Question 1:
Figure 1 shows the result of an experiment to study the effect of different concentrations of an antibiotic on bacteria growth.



(a) State one hypothesis for this experiment. [1 mark]

(b) State the variables in this experiment.
(i) Manipulated variable [1 mark]
(ii) Responding variable [1 mark]

(c) Write down one observation for this experiment. [1 mark]

(d) What is meant by antibiotic based on this experiment (operational definition). [1 mark]


Answer:
(a) A higher concentration of an antibiotic will kill more bacteria.

(b)(i) Concentration of an antibiotic.

(b)(ii) Clear area

(c) The clear area that surrounds the antibiotic disc of high concentration is larger/ wider than the clear area that surrounds the antibiotic disc of low concentration.

(d) Antibiotic is a substance that produces a clear area around the nutrient agar that contains bacteria.

Question 1:
Diagram 1 shows an experiment to study the effect of temperature on the growth of bacteria.



After 2 days, the appearance of the nutrient broth in each test tube is observed. The result recorded is shown in Table below.


(a) State the variables in this experiment.
(i) Manipulated variable [1 mark]
(ii) Responding variable [1 mark]


(b) State the hypothesis for this experiment. [1 mark]

(c) State the inference that can be made based on this experiment. [1 mark]

(d) Based on this experiment, state the operational definition for bacteria. [1 mark]


Answer:
(a)(i) Temperature

(a)(ii) Growth of bacteria

(b) A suitable temperature is essential for the growth of bacteria.

(c) Bacteria growth very fast at 37^oC

(d) Bacteria are tiny living organisms which grow and reproduce themselves under a suitable temperature.