3.6.1: Survival and response

Question 1

Suggest two advantages of simple reflexes.

Answer 1

1. Rapid;
2. Protect against damage to body tissues;
3. Do not have to be learnt;
4. Help escape from predators;
5. Enable homeostatic control.

Question 2

Give one advantage of taxis to organisms.

Answer 2

to avoid competition, to find a mate, increase dispersal, to avoid predators

Question 3

Use your knowledge of indoleacetic acid (IAA)
to explain the curved growth of a shoot

Answer 3

1. Tip produces IAA;
   Accept source/release for produces but ignore contains/stores IAA.
2. IAA diffuses (into shoot);
   Accept auxin for IAA.
   Accept IAA diffuses down.
3. (More) elongation of cells on one side (than other);

Question 4

Explain how the uneven distribution of IAA
causes a root to bend.

Answer 4

1. (IAA) at bottom of root/where AII concentration high inhibits
   expansion/elongation (of cells);
2. (IAA) at the top of the root/where IAA concentration low leads to
   expansion/elongation (of cells)