Growth in Organisms (Edexcel GCSE Biology: Combined Science)

State the name of the process by which cells become specialised.

An unspecialised bone marrow stem cell develops into a red blood cell.

Describe the changes which occur in an unspecialised cell in order for the cell to become a specialised cell such as a red blood cell.

State the importance of cell specialisation for an organism.

Cell specialisation is different in cells of plants compared to animals.

Which of the following correctly describes cell specialisation in plants?

(1)

Which of the following incorrectly describes cell specialisation in animals?

(1)

Fig. 1 shows a growth chart for baby boys showing how their mass changes between birth and 24 months.

Fig. 1

Give the mass of a child which was born in the 90th percentile.

At 6 months, the child had a mass of 8kg.

Identify which percentile the child was on at 6 months.

(1)

The midwife monitoring the child was not concerned about the change in percentile readings for this child.

Suggest why.

For the child in part (a) (ii), calculate the child's average gain in mass per month.

Babies that are born before 37 weeks of pregnancy are termed premature. There are growth charts specifically for monitoring the growth of premature infants until they reach the predicted due date for birth. At this point, the standard birth chart can be used.

Suggest why premature infants must be monitored in this way.

Plant growth occurs through three different cellular processes;

• division
• differentiation
• elongation

Describe these processes in the context of plant growth.

Name the key hormone responsible for cell elongation in plant cells.

A stimulus is a change which triggers a response.

Identify the stimulus which activates the hormone discussed in part (b)

(1)

Suggest why it is important that plant cells respond to the stimulus described in part (i)

Fig.1 shows a root hair cell which is a specialised cell found in plant roots.  

Identify one feature of this cell which has developed through the differentiation of an unspecialised cell and explain how that feature allows the cell to carry out its function.

The diagram in Fig.1 shows how unspecialised stem cells can develop into a variety of different cell types in the human body.

Fig.1

Name the process which occurs at X

Fig.2 shows a section of muscle tissue. The cells seen in the tissue from Fig. 2 have already been through process X identified in part (a). During this process, the cells synthesized many mitochondria.

Fig.2

(1)

Plant growth occurs through cell division at the growing roots and shoots. In these regions, meristem tissue is found which contains the stem cells of the plant.

Cells from this region of the plant can be used to grow entire new plants which are genetically identical to the parent plant.

State why bone marrow stem cells seen in part (a) cannot be used to develop all the different tissues of the human body in the same way.