Life Processes — Science STD 10 — Question

P, Q, R and S are four major types of phytohormones. P is a phytohormone which functions mainly as a growth inhibitor. It promotes the wilting and falling of leaves. Q, R and S are phytohormones which all promote growth of plants in various ways. Q is responsible for the phenomenon of phototropism in plants. R is involved mainly in shoot extensions. The phytohormone S helps in breaking the dormancy of seeds and buds. What are P, Q, R and S? Give one reason each for your choice.

Define the following in terms of gain or loss of hydrogen with one example:

1. Oxidation.
2. Reduction.

State the three common features of all the respiratory organs like skin, gills and lungs.

A non-metal A is an important constituent of our food and forms two oxides B and C. Oxide B is toxic whereas C causes global warming.

1. Identify A, B and C.
2. To which Group of Periodic Table does A belong?

Identify the members present at the bottom and top of a terrestrial food chain.

"Natural selection and speciation leads to evolution." Justify this statement.

What is meant by the ‘angle of incidence’ and the ‘angle of refraction’ for a ray of light? Draw a labelled ray diagram to show the angle of incidence and the angle of refraction for a refracted ray of light.

Zn is more electropositive than Fe. Therefore, it should get corroded faster than Fe. But it does not happen. Instead, it is used to galvanize iron. Explain why does it happen so?

Under what conditions permanent electromagnet is obtained if a current carrying solenoid is used? Support your answer with the help of a labelled circuit diagram.