IGCSE Biology Paper-3: Specimen Questions with Answers 258 - 259 of 358

Question 258

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Describe and explain what could happen when blood of different groups is mixed.

Explanation

Our immune system will produce antibodies against any blood antigens that we don՚t have in our own blood. That means people with type A blood create antibodies against B antigens. A person with type A blood receiving a transfusion of type B or AB blood would have an ABO incompatibility reaction. In an ABO incompatibility reaction, our immune system attacks the new blood cells and destroys them. In many cases this incorrect transfusion is fatal.

Others symptoms may include:

  • fever and chills
  • breathing difficulties
  • muscle aches
  • nausea
  • chest, abdominal, or back pain
  • blood in your urine
  • jaundice

Question 259

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Fig. shows the apparatus a student used to investigate how light intensity affects photosynthesis.

Light Intensity Affects

The student placed an aquatic plant under a funnel in a beaker of water.

During the investigation he placed the lamp at different distances from the aquatic plant.

(i) Describe how the rate of photosynthesis is affected by the distance of the lamp from the aquatic plant.

(ii) Predict the number of bubbles that would be produced if the lamp was placed 21 cm from the aquatic plant.

Explanation

  • As light intensity increases (distance between lamp and plant decreases) the volume of oxygen (or the rate of bubble production) increases. This indicates that the rate of photosynthesis increases with light intensity. However, at sufficiently high levels of light intensity, the rate oxygen evolution remains constant.
  • The relationship between the rate of photosynthesis and distance between light source and plant is inversely proportional with distance of light source. If the distance between plant and lamp increases then there is decrease in number of bubbles produced.
Distance of Lamp from Plant