natural selection

describe the process of natural selection:

• a population has a gene pool w/ a wide variety of alleles

• random mutation may introduce new alleles, increasing variation

• some alleles may make individuals better adapted to the environment (sometimes due to an environmental pressure)

• better adapted individuals are more likely to survive and reproduce - this is differential reproduction

• individuals that reproduce pass on their advantageous alleles to the next generation - heredity

• over many generations, advantageous alleles increase in frequency

what are the 4 main principles of natural selection?

• variation

• environmental pressure

• differential reproduction

• heredity

what does natural selection result in?

species being better adapted to their environment

what are the 3 types of adaptation?

• anatomical

• physiological

• behavioural

what are anatomical adaptations? provide an example:

• structural features of an organism’s body that increase its chance of survival

• e.g. whale blubber → keep warm

what are physiological adaptations? give an example:

• processes inside an organism’s body that increase its chance of survival

• e.g. brown bears hibernating over winter → conserves energy

what are behavioural adaptations? provide an example:

• ways in which an organism acts that increase its chance of survival and reproduction

• e.g. possums ‘playing dead’ → evades attack from predators

what is a genetic bottleneck?

• an event which causes a large reduction in population

• this reduces no. of different alleles in gene pool and so reduces genetic diversity

• survivors reproduce and a larger population is created from a few individuals

what is the founder effect?

• type of genetic bottleneck

• a few organisms from a pop start a new colony

• this means there are only a small no. of different alleles in the initial gene pool

• freq of allele in new colony may be different to original colony

why may the founder effect occur?

• migration

• natural disasters