the change over time in the proportion of individuals in a population differing in one or more inherited traits
what are the 2 random processes in evolution?
natural selection and sexual selection
what is the name of the random process in evolution?
genetic drift
what do the random and non random processes of evolution cause?
changes in allele frequency
how does natural selection work?
acts on genetic variation in populations
what happens when a population produces more offspring than the environment can support?
individuals with better suited variations to the environment survive for longer to produce more offspring, this passes on the alleles that conferred an advantage
what does natural selection result in?
the non random increase in frequency of advantageous alleles and non random decrease in frequency of deleterious alleles
what arises as a result of mutation?
variation
what is the original source of new sequences of DNA?
mutations
what type of alleles come from the new sequences of DNA?
novel alleles
what are the most common types of mutation?
harmful or neutral
what benefits the fitness of an individual?
a beneficial mutation
what type of process is sexual selection?
non random
a selection of alleles that increases the individual's chances of mating and producing offspring is...
sexual selection
what is an important factor in reproduction?
mutual attraction
what makes an individual more attractive to the opposite sex?
traits
examples of conspicuous physical traits
pronounced colouration, increased size, striking adornments and elaborate courtship
what effect do conspicuous physical traits have on an animal's survival?
decrease survival chances but increase success of obtaining mates
what does "higher fitness" mean?
greater success in obtaining mates
what can sexual selection lead to?
sexual dimorphism
what is sexual dimorphism?
physical differences between males and females of the same species
examples of sexual dimorphism
size, (males often are large than females) colouration, (female is inconspicuous and cryptically coloured to remain camouflaged on the nest. Males are conspicuously coloured for courtship and territorial behaviour) additional body parts (males have adornments e.g. antlers)
what 2 things determine reproductive success?
male-male rivalry and female choice
examples of male-male rivalry strategies
superior size an weaponry
how do females choose a mate?
assess the fitness of males
what does an impressive courtship display or good appearance indicate?
healthy male, low parasite burden and presence of advantageous genes
how does genetic drift occur?
chance
when does genetic drift occur?
when chance effects cause unpredictable fluctuations in allele frequency from one generation to the next
what type of traits don't have selection pressures?
neutral traits
why is genetic drift more important in small populations?
alleles are more likely to be lost from the gene pool
what are the names of the 2 types of genetic drift?
bottleneck effect and founder effect
when does the bottleneck effect occur?
when a population size is reduced for at least 1 generation
what might cause a bottleneck effect?
a natural disaster which reduces the population so that it rarely represents the actual genetic makeup of the initial population
what does the bottleneck effect result in?
leaves smaller variation among surviving individuals
how does the founder effect occur?
through the isolation of a few members of a population so the new gene pool isn't representative of the original gene pool
how does genetic drift affect a gene pool?
certain alleles may be under-represented or over-represented as allele frequency changes
how do selection pressures affect the rate of evolution?
strong selection pressures make the rate of evolution rapid
what are selection pressures?
the environmental factors that influence which individuals in a population pass on their alleles