The disadvantage of complexity of organisation in the higher organisms is that it leads to

Step 1: Analyze the question The question asks for a disadvantage of complex organisation in higher organisms (multicellular organisms with cells, tissues, organs and systems).

Step 2: Explain the concept In higher organisms, cells are specialised to do particular jobs (division of labour). This has benefits, but it also has a cost:

• Specialised cells cannot survive on their own. They depend on other cells for oxygen, food, waste removal and protection.
• If one organ or system fails (e.g. the heart or kidneys), the whole organism can be affected, and in serious cases it dies.

Step 3: Evaluate each option

• A. Mutual interdependence between component cells. This is a real disadvantage. Cells cannot live independently, and damage to one part affects the others.
• B. Internal structural specialization. This is an advantage because it gives efficiency. It is the feature of complexity itself, not a drawback.
• C. Increased adaptation to environment. This is clearly an advantage.
• D. Slower rate of diffusion of oxygen to individual cells. This is a real problem for large organisms because of a small surface-area-to-volume ratio. However, it is a consequence of large size, not of complexity of organisation. In fact, complexity (circulatory and respiratory systems) is the solution to this problem.

Step 4: Answer The disadvantage that comes directly from complex organisation is the mutual interdependence of cells, so the answer is A.

Tip: In WASSCE questions on levels of organisation, remember the pairing: specialisation = advantage, interdependence = disadvantage. Also watch out for option D. It sounds scientific, but it is linked to size, not to organisation.