Cultivation practices and crop yield are related to environmental conditions. Explain.

When Ashok visited his village,he observed that villagers were suffering from malnutrition. To curb malnutrition in the village,he suggested they select five or six fish species in a pond. This increased the fish yield from the pond. The villagers were surprised to see the results and asked him to help with the other two ponds in the village.
$(i)$ What name is given to this intensive fish farming?
$(ii)$ Write the basis on which the different fish species are selected.
$(iii)$ Ashok's initiative is worth praising. Give two reasons.

Suhasini's uncle was advised by his doctor to have an ultrasound scan of his abdomen. Her uncle did not know much about the details and significance of this test. He also felt that it was too expensive and thought of postponing it. When Suhasini learnt about her uncle's problems,she immediately decided to do something about it. She took the help of her family,friends and neighbours and arranged for the cost of the test. She also told her uncle that an ultrasound scan of his abdomen would enable the doctors to know of the condition of his kidneys without causing any (test related) harm to him. This test was expensive because of its set-up that needed an expensive apparatus.
Her uncle was convinced and had the required ultrasound scan of his abdomen done. The resulting information greatly helped his doctor to treat him well.
$(a)$ What according to you,are the values displayed by Suhasini and her family,friends and neighbours to help her uncle?
$(b)$ What type of wave is used in an ultrasound scan?

Bhetki,mullets,pearl spots and prawns are some of marine fish of high economic value.

$(a)$ Mention the harmful effects of infectious diseases on the health of cattle.
$(b)$ How can these diseases be controlled?

The changes brought by biotic and abiotic factors in food grains that are not stored properly include: