Unit 4- Genetic diversity + Adaptation =)

Question 1

Define genetic diversity.

spec

Answer 1

no. of diff. alleles of genes in a pop

Question 2

The spotted owl is a bird. Numbers of spotted owls have decreased over the past 50 years.
Explain how this decrease may affect genetic diversity. (2)

Answer 2

• ↓
• ↓ diff. alleles

Question 3

The genetic diversity of species is measured by comparing differences in the base sequence of DNA or differences in the base sequence of mRNA.
Give two other ways in which genetic diversity between species is measured. (2)

Answer 3

1. compare frequency of measurable/ observable characteristics
2. compare a.a. seq of the proteins encoded by DNA
   and mRNA

Question 4

Clostridium difficile is a bacterial species that causes disease in humans.
Antibiotic-resistant strains of C. difficile have become a common cause of infection acquired when in hospital.
Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria becoming a common cause of infection acquired when in hospital. (3)

Answer 4

• some bacteria have alleles for resistance
• exposure to antibiotics = selection pressure, resistant bacteria survive + reproduce
• ↑antibiotics used in hospitals –> ↑ freq. of resistant allele

Question 5

Explain how succession results in a wide variety of fish living on coral reefs.
Do not describe the process of succession. (2)

Answer 5

• ↑ variety of species
• ↑ diff habitats/ ↑ variety of food

Question 6

Mature leaves from slow-growing, shade-tolerant plants produce poisonous chemicals that are a defence against being eaten by herbivores.
Suggest how this benefits slow-growing, shade-tolerant plants. (2)

Answer 6

• in shade, so ↓ rate of photos
• long time for leaves to mature
• maintain large enough s.a. for photos

Question 7

The fruit fly has a gene that codes for an enzyme called alcohol dehydrogenase (AD). AD catalyses the breakdown of alcohol when alcohol is in the insects’ food.
The enzyme encoded by the ADF allele catalyses the breakdown of alcohol faster than the enzyme encoded by the ADS allele.
Alcohol is toxic to fruit flies. Suggest and explain why the frequency of the ADF allele increased during the 45 generations. (4)

Answer 7

• flies w/ ADF - selective advantage
• ↑ likely to reproduce
• pass on allele
• allele freq ↑

Question 8

Bt plants have been genetically modified to produce a toxin that kills insect pests.
Scientists have found that some species of insect pest have become resistant to the toxin produced by the Bt crop plants.
One farmer stated that the increase in the use of Bt crop plants had caused a mutation in one of the insect species and that this mutation had spread to other species of insect. Was he correct?
Explain your answer. (4)

Answer 8

1. mutations = random
2. only rate of mutation affected by environment
3. diff species x interbreed to produce fertile offspring
4. mutation x passed from 1 species to another