MODEL PAPER 7 Science - MODEL PAPER 7

Assertion (A): Ozone is very important layer of atmosphere.
Reason (R): Ozone protects the living organisms from harmful UV radiation of sun.

Assertion (A): Amoeba always produces two daughter amoebae while Plasmodium divides into many daughter cells.
Reason (R): Amoeba undergoes binary fission while Plasmodium undergoes multiple fission.

Assertion (A): Amoeba always produces two daughter amoebae while Plasmodium divides into many daughter cells.
Reason (R): Amoeba undergoes binary fission while Plasmodium undergoes multiple fission.

Assertion (A): Ozone is very important layer of atmosphere.
Reason (R): Ozone protects the living organisms from harmful UV radiation of sun.

Draw a labelled diagram of human eye. What is the significance of the blind spot?

i. Construct a terrestrial food chain comprising four trophic levels.
ii. What will happen if we kill all the organisms in one trophic level?
iii. Calculate the amount of energy available to the organisms at the fourth trophic level if the energy available to the
organisms at the second trophic level is 2000 J.

What is ozone? Show the reactions of formation of ozone from oxygen in the atmosphere? Name the pollutant and its role in depletion of ozone layer.

a. Figure shows a concave mirror with its pole at P, focus F and centre of curvature C. Draw a ray diagram to
show the formation of image of an object AB.
b. State three characteristics of the image formed.

What is lymph?

i. Several electric bulbs designed to be used on a 220V electric supply line are rated 10W. How many lamps can be connected in parallel with each other across the two wires of 220V line if the maximum allowable current is 5A?
ii. Calculate the cost of seeing 2 movies on colour T.V. daily for the month of September. Given wattage of colour T.V. = 60 W, duration of each movie is 2 hours 30 min and 1kWh costs Rs. 4

What should be the position of an object with respect to focus of a convex lens of focal length 20cm, so that its real and magnified image is obtained?

An individual inherits different traits from his parents. On what basis classification of traits as dominant and recessive is done?

i. Why is nutrition necessary for the human body?
ii. What causes the movement of food inside the alimentary canal?
iii. Why is the small intestine in herbivores longer than in carnivores?
iv. What will happen if the mucus is not secreted by the gastric glands?

A thin converging lens form a real magnified image and virtual magnified image of an object in front of it.
i. Write the positions of the objects in each case.
ii. Draw ray diagrams to show the image formation in each case.
iii. How will the following be affected on cutting this lens into two halves along the principal axis?
a. Focal length
b. Intensity of the image formed by half lens

Define the principal focus of concave mirror.

'Nervous and hormonal systems together perform the function of control and coordination in human beings.' Justify the statement.

State the basic requirements for sexual reproduction? Write the importance of such reproduction in nature?

Explain the mechanism of the cleaning action of soaps.

In animals, control and coordination are provided by nervous and muscular tissues. Touching a hot object is an urgent and dangerous situation for us. We need to detect it and respond to it. How do we detect that we are touching a hot object? All information from our environment is detected by the specialised tips of some nerve cells. These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So gustatory receptors will detect taste while olfactory receptors will detect the smell. This information, acquired at the end of the dendritic tip of a nerve cell, see figure, sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end.



(a) Name the largest cell present in the body.
(b) What is an axon ?
(c) Name one gustatory receptor and one olfactory receptor present in a human beings.

OR

Name the following parts of a neuron:
a. Where information is acquired.
b. Through which information travels as an electrical impulse.

A scale for measuring hydronium ion in a solution is called the pH scale. The pH of a neutral solution is 7. A value of less than 7 on the pH scale represents an acidic solution. As the pH value, increases from 7 to 14 it represents OH- ion concentration in solution i.e a basic solution.


(a) What is the pH range of the Human Body?
(b) The strength of acid and bases depends on which factor?

OR

If the pH of soil X is 7.5 while that of soil Y is 4.5, then which soil should be treated with powdered chalk to adjust its pH?