Cell - structure and functions — Science STD 8 — Question

What are the functions of the following parts of the eye?

1. Iris.
2. Eye-lens.
3. Ciliary muscles.
4. Retina.
5. Optic nerve.

Explain why sliding friction is less than static friction.

Name the part of the eye:

1. Which controls the amount of light entering the eye.
2. Which converges light rays to form the image.
3. On which image is formed.
4. Which carries the image to brain.
5. Which changes the curvature (or thickness) of eye-lens to focus objects lying at various distances.

X is a group of stars which is visible during the summer season in the early part of the night. It can be seen clearly in .the month of April in the northern part of the sky. It resembles a bowl with a handle. It also resembles a big kite with a tail.

1. What is the general name of groups of stars like X?
2. Write any two names of X.
3. Is it a part of our Solar System?
4. How many bright stars are usually observed in X?
5. Which famous star can be located in the sky with the help of X?

Which plastic is used:

1. For making uniforms of fire-men fire resistant?
2. For giving non-stick coating on frying pans?
3. For making handles of frying pans?
4. For making insulation (covering) of electric wires?
5. For making electric switches?
6. For making flexible water bottles?

An earthquake measures 3 on Richter Scale:

1. Would it be recorded by a seismograph?
2. Is it likely to cause much damage?

Which of the following are prokaryotic cells and which are eukaryotic cells?Amoeba cell, Bacterium cell, Human cheek cell, Blue-green algae cell, onion peel cell.

What are non-metals? Name five non-metals.

What is the major cause of air pollution? Write the various tips for minimising the wastage of petrol/ diesel while driving vehicles.

The species P and Q of wild animals are found only in a ‘particular area’. The species R of wild animals is listed in Red data book of India whereas species S of wild animals no longer exists anywhere on the earth.

1. What name is given to species like P and Q?
2. What are the species like R known as?
3. Name one species like R?
4. What is the special name of species like S?
5. Name one species like S?