Download Important Points for Revision-1

SOME IMPORTANT POINTS FOR REVISION FOR CLASS 7 SA – 2 EXAM (05 CHAPTERS)
Respiration in Organisms
1. Breathing is a part of respiration.
2. All organisms are made of small microscopic units called cells. A cell is the smallest structural and functional
unit of an organism.
3. Each cell of an organism performs certain functions such as nutrition, transport, excretion and reproduction.
To perform these functions, the cell needs energy. The food has stored energy, which is released during
respiration.
4. The process of breakdown of food in the cell with the release of energy is called cellular respiration.
5. All living organisms respire to get energy from food. During breathing, we breathe in air. You know that air
contains oxygen. We breathe out air which is rich in carbon dioxide. The air we breathe in is transported to all
parts of the body and ultimately to each cell. In the cells, oxygen in the air helps in the breakdown of food, and
energy is released.
6. In the cell, the food (glucose) is broken down into carbon dioxide and water using oxygen along with release
of energy.
7. When breakdown of glucose occurs with the use of oxygen it is called aerobic respiration. Food respiration
can also be broken down, without using oxygen. This is called anaerobic respiration.
8. There are some organisms such as yeast that can survive in the absence of air. They are called anaerobes.
They anaerobes get energy through anaerobic respiration. In the absence of oxygen, glucose breaks down into
alcohol and carbon dioxide, as given below:
9. Yeasts are single-celled organisms. They respire anaerobically and during this process yield alcohol. They
are, therefore, used to make wine and beer.
10. Our muscle cells can also respire anaerobically, but only for a short time, when there is a temporary
deficiency of oxygen. During heavy exercise, fast running, cycling, walking for many hours or heavy weight
lifting, the demand for energy is high. But the supply of oxygen to produce the energy is limited. Then
anaerobic respiration takes places in the muscle cells to fulfill the demand of energy:
11. After heavy exercise we sometimes get muscle cramps. The cramps occur when muscle cells respire
anaerobically. The partial breakdown of glucose produces lactic acid. The accumulation of lactic acid causes
muscle cramps. We get relief from cramps after a hot water bath or a massage. Hot water bath or massage
improves circulation of blood. As a result, the supply of oxygen to the muscle cells increases. The increase in
the supply of oxygen results in the complete breakdown of lactic acid into carbon dioxide and water.
12. Breathing means taking in air rich in oxygen and giving out air rich in carbon dioxide with the help of
respiratory organs. The taking in of air rich in oxygen into the body is called inhalation and inhalation giving out
of air rich in carbon dioxide is known as exhalation.
13. The number of times a person breathes in a minute is termed as the breathing rate (both inhalation and
exhalation take place). A breath means one inhalation plus one exhalation.
14. Whenever a person needs extra energy, he/she breathes faster. As a result more oxygen is supplied to our
cells. It speeds up the breakdown of food and more energy is released. That is why we feel hungry after a
physical activity.
15. We yawn when we are sleepy or drowsy in order to make available sufficient oxygen for our body.
16. On an average, an adult human being at rest breathes in and out 15–18 times in a minute. During heavy
exercise, the breathing rate can increase up to 25 times per minute. While we exercise, not only do we breathe
fast, we also take deep breaths and thus inhale more oxygen.
17. Lungs are present in the chest cavity. This cavity is surrounded by ribs on the sides. A large, muscular sheet
called diaphragm forms the floor of the chest cavity. Breathing involves the movement of the diaphragm and the
rib cage.
18. Mechanism of breathing: - Normally we take in air through our nostrils. When we inhale air, it passes
through our nostrils into the nasal cavity. From the nasal cavity, nasal cavity the air reaches our lungs through
the windpipe. During inhalation, ribs move up and outwards and diaphragm moves down. This movement
increases space in our chest cavity and air rushes into the lungs. The lungs get filled with air. During exhalation,
ribs move down and inwards, while diaphragm moves up to its former position. This reduces the size of the
chest cavity and air is pushed out of the lungs.
19. Smoking damages lungs. Smoking is also linked to cancer. It must be avoided.
20. The air around us has various types of unwanted particles, such as smoke, dust, pollens, etc. When we
inhale, the particles get trapped in the hair present in our nasal cavity. However, sometimes these particles may
get past the hair in the nasal cavity. Then they irritate the lining of the cavity, as a result of which we sneeze.
Sneezing expels these foreign particles from the inhaled air and a dust free, clean air enters our body.
When you sneeze, you should cover your nose so that the foreign particles you expel are not inhaled by other
persons.
21. Model to show mechanism of breathing: -
22. Effect of exhaled air on lime water: - When air is blown into lime water, it turns milky.
23. Inhaled air contains, more oxygen used to create energy and less carbon dioxide than exhaled air which
contains, more carbon dioxide produced as a waste product of energy production less oxygen as it has been used
in respiration
Gas exchange takes place by diffusion in the alveoli within the lungs. As a result the composition of inhaled and
exhaled air is different. Upon inhaling, a person takes air into the respiratory system, and the air travels into the
alveoli. Some air remains in the nasal cavity, trachea, bronchi and bronchioles to avoid creating a vacuum. The
air stays in the respiratory passageways, and it cannot be used by the body.
People inhale and exhale approximately 7 or 8 liters of air each minute or 11,000 liters per day. 5 percent of the
volume of air is consumed each time a person inhales and is converted to carbon dioxide. Thus, a person uses
around 550 liters of pure oxygen daily.
24. The normal amount of air breathed in and out at rest is called the tidal volume of air. The maximum amount
of air a person can inhale and exhale is known as the vital capacity. A person normally does not use his entire
vital capacity. When speaking or being active, a person takes in and lets out more air than the tidal volume.
25. At rest, the average adult inhales around 20 percent oxygen in the air and exhales about 15 percent oxygen
26. When inhaling, humans take in approximately 21 percent oxygen, 0.04 percent carbon dioxide and 79
percent nitrogen. On exhalation, humans give off approximately 16 percent oxygen, 4 percent carbon dioxide
and 79 percent nitrogen. Exhaled air also contains water vapor.
27. Red blood cells travel by vein to the lung; they give of carbon dioxide and take in oxygen.
28. Animals such as elephants, lions, cows, goats, frogs, lizards, snakes, birds, have lungs in their chest cavities
like the human beings.
29. Cockroach and small insects have small openings, called spiracles on the sides of their body. Insects have a
network of air tubes called tracheae for gas exchange. Oxygen rich air rushes through spiracles into the tracheal
tubes, diffuses into the body tissue, and reaches every cell of the body. Similarly, carbon dioxide from the cells
goes into the tracheal tubes and moves out through spiracles. These air tubes or tracheae are found only in
insects and not in any other group of animals.
30. Earthworms breathe through their skins. The skin of an earthworm feels moist and slimy on touching. Gases
can easily pass through them. Though frogs have pair of lungs like human beings, they can also breathe through
their skin, which is moist and slippery.
31. Whales and dolphins are not fish? They are mammals. People are mammals too. Mammals are the group of
animals that breath air using lungs, give birth to live young (rather than laying eggs), and feed their young with
mother’s milk. Fish use their gills to take oxygen from the water that they live in. But people get the oxygen we
need by breathing air, using our lungs. Whales and dolphins use their lungs to breathe air also.
That’s one reason why they come to the surface of the ocean. Sometimes they lie right at the surface of the
water, with just a part of their back sticking out. Whales and dolphins don’t have noses like you and me. Instead
they have a hole – called a “blow hole” – on top of their heads. Sometimes when a whale breathes air out of its
blow hole, it shows up as a spray or mist – called a “spout” – that can be seen many miles away. Blow holes are
surrounded by muscles that keep the hole closed when the whale or dolphin is under water and open it when the
animal is at the surface and needs to breathe. The blowhole seals immediately after he breathes so that he won’t
get water in his lungs.
32. Gills in fish help them to use oxygen dissolved in water. Gills are projections of the skin. Gills are well
supplied with blood vessels for exchange of gases.
33. Plants also respire for their survival. They also take in oxygen from the air and give out carbon dioxide. The
exchange of gases takes place through tiny pores called stomata. In the cells oxygen is used to break down
glucose into carbon dioxide and water as in other organisms. In plants each part can independently take in
oxygen from the air and give out carbon dioxide.
34. Stomata are mainly found on the bottom of leaves to reduce dehydration. Stomata play an important role in
photosynthesis as they allow the plant to absorb carbon dioxide from the environment. In exchange, stomata
allow oxygen, which is a waste product of photosynthesis, to be released. In the process, water vapor is also lost
as the internal parts of the leaves are exposed. To reduce exposure, stomata are found on the underside of the
leaves. They are protected from the sun as excessive heat can increase the rate of water vapor leaving and thus
wither the plant. Stomata also have guard cells around the epidermis that close when too much water is being
lost.
35. Like all other living cells of the plants, the root cells also need oxygen to generate energy. Roots take up air
from the air spaces present between the soil particles.
36. All living cells need air. In order for plants to be healthy, there needs to be a mixture of air and moisture in
the soil. The correct balance of air to moisture is important because roots breathe air and the moisture
surrounding the soil particles is part of the process that allow the roots to absorb both moisture and minerals for
the plant's life processes.
When a plant in a pot is overwatered, the excess water remains in the pot--completely saturating the plant's
roots. Roots require air to thrive and survive. If their soil is filled with water, the tiny root hairs are unable to
find any air in the soil and they drown. If the root hairs, which collect water and nutrients for the plant, are
compromised--the entire plant is in jeopardy.
NOW TRY TO ANSWER THE FOLLOWING QUESTIONS
1. In cockroaches, air enters the body through
(a) lungs
(b) gills
(c) spiracles
(d) skin
2. During heavy exercise, we get cramps in the legs due to the accumulation of
(a) carbon dioxide
(b) lactic acid
(c) alcohol
(d) water
3. Normal range of breathing rate per minute in an average adult person at rest is:
(a) 9–12
(b) 15–18
(c) 21–24
(d) 30–33
4. During exhalation, the ribs
(a) move outwards
(b) move downwards
(c) move upwards
(d) do not move at all
5. Sometimes when we do heavy exercise, anaerobic respiration takes place in our muscle cells. What is
produced during this process?
(a) alcohol and lactic acid
(b) alcohol and CO2
(c) lactic acid and CO2
(d) lactic acid only
6. Yeast is used in wine and beer industries because it respires
(a) aerobically producing oxygen.
(b) aerobically producing alcohol.
(c) anaerobically producing alcohol.
(d) anaerobically producing CO2.
7. During the process of exhalation, the ribs move
(a) down and inwards.
(b) up and inwards.
(c) down and outwards.
(d) up and outward.
8. Breathing is a process that
(a) provides O2 to the body.
(b) breaks down food to release energy.
(c) helps the body to get rid of CO2 .
(d) produces water in the cells.
9. Which of the following gives the correct combination of functions of breathing?
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (ii) and (iv)
10. Fish breathe with the help of gills which are richly supplied with blood vessels. The gills help the fish to
(a) take in oxygen from air.
(b) take in oxygen dissolved in water.
(c) absorb nutrients present in water.
(d) release waste substances in water.
11. Earthworms and frogs breathe through their skin because of which the skin of both the organisms is
(a) moist and rough.
(b) dry and rough.
(c) dry and slimy.
(d) moist and slimy.
12. The mountaineers carry oxygen with them because:
(a) At an altitude of more than 5 km there is no air.
(b) The amount of air available to a person is less than that available on the ground.
(c) The temperature of air is higher than that on the ground.
(d) The pressure of air is higher than that on the ground.
13. Fill in the blanks with suitable words.
(a) The roots of a plant take up oxygen from the ______ trapped between the ________ particles.
(b) Diaphragm forms the ___________ of the chest cavity.
(c) Exchange of gases in the leaves take place with the help of __________.
(d) Cockroaches breathe with the help of air tubes called ___________.
14. Pick the odd-one-out from each of the groups given below on the basis of respiratory organs. Give reason for
your answer.
(a) cockroach, grasshopper, snail, ant
(b) lizard, cow, earthworm, snake
(c) crocodile, whale, dolphin, fish
(d) snake, tadpole, crow, goat
15. Match the items in Column I with those in Column II:
Column I
Column II
(a) Yeast
(i) Earthworm
(b) Diaphragm
(ii) Gills
(c) Skin
(iii) Alcohol
(d) Leaves
(iv) Chest cavity
(e) Fish
(v) Stomata
(f) Frog
(vi) Lungs and skin
(vii) Tracheae
16. There are some sentences given below related to respiration in organisms. Write one word answer against
each description.
(i) The air tubes of insects (ii) Skeletal structures surrounding chest cavity (iii) Muscular floor of chest cavity (iv) Tiny pores on the surface of leaf (v) Small openings on the sides of the body of an insect (vi) The respiratory organs of human beings (vii) The openings through which we inhale (viii) An anaerobic organism (ix) An organism with tracheal system –
17. Which gas present in air is essential for aerobic respiration? What is the role of oxygen during respiration?
18. On an average, an adult human being at rest breathes 15–18 times per minute. The breathing rate, however,
may differ under different conditions. Arrange the following activities given in the box in order of increasing
breathing rates and give reason for your answer.
sleeping, cycling, brisk walk, watching T.V.
19. Whenever we feel drowsy or sleepy, we start yawning. Does yawning help us in anyway?
20. Insects and leaves of a plant have pores through which they exchange gases with the atmosphere. Can you
write two points of differences between these pores with respect to their position, number and extension into the
body?
21. Paheli participated in a 400 m race competition held at her school and won the race. When she came home
she had mixed feelings of joy and pain as she had cramps in her leg muscles. After a massage she was relieved
of the pain. Answer the following questions related to the situation.
(a) What can be the possible reasons for the pain in her legs?
(b) Why did she feel comfortable after a massage?
22. Observe the figures given below and answer the following.
(a) Which of the figures A or B indicates the process of inhalation and which the process of exhalation?
(b) In the figure label the arrows and indicate the direction of (i) movement of air (ii) movement of diaphragm
(iii) movement of ribs
23. Match the names of organisms in Column I with their organs of breathing given in Column II.
Transportation in Animals and Plants and Plants
1. All organisms need food, water and oxygen for survival. They need to transport all these to various parts of
their body. Further, animals need to transport wastes to parts from where they can be removed.
2. Blood is the fluid which flows in blood vessels. It transports substances like digested food from the small
intestine to the other parts of the body. It carries oxygen from the lungs to the cells of the body. It also transports
waste for removal from the body.
3. Blood is a liquid, which has cells of various kinds suspended in it. The fluid part of the blood is called
plasma. One type of cells are the red blood cells (RBC) which contain a red pigment called haemoglobin. The
blood also has white blood cells (WBC) which fight against germs that may enter our body. Another type of
cells called platelets are also present in the blood which help in blood clotting.
4. Haemoglobin bind with oxygen and transports it to all the parts of the body and ultimately to all the cells. It
will be difficult to provide oxygen efficiently to all the cells of the body without haemoglobin. The presence of
haemoglobin makes blood appear red.
5. Two types of blood vessels are present - the arteries and the veins. Arteries carry oxygen-rich blood from
the heart to all parts of the body. Since the blood flow is rapid and at a high pressure, the arteries have thick
elastic walls. Veins are the vessels which carry carbon dioxide-rich blood from all parts of the body back to the
heart. The veins have thin walls. There are valves present in veins which allow blood to flow only towards the
heart.
6. Schematic diagram of circulation: -
7. The pulmonary artery carries blood from the heart, so it is called an artery and not a vein. It carries carbon
dioxide-rich blood to the lungs. Pulmonary vein carries oxygen-rich blood from the lungs to the heart.
8. Arteries s divide into smaller vessels. On reaching the tissues, they divide further into extremely thin tubes
called capillaries. The capillaries join up to form veins which empty into the heart.
9. The heart is an organ which beats continuously to act as a pump for the transport of blood, which carries
other substances with it. The heart is located in the chest cavity with its lower tip slightly tilted towards the left.
The heart is roughly the size of our fist. To avoid the blood rich in oxygen and the blood rich in carbon dioxide
from mixing with each other, the heart has four chambers. The two upper chambers are called the atria and the
two lower chambers are called the ventricles. The partition between the chambers helps to avoid mixing up of
blood rich in oxygen with the blood rich in carbon dioxide.
10. Functioning of the circulatory system: -
11. As the heart pumps, the arteries expand and contract, this is the pulse. So, the pulse is simply the expansion
of the arteries. This expansion is caused by an increase in blood pressure pushing against the elastic walls of the
arteries each time our heart beats.
12. The number of beats per minute is called the pulse rate. A resting pulse rate person, usually has a pulse rate
between 72 and 80 beats per minute.
13. The walls of the chambers of the heart are made up of muscles. These muscles contract and relax
rhythmically. This rhythmic contraction followed by its relaxation constitutes a heartbeat. Heartbeat can be felt
by placing hand over the left hand side of the chest. The doctor feels the heartbeats with the help of an
instrument called a stethoscope.
14. A stethoscope is a device which amplifies the sound of the heart. It consists of a chest piece that carries a
sensitive diaphragm, two ear pieces and a tube joining the parts. Doctors can get clues about the condition of
your heart by listening through a stethoscope.
15. Each heart beat generates one pulse in the arteries and the pulse rate per minute indicates the rate of
heartbeat.
16. The rhythmic beating of the various chambers of the heart maintains circulation of blood and transport of
substances to the different parts of the body.
17. Animals such as sponges and Hydra do not posses any circulatory system. The water in which they live
brings food and oxygen as it enters their bodies. The water carries away waste materials and carbon dioxide as it
moves out. Thus, these animals do not need a circulatory fluid like the blood.
18. Carbon dioxide is removed as waste from the body through the lungs during exhalation. Undigested food is
removed during egestion.
19. When our cells perform their functions, certain waste products are released. These are toxic and hence need
to be removed from the body. The process of removal of wastes produced in the cells of the living organisms is
called excretion. The excretion parts involved in excretion forms the excretory system (The kindeys, ureters,
bladder and urethra form the excretory system).
20. The blood capillaries in the kidneys help in the removal of waste which is present in the blood. When the
blood reaches the two kidneys, it contains both useful and harmful substances. The useful substances are
absorbed back into the blood. The wastes dissolved in water are removed as urine. From the kidneys, the urine
goes into the urinary bladder through tube-like ureters. It is stored in the bladder and is passed out through the
urinary opening at the end of a muscular tube called urethra.
21. An adult human being normally passes about 1–1.8 L of urine in 24 hours, and the urine consists of 95%
water, 2.5 % urea and 2.5% other waste products.
22. We sweat on a hot summer day. The sweat contains water and salts. When we sweat, it helps to cool our
body.
23. Aquatic animals like fishes, excrete cell waste in gaseous form (ammonia) which directly dissolves in water.
Some land animals like birds, lizards, snakes excrete a semi-solid, white coloured compound (uric acid). The
major excretory product in humans is urea.
24. In the event of kidney failure, waste products start accumulating in the blood. Such persons cannot survive
unless their blood is filtered periodically through an artificial kidney. This process is called dialysis.
25. Plants take water and mineral nutrients from the soil through the roots and transport it to the leaves. The
leaves prepare food for the plant, using water and carbon dioxide during photosynthesis.
26. Food is the source of energy and every cell of an organism gets energy by the breakdown of glucose. The
cells use this energy to carry out vital activities of life. Therefore food must be made available to every cell of
an organism.
27. Plants absorb water and minerals by the roots. The roots have root hair. The root hair increase the surface
area of the root for the absorption of water and mineral nutrients dissolved in water. The root hair is in contact
with the water present between the soil particles. Plants have pipe-like vessels to transport water and nutrients
from the soil. The vessels are made of special cells, forming the vascular tissue. The vascular tissue for the
transport of water and nutrients in the plant is called the xylem. The food has to be transported to all parts of the
plant. This is done by the vascular tissue called the phloem. Thus, xylem and phloem transport substances in
plants.
28. A tissue is a group of tissue cells that perform specialized function in an organism.
29. For very short distances water can move from one cell to another. In the same way water reaches xylem
vessels of the root from the soil.
30. Plants release a lot of water by the process of transpiration. Plants absorb mineral nutrients and water from
the soil. Not all the water absorbed is utilized by the plant. The water evaporates through the stomata present on
the surface of the leaves by the process of transpiration. The evaporation of water from leaves generates a
suction pull which can pull water to great heights in the tall trees. Transpiration also cools the plant.
NOW TRY TO ANSWER THE FOLLOWING QUESTIONS
1. The muscular tube through which stored urine is passed out of the body is called –
(a) kidney
(b) ureter
(c) urethra
(d) urinary bladder
2. They are pipe-like, consisting of a group of specialised cells. They transport substances and form a two-way
traffic in plants. Which of the following terms qualify for the features mentioned above?
(a) Xylem tissue
(b) Vascular tissue
(c) Root hairs
(d) Phloem tissue
3. The absorption of nutrients and exchange of respiratory gases between blood and tissues takes place in –
(a) veins
(b) arteries
(c) heart
(d) capillaries
4. In which of the following parts of human body are sweat glands absent?
(a) Scalp
(b) Armpits
(c) Lips
(d) Palms
5. In a tall tree, which force is responsible for pulling water and minerals from the soil?
(a) Gravitational force
(b) Transportation force
(c) Suction force
(d) Conduction force
6. Aquatic animals like fish excrete their wastes in gaseous form as
(a) Oxygen
(b) Hydrogen
(c) Ammonia
(d) Nitrogen
7. In plants, water is transported through
(a) Xylem
(b) Phloem
(c) Stomata
(d) Root hair
8. Water absorption through roots can be increased by keeping the plants
(a) in the shade
(b) in dim light
(c) under the fan
(d) covered with a polythene bag
9. Fill in the blanks.
(i) The blood from the heart is transported to all parts of the body by the ___________________.
(ii) Haemoglobin is present in ________________ cells.
(iii) Arteries and veins are joined by a network of _____________________.
(iv) The rhythmic expansion and contraction of the heart is called _____________________.
(v) The main excretory product in human beings is _________________.
(vi) Sweat contains water and _________________.
(vii) Kidneys eliminate the waste materials in the liquid form called ____________.
(viii) Water reaches great heights in the trees because of suction pull caused by ______________.
10. Match structures given in Column I with functions given in Column II.
Column I
(i) Stomata
(ii) Xylem
Column II
(a) Absorption of water
(b) Transpiration
(iii) Root hairs
(c) Transport of food
(iv) Phloem
(d) Transport of water
(e) Synthesis of carbohydrates
11. Why is transport of materials necessary in a plant or in an animal? Explain.
12. What will happen if there are no platelets in the blood?
13. What are stomata? Give two functions of stomata.
14. Does transpiration serve any useful function in the plants? Explain.
15. What are the components of blood?
16. Why is blood needed by all the parts of a body?
17. What makes the blood look red?
18. Describe the function of the heart.
19. Why is it necessary to excrete waste products?
20. Draw a diagram of the human excretory system and label the various parts.
21. Veins have valves which allow blood to flow only in one direction. Arteries do not have valves. Yet the
blood flows in one direction only. Can you explain why?
22. What is the special feature present in a human heart which does not allow mixing of blood when oxygenrich and carbon dioxide-rich blood reach the heart?
23. Name the organ which is located in the chest cavity with its lower tip slightly tilted towards the left.
24. Arrange the following statements in the correct order in which they occur during the formation and removal
of urine in human beings.
(a) Ureters carry urine to the urinary bladder.
(b) Wastes dissolved in water is filtered out as urine in the kidneys.
(c) Urine stored in urinary bladder is passed out through the urinary opening at the end of the urethra.
(d) Blood containing useful and harmful substances reaches the kidneys for filtration.
(e) Useful substances are absorbed back into the blood.
12. Paheli uprooted a rose plant from the soil. Most of the root tips, with root hairs got left behind in the soil.
She planted it in a pot with new soil and watered it regularly. Will the plant grow or die? Give reason for your
answer.
13. (a) Name the only artery that carries carbon dioxide-rich blood.
(b) Why is it called an artery if it does not carry oxygen-rich blood?
14. Boojho’s uncle was hospitalised and put on dialysis after a severe infection in both of his kidneys. (a) What
is dialysis?
(b) When does it become necessary to take such a treatment?
15. Name the process and the organ which helps in removing the following wastes from the body. (a)
Carbondioxide (b) Undigested food (c) Urine (d) Sweat
16. While learning to ride a bicycle Boojho lost his balance and fell. He got bruises on his knees and it started
bleeding. However, the bleeding stopped after some time.
(a) Why did the bleeding stop?
(b) What would be the colour of the wounded area and why?
(c) Which type of blood cells are responsible for clotting of blood?
17. What is a stethoscope? What is its application?
18. Match the parts of the heart in Column I with the direction of flow of blood in Column II.
Column I
Column II
(i) Right ventricle
(a) Pushes blood into the pulmonary artery.
(ii) Pulmonary veins
(b) Take deoxygenated blood from the heart to lungs.
(iii) Left atrium
(c) Receives blood from different parts of the body.
(iv) Pulmonary arteries
(d) Bring oxygenated blood from lungs to the heart.
(v) Left ventricle
(e) Pushes blood into the aorta.
(vi) Right auricle
(f) Receives deoxygenated blood from the pulmonary veins.
19. Read the following terms given below.
root hairs, xylem, urethra, arteries, kidneys, veins, atria, capillaries, heart, ureter, phloem, urinary bladder.
Group the terms on the basis of the categories given below.
(a) Circulatory system of animals.
(b) Excretory system in human.
(c) Transport of substances in plants.
20. Fill in the blanks of the following paragraph using just two words – arteries and veins.
___ (a) ___ carry oxygen-rich blood from the heart to all parts of the body and ___ (b) ___ carry carbon
dioxide-rich blood from all parts of the body back to the heart. ___ (c) ___ have thin walls and __ (d) ___ have
thick elastic walls. Blood flows at high pressure in ___ (e) ____. Valves are present in __ (f) ___ which allow
blood to flow only towards the heart. __ (g) ___ divide into smaller vessels. These vessels further divide into
extremely thin tubes called capillaries. The capillaries join up to form ____ (h) _____.
21. While learning to ride a bicycle Boojho lost his balance and fell. He got bruises on his knees and it started
bleeding. However, the bleeding stopped after some time.
(a) Why did the bleeding stop?
(b) What would be the colour of the wounded area and why?
(c) Which type of blood cells are responsible for clotting of blood?
22. What is a stethoscope? What is its application?
Reproduction in Plants
1. To produce its kind is a characteristic of all living organisms.
2. The production of new individuals from their parents is known as reproduction.
3. There are different modes of reproduction in plants: (i) Asexual reproduction: - Plants can give rise to new plants without seeds or spores.
(ii) Sexual reproduction: - New plants are obtained from seeds.
4. Vegetative propagation is a type of asexual reproduction in which new plants are produced from roots,
stems, leaves and buds. Since reproduction is through the vegetative parts of the plant, it is known as vegetative
propagation.
5. Natural vegetative propagation can take place from the following parts of a plant:
1. Roots
2. Stem
3. Leaves
Vegetative propagation by roots: - Examples, sweet potato, dahlia.
Vegetative propagation by stem: - Examples, potato, ginger, turmeric.
Vegetative propagation by leaves: - Example, bryophyllum.
6. Following are some of the advantages of vegetative propagation: (i) The new plants produced by vegetative propagation are exactly like the parent plant i.e. the new plants
possess all characteristics of the parent plant.
(ii) The plants produced by vegetative propagation grow rapidly.
(iii) Desired varieties and qualities of fruits and plants can be produced by vegetative propagation.
(iv) Those plants can also be produced by vegetative propagation which do not produce seeds or which cannot
produce viable seeds.
(v) The desirable characters of a variety can be preserved indefinitely through vegetative reproduction.
7. Plants such as cacti produce new plants when their parts get detached from the main plant body. Each
detached part can grow into a new plant.
8. Artificial vegetative propagation is the deliberate production of new plants from parts of old plants by
humans. This can be done by following three methods:
1. Cutting
2. Layering
3. Grafting
Cutting: - This method is commonly used in rose and sugar cane. In this method one year old stem of root is cut
from a distance of 20 to 30 cm. and is buried in the moist soil in natural position. After sometime, roots develop
from this cutting and it grows into a new plant.
Layering: - This method of asexual reproduction is also used in the production of plants such as Bougainvillea,
jasmine, guava, strawberries, lemon, China rose etc.
This method of vegetative propagation is used in those plants whose soft branches occur near the ground such as
jasmine plant. In this method, a branch of the plant which is near to the ground is pulled towards the ground and
a part of this branch is covered with moist soil leaving the tip of this branch above the ground. After sometime,
roots develop from that part of the branch which was buried in the soil.
Grafting: - The plant of which the root system is taken is called ‘stock’, while the other plant of which the shoot
is selected is known as ‘scion’ or ‘graft’. This method of propagation is used in mango, apple, rose, banana,
pear, grape, pineapple and peach.
In this method of vegetative propagation the stems of two different plants are joined together so as to produce a
new plant containing the characters of both plants. Out of the two plants one plant has a strong root system
while the other has a better flower or fruit yield.
9. Budding in Yeast: - Most yeasts reproduce asexually by a process called budding. First, it produces a small
protuberance on the parent cell that grows to a full size and forms a bud. The nucleus of the parent cell splits
into a daughter nucleus and migrates into the daughter cell. The bud detaches from the mother’s body by
forming a constriction at the base. Budding will repeat to form a chain of bud cells. The daughter cell produced
during the budding process is generally smaller than the mother cell.
10. Fragmentation may be defined as the process of breaking up of parent animal into small parts, each of
which can grow into a new complete individual. This process of asexual reproduction is found in planaria,
spirogyra and hydra.
11. Spore formation: - The spores are asexual reproductive bodies. When spores are released they keep floating
in the air. As they are very light they can cover long distances. Each spore is covered by a hard protective coat
to withstand unfavourable conditions such as high temperature and low humidity. So they can survive for a long
time. Under favourable conditions, a spore germinates and develops into a new individual. Plants such as moss
and ferns also reproduce by means of spores.
12. The flowers are the reproductive parts of a plant. The stamens are the male reproductive part and the pistil
is the female reproductive part.
13. The flowers which contain either only the pistil or only the stamens are called unisexual flowers. The
flowers which contain both stamens and pistil are called bisexual flowers. Corn, papaya and cucumber produce
unisexual flowers, whereas mustard, rose and petunia have bisexual flowers. Both the male and the female
unisexual flowers may be present in the same plant or in different plants.
14. Anther contains pollen grains which produce male gametes. A pistil consists of stigma, style and ovary. The
ovary contains one or more ovules. The female gamete or egg is formed in an ovule. In sexual reproduction a
male and a female gamete fuse to form a zygote.
15. Generally pollen grains have a tough protective coat which prevents them from drying up. Since pollen
grains are light, they can be carried by wind or water. Insects visit flowers and carry away pollen on their
bodies. Some of the pollen lands on the stigma of a flower of the same kind. The transfer of pollen from the
anther to the stigma of a flower is called pollination.
16. If pollination the pollen lands on the stigma of the same flower it is called self-pollination. When selfpollination the pollen of a flower lands on the stigma of another flower of the same plant, or that of a different
plant of the same kind, it is called cross-pollination.
17. The cell which results after fusion of fusion the gametes is called a zygote. The process of fusion of male
and female gametes (to form a zygote) is called fertilization. The zygote develops into an embryo.
18. After fertilisation, the ovary grows into a fruit and other parts of the flower fall off. The fruit is the ripened
ovary. The seeds develop from the ovules. The seed contains an embryo enclosed in a protective seed coat.
Some fruits are fleshy and juicy such as mango, apple and orange. Some fruits are hard like almonds and
walnuts.
19. SEED DISPERSAL:- Plants make seeds that can grow into new plants, but if the seeds just fall to the
ground under the parent plant, they might not get enough sun, water or nutrients from the soil. Because plants
cannot walk around and take their seeds to other places, they have developed other methods to disperse (move)
their seeds. The most common methods are wind, water, animals and explosion.
Seeds are dispersed away from each other and from the parent plant so that there is less competition.
(i) Winged seeds such as those of drumstick and maple and, light seeds of grasses or hairy seeds of aak (Madar)
and hairy fruit of sunflower get blown off with the wind to faraway places.
(ii) Some seeds are dispersed by water. These fruits or seeds usually develop floating ability in the form of
spongy or fibrous outer coat as in coconut.
(iii) Some seeds are dispersed by animals, especially spiny seeds with hooks which get attached to the bodies of
animals and are carried to distant places. Examples are Xanthium) and Urena.
(iv) Some seeds are dispersed when the fruits burst with sudden jerks. The seeds are scattered far from the
parent plant. This happens in the case of castor and balsam.
Coconut
Lotus
Mangroo ve
20. Seed dispersal helps the plants to (i) prevent overcrowding, (ii) avoid competition for sunlight, water and
minerals and (iii) invade new habitats.
NOW TRY TO ANSWER THE FOLLOWING QUESTIONS
1. Which of the following parts of a plant take part in sexual reproduction?
(i) Flower (ii) Seed (iii) Fruit (iv) Branch
Choose the correct answer from below.
(a) (i) and (ii)
(b) (i), (ii) and (iii)
(c) (iii) and (iv)
(d) (ii), (iii) and (iv)
2. Lila observed that a pond with clear water was covered up with a green algae within a week. By which
method of reproduction did the algae spread so rapidly?
(a) Budding
(b) Sexual reproduction
(c) Fragmentation
(d) Pollination
3. Seeds of drumstick and maple are carried to long distances by wind because they possess
(a) winged seeds
(b) large and hairy seeds
(c) long and ridged fruits
(d) spiny seeds
4. The ‘eye’ of the potato plant is what
(a) the root is to any plant.
(b) the bud is to a flower.
(c) the bud is to Bryophyllum leaf.
(d) the anther is to stamen.
5. The ovaries of different flowers may contain
(a) only one ovule
(b) many ovules
(c) one to many ovules
(d) only two ovules
6. Which of the following statements is/are true for sexual reproduction in plants?
(i) Plants are obtained from seeds. (ii) Two plants are always essential. (iii) Fertilization can occur only after
pollination. (iv) Only insects are agents of pollination.
Choose from the options given below.
(a) (i) and (iii)
(b) (i) only
(c) (ii) and (iii)
(d) (i) and (iv)
7. Pollination refers to the
(a) transfer of pollen from anther to ovary.
(b) transfer of male gametes from anther to stigma.
(c) transfer of pollen from anther to stigma.
(d) transfer of pollen from anther to ovule.
8. The reproductive part of a plant is the
(a) leaf
(b) stem
(c) root
(d) flower
9. The process of fusion of the male and the female gametes is called
(a) fertilization
(b) pollination
(c) reproduction
(d) seed formation
10. Mature ovary forms the
(a) seed
(b) stamen
(c) pistil
(d) fruit
11. A spore producing plant is
(a) rose
(b) bread mould
(c) potato
(d) ginger
12. Bryophyllum can reproduce by its
(a) stem
(b) leaves
(c) roots
(d) flower
13. Pick the odd one out from the following on the basis of mode of reproduction and give reason for it.
Sugarcane, Potato, Rice, Rose
14. Fungus, moss and fern reproduce by a common method of asexual reproduction. Name the method.
15. One morning as Paheli strolled in her garden she noticed many small plants which were not there a week
ago. She wondered where they had come from as nobody had planted them there. Explain the reason for the
growth of these plants.
16. When you keep food items like bread and fruits outside for a long time especially during the rainy season,
you will observe a cottony growth on them. (a) What is this growth called? (b) How does the growth take place?
17. Coconut is a large and heavy fruit. How is it adapted for dispersal by water?
18. Match items in Column I with those in Column II:
Column I
Column II
(a) Bud
(i) Maple
(b) Eyes
(ii) Spirogyra
(c) Fragmentation
(iii) Yeast
(d) Wings
(iv) Bread mould
(e) Spores
(v) Potato
(vi) Rose
19. Boojho had the following parts of a rose plant – a leaf, roots, a branch, a flower, a bud and pollen grains.
Which of them can be used to grow a new rose plant?
20. Fill in the blanks:
(a) Production of new individuals from the vegetative part of parent is called_____________.
(b) A flower may have either male or female reproductive parts. Such a flower is called_____________.
(c) The transfer of pollen grains from the anther to the stigma of the same or of another flower of the same kind
is known as _____________.
(d) The fusion of male and female gametes is termed as _____________.
(e) Seed dispersal takes place by means of _____________, _____________ and _____________.
21. Describe the different methods of asexual reproduction. Give examples.
22. Explain what you understand by sexual reproduction.
23. State the main difference between asexual and sexual reproduction.
24. Sketch the reproductive parts of a flower.
25. Explain the difference between self-pollination and cross-pollination.
26. How does the process of fertilization take place in flowers?
27. Describe the various ways by which seeds are dispersed.
28. In the diagram given below label the parts marked (a), (b) and (c): -
29. There are some statements given below which describes functions of certain parts of a flower. Identify the
parts.
(a) The part which contains pollen grains (b) The part where the female gamete is formed (c) The female reproductive part where pollen grains germinate (d) The colourful part of flower which attracts insects –
30. Fill in the blanks with correct terms.
The male and female gametes fuse to form a _____(a)______ during the process of _____(b)______. This
grows into an _____(c) ______ which is enclosed within a seed. After fertilization the ovules develop into
_____(d)______ and the ovary develops into a _____(e)______ .
31. Write how the following seeds are dispersed.
(a) Seeds with wings.
(b) Small and light seeds.
(c) Seeds with spines/hooks.
32. In the diagram of a bisexual flower given below5, draw the missing part and label the parts marked (a), (b)
and (c). Also label the missing part that you draw.
Soil
1. Soil is one of the most important natural resources. It supports the growth of plants by holding the roots
firmly and supplying water and nutrients. It is the home for many organisms. Soil is essential for agriculture.
2. Polythene bags and plastics pollute the soil. They also kill the organisms living in the soil. Other substances
which pollute the soil are a number of waste products, chemicals and pesticides.
3. The use of polythene bags and plastics should be banned. Waste products and chemicals should be treated
before they are released into the soil. The use of pesticides should be minimized.
4. The rotting dead matter in the soil is called humus.
5. The soil is formed by the breaking down of rocks by the action of wind, water and climate. This process is
called weathering. The weathering nature of any soil depends upon the rocks from which it has been formed
and the type of vegetation that grows in it.
6. A vertical section through different layers of the soil is called the soil profile. Soil is composed of distinct
layers. These layers are referred to as horizons. Each layer differs in feel (texture), colour, depth and chemical
composition.
7. Soil profile: (I) The uppermost horizon is generally dark in colour as it is rich in humus and minerals. The humus makes the
soil fertile and provides nutrients to growing plants. This layer is generally soft, porous and can retain more
water. It is called the topsoil or the il A-horizon. This provides shelter for many living organisms such as
worms, rodents, moles and beetles. The roots of small plants are embedded entirely in the topsoil.
(II) The next layer has a lesser amount of humus but more of minerals. This layer is generally harder and more
compact and is called the B-horizon or the middle layer.
(III) The third layer is the C-horizon, which is made up of small lumps of rocks with cracks and crevices.
Below this layer is the bedrock, bedrock which is hard and difficult to dig with a spade.
8. The mixture of rock particles and humus is called the soil and humus is called and humus is called the soil the
soil. The soil is classified on the basis of the proportion of particles of various sizes: (i) If soil contains greater proportion of big particles it is called sandy soil sandy soil.
(ii) If the proportion of fine particles is relatively higher, then it is called clayey soil clayey soil.
(iii) If the amount of large and clayey soil fine particles is about the same, then the soil is called loamy.
9. Sandy soils tend to be light, well aerated and rather dry. Sand particles are quite large. They cannot fit closely
together, so there are large spaces between them. These spaces are filled with air (sand is well aerated). Water
can drain quickly through the spaces between the sand particles.
10. Clay particles, being much smaller, pack tightly together, leaving little space for air. Unlike sandy soil, water
can be held in the tiny gaps between the particles of clay. So clay soils have little air. But they are heavy as they
hold more water than the sandy soils.
11. The best topsoil for growing plants is loam. Loamy soil Loamy soil is a mixture of sand, Loamy soil clay
and another type of soil particle known as silt. Silt occurs as a deposit in river beds. The size of the silt particles
is between those of sand and clay. The loamy soil also has humus in it. It has the right water holding capacity
for the growth of plants.
12. Some soil properties: (i) Soil texture can influence whether soils are free draining, whether they hold water and how easy it is for
plant roots to grow.
(ii) Soil structure describes the way the sand, silt and clay particles are clumped together. Organic matter
(decaying plants and animals) and soil organisms like earthworms and bacteria influence soil structure. Clays,
organic matter and materials excreted by soil organisms bind the soil particles together to form aggregates. Soil
structure is important for plant growth, regulating the movement of air and water, influencing root development
and affecting nutrient availability.
(iii) Soil porosity refers to the pores within the soil. Porosity influences the movement of air and water. Healthy
soils have many pores between and within the aggregates. Poor quality soils have few visible pores, cracks or
holes.
(iv) Soil colours range from black to red to white. Sometimes it can even be blue! Soil colour mostly comes
from organic matter and iron. Topsoil is often dark because of organic matter. An even, single colour indicates
the soil is well drained. In contrast, rusty spots and grey patches (sometimes even a light blue in colour) indicate
poor drainage.
(v) Soil consistence refers to the ease with which an individual ped can be crushed by the fingers. Soil
consistence, and its description, depends on soil moisture content.
(vi) The most important effect of pH in the soil is on ion solubility, which in turn affects microbial and plant
growth. A pH range of 6.0 to 6.8 is ideal for most crops because it coincides with optimum solubility of the
most important plant nutrients. Some minor elements (e.g., iron) and most heavy metals are more soluble at
lower pH. This makes pH management important in controlling movement of heavy metals (and potential
groundwater contamination) in soil.
13. Finding percolation rate of water in soil (An activity): - Approx. 5 cm. diameter PVC pipe is taken and cut
into 20 cm long piece. At the place where the soil is collected, the pipe is placed about 2 cm deep in the ground.
200 mL water is poured in the pipe slowly. The time is noted when we start pouring water. When all the water
has percolated leaving the pipe empty, the time is noted again. We should be careful not to let the water spill
over or run down on the outside of the pipe while pouring. The rate of percolation is calculated by using the
following formula:
For example, suppose that for a certain sample, it took 20 minutes for 200 mL to percolate. So,
14. Moisture in the soil (An activity): - A boiling tube is taken. Two spoonfuls of a soil sample is put in it. It
is heated on a flame. On heating, water in the soil evaporates, moves up and condenses on the cooler inner
walls of the upper part of the boiling tube.
On a hot summer day, the vapour coming out of the soil, reflect the sunlight and the air above the soil seems to
shimmer.
15. Absorption of water by soil (An activity): - A plastic funnel is taken. A filter paper (or a piece of newspaper
sheet) is taken, folded and placed it as shown in the figure.
50g of dry, powdered soil is weighed and poured into the funnel. A certain amount of water is measured in a
measuring cylinder and poured drop by drop on the soil. A dropper can be used for this purpose. (Do not let all
the water fall at one spot.)
The water is poured all over the soil. The water is poured till it starts dripping. On subtracting the amount of
water left in the measuring cylinder from the amount we started with gives the amount of water retained by the
soil. The results are recorded in the following manner:
Weight of soil = 50g
Initial volume of water in the measuring cylinder = U mL
Final volume of water in the measuring cylinder = V mL
Volume of water absorbed by the soil = (U – V) mL
Weight of water absorbed by the soil = (U – V) g
(1 mL of water has weight equal to 1 g)
This activity is repeated with different soil samples.
16. Soil is affected by wind, rainfall, temperature, light and humidity. These are some important climatic
factors which affect the soil profile and bring changes in the soil structure. The climatic factors, as well as
the components of soil, determine the various types of vegetation and crops that might grow in any region.
(i) Clayey and loamy soils are both suitable for growing cereals like wheat, and gram. Such soils are good at
retaining water.
(ii) For paddy, soils rich in clay and organic matter and having a good capacity to retain water are ideal.
(iii) For lentils (masoor) and other pulses, loamy soils, which drain water easily, are required.
(iv) For cotton, sandy loam or loam, which drain water easily and can hold plenty of air, are more suitable.
17. The removal of land surface by water, wind or ice is known as erosion. Plant roots firmly bind the soil.
In the absence of plants, soil becomes loose. So it can be moved by wind and flowing water. Erosion of soil
is more severe in areas of little or no surface vegetation, such as desert or bare lands. So, cutting of trees and
deforestation should be prevented and effort should be made to increase the green areas.
NOW TRY TO ANSWER THE FOLLOWING QUESTIONS
1. In addition to the rock particles, the soil contains
(a) air and water
(b) water and plants
(c) minerals, organic matter, air and water
(d) water, air and plants
2. The water holding capacity is the highest in
(a) sandy soil
(b) clayey soil
(c) loamy soil
(d) mixture of sand and loam
3. The microorganisms present in the soil require moisture (water) and nutrients for growth and survival.
Choose from the options below the habitat (place) where the soil has plenty of water and nutrients.
(a) Desert
(b) Forest
(c) Open field
(d) Cricket ground
4. Availability of water and minerals in the soil for maximum absorption by roots is in the –
(a) B-horizon
(b) C-horizon
(c) A-horizon
(d) surface of soil
5. Soil conservation measures are mainly aimed at protecting which of the following?
(a) Plants
(b) Top soil
(c) Sub soil
(d) Soil organisms
6. Read the following statements with reference to soil.
(i) Weathering is a very fast process of soil formation. (ii) Percolation of water is faster in sandy soils. (iii)
Loamy soil contains only sand and clay. (iv) Top soil contains the maximum amount of humus. Choose the
correct statements from the above.
(a) (ii) and (iv)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (i) and (ii)
7. Soil has particles of different sizes. Arrange the words given below in increasing order of their particle
size.
Rock, Clay, Sand, Gravel, Silt
8. Read the following statements and give the appropriate terms for each of them.
(a) The process of breakdown of rocks by the action of wind, water, sunlight.
(b) Removal of top soil during heavy rains or strong winds.
(c) Accumulation of wastes in the soil generated by human activity which alter the features of soil.
(d) The process of movement of water into deeper layers of soil.
9. Is it a good practice to remove grass and small plants that are growing in an open, unused field? Give
reason to support your answer.
10. A man digging a pit found that he could dig with ease initially but digging became difficult as he went
deeper. He could not dig beyond a depth of 5 feet. Provide a suitable scientific explanation.
11. Locate the following zones in the diagram of soil profile given below: Top soil, Subsoil, C-horizon, Bedrock
12. Rajasthan is a desert state in India. Once while travelling to Rajasthan by train, Boojho observed several
streams and rivulets of rain water during the journey but to his surprise he did not see streams of water in the
desert region even during rains. Help Boojho find a suitable explanation for this.
13. Match the animals in Column I with their natural place of dwelling (habitat) in Column II.
14. Continuously water-logged soils are disadvantageous for plant growth. Why?
15. Why is soil erosion relatively less in dense forests as compared to barren, open fields? 16. Gardeners
gently dig up the soil around the roots of garden herbs (plants) frequently. Give reasons.
17. In towns and cities, generally, the bore wells have to be dug very deep to get water as compared to bore
wells dug in villages. Give suitable reasons.
18. Unscramble the following jumbled words related to soil.
19. How can a farmer convert acidic soil to neutral soil?
20. Match the items in Column I with those in Column II:
Column I
Column II
(i) A home for living organisms
(a) Large particles
(ii) Upper layer of the soil
(b) All kinds of soil
(iii) Sandy soil
(c) Dark in colour
(iv) Middle layer of the soil
(d) Small particles and packed tight
(v) Clayey soil
(e) Lesser amount of humus
21. Explain how soil is formed.
22. How is clayey soil useful for crops?
23. List the differences between clayey soil and sandy soil.
24. Sketch the cross section of soil and label the various layers.
25. Razia conducted an experiment in the field related to the rate of percolation. She observed that it took 40
min for 200 mL of water to percolate through the soil sample. Calculate the rate of percolation.
26. Explain how soil pollution and soil erosion could be prevented.
Motion and Time
1. The distance covered by an object in a unit time as the speed of speed the object.
2. When we say that a car is moving with a speed of 50 kilometres per hour, it implies that it will cover a
distance of 50 kilometres in one hour. However, a car seldom moves with a constant speed for one hour. In fact,
it starts moving slowly and then picks up speed. So, when we say that the car has a speed of 50 kilometres per
hour, we usually consider only the total distance covered by it in one hour. We do not bother whether the car has
been moving with a constant speed or not during that hour. The speed calculated here is actually the average
speed of the car.
3. Speed is the total distance covered divided by the total time taken.
4. If the speed of an object moving along a straight line keeps changing, its motion is said to be non-uniform.
On the other hand, an object moving along a straight line with a constant speed is said to be in uniform motion.
5. Our ancestors noticed that many events in nature repeat themselves after definite intervals of time. For
example, they found that the sun rises everyday in the morning. The time between one sunrise and the next was
called a day. Similarly, a month was measured from one new moon to the next. A year was fixed as the time
taken by the earth to complete one revolution of the sun.
6. A simple pendulum consists of a small metallic ball or a piece of stone suspended from a rigid stand by a
thread. The metallic ball is called the bob of the pendulum.
One of the most well-known periodic motions is that of a simple pendulum. The first figure given above shows
the pendulum at rest in its mean position. When the bob of the pendulum is released after taking it slightly to
one side, it begins to move to and fro [Refer the second figure]. The to and fro motion of a simple pendulum is
an example of a periodic or an oscillatory motion.
The pendulum is said to have completed one oscillation when oscillation its bob, starting from its mean position
O, moves to A, to B and back to O. The pendulum also completes one oscillation when its bob moves from one
extreme position A to the other extreme position B and comes back to A. The time taken by the pendulum to
complete one oscillation is called its time period.
7. The basic unit of time is a second. Its second symbol is s. Larger units of time are minutes (min) and hours
(h).
8. Unit of speed: - Since the speed is distance/time, the basic unit of speed is m/s. Of course, it could also be
expressed in other units such as m/min or km/h.
9. Many time measuring devices were used in different parts of the world before the pendulum clocks became
popular. Sundials, water clocks and sand clocks are some examples of such devices. Different designs of these
devices were developed in different parts of the world.
10
11. A speedometer is an instrument that indicates the speed of a vehicle, usually combined with a device known
as an odometer that records the distance traveled.
12. DISTANCE-TIME GRAPH: (I) The table shown below gives the odometer reading at different times of the journey: -
Time
(AM)
Odometer
reading
Distance from the
starting point
8:00 AM
36540 km
0 km
8:30 AM
36560 km
20 km
9:00 AM
36580 km
40 km
9:30 AM
36600 km
60 km
10:00 AM
36620 km
80 km
The table shown above gives the information about the distance moved by the bus only at some definite time
intervals. On the other hand, from the distance-time graph we can find the distance moved by the bus at any
instant of time. Suppose we want to know how much distance the bus had travelled at 8:15 AM. We mark the
point corresponding to the time (8:15 AM) on the x-axis. Suppose this point is A. Next we draw a line
perpendicular to the x-axis (or parallel to the y-axis) at point A. We then mark the point, T, on the graph at
which this perpendicular line intersects it. Next, we draw a line through the point T parallel to the x-axis. This
intersects the y-axis at the point B. The distance corresponding to the point B on the y-axis, OB, gives us the
distance in km covered by the bus at 8:15 AM.
(II) Boojho and Paheli found out the distance travelled by a car and the time taken by it to cover that distance.
Their data was made into a tabular form.
S. No.
Time
Distance
1
0
0
2
1 min
1 km
3
2 min
2 km
4
3 min
3 km
5
4 min
4 km
6
5 min
5 km
NOW TRY TO ANSWER THE FOLLOWING QUESTIONS
1. Which of the following cannot be used for measurement of time?
(a) A leaking tap.
(b) Simple pendulum.
(c) Shadow of an object during the day.
(d) Blinking of eyes.
2. Observe the figure given below: -
The time period of a simple pendulum is the time taken by it to travel from
(a) A to B and back to A.
(b) O to A, A to B and B to A.
(c) B to A, A to B and B to O.
(d) A to B.
3. The correct symbol to represent the speed of an object is
(a) 5 m/s
(b) 5 mp
(c) 5 m/s-1
(d) 5 s/m
4. Boojho walks to his school which is at a distance of 3 km from his home in 30 minutes. On reaching he finds
that the school is closed and comes back by a bicycle with his friend and reaches home in 20 minutes. His
average speed in km/h is
(a) 8.3
(b) 7.2
(c) 5
(d) 3.6
5. A car moves with a speed of 40 km/h for 15 minutes and then with a speed of 60 km/h for the next 15
minutes. The total distance covered by the car is:
(a) 100 km
(b) 25 km
(c) 15 km
(d) 10 km
6. An oscillating pendulum is shown below: -
Time taken by the bob to move from A to C is t 1 and from C to O is t 2. The time period of this simple
pendulum is
(a) (t 1 + t 2 )
(b) 2 (t 1 + t 2)
(c) 3 (t 1 + t 2)
(d) 4 (t 1 + t 2)
7. Two students were asked to plot a distance-time graph for the motion described by Table A and Table B.
The graph given above is true for
(a) both A and B.
(b) A only.
(c) B only.
(d) neither A nor B.
8. A bus travels 54 km in 90 minutes. The speed of the bus is
(a) 0.6 m/s
(b) 10 m/s
(c) 5.4 m/s
(d) 3.6 m/s
9. Which of the following distance-time graphs shows a truck moving with speed which is not constant?
10. The distance-time graph for the motion of two vehicles A and B is shown below. Which one of them is
moving faster?
11. If Boojho covers a certain distance in one hour and Paheli covers the same distance in two hours, who
travels in a higher speed?
12. The average age of children of Class VII is 12 years and 3 months. Express this age in seconds.
13. A spaceship travels 36,000 km in one hour. Express its speed in km/s.
14. The odometer of a car reads 57321.0 km when the clock shows the time 08:30 AM. What is the distance
moved by the car, if at 08:50 AM, the odometer reading has changed to 57336.0 km? Calculate the speed of the
car in km/min during this time. Express the speed in km/h also.
15. Complete the data of the table given below with the help of the distance-time graph given below the table:
16. Given below is the distance-time graph of the motion an object: -
(i) What will be the position of the object at 20s?
(ii) What will be the distance travelled by the object in 12s?
(iii) What is the average speed of the object?
17. Show the shape of the distance-time graph for the motion in the following cases:
(i) A car moving with a constant speed.
(ii) A car parked on a side road.
18. A simple pendulum takes 32 s to complete 20 oscillations. What is the time period of the pendulum?
19. The distance between two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the
speed of the train.
20. Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/s,
calculate the distance between her house and the school.
21. Starting from A, Paheli moves along a rectangular path ABCD as shown in given below. She takes 2
minutes to travel each side. Plot a distance-time graph and explain whether the motion is uniform or nonuniform.
22. Boojho goes to the football ground to play football. The distance time graph of his journey from his home to
the ground is as given below: -
(a) What does the graph between point B and C indicate about the motion of Boojho?
(b) Is the motion between 0 to 4 minutes uniform or nonuniform?
(c) What is his speed between 8 and 12 minutes of his journey?