MODEL PAPER 4 Science - MODEL PAPER 4

Assertion (A): Flow of energy in a food chain is unidirectional.
Reason (R): Energy captured by autotrophs does not revert back to the solar input and it passes to the herbivores.

Assertion (A): Deflection of the iron filings changes when current in the conductor varies.
Reason (R): Magnitude of the magnetic field does not change with the magnitude of current.

Assertion (A): Vagina is also called a birth canal.
Reason (R): During birth, the baby passes through the vagina.

Assertion (A): Corrosion of iron is commonly known as rusting.
Reason (R): Corrosion of iron occurs in presence of moist air.

Exposure to ultraviolet radiation causes eye disease like:

Assertion (A): Corrosion of iron is commonly known as rusting.
Reason (R): Corrosion of iron occurs in presence of moist air.

Assertion (A): Vagina is also called a birth canal.
Reason (R): During birth, the baby passes through the vagina.

Assertion (A): Deflection of the iron filings changes when current in the conductor varies.
Reason (R): Magnitude of the magnetic field does not change with the magnitude of current.

Assertion (A): Flow of energy in a food chain is unidirectional.
Reason (R): Energy captured by autotrophs does not revert back to the solar input and it passes to the herbivores.

In today's digital world, every human spends around a minimum eight hours with the digital electronic items which make their eyes to strain more and causes many eye problems. Still they undergo many exercises for their eyes during their working hours what would be your medical suggestion to reduce the stress and strain caused in the eyes?

Which of the following belong to the second trophic level?
i. Frog, butterfly, spider, rice weevil
ii. Parrot, frog, butterfly, spider.

Alisha digs a pit in her garden and puts the following items in it.
• paper cups
• glass bowls
• fruit peels
• rubber slippers
She then covers the pit with soil. Which item will decompose first?

What is meant by circulation?

Explain the process of digestion of food in mouth, stomach and small intestine in human body.

A student has three concave mirrors A, B and C of focal lengths 20 cm, 15 cm and 10 cm, respectively. For each concave mirror, he performs the experiment of image formation for three values of object distance of 30 cm, 10 cm and 20 cm.
Give reasons for the following:
i. For the three object distances, identify the mirror which will form an image equal in size to that of object. Find at least one value of object distance.
ii. Out of the three mirrors, identify the mirror which would be preferred to be used for shaving purpose.
iii. For the mirror B, draw ray diagram for image formation for any two given values of object distance.

What are Cartesian sign conventions used in spherical mirror? What is the mirror formula?

Name various plant hormones. Also give their physiological effects on plant growth and development.

i. Name the mode of reproduction of the following organisms and state the important feature of each mode:
a. Planaria
b. Hydra
c. Rhizopus
ii. We can develop new plants from the leaves of Bryophyllum. Comment.
iii. List two advantages of vegetative propagation over other modes of reproduction.

A student fixes a sheet of white paper on a drawing board using some adhesive materials. She places a bar magnet in the centre of it and sprinkles some iron filings uniformly around the bar magnet using a salt sprinkler.
On tapping the board gently, she observes that the iron filings have arranged themselves in a particular pattern.
(a) What makes iron filings arrange in a definite pattern?
(b) Draw a diagram to show this pattern of iron filings.
(c) How is the direction of magnetic field at a point determined using the field lines? Why do two magnetic
field lines not cross each other?
OR
How are the magnetic field lines of a bar magnet drawn using a small compass needle? Draw one magnetic field line each on both sides of the magnet.

We have seen that the different parts of our body have specific functions. Our mouth waters when we see the food we like without our meaning to. Our heart's beat without our thinking about it. In fact, we cannot control these actions easily by thinking about them even if we wanted to. So, in between the simple reflex actions like change in the size of the pupil, and the thought out actions such as moving a chair, there is another set of muscle movements over which we do not have any thinking control. Many of these involuntary actions are controlled by the mid-brain and hind-brain. All these involuntary actions including blood pressure, salivation and vomiting are controlled by the medulla in the hind-brain. Think about activities like walking in a straight line, riding a bicycle, picking up a pencil. These are possible due to a part of the hind-brain called the cerebellum. It is responsible for the precision of voluntary actions and maintaining the posture and balance of the body. Imagine what would happen if each of these events failed to take place if we were not thinking about it.

(a) Identify the part of the nervous system which controls the reflex action.
(b) Does reflex action involve all parts of the voluntary nervous system?
(c) Identify the part of the autonomic nervous system which controls involuntary actions.
OR
Beating of heart muscles, which type of action is this? Out of voluntary and involuntary action which is slower?