Topic 11 Flashcards
Genetic structure
description of genetic variation among individuals within a population
Gene flow
exchange of genetic material among populations resulting from dispersal
Genetic variation depends on number and variability of..
selection pressures acting on individuals with in a population
Low variation
few selection pressure w low variability
High variation
many selection pressures w high variability
To quantify the level of genetic variation in a population
-level of heterozygosity. more alleles in the gene pool more possible combinations of alleles is higher genetic variation
General pattern
smaller populations ten to have lower genetic diversity (variation) than larger population
2 mechanisms aperating to decrease geneitc diversity over time
- genetic drift
- interbreeding
Genetic drift =
random changes in allele frequencies within a population due to chance
Random
no discrimination between (or selection of) individuals with favourable or unfavourable traits
Chance
unpredictable change in environmental conditions
Genetic drift occurs in..
all populations and is a mechanisms of evolution
In small populations genetic drift..
occurs at a faster rate and is more likely to result in loss of an allele
Inbreeding
mating between relatives
In small populations the choice of mates ..
can be limited resulting in increased probability of mating w relatives
Interbreeding tends to..
increase homozygosity and decrease heterozygosity (related indiv. share similar traits
Eventually populations can become exclusively homozygous and if rare recessive genes are harmful homozygosity for recessive genes can result in..
reduces fitness and increase mortality
Interbreeding depression
loss of vitality and increased incidence of disease due to the expression of deleterious recessive alleles when genetic diversity decrease
Black robin in New Zealand
populations reduced significantly. 1980 5 individuals were remaining but one female. more 250 individuals but lower fitness 30% hatching failure. because good proportion of sperm are abnormal (non motile) so many eggs are never fertilized
2 key concepts needed to maintain genetic diversity
- effective population size
- minimum viable population
Effective population size
subset of males and females within a poulation that successfully breed. defines the number of indiv. passing genes to successive generations
Minimum viable population
number of individuals necessary to ensure the long term survival of a species.
Whatys crtitcal in conservation biology
-minimum viable populations. allows us to calculate how large a population of a particular species should be to assure its long term survival
