Chapter 18: Population and Evolution

Question 1

On the islands of the carribean, there are almost 150 species of lizards belonging to the genus Anolis. Scientists believe that these species evolved from 2 species found on mainland USA. Explain how the carribean species could have evolved. [6 marks]

Answer 1

1. geographical isolation
2. separate gene pools/no interbreeding/gene flow
3. variation due to mutation
4. different selection pressures/ different abiotic/biotic conditions
5. differential reproductive success/selected orgainsms survive and reproduce
6. leads to change/increase in allele frequency

Question 2

Penicillin has been the antibiotic of choice for the treatment of bacterial meningitis. Since the year 2000, strains of Neisseria meningitidis that are resistant to penicillin, sulfonamides and rifampin have been discovered in the UK.
Describe how a population of Neisseria meningitidis can become resistant to these antibiotics. [4 marks]

Answer 2

1. mutation
2. results in Nm cell with allele for resistance to one antibiotic
3. this cell survives and passes the allele for resistance to offspring
4. process repeated with different genes conferring resistance to each of the other two antibiotics

Question 3

Anolis sangrei is a species of lizard that is found on some of the smallest carribean islands. Describe how you could use the mark release recapture method to estimate the total number of Anolis sangrei on one of these islands [4 marks]

Answer 3

1. capture/collect sample, mark and release
2. method of marking does not harm lizard/make it more visible to predators
3. leave sufficient time for lizards to randomly distribute before collecting a second sample
4. population = number in the first sample x number in the second sample/ divided by number recaptured

Question 4

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. Explain how these different species evolved. [5 marks]

Answer 4

1. geographical isolation
2. variation due to mutation
3. different environmental/ abiotic/biotic conditions/selection pressures
4. selection for different/ advantageous, features/characteristics/mutation//allele/differential reproductive success/selected organisms survive and reproduce
5. leads to a change in allele frequency

Question 5

Lemurs are small mammals. Lemurs live in trees and feed on leaves and fruit. Scientists used a computer program to predict the expected distribution of two species of lemur, Eulemur rufus and Eulemur rufifrons, on the island of Madagascar. These predictions were based on the environmental needs of each species.
Then, the scientists determined the actual distribution of these two species of lemur on the island of Madagascar.
Using all the information, suggest how speciation happened to produce two species of lemur. [5 marks]

Answer 5

1. geographical isolation or allopatric speciation
2. reproductive separation/isolation or no gene flow or gene pools separate
3. different selection pressures or different environmental/ abiotic conditions/factors
4. variation due to mutation
5. advantageous alleles are passed on or change in frequency of alleles
6. eventually different species cannot interbreed to produce fertile offspring