evolution 1.7 Flashcards
what is selection
non-random change in frequencies of some genetic sequences (alleles) within a population
the frequencies of some dna sequences within a population:
increase because they are selected for
decrease because they are selected against
natural selection
non random
increase in frequency of dna that increase survival
reduction in deleterious sequences.
why does variation exist within one species
mutations
why is there a struggle for existence
species produce to many off spring
who are more likely to survive
those with favourable genes that are better adapted to the environment
why does increased gene frequency happen
favourable genes become more common within species due to increased reproduction
why does decreased gene frequency occur
those with less favourable genes are less likely to survive and pass on their genes to offspring
quantitiive traits
measurable phenotypes
continuous variables
due to polygenic inheritance (controlled by the interaction of several genes)
stabilising selection
average phenotypes are selected for
extreme phenotypes are selected against
occurs in an unchanging environment
mean remains the same (genetic diversity in population decreases)
