2012 Unit 2 Jan

Question 1

Describe the function of a chloroplast.

Answer 1

• Absorbs/traps/uses light;
• For photosynthesis;
• Produces carbohydrates/sugars/ lipids/protein;

Question 2

Describe what happens during anaphase that results in the production of two genetically identical cells.

Answer 2

• Sister chromatids

* To (opposite) poles/ends/sides;

Question 3

Use your knowledge of the cell cycle to explain why some cells had 8.4 units of DNA
and others had only 4.2 units.

Answer 3

• 8.4/cells with twice DNA content = replicated DNA

* 4.2 = DNA not replicated

Question 4

Describe how the results could show that the catfish belong to the same species.

Answer 4

• Fertile offspring produced;

Question 5

Give two ways in which courtship increases the probability of successful mating.

Answer 5

• Recognises same species;
• Stimulates release of gametes;
• Recognises opposite sex;
• Indication of sexual maturity
• Formation of a bond between two organisims

Question 6

Explain how this mutation leads to the formation of non-functioning PAH.

Answer 6

• Change in base sequence
• Change in primary structure
• Change in hydrogen bonds
• Alters tertiary structure
• Change in active site
• Substrate not complementary
• No enzyme-substrate complexes form;

Question 7

Suggest how the spread of this mutation may have occurred.

Answer 7

• Interbreeding

* Migration

Question 8

Frequent treatment with vancomycin can result in resistant strains of bacteria. Explain
how.

Answer 8

• Mutation present/occurs
• Resistance gene
• Resistant bacteria (survive and) reproduce
• Vertical (gene) transmission / Horizontal (gene) transmission

Question 9

Use your knowledge of gene transmission to explain how the gene was passed from
one species of bacterium to another.

Answer 9

• Horizontal (gene) transmission
• Via conjugation/
• Plasmid/Gene/DNA replicated
• Plasmid transferred

Question 10

Scientists can use protein structure to investigate the evolutionary relationships
between different species. Explain why.

Answer 10

• Amino acid sequences / primary structure;
• Closer the (amino acid) sequence the closer the relationship
• Protein structure) related to
(DNA) base/triplet sequence

Question 11

Comparing the base sequence of genes provides more evolutionary information than
comparing the structure of proteins. Explain why.

Answer 11

• More bases than amino acids / longer base sequence than amino acid sequence
• Introns
• Degeneracy of code / more than one code for each amino acid

Question 12

Explain the importance of taking a large number of samples at each site.

Answer 12

• Produces a more reliable mean/

Question 13

Explain the importance of taking samples at random.

Answer 13

• Removes bias;

Question 14

Explain the effect of developing this golf course on the index of diversity of insects.

Answer 14

• Increase in variety of plants/shrubs/grass
• More habitats
• Greater variety of food sources

Question 15

Root pressure moves water through the xylem. Describe what causes root pressure

Answer 15

• Active transport by endodermis
• ions/salts into xylem;
• Lowers water potential (in xylem);
• (Water enters) by osmosis

Question 16

The results of this investigation support the cohesion tension theory. Explain how.

Answer 16

• Movement starts higher up;

* Creates tension/’negative pressure’/

Question 17

Explain how oxygen is loaded, transported and unloaded in the blood.

Answer 17

• Haemoglobin carries oxygen / has a high affinity for oxygen / oxyhaemoglobin;
• In red blood cells;
• Loading/uptake in lungs;
• At high p.O2;
• Unloads/ dissociates to respiring cells/tissues;
• At low p.O2;
• Unloading linked to higher carbon dioxide

Question 18

Why was it

important that the larvae of both species were kept at the same temperature?

Answer 18

• Allows comparison
• Different temperature) affects enzymes;
• (Different temperature) affects respiration/metabolism;
• (Different temperature) affects amount of dissolved oxygen;

Question 19

Give two features of the design of this investigation that would ensure the reliability of
the results obtained.

Answer 19

• Large sample
• Long time period
• Different countries