natural selection and artificial selection Flashcards
selection pressures
external agents which affect an organisms ability to survive in a given environment
selection pressures can be…
negative (decrease trait occurrence)
positive (increase trait occurrence)
may not remain constant, leading to changes in what constitutes a beneficial adaptation
Types of selection pressures
resource availability
environmental conditions
biological factors
natural disasters and weather
resource avaliability
presence of sufficient food, habitat, and mates
biological factors
predators and pathogens
environmental conditions
temperature, weather conditions or geographical access (human skin pigmentation is an adaptation to UV levels)
natural selection
process by which characteristics of a population change over many generations as organisms with heritage traits survive and reproduce, passing their traits to offspring
fitness
measure of an individual reproductive success
average contribution to the gene pool of the next generation
fitness is shown through number of offspring an individual produces that survive long enough to reproduce
changing allele frequencies
variation is heritable (genetics) and determined by alleles
due to natural selection
the proportion of different alleles will change across generations (evolution)
artificial selection
selective pressure exerted by humans on populations in order to improve or modify particular desirable traits
agriculture
corn selected for larger, juicier kernels
horse breeding
artifcial selection
race horses for speed, draft horses for power
cow breeding
selectively bred for milk production, farmers have also targeted the breeding of cows with mutation for increased muscle mass (more edible lean meat)
