Experiment 9.1 (Form 5 Biology Textbook Exercise and Answer)

Experiment 9.1 – The Effects of Intraspecific and Interspecific Competitions among Organisms:

Problem statement
What are the effects of intraspecific and interspecific competitions among organisms?

To study the effects of intraspecific and interspecific competitions among organisms

If the competition among organisms is high, the growth of organisms becomes slow.

Manipulated variable: Types of seeds
responding variable: Height of seedlings
Constant variable: Amount and type of soil, amount of water sprinkled, fertilisers, light intensity

Fertilised soil, 120 corn seeds, 120 paddy seeds

Three plastic trays with the measurements of 50 cm × 40 cm × 10 cm, a ruler, a mini shovel


1. Label all plastic trays as A, B and C (Figure 9.12).

2. Randomly choose 30 corn seeds (C) and 30 paddy seeds (P).

3. Sow:
(a) 20 corn seeds in tray A
(b) 20 paddy seeds in tray B
(c) 10 corn seeds and 10 paddy seeds in tray C

4. Ensure the distance between each seed is 10 cm whereas the distance between the seeds and the edge of the tray is 5 cm.

5. Put all the trays in a shady place.

6. Water every tray with the same amount of water.

7. After a month, randomly select:
(a) 10 corn seedlings from tray A
(b) 10 paddy seedlings from tray B
(c) 5 corn seedlings and 5 paddy seedlings from tray C.

8. Measure and record the height of every seedling and their average into a table.

9. Based on the table, plot a bar graph using the height of the seedlings in centimetres.


1. Name the type of competition that has taken place in trays A, B and C.

2. What are the sources that cause the competition in trays A, B and C?

3. Which species is more adaptive in the competition in tray C? Explain.

4. Compare the heights of:
(a) Corn seedlings in trays A and C.
(b) Paddy seedlings in trays B and C. Explain your answer.

Is the hypothesis accepted? Suggest a suitable conclusion.



Tray A – Intraspecific
Tray B – Intraspecific
Tray C – Interspecific

2. Trays A, B and C – Compete to get minerals, water and sunlight

3. Based on students’ experiment

4. Based on students’ experiment

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