Give some examples of non-standard units of measurement.
Length of foot, the width of a finger, the distance of a step are some of the non-standard units of measurement.

What is the SI Unit of length?
The International system of Unit (SI Unit) of length is Metre.

What is rectilinear motion?
Motion in a straight line is called rectilinear motion.

What is circular motion?
In Circular motion an object moves such that its distance from a fixed point remains the same.

What is periodic motion?
Motion that repeats itself after some period of time is called periodic motion.

Give three examples of periodic motion.
Motion of a swing, Motion of a needle of a sewing machine, Motion of the pendulum of a clock.

Express the following in KM.
a) 3450 metre – 3.45 KM
b) 4500 Metre – 4.5 KM

Why could you not use an elastic measuring tape to measure distance?
We should not use an elastic measuring tape to measure distance as the tape when used by different persons the distance measured would be different.

What is a habitat?
The surroundings where organisms live is called a habitat

How is cactus adapted to survive in a desert?
Desert plant like cactus lose very little water through transpiration. The leaves in the desert plants are either absent, very small or they are present in the shape of pines. This helps in reducing loss of water from the leaves through transpiration. Thus the cactus plants adapt themselves to survive in desert.

What is adaptation?
The presence of specific features and habits, which enable a plant or an animal to live a particular habitat, is called adaptation.

Name some abiotic components.
Various non-living things such as rocks, soil, air and water in the habitat constitute its abiotic components.
Sunlight and heat also form abiotic components

Give some common characteristics or features of living things.
• Living things grow
• Living things respire
• Living things respond to stimuli
• Living things reproduce their own kinds.
• Some lay eggs and hatch them
• Some give birth to young ones.
• Living things move.

What are predators?
• Predators are animals that kill weak animals like deer.
• Lion and tiger are examples of predators.

What is terrestrial habitats?
The plants and animals that live on land are said to live in terrestrial habitats. Some examples of terrestrial habitats are Forests, Grasslands, deserts, coastal and mountain regions.

What is a ball and socket joint?
The shoulder joint is an example of ball and socket joint in this the rounded end of the ball fits into the cavity of the other bone.

How do snakes move?
The snakes have a long backbone. They have many thin muscles. They are connected to each other even though they are far from one another. They also inter connect the backbone ribs and skin. The snakes body curves into many loops. Each loop of the snake gives it a forward push by pressing against the ground. Since its long body makes many loops each loop gives it this push. The snake moves forward very fast and not in a straight line

What are called herbs?
Plants with green and tender stems are called herbs. They are usually short and may not have many branches.

What are shrubs?
Some plants have the stem branching out near the base. The stem is hard but not very thick. Such plants are called shrubs.

What are trees?
Some plants are very tall and have hard and thick brown stem. The stems have branches in the upper part, much above the ground. Such plants are called trees.

What are creepers and climbers?
Plants with weak stem that cannot stand upright and spread on the ground are called creepers, while those that take support on neighbouring plants are called climbers.

What is photosynthesis?
Leaves prepares their food in the presence of sunlight and a green coloured substance present in them. For this they use water and carbon dioxide from air. This is called photosynthesis. Oxygen is given out in this process.

What re the different kinds of roots?
The different kinds of roots are:
• Tap root
• Fibrous roots.
• Lateral roots.

Draw a diagram of the leaf and mark its parts.


Give two examples of reversible changes.
Melting of wax, salt dissolved in water, Water to ice and again ice to water.

Give few examples of irreversible changes.
Sawing of wood.
Cooking of food.

What changes takes place on heating of objects.
Heat expands objects. Heat changes shapes,