7: Populations Flashcards
(18 cards)
Species definition?
A group of similar organisms that can reproduce to give fertile offspring
Population definition?
A group of organisms of the same species living in a particular area at a particular time
What does the Hardy-Weinberg model predict?
That the frequencies of alleles in a population won’t change from one generation to the next
Gene pool definition?
The complete range of alleles present in a population
What conditions is the Hardy-Weinberg principle true under?
Large population - no immigration, emigration, mutations or natural selection
Random mating
What are the Hardy-Weinberg equations?
p + q = 1
p2 + 2pq + q2 = 1
Variation definition?
the differences that exist between individuals
Evolution definition?
a change in allele frequency over time
Stabilising selection definition?
Where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce
When does stabilising selection occur?
When the environment isn’t changing
Directional selection definition?
Where individuals with alleles for a single extreme phenotype are more likely to survive and reproduce
Disruptive selection definition?
Where individuals with alleles for extreme phenotypes at either end of the range are more likely to survive and reproduce
Speciation definition?
the development of a new species from an existing species
When does speciation occur?
When populations of the same species become reproductively isolated
What is allopatric speciation?
Geographical isolation leading to the populations experiencing different selection pressures so different changes in allele frequencies
What is sympatric speciation?
Speciation without geographical isolation - within a population
Changes leading to reproductive isolation include?
Seasonal, mechanical, behavioural
What is genetic drift?
When chance, rather than environment, dictates which individuals survive, breed and pass on their alleles
