1.4 Cell differentiation
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What is meant by cell differentiation?
Choose one answer.
Correct Not quite: the answer is A cell becoming specialised for a particular job
Mark scheme
B (A cell becoming specialised for a particular job)
Model answer
B: A cell becoming specialised for a particular job. Differentiation is how a cell changes to become specialised.
Describe one difference between differentiation in animal cells and in plant cells.
Mark scheme
- most animal cells differentiate at an early stage / in the embryo (1)
- many plant cells can differentiate throughout life (1)
Model answer
Most animal cells differentiate early in development, but many plant cells keep the ability to differentiate throughout the life of the plant.
State two uses of cell division in a mature animal.
Mark scheme
Any two from:
- repair of damaged tissue (1)
- replacement of cells that are worn out / lost, such as skin or blood cells (1)
Model answer
Cell division repairs damaged tissue and replaces cells that have worn out, such as skin cells.
A gardener takes a cutting from a plant. The cutting grows new roots.
Explain why a plant can do this but a human cannot grow a new arm.
Mark scheme
- plants have meristems / many plant cells keep the ability to differentiate (1)
- these cells can become the cell types needed to make new roots (1)
- most animal cells are already specialised and cannot change into other types (1)
Model answer
A plant keeps unspecialised cells in its meristems, and many other plant cells can differentiate throughout life, so they can become the cells needed to make new roots. Most animal cells are specialised and cannot change type, so a human cannot grow new limbs.
Describe how a plant root grows longer.
Mark scheme
- cells divide by mitosis at the tip / in the meristem (1)
- the new cells take in water and get longer / elongate (1)
- the cells then differentiate / become specialised (1)
Model answer
Cells in the meristem at the tip divide by mitosis to make more cells. The new cells then take in water and elongate, which makes the root longer, and then they differentiate into specialised cells.
A fertilised egg divides to form an embryo. Later, the cells in the embryo become different types of cell.
Explain why this is important for a large organism.
Mark scheme
Any four from:
- cells need to be specialised to do different jobs (1)
- for example muscle cells contract / nerve cells carry impulses (1)
- specialised cells have different sub-cellular structures, such as many mitochondria in muscle cells (1)
- specialised cells work more efficiently than unspecialised ones (1)
- specialised cells make tissues, organs and organ systems (1)
- so the organism can be large and complex / one type of cell cannot do every job (1)
Model answer
A large organism needs different cells to do different jobs, for example muscle cells to contract and nerve cells to carry impulses. As cells differentiate they gain the sub-cellular structures they need, such as many mitochondria in a muscle cell, so each type does its job efficiently. The specialised cells make up tissues, organs and organ systems, which allows the organism to be large and complex.
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