(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...
Question 1 Report
(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.
Answer Details
(a)(i) The cell theory
The cell theory states that:
- All living organisms are made up of one or more cells, and of the products of cells.
- The cell is the basic structural and functional unit of life (the smallest unit that can carry out life processes).
- All cells arise from pre-existing cells by cell division.
(a)(ii) Two scientists who contributed to the cell theory
Robert Hooke and Matthias Jakob Schleiden. (Theodor Schwann and Rudolf Virchow also made important contributions.)
(b) Large labelled diagram of a typical plant cell
The diagram shows the rigid cellulose cell wall forming the outer boundary, the cell (plasma) membrane lining it, the cytoplasm in which the organelles are suspended, the nucleus with its nuclear membrane and nucleolus, the large central vacuole bounded by the tonoplast, several green chloroplasts, and the mitochondria.
(c) Three ways a typical plant cell differs from a typical animal cell
| Plant cell | Animal cell |
|---|---|
| Has a cellulose cell wall outside the membrane | Has no cell wall; bounded only by the cell membrane |
| Possesses chloroplasts | Has no chloroplasts |
| Has one large permanent central vacuole | Vacuoles absent, or small and temporary |
(d) Differences between Hydra and mammals
| Feature | Hydra | Mammals |
|---|---|---|
| (i) Level of organisation | Tissue level of organisation | Organ / organ-system level of organisation |
| (ii) Symmetry | Radial symmetry | Bilateral symmetry |
| (iii) Number of body layers | Two body layers - diploblastic (ectoderm and endoderm) | Three body layers - triploblastic (ectoderm, mesoderm and endoderm) |
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