mechanisms of evolution

Question 1

what makes evolution possible

Answer 1

• genetic variation in individuals
• sexual reproduction: each offspring gets new combo of alleles (genetically unique)
• mutations

Question 2

what do evolution and natural selection impact

Answer 2

• populations evolve, not individuals
• natural selection impacts individuals, but only apparent over time

Question 3

allele frequencies

Answer 3

number of copies of an allele in comparison to total number of alleles in population

Question 4

microevolution

Answer 4

• when frequency of an allele changes, microevolution has occurred
• small events that lead to evolution in a population

Question 5

gene pool

Answer 5

• all alleles of all individuals in a population
• geneticists focus on gene pool when studying evolution at population level

Question 6

how can gene pool change

Answer 6

• mutations
• gene flow
• non-random mating
• genetic drift
• natural selection

Question 7

mutations

Answer 7

• change in DNA structure which changes the genotypes and phenotypes of a population
• original source of variation that leads to change in traits

Question 8

gene flow

Answer 8

• migration
• net movement of alleles of population due to migration of individuals
• alleles in one population go to another due to migration, mating, or transfer of genetic material

Question 9

non-random mating

Answer 9

• inbreeding or mate selection for specific phenotype
• sexual selection: natural selectoin for mating where men compete for female’s choice
• leads to sexual dimorphism

Question 10

genetic drift

Answer 10

• change in allele frequency due to chance events
• bottleneck effect and founder effect

Question 11

bottleneck effect

Answer 11

• severe event (natural disaster, disease, famine) reduces size of population
• small sample of alleles are in survivors
• some genes RANDOMLY more expressed than others in survivors
• inverse relationship: small pop=big impact, big pop=small impact

Question 12

founder effect

Answer 12

• new populations formed by few individuals (founders)
• founders only have some alleles from original population
• diversity in new gene pool is limited
• occurs in islands and isolated populations

Question 13

natural selection

Answer 13

• environment selects individuals with traits better suited
• over time, allele frequencies can change

Question 14

forms of natural selection

Answer 14

• stabilizing selection
• directional selection
• disruptive selection

Question 15

stabilizing selection

Answer 15

• natural selection favours intermediate, against extremes
• more middle, less small+big

Question 16

directional selection

Answer 16

• favours phenotypes of one extreme
• more big or small, less middle

Question 17

disruptive/diversifying selection

Answer 17

• favours both extremes in phenotype range
• can lead to elimination of intermediate trait
• more big and small, less/no middle

Question 18

what’s special about natural selection

Answer 18

only natural selection usually leads to adaptation out of all microevolution causes