Practice Question

Q1. Define the term cell differentiation.

Cell differentiation is the process by which an unspecialised cell develops into a specialised cell by acquiring different sub-cellular structures so it can carry out a particular function.

2. Explain why cell differentiation is important in multicellular organisms.

Differentiation allows cells to become specialised for specific functions. This enables the formation of tissues, organs and organ systems, which work together to keep the organism alive. Without differentiation, all cells would be the same and could not perform the variety of functions needed.

3. Describe one difference between cell differentiation in plants and animals.

In animals, most cells differentiate at an early stage of development and then lose this ability. In plants, many cells (especially in meristems) can retain the ability to differentiate throughout life.

4. Give one example of a specialised animal cell. Describe one of its adaptations and explain how that helps it carry out its function.

A sperm cell has a tail that allows it to swim towards the egg for fertilisation. It also contains many mitochondria to release energy needed for movement.

5. A sperm cell contains many mitochondria. Explain why.

The mitochondria release energy by aerobic respiration, which is needed to power the movement of the tail so the sperm can swim to reach the egg.

6. Compare the roles of xylem cells and phloem cells in plants, and explain how their structures are adapted for these roles.

Xylem cells transport water and minerals from the roots to the rest of the plant. They are hollow and strengthened with lignin, forming long tubes for efficient water transport.
Phloem cells transport sugars produced by photosynthesis. They have sieve plates to allow the flow of dissolved sugars and companion cells with many mitochondria to provide energy for active transport.

7. Why can cuttings from plants be used to grow whole new plants, but this is not possible in most animals?

Plant cells can continue to differentiate throughout life, so cuttings can form roots, stems and leaves to grow into a new plant. In animals, most cells become specialised early and cannot change into other cell types, so they cannot regrow a whole organism.

8. In mature animals, what is the main purpose of cell division? Give two examples of tissues where this happens.

In mature animals, cell division is mainly for repair and replacement of damaged or worn-out cells. Examples include skin cells and blood cells.

9.Discuss how cell differentiation allows organisms to grow and survive. In your answer, you should refer to both plants and animals.

Cell differentiation allows unspecialised cells to become specialised, with structures suited to particular functions. In animals, this mainly happens at an early stage of development. For example, nerve cells form long axons and dendrites to transmit signals, and muscle cells develop protein filaments and many mitochondria to contract. In mature animals, cell division is mainly for repair and replacement.
In plants, many cells retain the ability to differentiate throughout life. For example, xylem cells form hollow tubes strengthened with lignin to transport water, while phloem cells form sieve tubes for sugar transport. Because plant cells can differentiate at any stage, plants can grow continuously and regenerate from cuttings.
This specialisation of cells ensures organisms can perform all the processes needed for survival, such as movement, transport, communication and photosynthesis.