(a) What is growth? (b) State two differences each between; (i) growth in plants and...
(a) What is growth?
(b) State two differences each between;
(i) growth in plants and animals
(ii) metamorphosis in housefly and toad.
(c) Name two hormones each involved in:
(i) plant growth
(ii) animal growth.
(d) State the effects of the hormones named in (c) above.
(e) Name the type of germination which takes place in:
(i) monocotyledonous plants
(ii) dicotyledonous plants.
(f) In a tabular form state four differences between the forms of germination named in (e) above.
Explanation
(a) Growth: Irreversible/permanent increase; in size/dry mass/weight; due to the addition of living protoplasmic material.
(b)i
| Growth in plants | Growth in animals |
| -Mainly restricted to growing regions/apical meristem -Continuous throughout life (in growing regions) -Indefinite number of parts | -Diffuse/takes place in all parts of the body/intercalary - limited to a certain period in life -Definite period of part |
(ii) Metamorphosis
| Housefly | Toad |
| -Takes place on land -Pupal/resting stage present -Takes shorter time | -takes place in water -No pupal/resting stage -Takes longer time |
(c) & (d) Names of growth hormones and their effects
(i) Plants: Cytokinins
- Stimulates lateral buds into branches
- Promotes growth of lateral roots
- Cell division in apical meristems; elongation
- Breaking dormancy in seeds Auxins
- Rapid cell division of apical region of shoots; elongation Gibberellins
- Cell elongation; stimulates growth in dwarf varieties; induces dormant seeds to germinate
- increases fruit size.
Animals: Thyroxin
- Regulates growth and development of cells. Growth hormones from pituitary gland
- Stimulates growth of long bones.. Sex hormones any correctly named sex hormone
-Stimulates growth of sex organs.
(e)(i)Monocotyledons- Hypogeal germination
(ii)Dicotyledons- Epigeal germination.
(f) Differences between
| Epigeal germination | Hypogeal germination |
| Testa splits | pericarp splits |
| Hypocotyl emerges uncovered | Hypocotyl covered by the sheat/coleorrhiza |
| cotyledons are carried above the soil | cotyledons remains in the soil |
| Energy obtain from food stored in the cotyledon | energy obtained from food stored in the endosperm |
| hypocotyl elongates | epicotyl elongates |
| cotyledon is the first photosynthetic tissues | foilage leaves are the first photosynthetic tissue |