Our Environment — Science STD 10 — Question

Can you suggest some changes in your school which would make it environment-friendly?

The growing size of the human population is a cause of concern for all people. The rate of birth and death in a given population will determine its size. Reproduction is the process by which organisms increase their population. The process of sexual maturation for reproduction is gradual and takes place while general body growth is still going on. Some degree of sexual maturation does not necessarily mean that the mind or body is ready for sexual acts or for having and bringing up children. Various contraceptive devices are being used by human beings to control the size of population.

1. List two common signs of sexual maturation in boys and girls.
2. What is the result of reckless female foeticide?
3. Which contraceptive method changes the hormonal balance of the body?
4. Write two factors that determine the size of a population.

How do variations occur in offspring? Explain.

How are oxygen and carbon dioxide transported in human beings? How are lungs designed to maximise the area for exchange of gases?

Give the exact location and function of the cerebellum.

What is Debereiner’s law of triads? Explain with the help of one example of a Dobereiner’s triad.

A coil is connected to a galvanometer. When the N-pole of magnet is pushed into the coil, the galvanometer deflected to the right. What deflection, if any, is observed when:

1. The N-pole is removed?
2. The S-pole is inserted?
3. The magnet is a rest in the coil?

State Fleming’s left-hand rule. Explain it with the help of labelled diagrams.

a. Draw a diagram of human alimentary canal and label - gall bladder, pancreas, liver and small intestine on it.
b. Give two reasons to explain why absorption of digested food occurs mainly in the small intestine.