[Biology SPM] Exam Pointers II

Source: Maths & Science Guide

Revision

1. How do you separate blood into plasma and its cells?
   
   
2. Two types of land snails with brown and green shell colours are studied on a grassland habitat covered with dead woods, twigs and fallen leaves. State why quadrat sampling is inappropriate in the above investigation.
   
   
3. Name the substrate on which the enzyme lipase acts.

Frequent Mistakes

Student answers:

1. By centrifuging at high speed for a few minutes, the blood can be separated into plasma and its cells.
   
   
2. Quadrat sampling is time consuming and tedious to carry out.
   
   
3. Fats.

Tutor's comments:

1. A sampling method is chosen based on the animal studied. The student should have made some reference to the land snails.
   
   
2. Fats are a smaller group of a larger family of lipids. Lipids include triglycerides (fats and oils), phospholipids and steroids.

Correct Answer

1. By centrifuging blood at high speed for a few minutes. Subsequently, it separetes into two layers - the plasma layer on top and the cells at the bottom.
   
   
2. Since land snails are mobile organisms, they can move out of the quadrats. Hence, findings based on this technique will not be reliable.
   
   
3. Lipids.