Unit 2: Key area 2.1 - Drift and Selection Flashcards
Define: Evolution
The process by which different kinds of living organisms are believed to have developed from earlier forms during the history of the Earth.
Define: Species
A species is a group of populations that can interbreed in nature.
Define: Genetic Drift
The changes seen in the alleles of a population due purely to chance
Define: Neutral Mutations
Mutations that do not give a selective advantage or disadvantage therefore subject to genetic drift.
Define: Bottleneck Effect
Occurs when there is a disaster of some sort that reduces a population to a small handful which rarely represents the actual genetic makeup of the initial population.
When does the founder effect occur?
Occurs when there is a lack of genetic variation due to a small mating population.
Both bottleneck effect and founder effect provide an opportunity for what evolutionary process to take over?
Genetic Drift
Define: Carrying Capacity
The population that can be sustained by a particular environment
Define: Natural Selection
The differential survival and reproduction of individuals due to differences in phenotype
When population growth takes the population above the carrying capacity, this leads to what, to alter the carrying capacity?
Environmental Change
List four living changes that could take place in an ecosystem to reduce population in an environment?
- Migration 2. Competition 3. Disease 4.Change of Species
List two abiotic (non-living) changes that could take place in an ecosystem to reduce population in an environment?
- Climate changes 2. Geological processes - tectonic plate movement
Changes in the ecosytem cause some organisms to struggle for surivial this is known as
selective pressure
Evolution can occur through what three processes?
Genetic drfit, Natural Selection and Sexual Selection
Define Genetic drift:
Random change in how frequently a particular allele occurs within a population
Does genetic drift have a bigger or smaller effect on small gene pools?
Bigger
Why do certain alleles occur more frequently within a population?
Because they confer a selective advantage
Alleles that offer an advantage occur more frequently becasue they?
Increase the chance that the individuals can compete and survive to pass the advantageous allele on to future generations.
Novel alleles arising in a situation is usually due to?
Random mutaiton
Fitness can be measured in two terms which are?
- Absolute fitness 2. Relative fitness
Define: absolute fitness
Ratio of frequencies of a particular genotype from one generation to the next.
If the absolute freqency of an genotype is 1, then?
The frequency of the genotype is stable
A value greater than 1 in the absolute fitness conveys an
Increase in the genotype
A value less than 1 in the absolute fitness conveys a
decrease in the frequency of a genotype
Define: Relative Fitness
Ratio of surviving offspring of one geotype compared with the other genotype
Purple pea plants are the most reproductively successful so have a relative fitness of one, white pea plants are only 65% as successful so have a relative fintess of ?
0.65
