Mechanisms Of Evolution Flashcards
What does the allele frequency reflect?
The populations genetic diversity
Evolution
The process by which new species can develop from previous forms.
Natural Selection
The process by which individuals with traits that make them better suited to the environment tend to survive and reproduce. It acts upon the alleles in a population and can change the frequency of alleles present in a gene pool.
Natural selection selects for…
Beneficial alleles and the frequency of alleles in the populations gene pool will increase.
Selection pressure
An abiotic or biotic environmental factor that affects the survival of an individual and therefore influences the reproductive success in a population. When environmental factors change, it causes different alleles to be selected for/against.
Populations that have very low genetic diversity…
Are less likely to survive a change in the environment. It is unlikely these populations will have alleles in the gene pool that give certain; individuals a survival advantage in the new environmental conditions so the population may go extinct.
What mutations are selected for and against?
Beneficial mutations -> selected for and will become more common in a gene pool
Harmful mutations -> selected against
Sexual selection
Females are the selection pressure and males attempt to out-compete others for access to females, by carrying out displays that prove their fitness.
Females will show a preference for certain traits and they will become more common in the gene pool.
Artificial selection
Breeding together of organisms by humans to produce desirable traits.
What does breeding closely related individuals together do?
It can increase the chances that resulting offspring will produce desired traits. But chances of harmful alleles being expressed are also increased.
Gene flow (immigration and emigration)
When genetic information is moved from one population to another. Immigration adds new alleles to a gene pool and emigration reduces a populations genetic diversity.
Genetic drift and what acts as a buffer
The change in allele frequency within a population from generation to generation, due to chance rather than a selection pressure.
Large populations act as a buffer against random loss of alleles due to genetic drift.
Fixed allele
Only variant of a gene in a populatin
Founder effect
When a small number of individuals establish a new population by emigrating to a new, isolated location.
Alleles present are unlikely to be representative of entire previous population
These populations are subject to strong genetic drift.
Bottleneck effect
When a population undergoes a sudden reduction in size, usually caused by a catastrophic event.
Population left will have reduced genetic diversity, likely inbreeding as well which leads to harmful genetic conditions.
