Microevol

Similarity 1. Both driven by natural selection . Difference 2. Microevol is characterised by smaller scale changes in alleles freq at a population level in a short time period . 3. Macroevol is characterised by the accumulation of microevolution events which lead to _larger scale changes in phenotypes across different species and populations within a longer time period

Define microevol 1. Microevol is (small scale) changes in allele freq in a population or species over many generations. . 2. Individuals cannot evolve as they cannot adapt within their lifetime by changing their alleles . 3. Population can evolve as there is variation for natural selection to act upon individuals in a population . Exp how natural selection works 4. This leads to passing down of advantageous alleles to successive generations in a population . 5. The freq of those advantageous alleles increases over many generations . Hence a change in allele freq can only occur in a population, not individuals

It is small scale changes in allele freq at a population level (within a short period of time)

It is the accumulation of microevol events, leading to large scale changes in phenotypes across different populations and species within a longer time period

• It is a group of organisms occupying the same geographical location and are the same species . • where individuals share a common gene pool and can interbreed to produce fertile, viable offspring

• Random mating • No gene flow • No mutation • No natural selection • Population extremely large - Large populations have greater gene pool stability

• Mutation»_space; variation - Spontaneous mutation leads to genetic variation in (trait) between individuals in a population . • Selective pressure - environment Selection pressure is (state) . • Advantage - Individuals with (adv trait) are at a selective advantage and tend to survive better by (trait) . • Survive and repro - Indiciuals w adv traits survive and reproduce more successfully, passing down adv alleles to subsequent generations of offspring . • Change in allele freq - leads to changes in allele freq over many generations - Freq of allele coding for (adv trait) increases. - % of disadv alleles decreases . • (Type of selection) - state which phenotype favoured - state which phenotype eliminated

(Opposite of Hardy-Weinberg equilibrium) . 1. Non-random mating - natural selection acting upon adv alleles . 2. Gene flow - migrate in and out of population . 3. Spontaneous mutations - mutations in gene and chromosome, - lead to changes in DNA seq to produce new alleles - causes variation in a population . 4. Natural selection - Indivs do not have equal fitness - they \don’t have equal chances of survival_ - Due to variation and diff selection pressures - Only those with selective advantage w survive and reproduce . 5. Small population - Small populations have less gene pool stability - More likely to have \random changes in allele freq_ - eg: after genetic drift they may have random elimination of one or more genotypes

• Movement of alleles and genes between populations . • often due to movement of fertile individuals from one population to another and successfully breeding

• Random chance event (disaster/disease) destroys a large number of individuals . • causing large-scale temporary reduction in population size . • Some alleles could be over represented under represented or completely eliminated • Gene pool is greatly reduced

• Due to heterozygous protection in diploid individuals . • The dominant allele masks the phenotypic expression of the recessive allele so individuals do not show the recessive allele . • Since natural selection only acts on phenotypes and not genotypes • the freq of recessive allele is never zero • as heterozygotes with high survivability will reproduce and pass down alleles to offspring