Life Processes — Science STD 10 — Question

What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Draw labelled ray diagrams to show the formation of images in cases (i) and (ii)above (The diagrams may not be according to scale).

Find the position and size of the virtual image formed when an object 2cm tall is placed 20cm from:

1. A diverging lens of focal length 40cm.
2. A converging lens of focal length 40cm.

If the image formed by mirror for all positions of the object placed in front of it is always virtual and diminished, state the type of the mirror. Draw a ray diagram in support of your answer. Where are such mirrors commonly used and why?

How is food transported in plants?

How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?

An element A reacts with water to form a compound B which is used in white washing. The compound B on heating forms an oxide C which on treatment with water gives back B. Identify A, B and C and give the reactions involved.

Atoms of seven elements A, B, C, D, E, F and G have a different number of electronic shells but have the same number of electrons in their outermost shells. The elements A and C combine with chlorine to form an acid and common salt respectively. The oxide of element A is liquid at room temperature and is a neutral substance, while the oxides of the remaining six elements are basic in nature. Based on the above information answer the following questions:

1. What could the element A be?
2. Will elements A to G belong to the same period or same group of the periodic table?
3. Write the formula of the compound formed by the reaction of the element A with oxygen.
4. Show the formation of the compound by a combination of element C with chlorine with the help of electronic structure.
5. What would be the ratio of number of combining atoms in a compound formed by the combination of element A with carbon?
6. Which one of the given elements is likely to have the smallest atomic radius?

Human body is made up of five important components, of which water is the main component. Food as well as potable water are essential for every human being. The food is obtained from plants through agriculture. Pesticides are being used extensively for a high yield in the fields. These pesticides are absorbed by the plants from the soil along with water and minerals and from the water bodies these pesticides are taken up by the aquatic animals and plants. As these chemicals are not biodegradable, they get accumulated progressively at each trophic level. The maximum concentration of these chemicals gets accumulated in our bodies and greatly affects the health of our mind and body.

1. Why is the maximum concentration of pesticides found in human beings?
2. Give one method which could be applied to reduce our intake of pesticides through food to some extent.
3. Various steps in a food chain represent:

1. Food web.
2. Trophic level.
3. Ecosystem.
4. Biomagnification.

4. With regard to various food chains operating in an ecosystem, man is a:

1. Consumer.
2. Producer.
3. Producer and consumer.
4. Producer and decomposer.

Write the main difference between auxins and cytokinin.