Natural selection Flashcards
what is selection pressure
the environmental factors that limit population of a species include predation, disease and competition
what is evolution dependent on
organisms which produce offsprings that can be supported by available food
whether there is genetic variety within the population
the variety of phenotypes in the population
why doesn’t numbers of organism increase exponentially
death rate is high due to predation, competition
however how has the population size been maintained and why
however the high reproductive rate have evolved to ensure that a sufficient large population survives to breed to produce next generation
how do some species survive with lower reproductive rates
they have higher degree of parental care and consequently lower death rates to maintain population size
what is the link between natural selection and over production
many individuals of a species there is intraspecific competition , the greater the number of population the greater the competition so more will die and those best adapted are likely to survive
what is role of variation in natural selection
having wide range of gentetically different phenotypes allow them to survive in case of changes in environment
what Is stabalsing selection
preserves the phenotype of a population favouring the average individuals selecing against the extremes
what is directional selection
changes in the phenotypes of the population by favouring the phenotypes tjat vary in one directiom from the mean of the population
what is distruptive selction
favours individuals with extreme phenotypes rather than those with phenotypes around the mean, when environment takes two distinct forms
comment on its community but why is it needed
least common but brings about evolutionary change, when the environment take two or more distinct forms#
