12.3 Exam preparation

Question 1 (SL and HL)

The table below gives brain and body masses for a number of animals. 

Animal

Approximate mean body mass (Kg)

Brain mass (g)

House sparrow (bird)

0.032

1

Rat

0.4

2

Human

60

1350

Alligator

400

8

Blue Whale

140,000

9000 

 

I. Describe the relationship between brain size and body size (2 marks)

II. Outline which animal of those listed above has the smallest brain mass in relation to their body size (2 marks)

III. Suggest one reason why birds generally have a large brain mass for their body size (1 mark)

IV. The proportion by volume of the cerebral cortex of the rat is 31%and of the human is 77%. Suggest one reason for this difference (1 mark)

Mark scheme

I. a positive correlation (not proportional)

   b outlier/alligator does not match the correlation

II. a alligator

    b 8g brain for 400 Kg body size or calculation of ratio

III. a flight/homeostasis/migration/social behaviour

IV. a cognitive functions/intelligence

Guidance and comments

Brain mass increases with body size but the brain mass: body mass ratio varies with the role of the brain.

See subtopic A2