How do Organisms Reproduce? — Science STD 10 — Question

A food chain consists of fish, larvae, phytoplanktons and birds. The level of pesticides in water in which the fish, larvae and phytoplanktons live is quite high.

1. In which organisms the pesticides enter from the polluted water? What is this level of organisms known as?
2. Which organism will have the maximum amount of pesticides accumulated through the food chain? What is this process known as?
3. Write the food chain comprising all the organisms mentioned above.
4. Which other organism you could write in place of bird in the above food chain?

Distinguish between Direct current and alternating current.

How much time a satellite in an orbit at height 35780 Km above earth's surface would take, if the mass of the earth would have been four times its original mass?

Explain how, sex is determined in human babies.

Read the following paragraph and answer the questions:
If heat is exchanged between a hot and cold object, the temperature of the cold object goes on increasing due to gain of energy and the temperature of the hot object goes on decreasing due to loss of energy.

The change in temperature continues till the temperatures of both the objects attain the same value. In this process, the cold object gains heat energy and the hot object loses’ heat energy. If the system of both the objects is isolated from the environment by keeping it inside a heat resistant box (meaning that the energy exchange takes place between the two objects only), then no energy can flow from inside the box or come into the box.
(1) Heat is transferred from where to where?
(2) Which principle do we learn about from this process?
(3) How will you state the principle briefly?
(4) Which property of the substance is measured using this principle?

An object is placed 10cm from a lens of focal length 5cm. Draw the ray diagrams to show the formation of image if the lens is:

1. Converging, and
2. Diverging.

What challenges did Mendeleev face in following periodic law?

A, B and C are three living organisms. The organism A is a unicellullar fungus which can live without air. It is used in the commercial production of an organic compound P from molasses. The organism B is a unicellular animal which lives in water and feeds and moves by using pseudopodia. It breathes through an organelle Q. The organism C is a tiny animal which acts as a carrier of malarial parasite. It breathes and respires through a kind of tiny holes R and air - tubes S in its body.

1. What are organisms A, B and C?
2. Name P, Q, R and S.
3. Which organism/ organisms undergo aerobic respiration?
4. Which organism/ organisms undergo anaerobic respiration?

The descriptions of five kinds of images are given below:

1. Diminished and virtual.
2. Enlarged and real.
3. Enlarged and erect.
4. Real and inverted.
5. Virtual and the same size.

Which one of these describes the image formed:

1. On the retina of the eye?
2. By a magnifying glass?
3. By a convex driving mirror on a car?
4. By a plane mirror?
5. on the screen of a slide projector?

Obtain the mathematical expression for the heat generated in a metallic conductor by electric current (Joule’s law).