convergence and divergence in evolution

Question 1

convergent evolution

Answer 1

• species not closely related independently evolve similar traits to adapt to similar environments
• eg. bees and hawks
• eg. flightless birds

Question 2

divergent evolution

Answer 2

• traits of common ancestors evolve different variations
• eg. human and horse limbs
• speciation

Question 3

speciation

Answer 3

• new species that are genetically distinct

- cladogenesis

Question 4

extinction

Answer 4

• eg. dodo ; sabre-tooth tigers

- speciation occurs after mass extinction due to less competition

Question 5

causes of speciation

Answer 5

• geographic : isolation

- sympatric : same geographical area

Question 6

allopatric

Answer 6

• erosion ; earthquakes ; volcanoes
• lake dries ; newly formed islands ; sea currents
• becomes separated
• no gene flow
• natural selection due to different environmental conditions
• individuals of two populations become different
• not able to reproduce together

Question 7

sympatric

Answer 7

• no geographic isolation
• hybridisation and polyploidy
• can not interbreed with parental species
• eg. galapagos finches

Question 8

how did different species arise?

Answer 8

• absence of pre-existing predators
• no competition
• empty ecological niches

Question 9

stages of speciation

Answer 9

• division of habitat

- division of resources : specialisation ; competition ; change in diet and adaptation to acquire food

Question 10

cichlid fish

Answer 10

• isolation
• enormous diversity
• empty ecological niches
• no competition
• no pre-existing predators
• early stages of diversification
• speciation
• unique characteristics : jaws

Question 11

division by sexual selection

Answer 11

• reproductive strategies

- leads to evolution by differentiation