Conservation of plants and animals — Science STD 8 — Question

X and Y are the two types of animals. The animals like X undergo external fertilization whereas animals like Y undergo internal fertilization. The animals like X lay eggs from which baby animals are hatched. On the other hand, in animals like Y, the young one develops inside the uterus of mother which then gives birth to the baby.

1. What is the general name of animals like X?
2. Give two examples of animals like X?
3. What is the general name of animals like Y?
4. Write the names if two animals like Y.

What can be done to retain our ‘green wealth’ for the future generations?

What is night blindness? What causes night blindness?

Name one source and one harmful effect of each of the following air pollutants:

1. Sulphur dioxide.
2. Nitrogen oxides.
3. Carbon monoxide.
4. Chlorofluorocarbons (CFCs).

The substance W is a fossil fuel. It occurs deep below the ground in certain areas of the earth. Another fossil fuel X is found trapped above the deposits of W. When W is subjected to a process called Y, then a number of different products are collected at different temperature ranges which are put to different uses. A special grade of product Z obtained in this way is used as aviation fuel in jet aeroplanes.

1. What are (i) W, and (ii) X ?
2. What is the physical state of (i) W, and (ii) X ?
3. Name the process Y.
4. Name the product Z.

What are the various purposes for which the forest trees are cut?

At many places the wastewater containing human excreta from homes and carried in big underground pipes is dumped into a river as such which pollutes the river water.

1. What is the common name of such wastewater?
2. Name five types of harmful organisms contained in it.
3. Name any five human diseases caused by drinking river water contaminated with such wastewater.

Identify the actions involved in the following situations as push or pull, or both:

1. Opening a drawer.
2. A cricket ball hit by a batsman.
3. Drawing a bucket of water from a well.
4. moving a book placed on a table.
5. A football player taking a penalty corner.
6. Moving a wheel barrow.

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.

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?