TOPIC 4

Question 1

Explain the events that lead to natural selection within a species. (6)

Answer 1

Variation:
- variation within species
- due to random mutation
- creates diff. phenotypes

Changes in allele frequency:
- only individual w/ advantageous allele will survive to reproduce

• & pass their advantageous allele onto future generations
• this can lead to an entirely new species

Question 2

State purpose of bionomial system of naming organisms. (1)

Answer 2

• enables clear communication between scientists.

Question 3

Describe the new system and give reasons for the change. (3)

Answer 3

• consists of 3 domains
• Archaea, Bacteria, Eukaryotes
• provides more evolutionary evidence

Question 4

State the role of cellulose and how its structure relates to its function. (3)

Answer 4

• provides strength
• straight glucose chains joined by Hydrogen bonds
• formation of macrofibrils

Question 5

Explain how amylopectin structure allows it to be hydrolysed quickly. (3)

Answer 5

• contains 1-6 glycosidic bonds
  = highly branched
• lots of terminal glucose monomers

Question 6

Describe 2 similarities and differences between cellulose and starch. (4)

Answer 6

Similarities:
- both have glycosidic bonds
- 1-4 links

Differences:
- starch has coiled structure, cellulose is straight

• starch has 1-6 bonds , cellulose doesn’t

Question 7

Describe a double-blind trial. (4)

Answer 7

• large group
• similar in age/gender
• 2 groups: 1 given new drug, 1 given placebo
• neither patients nor doctors know who is in which group