Biology Paper 2, Nov/Dec 2015

Question 3


  1. A sample of garden soil was placed in a measuring cylinder, enough water was added to it. It was shaken and allowed to settle for 30 minutes. Draw a diagram 6cm-8cm long to show the various layers formed and label fully.             [7 marks]
  2. State four reasons why each of the following soils is not suitable for crop production:
    1. Clayey;
    2. Sandy.              [8 marks]
  3. (i) List two examples of refuse.        [2 marks]

(ii)  State three ways in which refuse is disposed of in the community.  [3 marks]

Observation

The diagram of soil profile showing different layers of garden soil was poorly drawn by majority of the candidates. Many candidates drew without the appropriate ways of labeling; spelling errors and no indication of the soil layers. Many candidates mistook sewage for refuse and hence could not give examples.


The expected answers are:
3 (a)    Diagram showing different layers of garden soil



Title (T)                                x1
Quality (Q)
Size (Sz) (6-8cm)                         x1
Clarity of lines (CL)                        x1
Neatness of labels (NL)                     x1

Details (D)
At least 3 layers shown (SL)                    x1

 Labels (L)
Measuring cylinder; humus/organic matter; clay; silt; fine sand; coarse sand; gravel; water with clay in suspension and mineral salts in solution. 

                                   

NOTE: Spellings of labels must be correct to score.

 

(b)   Reasons why clayey soil and sandy soil are not suitable for crop production

  • Clayey Soil

- Small soil particles; lead to less air space/high water retention/low water drainage; soil becomes water logged easily;
- small amount of oxygen supports few nitrifying bacteria/low in nitrates;
- has few organisms/little humus/low soil nutrients;
- heavy and sticky makes it difficult to cultivate;
- very hard when dry which makes it difficult for plant growth.                       

  • Sandy Soil
  • Large/coarse soil particles create more air spaces/it is porous;
  • low water retention/high water drainage which makes minerals easily washed out/leached;
  • small amount of water makes soil dry therefore plants and animals/organisms find it hard/difficult to get water;
  • Soil is light and is easily blown away/eroded.                                        

 

(c) (i)  Examples of refuse
Waste papers; food remnants/domestic waste; cans; plant materials/cobs of maize; yam; cassava; plantain/banana peels; plastic wastes and containers and any other correct example.

                                   
(ii) Methods of disposal
Burning/incineration; controlled dumping; recycling/biodegradation; burying.