Question 2
- The diagram below are illustration of experimental setups labelled A, B, C and D used to investigate a biological process. Study them and answer questions 2(a) and 2(b).
(a) State the aim of the experiment
[1 mark]
(b) Complete the table below using setups A, B, C and D.
Setup |
Observation |
Reason for Observation |
Conclusion
|
A |
|
|
|
B |
|
|
|
C |
|
|
|
D |
|
|
|
[12 marks]
(c) Outline the process of germination in a cowpea seedling. [5 marks]
(d) (i) Name the type of germination that would be observed in a cowpea seedling.
[1 mark]
(ii) Give one reason for the answer in 2(d)(i). [1 mark]
(e) Name two food substances present in cowpea seedlings. [2 marks]
(f) List three parts of a germinating cowpea seedling. [3 marks]
Observation
Candidates’ performance was poorest in this question. Many could neither state the aim of the experimental setup, nor the process involved in a cowpea seedling. This is an indication that many of the candidates did not perform any experiments in Biology while in a school.
The expected answers are:
(a) Aim of the experiment
To investigate conditions necessary for seed germination/to show that air/oxygen, water, suitable temperature/warmth are necessary for germination.
(b) Table
Setup |
Observation |
Reason for observation |
Conclusion |
A |
No change in cowpea |
Moisture/water absent |
Water is necessary for germination of seeds |
B |
Germination observed in cowpea seeds/seeds germinated |
Water/suitable temperature/warmth viable seeds and air/oxygen present |
Water, suitable temperature/warmth; viable seeds and air/oxygen are necessary for germination of seeds |
C |
No change in cowpea |
Air/oxygen not present/absent |
air/oxygen is necessary for germination |
D |
No change in cowpea |
Suitable temperature not present/absent |
suitable temperature is necessary for germination |
(c) Process of germination
- Seeds absorb water/imbibition of water;
- Seed swells/testa breaks;
- Enzymes are activated;
- Stored food is broken down/digested to release nutrients;
- Embryo absorbs nutrients;
- Radicle grows/bursts out and grows downwards;
- Roots appears;
- The hypocotyl elongates and pushes the cotyledons above the soil;
- Plumule then grows out/epicotyl elongates to push plumule out.
- Foliage leaves appear.
(d) (i) Type of germination observed in cowpea seedlings
Epigeal.
Note: spellings must be correct to score.
(ii) Reason for the answer in 2(d)(i)
Cotyledons will be carried above the soil level/hypocotyl elongates more than epicotyl.
(e) Food substances present in cowpea seedling
- Starch/carbohydrate;
- Protein;
- Fats and oil.
(f) Parts of a germinating cowpea seedling
- epicotyl;
- hypocotyl;
- plumule;
- radicle;
- cotyledon;
- testa/seed coat;
- foliage leaf;
- tap root;
- secondary root.