Life Processes — Science STD 10 — Question

The chemical substance P is made and secreted by the meristematic tissue at the tip of stem (or shoot) of a plant. The chemical substance P is responsible for a phenomenon Q in plants in which the stem bends towards a source of light. The same chemical substance P has an opposite effect on the root of a plant. It causes the root of a plant to bend away from the source of light in a process called R.

1. What is the chemical substance P?
2. State whether P prefers to remains in the sunlit side of a stem or in shade.
3. What is the effect of substance P on the rate of growth of (i) a root, and (ii) a stem?
4. What is the name of process (i) Q, and (ii) R?
5. What is the general name of chemical substances like P? Name another substance which belongs to this class of chemical substances.

What is electrical resistivity of a material? What is its unit? Describe an experiment to study the factors on which the resistance of conducting wire depends.

State and explain the various methods for preventing or retarding rancidity of food.

Give a brief idea of the formation of the fossil.

A thickened underground stem X of a plant which is swollen with stored food has a number of points Y on its surface. When the old stem X is planted in the soil of a field in the next growing season, then each point Y present on its surface grows into a new plant.

1. What is the general name of the underground stems like X?
2. Give one example of X.
3. What are points Y present on X known as?
4. Is it necessary to plant the whole of stem X in the ground to obtain its new plants? Explain your answer.
5. What is the name of this method of reproduction of plants?
6. What is the advantage of growing new plants from the underground stems like X?

An element is placed in 2nd Group and 3rd Period of the Periodic Table, burns in presence of oxygen to form a basic oxide.

1. Identify the element.
2. Write the electronic configuration.
3. Write the balanced equation when it burns in the presence of air.
4. Write a balanced equation when this oxide is dissolved in water.
5. Draw the electron dot structure for the formation of this oxide.

Trace the path of sperm during ejaculation and mention the gland and their functions associated with the male reproductive system.

What are detergents chemically? List two merits and two demerits of using detergents for cleansing. State the reason for the suitability of detergents for washing, event in the case of water having calcium and magnesium ions.

A liquid X of colour Y circulates in the human body only in one direction: from body tissues to the heart. Among other things, liquid X contains germs from cells and dead cells. The liquid X is cleaned of germs and dead cells by a special type of white blood cells called Z. This cleaned liquid is then put into blood circulatory system in subclavian veins.

1. What is (i) liquid X and (ii) colour Y?
2. What are Z.
3. The liquid X is somewhat similar to a component of blood. Name this component.
4. Why is liquid X not red?

When an insect sits on the flower of a plant then some particles A present in the top of little stalks in the flower attach to its body hair. When this insect now sits on the flower of another similar plant, then particles A attached to the hair of insect are put on the top of a flask-shaped organ at the centre of flower. The particle A grows a long tube b from the top of flask-shaped organ through which C moves down and reaches the bottom part of flask-shaped organ. Here C fuses with the nucleus of d contained in structure E. the fusion of C and D forms a new cell f which grows and develops into a seed of the plant.

1. What are particles A? What is the process of transferring A from one flower to another flower of similar plant by the insect known as?
2. What is the name of tube B?
3. What is C which moves down through the tube B?
4. Name D and E.
5. What is F?