Question

(a) Fig. 1.1 is a photograph of blood as seen under a microscope. 

(i) Use a label and a label line on Fig. 1.1 to identify a white blood cell. 

▶️Answer/Explanation

White blood cell labelled correctly on Fig. 1.1.

(ii) Name one other type of cell visible in Fig. 1.1. 

▶️Answer/Explanation

Red blood cell.

(b) White blood cells produce antibodies that fight infection in the body. The graph in Fig. 1.2 shows how the number of antibodies in the blood changes for 15 days after a person is infected by a pathogen. 

(i) Use Fig. 1.2 to identify on which day there are the most antibodies in the blood. 

▶️Answer/Explanation

Day 12.

(ii) Suggest one reason why there is a decrease in the number of antibodies in the blood as shown in Fig. 1.2.

▶️Answer/Explanation

The pathogen was destroyed, so fewer antibodies are needed.

(c) Twenty days after the first infection, the same person is infected with a different pathogen. Draw a line on Fig. 1.2 to suggest how the number of antibodies in the blood changes from day 15. 

▶️Answer/Explanation

Line decreasing or flat from 15–20 days, then increasing and decreasing again.

(d) Platelets are also found in the blood. State the function of platelets.

▶️Answer/Explanation

Blood clotting.