genetic diversity Flashcards
(16 cards)
what is genetic diversity?
total number of genetic characteristics in the genetic makeup of a species.
what are alleles and how do they arise?
variations of a particular gene or versions of DNA sequence.
arise by mutation.
what is a population?
a group of organisms of the same species in a particular space and time, that can interbreed to produce fertile offspring.
explain the importance of genetic diversity.
- enables natural selection to occur.
- in certain environments a new allele of a gene might benefit its possessor.
- gives possessor selective advantage which increases chances of survival and reproductive success.
what is evolution?
a change in allele frequency over many generations in a population, occurring through the process of natural selection.
why is adaptation and selection important?
adaptation and selection are major factors in evolution and contribute to the diversity of living organisms.
what are the principles of natural selection in evolution of populations?
Mutation
Advantage
Reproduction
Inheritance
Allele frequency
explain the principles of natural selection in the evolution of populations.
mutation - random gene mutations can result in new alleles of a gene.
advantage - in certain environments the new allele might benefit its possessor, as the organism has a selective advantage.
reproduction - possessors are more likely to survive and have increased reproductive success.
inheritance - advantageous allele is inherited by members of the next generation (offspring).
allele frequency - over many generations allele increases in frequency in the population.
what is natural selection?
when a random mutation can result in new alleles of a gene (advantageous, neutral, or disadvantageous alleles).
what was Lamark’s theory?
inheritance of acquired characteristics - if an organism changes during life in order to adapt to its environment, those changes are passed onto its offspring e.g giraffe necks.
describe three types of adaptations.
anatomical - structural/physical features that increase chance of survival.
physiological - processes/chemical reactions that increase chance of survival.
behavioural - ways in which an organism acts that increase chance of survival.
what are the two types of selection?
directional selection
stabilising selection
describe and explain directional selection.
organisms with an extreme variation of a trait have a selective advantage e.g bacteria with high level of resistance to a particular antibiotic.
- leads to increased frequency of organisms with extreme trait.
- normal distribution curve shifts towards extreme trait.
describe and explain stabilising selection.
organisms with an average variation of a trait e.g babies with an average weight.
- stable environment, selection operates against both extremes of a range, reducing variability.
- increased frequency of organisms with average trait.
- normal distribution curve similar, less variation around mean.
what is stabilising selection?
natural selection that keeps allele frequencies relatively constant over generations - this means things stay as they are unless there is a change in the environment e.g human birth weight.
what is directional stabilisation?
natural selection that produces a gradual change in allele frequencies over several generations - this usually happens when there is a change in environment/selection pressures or a new allele has appeared in the population that is advantageous e.g antibiotic-resistant bacteria strains are becoming more common due to the overuse of antibiotics.
