1. A diagram of the human heart is shown in the figure below. Identify the structures labelled A–H.
Answer
A = Vena cava,
2. Describe the movement of water through a plant.
Answer
Water enters the roots via osmosis, moves into the xylem, travels upward through the xylem, and reaches the leaves, where it evaporates into the air spaces of the leaf before diffusing out through the stomata into the surrounding air.
3. The part of a plant that is considered to be a source or sink can change depending on the season. In the growing season (generally spring and summer), sinks are the actively growing parts of the plant such as new leaves. Sinks are the sugar storage locations, such as roots, tubers and bulbs. If the plant loses its leaves at the end of the growing season, these roots, tubers or bulbs are considered sources at the start of the next growing season. Explain why.
Answer
The source is part of a plant that produces carbohydrates. The sink is part of a plant that uses or stores carbohydrates. In the new growing season, the sink could become the source as it provides the sugars for the plant to use for growth, as it is not yet able to photosynthesise without any leaves.
4. The figure below shows the relationship between the mass of molecules and the permeability of the capillaries and lymph vessels. Describe this relationship.
Answer
As molecule density increases, permeability into the blood decreases. The decrease is very steep initially and then decreases more steadily. As molecule density increases, permeability of lymph vessels increases steadily.
5. Arteries and veins carry out different roles within our bodies. Describe and explain how their structures relate to their function.
Answer
Arteries: Thick elastic walls, so they can stretch and recoil with changing pressure. A smooth endothelium, so friction is reduced. A thick muscle layer, so pressure is maintained.
Veins: Valves, so backflow of blood is prevented. Walls are thinner, with less muscle and elastic tissue, because they do not have to withstand high pressure.
6. There are valves in the lymph vessel. Suggest why these are important.
Answer
These valves prevent backflow.
7. Lymph vessels in legs are between muscles. People who walk more have faster flow of lymph in their legs. Explain why.
Answer
Muscle contractions squeeze the lymph vessels, propelling the lymph forward and upward.
8. The figure below shows the volume changes in the left ventricle of the heart during two cardiac cycles. Between which times is the ventricle contracting ?
Answer
Between 2.2 - 4.8 and between
9. Use the figure above to calculate the volume of blood pumped per minute by the left ventricle.
Answer
80 cm3 pumped per cycle and each cycle lasts 0.74 seconds. So
10. The figure below shows the volume changes in the left ventricle of the heart during two cardiac cycles. State which of the times, A, B, C or D, is when the semi-lunar valve opens or the atrio-ventricular valve closes.
Answer
The semi-lunar valve opens at B and the atrio-ventricular valve closes at A.