genetic diversity Flashcards
what is an allele?
Different versions of the same gene, giving us slightly different phenotypes
What is genetic diversity?
Measure of the number of different alleles of each gene in a species or population
What is gene pool?
All the alleles available within a particular species/population
stages of natural selection
- random mutation forms new alleles
- diversity increases
- some individuals have an advantage over others
- able to survive and reproduce
- alleles passed onto offspring
- allele frequency increases
why is natural selection important?
- allows organisms to become better adapted to their environment, allowing them to survive
- behaviour, physiological, anatomical adaptations
what are the three ways natural selection can affect the population
- directional selection
- stabilising selection
- disruptive selection
What is directional selection?
- directional selection selects for one of the extreme phenotypes
- range of phenotypes shifts in one direction
what is stabilising selection?
- natural selection selects for the middle range phenotypes (against both extremes - more shows the middle range)
What is disruptive selection?
- natural selection selects for the two extremes and against the middle range phenotypes
- causes new species to appear
What is a species?
A group of organisms with similar features that can interbreed to produce fertile offspring
Issues with species definition
- members of the same species can look very different from each other and still produce fertile offspring
- members of different species can also look similar and may occupy the same habitat so can be difficult to tell apart
what is courtship behaviour?
Set of behaviours exhibited by male or female members to attract a male, only members of the same species will respond
why does courtship allow successful reproduction?
- recognise members of the same species
- identify a mate that is capable of breeding
- form a pair bond
- synchronise mating
what are the three other ways genetic diversity can be changed?
- gene flow
- genetic bottlenecks
- the founder effective
What is gene flow?
- organisms from another population migrate between populations changing the alleles available
- this can also change allele frequencies in the gene pool of a population , species
what is a genetic bottleneck?
- describes the effect of a very sudden reduction in population e.g. natural disaster, hunting
- some alleles are lost, when reproduction occurs the new population is limited in alleles
what is the founder effect?
- when organisms form a population start a new colony, initially the gene pool has only a few alleles
- the gene pool of the new colony may be very different to that of the original population e.g. rare alleles now more common (usually recessive)
- can be caused by migration, geographical separation
