genetic diversity and adaptation Flashcards
What is a mutation
random change to quantity or base sequence of DNA
What are the types of mutation
gene- changes to nucleotide bases or sequence of bases in DNA (micro)
chromosome- changes to structure of part or whole chromosomes (macro)
Types of mutation
Substition of bases- nucleotide is replaced with another. Can result in multiple outcomes
genetic diversity
total number of different alleles in a population
population
group of individuals of the same species that live in the same place and can interbreed
Natural selection process
1- variation exists within gene pool. New alleles will be created by mutations
2- best adapted survive and reproduce (have more reproductive success)
3-best alleles are passed on
4- successful allele frequency increases as these alleles give the organism an advantage over other individuals within the population
what is selection
process by which organisms that are better adapted to their environment tend to survive and breed, while those who are less well adapted tend not to
directional selection
Occurs as a result of a change in the environment. Favours individuals varying in 1 direction from the mean (extreme phenotypes)
Results in a change in characteristics within the population with more organisms having the extreme phenotype
This causes normal distribution curve to shift to left or right but remain the same shape
IF environmental change is great enough may beno phenotype suited to new conditions so population will die out
stabilising selection
If environmental conditions remain stable it is individuals with phenotypes closest to the mean that are favoured.
These individuals are more likely to pass on their alleles to the next generation and those individuals with extreme phenotypes are less likely to
causes distribution curve to become narrower or higher but mean does not change
Stabilising selection therefore tends to eliminate phenotypes at the extreme
Disruptive selection
occurs when both extreme traits are favoured in an environment. Disruptive selection increases genetic and phenotypic diversity in a population, since more than one phenotype, or physical trait, is favoured.
eg short tails help keep predators from catching you on the ground and long tails are good for balance in trees but medium tails dont help
sexual selection
involves random mutations affecting what is considered to be sexually attractive when there is competition for mates
Types of adaptations
1- behavioural- eg mating rituals, hibernation, migration
2-anatomical- structural changes to help survival eg thicker fur in artic foxes compared to those in warmer climates
3-physiological- changes to internal organs, tissues and cells to help survival eg oxidation of fat rather than carbohydrates in kangaroo rats to produce additional water in dry dessert environments, venom production in snakes
