(a) In a tabular form distinguish between tropic movement and nastic movement (b) Explain how...
(a) In a tabular form distinguish between tropic movement and nastic movement
(b) Explain how light brings about tropic movement in the stem and root of a flowering plant.
(c) What would be observed when a growing seedling is placed horizontally?
(d) State five functions of the pituitary gland
(e) State two difference between growth in plants and growth in animals.
Explanation
(a) Difference between tropic movement and nastic movement
| Tropic movement | Nastic movement |
| It is a growth movement | not a growth movement |
| Response to unilateral stimulus | response to diffuse stimulus |
| Slow response | Fast response |
| Not reversible | Reversible |
| Not due to cell tugor | Due to changes in cell tugor |
| Directional/positive /negative response | positive nor negative response |
(b) How light brings about tropic movement in stem and root of a flowering plant:
(i) When unilateral light falls on the stem, the auxin/growth hormone/IAA is displaced from the lighted to the dark side.
(ii) The increase in auxin concentration on the dark side increases growth on that side causing the stem to bend towards the light/positive phototropism.
Roots:
(i) The auxin is displaced from the lighted side to the dark side.
(ii) The increase in auxin concentration retards growth on the dark side causing the root to bend away from the light/negative phototropism.
(c) The following would be observed when a growing seedling is placed horizontally:
(i) Shoot bends upwards, showing negative geotropism/positive phototropism.
(ii) Root bends downwards, showing positive geotropism/negative phototropism.
(d) Functions of the Pituitary gland:
(i) Stimulates growth/growth of long bones/cell division.
(ii) Stimulates production of sex-hormones/named sex hormones.
(iii) Stimulates production of anti-diuretic hormone/ADH/regulation of water re-absorption in the kidney/osmos regulation.
(iv) Produces hormones which control other endocrine glands/stimulates thyroid gland/adrenal cortex.
(v) Stimulates protein synthesis.
(vi) Induces birth by contraction of uterine muscles/production of oxytoxin.
(vii) Induces milk secretion/produces prolactin.
(viii) Controls egg and sperm production.
(e) Differences between growth in plants and animals:
| Growth in plants | Growth in animals |
| Unlimited growth/growth through out life | limited growth/growth stops after a period of time |
| No fixed number of organs | fixed numbers of organs (e.g two eyes,ears etc) |
| limited to specific region | not restricted/intercalary |