B 11.4 variation and selection

Variation

Difference between individuals of the same species

cause of phenotypic variations

genetic + environmental factors

Continuous variations

range of phenotypes

eg. height in humans

Discontinues variations cause

caused by genes alone

eg. blood type in humans

mutation

change in a gene or a chromosome

cause of increase in mutations

ionizing radiation

chemicals

Success of natural selection

variation within population

production of offspring - reproduction - passing down alleles

competition for resources - survival

evolution

change in features of a population over time

adaptation

result of natural selection

selective breeding

human selection of individuals with desirable features → crossing these individuals → selection of offspring that have the features

3. artificial selection

human intervention

results in features beneficial to humans

takes less time than natural