3.7.3 - EVOLUTION + SPECIATION

Question 1

variation in flower colour is considered one of the factors involved in the evolution of the following two species of monkeyflower.

• erythranthe lewisii (great purple monkeyflower), which has pink flowers, is mostly found at higher altitudes (1600-3000 metres) and attracts bumblebees.
• erythranthe cardinalis (scarlet monkeyflower) which has red flowers, is mostly found at lower altitudes (up to 2000 metres) and attracts hummingbirds.

bumblebees and hummingbirds are important in the pollination of flowers. pollination involves the transfer of male gametes to female gametes.

explain the different processes that may have been involved in the evolution of these two species of monkeyflower. use the information provided to justify your answer (5)

Answer 1

1. geographical isolation due to altitude
2. allopatric speciation due to isolation
3. different selection pressures OR environment
4. however, both plants found in same habitat
5. so possibly sympatric speciation
6. variation due to mutations
7. reproductive isolation due to different altitudes
8. change in allele frequency
9. different species can no longer breed to produce fertile offspring

Question 2

suggest two reasons for conserving rainforests (2)

Answer 2

1. reduces climate change
2. conserve species OR for biodiversity
3. conserve/provides habitats

Question 3

what is sympatric speciation? (2)

Answer 3

1. formation of a new species / reproductive isolation
2. from a population living in the same place

Question 4

there are nine subspecies of giraffe. these subspecies evolved when populations of giraffe were separates for long time periods. each subspecies has distinct coloured skin markings. some biologists have suggested that up to six of these subspecies should be classified as different species.

explain how different subspecies of giraffe may have evolved from a common ancestor.

use information from the passage in your answer (5)

Answer 4

1. no interbreeding / gene pools are separate / geographical isolation
2. mutation linked to different markings/colours
3. selection/survival linked to different markings/colours
4. differential reproductive success
5. change/increase in allele frequency

Question 5

there are nine subspecies of giraffe. these subspecies evolved when populations of giraffe were separates for long time periods. each subspecies has distinct coloured skin markings. some biologists have suggested that up to six of these subspecies should be classified as different species.

biologists compared the mitochondrial DNA of the different subspecies of giraffe. they used the results from comparing this DNA to conclude that six of the nine subspecies are separate species

suggest how they came to this conclusion (2)

Answer 5

1. comparing base sequence
2. different in six species / similar in three subspecies

Question 6

lord howe island in the tasman sea possesses two species of palm tree which have arisen via sympatric speciation. the two species diverged from each other after the island was formed 6.5 million years ago. the flowering times of the two species are different.

using this information, suggest how these two species of palm tree arose by sympatric speciation (5)

Answer 6

1. occurs in same environment
2. mutations caused the different flowering times
3. reproductive isolation / gene pools remain separate / no gene flow
4. different alleles passed on/selected OR change in allele frequency
5. disruptive selection
6. eventually different species cannot interbreed to produce fertile offspring

Question 8

changes in ecosystems can lead to speciation. in southern california 10000 years ago, a number of interconnecting lakes contained a single species of pupfish.

increasing temperatures caused evaporation and the formation of separate, smaller lakes and streams. this led to the formation of a number of different species of pupfish.

explain how these different species evolved (5)

Answer 8

1. geographical isolation
2. separate gene pools/no interbreeding
3. variation due to mutation
4. different environmental/abiotic/biotic conditions/selection pressures
5. selection for different alleles/characteristucs
6. differential reproductive success
7. leads to change in allele frequency
8. occurs over a long period of time