$(a)$ State two differences between egg layers and broilers.
$(b)$ How can poultry fowl be prevented from various diseases? State any three methods.

How can genetically modified crops be obtained?

The figure shows two crop fields [Plots $A$ and $B$] that have been treated with manures and chemical fertilizers,respectively,while keeping other environmental factors constant. Observe the graph and answer the following questions.
$(i)$ Why does plot $B$ show a sudden increase and then a gradual decrease in yield?
$(ii)$ Why is the highest peak in the plot $A$ graph slightly delayed?
$(iii)$ What is the reason for the different patterns of the two graphs?

Discuss the role of hybridisation in crop improvement.

The number of dengue cases has increased in Sana's village in the last one year. She read in her textbook that diseases like dengue spread through mosquitoes which breed in stagnant water. She immediately suggested to her friends that they should kill the mosquitoes in water bodies in the locality. They also took the help of the nearest municipal office.
$(a)$ Which preventive measures do you suggest for the prevention of such diseases caused by mosquitoes? Mention any two measures.
$(b)$ Which values are displayed by Sana in taking this initiative?
$(c)$ Suggest one school activity to promote such values in school students.

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?