(a) State two advantages of complex structural organisation in higher organisms. (b) (i) List two differences between colonial organisms and filamentous org...
Question 1 Report
(a) State two advantages of complex structural organisation in higher organisms.
(b) (i) List two differences between colonial organisms and filamentous organisms.
(ii) Give one example each of a colonial organisms and a eke filamentous
(c) Make a labelled diagram 10 - 12 cm long to show the structure of a named filamentous alga.
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Answer Details
(a) Two advantages of complex structural organisation in higher organisms
- Division of labour through cellular differentiation: similar cells become grouped and specialised into tissues, organs and systems, so that each part carries out one particular function efficiently (for example, muscle cells for movement and nerve cells for coordination). This mutual interdependence between cells increases overall efficiency.
- Greater adaptation and independence from the environment: the specialised systems (circulatory, respiratory, excretory) allow the organism to maintain a stable internal environment, grow larger in size and survive in varied or changing external conditions.
(b)(i) Two differences between colonial organisms and filamentous organisms
| Colonial organism | Filamentous organism |
|---|---|
| Identical cells form a loose ball or mass with no true intercellular cross wall between them. | Identical cells are joined end to end by intercellular cross walls to form a thread-like, linear structure. |
| Cells are linked by cytoplasmic bridges and are physiologically dependent on one another. | Each cell is physiologically independent and can carry out its life processes on its own. |
(b)(ii) Examples
- Colonial organism: Volvox (or Pandorina).
- Filamentous organism: Spirogyra (a filamentous alga).
(c) Labelled diagram of the structure of a named filamentous alga (Spirogyra)
The diagram below (drawn 10 to 12 cm long) shows part of a Spirogyra filament: a chain of long, cylindrical cells joined end to end by cross walls, each cell containing one or more spiral (ribbon-like) chloroplasts bearing pyrenoids, with the nucleus suspended in the centre by cytoplasmic strands.
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