Kavita,the science teacher,was teaching her students about the types of diseases based on duration: acute and chronic diseases. She also discussed their ability to spread in public and their immediate causes.
$(a)$ What are acute and chronic diseases? Give one example of each.
$(b)$ Name the type of diseases which spread by coming in contact with a sick person. Name the different types of organisms which cause diseases.

Write the modes by which insects affect the crop yield.

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.

The preventive and control measures which are used before grains are stored for future use include:

$(a)$ State two characteristics of a healthy animal.
$(b)$ State any four characteristics of storage structure for grains.

$A$ farmer wanted to invest some money in fish farming. But he did not get right guidance.
$(a)$ How can you guide him for a profitable business in spite of limitations of fish farming?
$(b)$ What is the limitation of fish farming?