Adaptation and variation

causes of adaptations

lifestyle, diet, environment

physiological adaptations

adaptations in an animal’s body processes, e.g. some snakes produce venom to defend themselves against predators

anatomical adaptations

adaptations in an animal’s shape and structure, e.g. the bat forelimb forms wings, improving their access to suitable food sources

behavioural adaptations

adaptations in an animal’s language, tool use and survival strategies, e.g. migration in some bird species to avoid harsh environments

evolution

a change in characteristics over several generations

speciation

the formation of a new species as part of the evolutionary process

variation

differences between organisms

e.g. diet, behaviour and aesthetics

linked to differences in DNA

heritable - passed from parents to offspring

natural selection

some give animals advantage over other animals e.g. being able to run for longer, reach higher branches or have better camouflage

animals with advantageous alleles/variation are more likely to survive and reproduce - heritable, so goes to offspring too

polar bear adaptations

large feet with fur on the soles - improve grip on the ice

small surface area to volume ratio and small ears - reduce heat loss

strong legs - help catch prey when swimming and running

thick layer of adipose under the skin - for insulation and energy

thick white fur - for insulation and camouflage

sharp teeth and claws - feeding and defending

pregnant females hibernate

highly developed sense of smell and hearing

types of selection pressures that affect variation

stabilising selection pressure

directional selection pressure

diversifying/disruptive selection pressure

stabilising selection pressure

reduces variation between animals’ DNA

extreme phenotypes are reduced, and proportion of animals with the average phenotype is increased

directional selection pressure

encourages a new phenotype usually in response to environmental changes

diversifying/disruptive selection pressure

increases variation between animals’ DNA

extreme phenotypes become more common and average phenotypes are reduced