(a)(i) Explain briefly the cell theory.
(ii) Name two scientists who contributed to the development of the cell theory.
(b) Make a large labelled diagram of a typical plant cell.
(c) List three ways in which a typical plant cell differs from a typical animal cell.
(d) State one difference each between Hydra and the mammals with respect to:
(i) level of organisation; (ii) symmetry; (iii) number of body layers.
Explanation
(a)(i) Cell theory states that:
(1) the cell is the smallest unit of life.
(2) The cell is the unit of function of life.
(3) New cells are produced from existing cells.
(4) All living things have cells and cell products.
(ii)(1) Robert Hook
(2) M. J. Schleiden
(c) Differences between a plant and animal cell are:
| Plant cell | Animal cell |
|
(1) Possesses large vacuole |
- Has small vacuole |
(d) Difference between Hydra and mammal:
(i) Level of organization: Hydra is organised in the tissue level while mammal is organised in the system level
(ii) Symmetry: Hydra is radially symmetrical while mammal possesses bilateral symmetry
(iii) Hydra possesses two body layers, e.g. ectoderm and endoderm while mammal possesses three layers.