unit 4

Question 1

What type of evolution would describe animals which share similar structures but live in a variety of landscapes?

Answer 1

Divergent evolution.

Question 2

Shrimp have been separated by a geological barrier into 2 groups. When put together, they snap aggressively. There was no successful mating. This is best explained by:

a) sexual selection
b) reproductive isolation
c) genetic drift
d) natural selection

Answer 2

The refusal of shrimps from geographically isolated populations to interbreed is an example of reproductive isolation.
Since there were no matings there is no evidence of sexual selection.

Question 3

How will a DNA probe bind to a specific fragment of DNA?

Answer 3

The DNA probe will anneal backwards to the single strand because DNA is anti-parallel and the sequence is complementary to the GATTACA DNA probe.

Question 4

What is meant by the term ‘rational drug design’?

Answer 4

• identify the molecular cause of a disease/disorder, does not affect any other system or is
specific to disease/disorder
• design of a medication (drug) that uses a complementary shape of the molecule to stop a
reaction or that binds to the active site/receptor

Question 5

Describe 3 situations where only very small DNA samples may be available for sampling and PCR can be used.

Answer 5

• In crime scene investigations. Availability of small samples of blood; to get a DNA fingerprint of the person whose blood it is.
  This may also include semen investigation for a rape victim (people generally hear crime and think blood.)
• Archaeological and/or paleontological investigations.
• Paternity testing.

Question 6

Define gene flow and suggest how it can occur.

Answer 6

• Gene flow refers to the movement of alleles between populations by interbreeding.
• Can occur of populations are within a close proximity

Question 7

Explain how a small population would be at risk of extinction. (3)

Answer 7

• A small population size would mean a limited gene pool
• reduced variation would reduce the chances of survival
  if there were an environmental change
• the chance of a favourable characteristic existing in the population is unlikely as individuals would all be genetically similar

Question 8

Outline steps in DNA hybridisation.

Answer 8

1. DNA is heated to break the bonds/separate the strands.
2. Single strands from both species are mixed together and cooled.
3. The resulting hybrid DNA is then reheated and the temperature at which the DNA becomes
   single-stranded is noted.

Question 9

How does the technique of DNA hybridisation illustrate the relationship between species?

Answer 9

The temperature at which the DNA becomes single stranded indicates the degree of complementary base pairing and the higher the temperature the more closely related the two species are.

Question 10

Characteristics of species that classify it as homo, not Australopithecus.

Answer 10

• a flatter face
• a more parabolic jaw
• a relatively larger brain case
• teeth of a more uniform shape.

Question 11

Explain why is it important to have genetic screening programs for newborn babies?

Answer 11

• provides parents, doctors, etc. with information

- allows actions such as treatment or diet modification

Question 12

State two ethical implications of the genetic screening of newborn babies.

Answer 12

• who has access to the data
• the rights of the individual in the future to this information
• the rights of the newborn baby
• privacy of the individual
• whether the data is secure

Question 13

What is meant by the term vector?

Answer 13

A means of transferring/transporting foreign/desired DNA into a cell/organism.

Question 14

Describe how restriction enzymes are used to help insert a gene.

Answer 14

The restriction enzymes are used to cut the ends of the plasmid and the desired gene so that the
gene will insert into the plasmid.

Question 15

As a result of such intense hunting, the Northern elephant seal's population size decreased. Eventually, the numbers recovered. This is an example of..?  
A. natural selection.
B. gene flow.
C. a population bottleneck.
D. increased genetic variation.

Answer 15

B. a population bottleneck is a sharp reduction in the size of a population due to environmental events or human activities.

Question 16

Dominant bulls are able to mate with up to 100 females in a breeding season. With so much
of a colony’s offspring descended from one dominant male
A. genetic diversity increases.
B. the species is more vulnerable to diseases and genetic mutations.
C. the genome of the Northern elephant seal decreases.
D. there will be an increase in genetic mutations in the population.

Answer 16

B is correct – with reduction in gene pool and genetic diversity, the species is more vulnerable
to diseases and genetic mutations.
The genome is the genetic material of an organism; the Northern elephant seal
genome does not change in size, just in diversity.

Question 17

When will a new species arise from a common ancestor?

Answer 17

Populations of the ancestral species become reproductively isolated from one another.
If two species are reproductively isolated from one another they are said to have
speciated; hence a new species has arisen.

Question 18

What can the molecular clock be used for?

Answer 18

Estimate the dates of evolutionary events such as the divergence of a species.

Question 19

Structural evidence that could be used to classify groups into species.

Answer 19

• The individuals within a species would be able to breed with each other and produce fertile
  offspring.
• Anatomical features and the individuals within a species would have more characteristics in
  common with each other than with those of a different species