Question 11:
There are two water taps on two different walls of the fence. One of the water taps on the wall of the fence is broken, causing water to drip out continuously.
Diagram 10 shows the condition of the wall of the fence after a month.
Based on the situation in Diagram 10, plan an experiment in the laboratory by using two sterile Petri dish containing moist nutrient agar, Bacillus sp. culture solution, wire loop, cellophane tape and oven to study one factor that affects the growth of microorganisms.
The experiment planning should include the following criteria:
(a) Problem statement [1 mark]
(b) Hypothesis [1 mark]
(c)(i) Manipulated variable [1 mark]
(ii) Ways to control the manipulated variable [1 mark]
(d)(i) Responding variable [1 mark]
(ii) Ways to control the responding variable [1 mark]
(e) Tabulation of data [2 marks]
(f) Two precautionary steps when carrying out the experiment [2 marks]
Answer:
(a) What is the effect of moisture on the growth of Bacillus sp.?
(b) Low moisture inhibits the growth of Bacillus sp.
(c)(i) Moisture of the nutrient agar.
(c)(ii) One Petri dish is heated in the oven so that the agar becomes dry while the other is kept moist.
(d)(i) Number of Bacillus sp. colonies.
(d)(ii) Count and record the number of bacterial colonies after three days.
(e)
(f)
1. Wash hands with soap before and after the experiment.
2. Sterilise all apparatus and waste materials after the experiment
There are two water taps on two different walls of the fence. One of the water taps on the wall of the fence is broken, causing water to drip out continuously.
Diagram 10 shows the condition of the wall of the fence after a month.
Based on the situation in Diagram 10, plan an experiment in the laboratory by using two sterile Petri dish containing moist nutrient agar, Bacillus sp. culture solution, wire loop, cellophane tape and oven to study one factor that affects the growth of microorganisms.
The experiment planning should include the following criteria:
(a) Problem statement [1 mark]
(b) Hypothesis [1 mark]
(c)(i) Manipulated variable [1 mark]
(ii) Ways to control the manipulated variable [1 mark]
(d)(i) Responding variable [1 mark]
(ii) Ways to control the responding variable [1 mark]
(e) Tabulation of data [2 marks]
(f) Two precautionary steps when carrying out the experiment [2 marks]
Answer:
(a) What is the effect of moisture on the growth of Bacillus sp.?
(b) Low moisture inhibits the growth of Bacillus sp.
(c)(i) Moisture of the nutrient agar.
(c)(ii) One Petri dish is heated in the oven so that the agar becomes dry while the other is kept moist.
(d)(i) Number of Bacillus sp. colonies.
(d)(ii) Count and record the number of bacterial colonies after three days.
(e)
(f)
1. Wash hands with soap before and after the experiment.
2. Sterilise all apparatus and waste materials after the experiment