Both plants and animals are interdependent on each other for their survival. Plants cannot survive for long without animals, as they need CO₂ for photosynthesis, which is exhaled by animals. Similarly, in absence of plants, there will be no oxygen for animals to breathe in Hence we can say that both need each other and the balance of oxygen and carbon dioxide in the atmosphere is maintained by their presence.

Synthetic fibres are more advantageous and economical than natural fibres due to following reasons:
(i) synthetic fibres are cheap
(ii) more resistant to water
(iii) high mechanical strength
(iv) easy to wash and handle
(v) dry up quickly.

Waste recycling has some significant advantages. It:
(i) leads to less utilization of raw materials.
(ii) reduces environment impacts arising from waste treatment and disposal.
(iii) makes the surroundings cleaner and healthier.
(iv) saves our landfill space.
(v) saves money.
(vi) reduces the amount of energy required to manufacture new products.

When two or more than two electric cells are connected together in such a way that the positive terminal of one cell is connected to the negative terminal of the other, then we call it a battery. A simple connection showing the combination of two electric cells to form a battery is shown below:

The movement depends on the type of joints which join two bones together. The body parts having ball and socket joint move in all directions while the body parts having hinge joint move only in one direction.

No, it will not turn blue-black because the stored starch would have been used up by the plant when kept in a dark room for a few days. Starch would not be synthesized due to absence of sunlight.

The light always travels in a straight line. This can be shown by performing a simple activity. For this, first of all let us take three cardboards of equal size. Now, a hole is made'at the centre of each cardboard at the same level. The three cardboard are placed on a flat table and aligned linearly as shown in the figure.
A candle is lighted at one end of the table with its flame at the level of the holes and is seen at the other end. It is observed that the light of the candle is seen effortlessly. Now, the middle one of the three cardboards is displaced from its position. Now, we are unable to see the light. The reason behind this is that the light travelling in the straight line is obstructed due the misalignment of the cardboards. This proves that light always travels in a straight line

Sieving is a process used for separating solid components of mixtutres varying in size.
It allows the fine particles to pass through the holes of the .sieve while the bigger particles remain on the sieve. It is used to separate pebbles and stones from the sand

Sprouted seeds are the seeds with seedlings. Seeds are first soaked in water for one day. The water is drained and the seeds are kept wrapped in a wet cloth and left for one more day. After sprouting, they can be eaten raw. They can also be boiled. They can also be made into a tasty snack by adding spices to them.

(i) Length of the scale, that you are using to measure, must be greater than the length of the object.
(ii) The eye must be placed just above the point, that you are reading, otherwise there will be an error due to parallax.
(iii) If the zero mark of the scale is damaged or the edge of the scale is not smooth, then start the measurement from another mark

Some common food items, their ingredients and sources are listed below:

Here, the two phenomena we must check. One is the usage of conductors and the other is insulators which can stop the flow of electric current. We observe that the one end of screw driver is made up of metal and the other is made up of an insulator. Thus, electric current starts through one end but stops at the other end and hence, current cannot flow through it. Thus, bulb will not glow.

Two adaptations of aquatic plants are
(i) The roots of these plants are small just to keep plant in place.
(ii) Stems are hollow with large spaces which help in floating.

An earthworm is called as farmer's friend as it eats its way through the soil thereby loosening the soil. Also, earthworm's body excretes the undigested materials that increase the fertility of soil.

Those substances which allow the transmission of heat through them are called conductors of heat. e.g. iron, steel, copper, aluminum, etc., and the substances which do not allow heat to pass through them are called poor/non-conductors of heat, e.g. wood, rubber, plastic, cotton piece, etc.

Melting of wax is a reversible change because solid wax melts on heating and melted wax becomes solid on cooling. Melting of wax is a change which can be reversed, whereas burning of wax is an irreversible change we cannot combine all the products of burning of wax to get back the original candle. Therefore, burning of wax is a Change which cannot be reversed.

The process of making yarn from fibres is called spinning. In this process, fibres from a mass of cotton wool are drawn out and twisted.This brings the fibres together to form a yarn.
A simple device used for spinning is a hand spindle also known as takli. Another hand operated device used for spinning is charkha.

Tasty food is not always nutritious and nutritious food may not always be tasty to eat. Certain examples in favour of the above statement are
(i) Potato chips are tasty to eat but not nutritious as they contain huge amount of fats.
(ii) Green leafy vegetables either boiled or steamed are very nutritious but not good in taste.
(iii) Certain fast foods like pizza, burger, etc., are very good to taste but are not nutritious as they contain huge amount of fat.

Sieving is a method by which fine particles are separated from bigger particles by using a sieve. It is used in a flour mill, our homes and at construction sites.
In a flour mill, impurities like husk and stones are removed from wheat before grinding. At construction sites, pebbles and stones are removed from sand by sieving.

People living in different regions of our country use different methods of cooking food depending upon the availability of food products, e.g. in Northern India, wheat is grown, so people eat chapati as a staple food, where as in South India, people are rice eaters because rice is produced there in large quantity.