WAEC Biology Past Question 21

biology question

WAEC Biology Past Question 21

a) (i)List 2 diseases each of plants and animals caused by bacteria

ii) State three ways in which bacteria are useful

b) State three ways by which mosquitos can be controlled and state the reasons for each method

c) Describe an experiment to demonstrate the presence of bacteria under the finger nails


Question extracted from June 1993 SSCE Biology 2 Section B Essay Question number 1



(a)(i) Diseases of plants caused by bacteria are:

(i) Soft roots, (ii) blight, wilts, crown gall.

Diseases of animals caused by bacteria are tuberculosis, cholera, leprosy, gonorrhea, syphilis, diphtheria and tetanus

(ii) Ways in which bacteria are useful are:


(1) Some bacteria are used in the preparation of cheese, butter and vinegar.

Bacteria, along with yeasts and molds, are used to prepare many fermented foods such as yogurt, vinegar and wine. Bacteria that are capable of degrading organic compounds have also been instrumental in cleaning up oil spills.


(2) A few are used in the production of antibiotics, enzymes, vitamins and amino acids for commercial purposes.


(3) Certain bacteria in soil are very useful in nitrogen fixation. Nitrogen in its naturally occurring form, nitrogen gas, cannot be used by plants nor animals. Nitrogen fixing bacteria convert nitrogen to a form that can be used by living organisms. In leguminous plants, bacteria like Rhizobium that are seen in the root nodules change atmospheric nitrogen to soil nitrogen boosting and elevating the nitrogen content of the soil.


(4) A few bacteria help in the digestion of cellulose:

Good bacteria also aids in healthy digestion. Bad eating habits and fatty foods can make you irregular or uncomfortable. The good bacteria found in sources like yogurt help to break down enzymes in order to make digestion occur without any trouble. Some bacteria promote absorption of nutrients, giving you a healthier body.


(5) A few bacteria assist in the fermentation of alcohol and beverages.


(6) Certain bacteria known as sewage bacteria assist in the decomposition of sewage into harmless substances that could be utilized as manure.


(7)Soil bacteria are the reason why nutrients are available today. Bacteria in the soil decompose dead matter. In doing that, they not only break down dead matter into soil material, they also make available for use the nutrients that were stored up in the dead plants or animals. Bacteria perform chemical reactions with carbon containing compounds in decaying plant and animal tissues to produce carbon dioxide, which plants use to produce food.


(b) Mosquitoes can be controlled in the following ways:

(1) Bush around the surrounding should be cleared to prevent breeding grounds for mosquito

(2) Mosquito net should be provided or fitted to our windows to prevent mosquitoes from coming inside to suck the human blood.

(3)Apply insecticides to kill mosquito or pour kerosene or oil on stagnant water around the house. The reason for this is to prevent breeding.

(c) Experiment to show the presence of bacteria under the finger nails


Aim: To show the presence of bacteria under the finger nails.


Apparatus: Incubator, inoculating loop, nail cutter, petridish, blood agar, microscope and cover slip.


Procedure: Cut the finger nails and put the cut finger nails in a petridish which have the blood agar. Then incubate at 37°C for two days.


Observation: After following the above procedure, it was observed that colonies of bacteria were growing on the bIood agar. When gram staining test was carried out clusters of cocci bacteria was observed.


Conclusion: The growth of cocci bacteria proves that bacteria grow on finger nails.

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