Question

Give reasons.
(a) Diseases spread on a large scale during periods of heavy rainfall and floods.
(b) There is a possibility of food poisoning if we eat stale food.
(c) Soil is turned over during tilling.
(d) Fungus grows quickly in moist or humid conditions.
(e) A refrigerator is used in almost every home.
(f) Bread 'rises' during baking.
(g) Fodder is soaked in water before offering to cattle.

Answer 1

a. Diseases spread on a large scale during periods of heavy rainfall and floods because it provides the optimum conditions for the growth of vectors which transmit diseases. After heavy rainfall and floods, water gets accumulated at places and acts as breeding grounds for mosquitoes and other vectors. These vectors lead to transmission of the microorganisms to their host and result in the development of disease.
For example, malaria is caused by a virus which is transmitted by a mosquito.

b. There is a possibility of food poisoning if we eat stale food because there are chances that it can be infested by microorganisms. Bacteria and fungi can infect the foods which are stored for longer durations of time. For example, the greenish powdery substance which is seen on stale breads is an example of fungus infection.

c. Tilling is a mechanical procedure of agitating soil where the top layer is mixed with the lower layers of soil. This promotes the mixing of organic matter throughout the soil and also promotes the growth of microorganism. These microorganisms help in the conversion of organic matter.

d. Fungus grows quickly in moist or humid conditions because these are the favourable conditions for its growth. Fungus is not seen growing in areas which are well exposed to sunlight.

e. Refrigerator is used in almost every home because it prevents the spoilage of food. Refrigerator provides an optimum environment for storage of vegetable, fruits, cooked and uncooked food. If an optimum temperature is not provided, it can lead to the growth of bacteria and fungi thus leading to spoilage of food.

f. Bread rises during baking because of addition of yeast to its dough. Yeast cells respire anaerobically and liberates CO₂ in the process. When yeast cells are added to the bread dough, they utilise the nutrients (carbohydrates) found in the dough and respire anaerobically. Also, they multiply at a very fast rate under such favourable conditions. As a result of the growing bacterial population, large amount of CO₂ is released that makes the dough very soft and fluffy, and thus improves the quality of the bread.

g. Fodder is soaked in water before offering it to cattles because it may contain seeds which have been left behind after harvesting. Soaking this fodder helps in the sprouting of these seeds/grains and thus increases the nutritional value of the fodder.