National 4 Biology

Unit 2 Cell Biology

Homework Questions

Key Area 1 – Sexual and asexual reproduction and their importance for survival of species

1. The diagram below shows a section through a flower.

Complete the following table using information from the diagram.

Letter / Name of structure / Function
anther
B / sepal
collects pollen
G / site of fertilisation

2. Use words from the list to complete the following sentences.

Each word may be used once, more than once or not at all.

List

Water nucleus membrane placenta yolk

Fertilisation occurs when the ______of a sperm cell fuses with the ______of an egg cell.

In mammals this happens inside the female body. In most fish, sperm are deposited in the surrounding ______close to the eggs.

Key Area 2 – Propagating and growing plants

1. Read the following passage carefully.

Potato Blight

Blight is a disease that can affect potato plants. Blight is caused by a fungus that is spread through the air during cool, moist weather. The leaves of affected plants first turn black. The potatoes then begin to rot in the soil.

Often the blighted potatoes look normal from the outside. When they are cut in half, however, the inside is black and rotten and cannot be eaten.

In 1845, Ireland’s potato crop was badly affected by blight and a third of all potatoes were destroyed, causing famine. Farmers today spray potato plants with chemicals which prevent the disease.

(a) Use the information in the passage to answer the following questions.

(i) Describe the weather conditions which allow the potato blight to spread.

______

(ii) What is the first sign of the disease?

______

(iii) Fully describe the appearance of a blighted potato when it is cut in half.

______

(b) Name the type of chemical which farmers would spray onto potato plants to prevent this type of disease.

______

(c) Potato tubers are food storage organs. Name one other type of food storage organ.

______

(d) Name the process by which plants produce food in sunlight.

______

2. The diagram below shows a method of artificial plant propagation.

(a) Name this method of artificial propagation.

______

(b) State one feature in the diagram that reduces water loss.

______

(c) Describe an additional step which could be taken to encourage root growth

______

Key Area 3 – Commercial use of plants

1. A greenhouse is shown in the photograph below.

(a) (i) What is the function of the thermostat in the greenhouse?

______

(ii) Describe one method of providing ventilation in this greenhouse.

______

(b) The table below shows the temperatures taken inside and outside a greenhouse over a 24 hour period in winter.

Time (hours) / Temperature (°C)
Inside / Outside
0 / 14 / 0
4 / 14 / 3
8 / 15 / 4
12 / 14 / 6
16 / 15 / 5
20 / 13 / 3
24 / 14 / 2

On the grid below, complete the line graph by:

(i) Providing a scale for the horizontal axis;

(ii) Providing a label for the horizontal axis;

(iii) Plotting the results for the temperature outside the greenhouse.

Key Area 4 – Genetic information

1. The diagram below shows two chromosomes from a child. Genes for eye colour, tongue-rolling ability and type of ear lobes are found on the chromosomes. The forms of each gene are represented by letters. The capital letter represents the dominant form of the gene.

Complete the following sentence by underlining the correct option in each bracket.

The child will have (blue/brown) eyes, (will/will not) be able to roll their tongue and will have (attached/unattached) ear lobes.

Key Area 5 – Growth and development of different organisms

1. The mass of tar in four different brands of cigarette is shown below.

(a) Calculate the average mass of tar in the four brands of cigarette.

Space for calculation

______mg

(b) State one health risk that is increased by regularly smoking cigarettes.

______

(c) Cigarette smoke also contains carbon monoxide.

Describe the effect carbon monoxide has on the ability of the blood to carry oxygen.

______

______

Key Area 6 – Biological actions in response to internal and external changes to maintain stable body conditions

Decide if each statement about blood glucose and body temperature is TRUE or FALSE then tick () the correct box.

If the statement is FALSE, write the correct word(s) in the Correction box to replace the word(s) underlined in the statement.

Statement
/ True
/ False / Correction
The liver produces insulin and glucagon.
Insulin is produced if there is too much glucose in the blood.
The average human core body temperature is 40°C.
Your body will shiver if it gets too hot.