(a) (i) List two diseases each of plants and animals caused by bacteria. (ii) State three ways in which bacteria are useful. (b) State three methods by whic...
Question 1 Report
(a) (i) List two diseases each of plants and animals caused by bacteria.
(ii) State three ways in which bacteria are useful.
(b) State three methods by which mosquitoes can be controlled and state the reason for each method
(c) Describe an experiment to demostrate the presence of bacteria under the finger nails
Answer Details
(a)(i) Two diseases each caused by bacteria
Plants: bacterial wilt of tomato; bacterial soft rot of yam/cassava (bacterial leaf blight of rice is also acceptable).
Animals (including man): tuberculosis; cholera (others: tetanus, gonorrhoea, anthrax, typhoid).
(a)(ii) Three ways in which bacteria are useful
- Decay bacteria (decomposers) break down dead organisms and recycle nutrients in the soil.
- Nitrogen-fixing and nitrifying bacteria enrich the soil with nitrogenous compounds for plant growth.
- Bacteria are used in industry to make food and drugs, e.g. yoghurt and cheese production, and antibiotics; some also aid digestion in the gut.
(b) Three methods of controlling mosquitoes and the reason for each
| Method | Reason |
|---|---|
| Draining or filling stagnant water and clearing bushes | Removes the breeding sites where mosquitoes lay eggs and larvae develop |
| Spraying oil or insecticide on stagnant water surfaces | Suffocates the larvae and pupae / kills them, cutting the life cycle |
| Using insecticide-treated nets and closing houses | Prevents adult mosquitoes from biting and spreading the malaria parasite |
(c) Experiment to demonstrate the presence of bacteria under the finger nails
- Prepare two sterile Petri dishes containing sterile nutrient agar (A and B).
- Dish A: with an unwashed finger, scrape the material under the finger nails and gently streak it across the agar surface, then cover.
- Dish B: leave untouched (or streak with a finger washed thoroughly with soap and disinfectant) to act as the control.
- Incubate both dishes at about 37 °C for 2 to 3 days.
- Observation: numerous colonies of bacteria grow on dish A, while the control B remains clear or nearly clear.
- Conclusion: the growth of colonies on A shows that bacteria were present under the finger nails.
Download The App On Google Playstore
Everything you need to excel in your exams
