Metals and Non-Metals — Science STD 10 — Question

Nocturnal animals (animals which sleep during the day and come out at night) tend to have wide pupils and lot of rods in their retinas. Suggest reasons for this.

What is meant by ‘heteroatom’? Give examples. Write the names and formulae of two organic compounds containing different heteroatoms.

When a person breathes in air, the air enters into his body through an organ Ahaving two holes B in it. The air then passes through pharynx and larynx and enters into a tube C. The tube C divides into two smaller tubes D at its lower end. The two smaller tubes are attached to two respiratory organs E. Each smaller tube divides inside the organs E to form a large number of still smaller tubes called F. The smallest tubes F have air-sacs G at their ends in which gaseous exchange takes place in the body of the person. What are A, B, C, D, E, F and G?

With which human organ systems (or human systems) are the following associated?

1. Vena cava.
2. Glomerulus.
3. Alveoli.
4. Villi.

What changes take place in the flower after fertilisation which lead to the formation of seeds and fruit?

When the leaves of a sensitive plant are touched with a finger, they fold up and when light fades at dusk, the petals of a dandelion flower close.

1. State one way in which the above two processes are similar.
2. State two ways in which the above two processes differ.

Why does the sky appear dark (or black) to an astronaut instead of blue?

How does use of a fuse wire protect electrical appliances?

Explain giving one example of each, the unisexual and the bisexual flowers.