do most mutations occur
somatic
in what type of cells do mutation have to occur to be passed on
gametes, only small fraction of these spread through pop
what is genetic drift, what does it explain
- random evolutionary changes in a population
- Describes how allele frequencies can fluctuate unpredictably from one generation to the next
- major factor altering allele frequency
what causes genetic drift in a small population
- bottleneck effect
- founder effect
what is the bottleneck effect (genetic drift)
occurs when number of individuels in a pop drastically reduce because of a disaster, by chance, some alleles will be overrep and some underep
what is the founder effect (genetic drift)
when a few indivuduels become isolated from a larger population
small fraction establishes a new colony
bring only small fraction of genetic variability of original population
what is gene flow
transfer of alleles from one pop to another potentially altering gene frequencies
what is a consequence of gene flow
- mixing of indiv between pop reduces differences between pop over time
- can counter genetic drift and natural selection
of all the factors that can change a gene pool, which can lead to adaptation of an organism to its environment
natural selection
what is a consequence of naturel selection on genetype
can alter frequency of certain genotypes
