Science: Class 7th: Chapter 11 Transportation in Animals and Plants

Question 1:

Match structures given in Column I with functions given in Column II.

Column- IColumn-II
(i) Stomata(a) Absorption of water
(ii) Xylem(b) Transpiration
(iii) Root hairs(c) Transport of food
(iv) Phloem(d) Transport of water
(e) Synthesis of carbohydrates

Answer:

Column- IColumn-II
(i) Stomata(b) Transpiration
(ii) Xylem(d) Transport of water
(iii) Root hairs(a) Absorption of water
(iv) Phloem(c) Transport of food

Question 2:

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

_____________. 

Answer:

(i) The blood from the heart is transported to all parts of the body by the arteries .

(ii) Haemoglobin is present in red blood cells.

(iii) Arteries and veins are joined by a network of capillaries.

(iv) The rhythmic expansion and contraction of the heart is called heartbeat.

(v) The main excretory product in human beings is urea .

(vi) Sweat contains water and salts .

(vii) Kidneys eliminate the waste materials in the liquid form called urine .

(viii) Water reaches great heights in the trees because of suction pull caused by transpiration .

Question 3:

Choose the correct option:

(a) In plants, water is transported through

(i) xylem

(ii) phloem

(iii) stomata

(iv) root hair

(b) Water absorption through roots can be increased by keeping the plants

(i) in the shade

(ii) in dim light

(iii) under the fan

(iv) covered with a polythene bag

Answer:

a) i) Xylem

b) iii) under the fan

Question 4:

Why is transport of materials necessary in a plant or in an animal? Explain.

Answer:

Transport of materials is necessary in a plant or an animal for the following reasons:

  • To transport food to various parts of the body
  • Animals need to transport wastes to parts from where they can be removed.

Question 5:

What will happen if there are no platelets in the blood?

Answer:

If there are no platelets, then blood will not clot as platelets release blood clotting factor at the site of injury.

Question 6:

What are stomata? Give two functions of stomata.

Answer:

Tiny pores present on the leaf surface are known as stomata.

Functions of stomata

  • Helps in exchange of gases
  • Evaporation of water through leaves occurs due to stomata.

Question 7:

Does transpiration serve any useful function in the plants? Explain.

Answer:

Transpiration serves following function in plants

  • It helps in lowering temperature of plants, thus preventing heat injury of plants.
  • Helps in transpiration pull, which helps in raining water in higher plants.
  • It also causes loss of water absorbed by plants.

Question 8:

What are the components of blood?

Answer:

Red blood cells, white blood cells, platelets and plasma.

Question 9:

Why is blood needed by all the parts of a body?

Answer:

Blood is a significant part of transport system in our body, and we need blood for the following reasons:

  • For the transport of oxygen to all parts of our body
  • To expel out carbon dioxide from our body
  • To transmit heat thus helping in the regulation of body temperature.
  • It is required to fight out infections and diseases.

Question 10:

What makes the blood look red?

Answer:

Haemoglobin, a red pigment present in the blood makes it look red.

Question 11:

Describe the function of the heart.

Answer:

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 has four chambers. The two upper chambers are called the atria (singular: atrium), and the two lower chambers are called the ventricles. The partition between the chambers helps to avoid mixing up blood-rich in oxygen with the blood-rich in carbon dioxide. Blood flows from the heart to the lungs and back to the heart from where it is pumped to the rest of the body.

Question 12:

Why is it necessary to excrete waste products?

Answer:

When our cells perform their functions, certain waste products are released. These are toxic and hence need to be removed from the body.

Question 13:

Draw a diagram of the human excretory system and label the various parts.

Answer:

Science: Class 7th: Chapter 18 Wastewater Story

Question 1:

Fill in the blanks:

(a) Cleaning of water is a process of removing ____________.

(b) Wastewater released by houses is called ____________.

(c) Dried ____________ is used as manure.

(d) Drains get blocked by ____________ and ____________.

Answer:

(a) Cleaning of water is a process of removing pollutants.

(b) Wastewater released by houses is called sewage.

(c) Dried sludge is used as manure.

(d) Drains get blocked by cooking oil and fats.

Question 2:

What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

Answer:

Wastewater released by houses is called sewage. Untreated sewage should not be discharged untreated into the sea because sewage consists of pollutants and harmful microorganisms which will contaminate water causing disease in people using contaminated water.

Question 3:

Why should oils and fats be not released in the drain? Explain.

Answer:

Oils and fats should not be released in the drain because drains get blocked by cooking oil and fats.

Question 4:

Describe the steps involved in getting clarified water from wastewater.

Answer:

Use an aerator from an aquarium to bubble air through the sample in the glass jar. Allow several hours for aeration; leave the aerator attached overnight. If you do not have an aerator, use a mechanical stirrer or a mixer. This reduces the foul smell of wastewater.

Then, the water is filtered through the layers of sand, fine gravel, and medium gravel. Filtration makes the wastewater clean from various types of pollutants. The water is filtered continuously until it becomes clear. Water is disinfected by using a chlorine tablet.

Question 5:

What is sludge? Explain how it is treated.

Answer:

Solids like faeces settle at the bottom while treating sewage, and this material is called sludge. Sludge can be treated as follows

Sludge is removed using a skimmer and then transferred to a tank where it is decomposed by anaerobic bacteria to produce biogas. 

Question 6:

Untreated human excreta is a health hazard. Explain

Answer:

Untreated human excreta is a health hazard because it consists of various disease-causing microorganisms and pollutants that will contaminate the soil and water resource from where people draw water for drinking and domestic purposes. When people use water contaminated with human excreta, they get diseases like Cholera, Typhoid, Dysentery and Hepatitis.

Question 7:

Name two chemicals used to disinfect water

Answer:

Chlorine and Ozone are used to disinfect water.

Question 8:

Explain the function of bar screens in a wastewater treatment plant.

Answer:

Bar screen removes large objects like rags, sticks, cans, plastic packets and napkins.

Question 9:

Explain the relationship between sanitation and disease.

Answer:

Sanitisation and disease are interrelated as lack of sanitation lead to illness and good sanitation practices prevent the diseases.

Question 10:

Outline your role as an active citizen in relation to sanitation.

Answer:

Every citizen has a role to play in maintaining proper sanitisation. Following are the things we should follow to play an active role.

  • Ensure that our surroundings are kept clean.
  • The sewage system in the house should be properly managed
  • Report to the concerned authority immediately in case of leakages in sewage pipes.

Question 11:

Here is a crossword puzzle: 

Puzzles on waste water story

Across

3. Liquid waste products

4. Solid waste extracted in sewage treatment

6. A word related to hygiene

8. Waste matter discharged from human body

Down

1. Used water

2. A pipe carrying sewage

5. Microorganisms which causes cholera

7. A chemical to disinfect water

Answer:

Across

3. Sewage

4. Sludge

6. Sanitation

8. Excreta

Down

1. Wastewater

2. Sewer

5. Bacteria

7. Ozone

Question 12:

Study the following statements about ozone:

(a) It is essential for breathing of living organisms.

(b) It is used to disinfect water.

(c) It absorbs ultraviolet rays.

(d) Its proportion in air is about 3%. 

Which of these statements are correct?

(i) (a), (b) and (c)

(ii) (b) and (c)

(iii) (a) and (d)

(iv) All four

Answer:

(ii) (b) and (c)

Science: Class 7th: Chapter 17 Forests: Our Lifeline

Question 1:

Explain how animals dwelling in the forest help it grow and regenerate.

Answer:

Animals dwelling in the forest help it grow and regenerate in the following ways:

  • Animals help in dispersing plant seeds.
  • Decaying animal dung provides nutrients for plants to grow.
  • Microorganisms convert the dead plants and animals to humus.

Question 2:

Explain how forests prevent floods.

Answer:

Plants in the forests will not allow the rainwater to fall directly on earth and these plants also hold water which helps in preventing floods.

Question 3:

What are decomposers? Name any two of them. What do they do in the forest?

Answer:

The micro-organisms which convert the dead plants and animals to humus are known as decomposers. Example: bacteria and Fungi. They help in recycling of nutrients by decomposing dead plants and animals.

Question 4:

Explain the role of forest in maintaining the balance between oxygen and carbon dioxide in the atmosphere.

Answer:

Plants in the forests consume carbon dioxide and release oxygen by photosynthesis. This helps in balancing oxygen and carbon dioxide in the atmosphere.

Question 5:

Explain why there is no waste in a forest.

Answer:

There is no waste in a forest because waste created is biodegradable, which gets converted to humus by the action of microorganism.

Question 6:

List five products we get from forests?

Answer:

i) Medicines

ii) Spices

iii) Wood

iv) Paper

v) Gum

Question 7:

Fill in the blanks:

(a) The insects, butterflies, honeybees and birds help flowering plants in __________.

(b) A forest is a purifier of _________and __________.

(c) Herbs form the _________ layer in the forest.

(d) The decaying leaves and animal droppings in a forest enrich the ________.

Answer:

(a) The insects, butterflies, honey bees, and birds help flowering plants in pollination.

(b) A forest is a purifier of air and water .

(c) Herbs form the lowest layer in the forest.

(d) The decaying leaves and animal droppings in a forest enrich the soil.

Question 8:

Why should we worry about the conditions and issues related to forests far from us?

Answer:

We should worry about the forest for the following reasons.

  • A decrease in forest results in an increase in Carbon dioxide content in the atmosphere this results in global warming.
  • Depletion of forests results in soil erosion
  • Decreases in forest adversely affect the lives of animals living in the forest.
  • Absence of forests leads to flooding more often.
  • Due to the reduction of forest land will turn barren which is called desertification.

Question 9:

Explain why there is a need for a variety of animals and plants in a forest.

Answer:

Variety of plants and animals in the forests helps plants to regenerate and grow. More excellent range of plants supports herbivores, which in turn serve as food for carnivores. Decomposers turn dead animals and plants into humus; thereby maintain nutrient recycling. This wide variety makes forest a dynamic living entity.

Question 10:

In Fig. 17.15, the artist has forgotten to put the labels and directions on the arrows. Mark the directions on the arrows and label the diagram using the following labels: clouds, rain, atmosphere, carbon dioxide, oxygen, plants, animals, soil, roots, water table.

forests our lifeline

Answer:

forests our lifeline

Question 11:

Which of the following is not a forest product?

(i) Gum

(ii) Plywood

(iii) Sealing wax

(iv) Kerosene

Answer:

(iv) Kerosene

Question 12:

Which of the following statements is not correct?

(i) Forests protect the soil from erosion.

(ii) Plants and animals in a forest are not dependent on one another.

(iii) Forests influence the climate and water cycle.

(iv) Soil helps forests to grow and regenerate.

Answer:

(ii) Plants and animals in a forest are not dependent on one another – is incorrect

Question 13:

Microorganisms act upon the dead plants to produce

(i) sand (ii) mushrooms (iii) humus (iv) wood

Answer:

(iii) humus

Science: Class 7th: Chapter 16 Water: A Precious Resource

Question 1:

Mark ‘T’ if the statement is true and ‘F’ if it is false:

(a) The freshwater stored in the ground is much more than that present in the rivers and lakes of the world. (T/F)

(b) Water shortage is a problem faced only by people living in rural areas. (T/F)

(c) Water from rivers is the only source for irrigation in the fields. (T/F)

(d) Rain is the ultimate source of water. (T/F)

Answer:

(a) T 

(b) F 

(c) F 

(d) T

Question 2:

Explain how groundwater is recharged.

Answer:

The groundwater is recharged through the process of infiltration. Infiltration means seeping of water from rivers and lakes into the empty spaces and cracks deep below the ground.

Question 3:

There are ten tube wells in a lane of fifty houses. What could be the long-term impact on the water table?

Answer:

The effect on the water table depends on the replenishment of underground water. Only five families will share a tubewell, the water used for daily domestic purposes will not affect the water table. But if there is a shortage of rain, the water used by the family will not be replenished and the water table will fall down.

Question 4:

You have been asked to maintain a garden. How will you minimise the use of water?

Ans.To minimise the wastage of water we will use the drip irrigation which throws the water at the base of plants. We will check the leakages in the water pipes and arrange small pits for rainwater harvesting. The collected rainwater will be used later.

Question 5:

Explain the factors responsible for the depletion of the water table.

Answer:

Various factors responsible for the depletion of water table are:

(i) Increased population: Demand of water has been increased by the increased population. As the number of humans increases, the consumption of water also increases.

(ii) Increasing industries: All industries need water. As the number of human population increases, the number of industries are also increased which definitely increases the consumption of water.

(iii) Lack of water conservation techniques: Main source of water on earth and for the underground water is rain. The water of the rain, if conserved, can increase the ground water level. But this is not done due to lack of water conservative techniques.

(iv) Agricultural activities: India is a country which depends on agriculture. The land used for cultivation has increased. So, the consumption of water for agriculture has increased. Irregular rainfall has increased the consumption of groundwater. This has increased the depletion of groundwater.

Question 6:

Fill in the blanks with the appropriate answers: .

(a) People obtain groundwater through ________ and _________.

(b) Three forms of water are solid, ________ and __________.

(c) The water bearing layer of the earth is ___________.

(d) The process of water seepage into the ground is called __________.

Answer:

(a) wells, hand pumps

(b) liquid, gas

(c) aquifer

(d) infiltration

Question 7:

Which one of the following is not responsible for the water shortage?

(i) Rapid growth of industries

(ii) Increasing population

(iii) Heavy rainfall

(iv) Mismanagement of water resources

Answer:

(iii) heavy rainfall

Question 8:

Choose the correct option. The total water

(i) in the lakes and rivers of the world remains constant.

(ii) under the ground remains constant.

(iii) in the seas and oceans of the world remains constant.

(iv) of the world remains constant.

Answer:

(iv) of the world remains constant.

Question 9:

Make a sketch showing groundwater and water table. Label it.

Answer:

Science: Class 7th: Chapter 15 Light

Question 1:

Fill in the blanks:

(a) An image that cannot be obtained on a screen is called ___________ .

(b) Image formed by a convex is __________ always virtual and smaller in size.

(c) An image formed by a __________ mirror is always of the same size as that of the object.

(d) An image which can be obtained on a screen is called a __________ image.

(e) An image formed by a concave __________ cannot be obtained on a screen.

Answer:

(a) virtual image 

(b) mirror 

(c) plane 

(d) real 

(e) lens

Question 2:

Mark ‘T’ if the statement is true and ‘F’ if it is false:

(a) We can obtain an enlarged and erect image by a convex mirror. (T/F)

(b) A concave lens always form a virtual image. (T/F)

(c) We can obtain a real, enlarged and inverted image by a concave mirror. (T/F)

(d) A real image cannot be obtained on a screen. (T/F)

(e) A concave mirror always form a real image. (T/F)

Answer:

(a) F 

(b) T 

(c) T 

(d) F 

(e) F

Question 3:

Match the items given in Column I with one or more items of Column II.

COLUMN ICOLUMN II
(a) Plane Mirror(i)Used as a magnifying glass
(b)Convex Mirror(ii)Can form images of objects spread    over a large area.
(c)Convex Lens(iii) Used by dentists to see enlarged images of teeth.
(d)Concave Mirror(iv)The image is always inverted and magnified
(e)Concave Lens(v)The image is erect and of the same size as the object.
(vi)The image is erect and smaller in size than the object.

Answer:

(a) – (v)

(b) – (ii) and (vi)

(c) – (i)

(d) – (iii)

(e) – (vi)

Question 4:

State the characteristics of the image formed by a plane mirror.

Answer:

(i) Plane mirror forms an erect image.

(ii) It forms a virtual image.

(iii) Size of the image is the same as that of the object.

(iv)Image is formed at the same distance behind the mirror as the object stands in front of it.

(v) Image formed is a laterally inverted image i.e., the right hand side of the object seems to be the left hand side and vice-versa.

Question 5:

Find out the letters of English alphabet or any other language known to you in which the image formed in a plane mirror appears exactly like the letter itself. Discuss your findings.

Answer:

Letters like A, H, I, M, O, T, U ,V, W etc. appear the same when seen through a plane mirror.

Question 6:

What is a virtual image? Give one situation where a virtual image is formed.

Answer:

The image which cannot be taken on a screen is called a virtual image. When some object is placed very close to the concave mirror we don’t get any image on the white screen placed behind the mirror. Such an image is called a virtual image.

Question 7:

State two differences between a convex and a concave lens.

Answer:

CONVEX LENSCONCAVE LENS
Convex lens can form both real and virtual images.Concave lens always forms a virtual image.
It can form magnified image.Image is always diminished in size.

Question 8:

Give one use each of a concave and a convex mirror.

Answer:

Use of concave mirror:

Concave mirror is used by dentists to examine the teeth.

Use of convex mirror:

Convex mirror is used as side view mirror in vehicles.

Question 9:

Which type of mirror can form a real image?

Answer:

Concave mirror can form a real image.

Question 10:

Which type of lens always forms a virtual image?

Answer:

Concave lens always forms a virtual image.

Choose the correct option in Questions 11-13:

Question 11:

A virtual image larger than the object can be produced by a

(i) concave lens (ii) concave mirror (iii) convex mirror (iv) plane mirror

Answer:

(ii) concave mirror

Question 12:

David is observing his image in a plane mirror. The distance between the mirror and his image is 4 m. If he moves 1 m towards the mirror, then the distance between David and his image will be

(i) 3 m (ii) 5 m (iii) 6 m (iv) 8 m

Answer:

(iii) 6 m

Question 13: 

The rear view mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 m/s. The driver sees in his rear mew mirror the image of a truck parked behind his car. The speed at which the image of the truck appears to approach the driver will be

(i) 1 m/s (ii) 2 m/s (iii) 4 m/s {iv) 8 m/s

Answer:

(ii) 4 m/s

Science: Class 7th: Chapter 14 Electric Current and its Effects

Question 1:

Draw in your notebook the symbols to represent the following components of electrical circuits: connecting wires, switch in the ‘OFF’ position, bulb, cell, switch in the ‘ON’ position, and battery.

Answer:

Electric currents symbols

Question 2:

Draw the circuit diagram to represent the circuit shown in Fig.14.21.

circuit diagram

Answer:

circuit diagram

Question 3:

Fig.14.22 shows four cells fixed on a board. Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells.

baterry cell

Answer:

completed circuit

Question 4:

The bulb in the circuit shown in Fig.14.23 does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.

wrong electric circuit

Answer:

In the circuit above, the bulb is connected on either side.

circuit diagram

Question 5:

Name any two effects of electric current.

Answer:

i) Heating effect of electric current

ii) Magnetic effect of electric current

Question 6:

When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.

Answer:

When the current is switched on through a wire, a magnetic field is created around it hence we see deflection in the compass needle kept nearby.

Question 7:

Will the compass needle show deflection when the switch in the circuit shown by Fig.14.24 is closed?

compass needle

Answer:

No , the compass needle does not show deflection when the circuit is closed, a magnetic field is not created until current is flowing through the circuit.

Question 8:

Fill in the blanks:

(a) Longer line in the symbol for a cell represents its ________ terminal.

(b) The combination of two or more cells is called a __________ .

(c) When current is switched ‘on’ in a room heater, it ___________.

(d) The safety device based on the heating effect of electric current is called a ______________.

Answer:

(a) Longer line in the symbol for a cell represents its positive terminal.

(b) The combination of two or more cells is called a battery.

(c) When current is switched ‘on’ in a room heater, it produces heat .

(d) The safety device based on the heating effect of electric current is called a fuse. 

Question 9:

Mark ‘T’ if the statement is true and ‘F’ if it is false:

(a) To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell. (T/F)

(b) When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. (T/F)

(c) An electromagnet does not attract a piece of iron. (T/F)

(d) An electric bell has an electromagnet. (T/F)

Answer:

a) False

b) True

c) False

d) True

Question 10:

Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.

Answer:

No, because plastic does not have magnetic property to get attracted to a magnet hence magnet cannot be used to separate plastic bags.

Question 11:

An electrician is carrying out some repairs in your house. He wants to replace a fuse with a piece of wire. Would you agree? Give reasons for your response.

Answer:

It is not a wise idea to replace the fuse by a piece of wire, as it has a very low melting point. In case of metal pieces, melting point will be high and the circuit will be intact in case there is overload or overheat.

Question 12:

Zubeda made an electric circuit using a cell holder shown in Fig. 14.4, a switch and a bulb. When she put the switch in the ‘ON’ position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.

incomplete circuit diagram

Answer:

Reasons maybe two

i) The connecting wire may be loose

ii) The electric cell may be used up

iii) switch may not be functioning well

iv) cell power has been exhausted

Question 13:

In the circuit shown in Fig. 14.25

circuit diagram

(i) Would any of the bulbs glow when the switch is in the ‘OFF’ position?

(ii) What will be the order in which the bulbs A, B and C will glow when the switch is moved to the ‘ON’ position?

Answer:

i) No, the bulb will not glow as the circuit is not complete when the switch is off

ii) If the switch is On, all the bulbs glow simultaneously.

Science: Class 7th: Chapter 13 Motion and Time

Question 1:

Classify the following as motion along a straight line, circular or oscillatory motion:

(i) Motion of your hands while running.

(ii) Motion of a horse pulling a cart on a straight road.

(iii) Motion of a child in a merry-go-round.

(iv) Motion of a child on a see-saw.

(v) Motion of the hammer of an electric bell.

(vi) Motion of a train on a straight bridge.

Answer:

i) Oscillatory

ii) Motion along a straight line

iii) Circular motion

iv) Oscillatory motion

v) Oscillatory motion

vi) Motion along a straight line.

Question 2:

Which of the following are not correct?

(i) The basic unit of time is second.

(ii) Every object moves with a constant speed.

(iii) Distances between two cities are measured in kilometres.

(iv) The time period of a given pendulum is constant.

(v) The speed of a train is expressed in m/h.

Answer:

Incorrect statements are:

(ii) Every object moves with a constant speed.

(iv) The time period of a given pendulum is constant.

(v) The speed of a train is expressed in m/h.

Question 3:

A simple pendulum takes 32 s to complete 20 oscillations. What is the time period of the pendulum?

Answer:

Number of oscillations = 20

Total time taken to complete 20 oscillations = 32 s

time period calculation

Question 4:

The distance between two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the speed of the train.

Answer:

Distance between two stations = 240 kms

Total time take = 4 hrs/240 minutes

Speed calculation

= 60 km/h

Question 5:

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.

Answer:

Initial reading of the odometer = 57321.0

Final reading of the odometer = 57336.0

Distance covered by the car = Final reading of the odometer – Initial reading of the odometer

= 57336.0 – 57321.0 = 15 kms

Starting time of car is 8:30 and it stops at 8: 50

Hence, time taken by car = 20 mins

speed calculation

= 45 km/h

Question 6:

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.

Answer:

Time taken by Salma to reach her school by bicycle = 15 mins= 15 x 60 = 90 s

Speed of Salma’s bicycle= 2m/s

Speed formula

Distance covered = speed x time taken

= 2 x 900 = 1800 m

1000m = 1 km

distance covered calculation

= 1.8 kms

Question 7:

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.

Answer:

(i)

Distance time graph

(ii)

Distance time graph

Question 8:

Which of the following relations is correct?

(i) Speed = Distance × Time

(ii) Speed = Distance/Time

(iii) Speed = Time/Distance

(iv) Speed = 1/Distance x Time

Answer:

(ii) Speed = Distance/Time

Question 9:

The basic unit of speed is:

(i) km/min

(ii) m/min

(iii) km/h

(iv) m/s

Answer:

(iv) m/s

Question 10:

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:

(i) 100 km (ii) 25 km (iii) 15 km (iv) 10 km

Answer:

(ii) 25 km

Calculation:

When the speed of the car is 40 km/h

Time taken = 15 min = 15/60 = 0.25 h

Speed formula

Distance covered d1 = speed x time taken

= 40 x 0.25 = 10 kms

When the speed of the Car is 60 km/ h

Speed formula

Distance covered d2 = speed x time taken

= 60 x 0.25= 15 kms

Total distance covered by the car = d1 + d2

= 10 + 15

= 25 kms

Question 11:

Suppose the two photographs, shown in Fig. 13.1 and Fig. 13.2, had been taken at an interval of 10 seconds. If a distance of 100 metres is shown by 1 cm in these photographs, calculate the speed of the fastest car.

Speed calculation

Answer:

The distance covered by the blue car (as evident from the photograph) from one horizontal white strip to another, which is measured by scale is 1.2 cm.

It is given that 1 cm is equivalent to 100 m.

Therefore, 1.2 cm is equivalent to 120 m.

Distance travelled by the car = 120 m

Time taken to cover this distance = Time interval between the two photographs = 10 s

Speed formula

= 120/10

= 12 m/s

Question 12:

Fig. 13.15 shows the distance-time graph for the motion of two vehicles A and B. Which one of them is moving faster?

Distance time graph

Answer:

Vehicle A is moving faster than vehicle B.

Question 13:

Which of the following distance-time graphs shows a truck moving with speed which is not constant?

Distance time graph
Distance time graph

Answer:

(iii)

Science: Class 7th: Chapter 12 Reproduction in Plants

Question 1:

Fill in the blanks:

(a) Production of new individuals from the vegetative part of the 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 __________.

Answer:

(a) vegetative reproduction 

(b) unisexual flower 

(c) pollination 

(d) fertilization 

(e) wind, water

Question 2:

Describe the different methods of asexual reproduction. Give examples.

Answer: 

Different methods of asexual reproduction are:

(a) Binary Fission: This process takes place in unicellular organisms. Parent cell elongates and gets divided into two identical daughter cells. Each daughter cell grows into an independent adult.

(b) Endospore Formation: In this method the spore wall is formed around a bacterial cell to form an endospore. This endospore germinates to form an active bacterium under favourable conditions.

(c) Fragmentation: In this process, the body of the organism breaks up into two parts. Then each part grows into a new filament thus forming two organisms from a single one.

(d) Spore Formation: The spores are tiny spherical unicellular structures protected by thick walls. The spores are stored in a hard outer covering and this is called sporangium. Under favourable conditions the hard cover breaks and spores spread for germination.

(e) Budding: In yeast, new organisms are produced by the bud formation from the parent organism. After growing to full size, the bud gets detached and forms a new independent individual.

(f) Vegetative propagation: When vegetative parts of a plant like stems, leaves and root etc., give rise to new ones, it is.called vegetative propagation.

Question 3:

Explain what you understand by sexual reproduction.

Answer:

Sexual reproduction means involvement of two parents in the process of reproduction. It is found mainly in higher plants where male gamete and female gamete fuse to form a zygote. These zygotes develop into individuals which are not identical. Offsprings inherit the characteristics of both the parents. In sexual reproduction both parents survive after the process of reproduction.

Question 4:

State the main difference between asexual and sexual reproduction.

Answer:

Asexual ReproductionSexual Reproduction
Single parents are involved.Two parents are involved.
No gamete formation takes place.Gametes are formed.
New organism is similar to parents.New organism is different from the parents.

Question 5:

Sketch the reproductive parts of a flower.

Answer:

Question 6:

Explain the difference between self-pollination and cross-pollination.

Answer:

Self PollinationCross Pollination
It involves the transfer of pollen from the stamen to the pistil of the same flower.It involves the transfer of pollen from the stamen of one flower to the pistil of another flower of the same plant or that of a different plant of the same kind.
It occurs only in bisexual flowers.It occurs in both unisexual and bisexual flowers.

Question 7:

How does the process of fertilization take place in flowers?

Answer:

When the pollen grain reaches the stigma of a same species flower, it starts growing out into the pollen tube of the stigma. This tube continues to grow inside the style till it reaches the ovule. Male cells are released into the ovule for the fertilization with the female egg cell and thus the zygote is formed. After this process of fertilization, the ovary develops into fruit and ovule into seeds.

Question 8:

Describe the various ways by which seeds are dispersed.

Answer: 

Following are the ways in which the seeds are dispersed:

(i) Some light seeds like that of madar, which are hairy, dry and small are carried away by the wind to different places.

(ii) Spiny seeds and fruits like that of xanthium and urena, stick to the clothes of passers by and animals. These seeds are carried away by these agents to different places.

(iii) In some plants having heavy seeds like that of coconut, water acts as the dispersing agents.

(iv) Some seeds are dispersed with the fruit burst like in the case of balsam and castor.

Q.9.Match items in Column I with those in Column II.

COLUMN ICOLUMN II
(a) Bud(i) Maple
(b)Eyes(ii) Spirogyra
(c) Fragmentation(iii)Yeast
(d) Wings(iv)Bread Mould
(e) Spores(v)Potato
(vi)Rose

Answer:

COLUMN ICOLUMN II
(a)Bud(iii)Yeast
(b)Eyes(v)Potato
(c)Fragmentation(ii)Spirogyra
(d)Wings(i)Maple
(e)Spores(iv)Bread Mould
(vi)Rose

Question 10:

Tick the correct answer:

(a) The reproductive part of a plant is the

(i) leaf (ii) stem (iii) root (iv) flower

(b) The process of fusion of the male and the female gametes is called

(i) fertilisation (ii) pollination (iii) reproduction (iv) seed formation

c) Mature ovary forms the

(i) seed (ii) stamen (iii) pistil (iv) fruit

(d) A spore producing plant is

(i) rose (ii) bread mould (iii) potato (iv) ginger

(e) Bryophyllum can be reproduced by its

(i) stem (ii) leaves (iii) roots (iv) flower

Answer:

(a) (iv) flower 

(b) (i) fertilisation 

(c) (iv) fruit 

(d) (ii) bread mould 

(e) (ii) leaves

Science: Class 7th: Chapter 10 Respiration in Organisms

Question 1:

Why does an athlete breathe faster and deeper than usual after finishing the race?

Answer:

The athlete needs a lot of energy during the race, and for the release of energy, they need a lot of Oxygen; hence they breathe faster and more profoundly than usual after finishing the race.

Question 2:

List the similarities and differences between aerobic and anaerobic respiration.

Answer:

Similarities: In both kinds of respiration, food particles are broken down to finer constituents.

Differences:

Aerobic respirationAnaerobic respiration
Takes place in the presence of OxygenTakes place in the absence of Oxygen
End products are CO2 and H2OEnd products are CO2 and alcohol
Produces a large amount of energyThe energy released is less when compared to aerobic respiration
It occurs in most plants and animalsOccurs in yeast and some bacteria

Question 3:

Why do we often sneeze when we inhale a lot of dust-laden air?

Answer:

When we inhale dust-laden air, dust irritates the nose; as reflexive action, dust is thrown out through sneezing.

Question 4:

Take three test-tubes. Fill ¾th of each with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of CO2 ?

Answer:

Test tube A will have the highest concentration of CO2 because test-tube A will have Snail which expels out CO2 into the tube. In tube C, there is a plant which will inhale CO2 to decrease CO2 concentration in the tube C.

Question 5:

Tick the correct answer:

(a) In cockroaches, air enters the body through

(i) lungs (ii) gills (iii) spiracles (iv) skin

(b) During heavy exercise, we get cramps in the legs due to the accumulation of

(i) carbon dioxide (ii) lactic acid (iii) alcohol (iv) water

(c) Normal range of breathing rate per minute in an average adult person at rest is:

(i) 9–12 (ii) 15–18 (iii) 21–24 (iv) 30–33

(d) During exhalation, the ribs

(i) move outwards (ii) move downwards (iii) move upwards (iv) do not move at all

Answer:

a) (iii) spiracles

b) (ii) lactic acid

c) (ii) 15–18

d) (ii) move downwards

Question 6:

Match the items in Column I with those in Column II:

Column IColumn 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) Trachae

Answer:

Column IColumn II
(a) Yeast(iii) Alcohol
(b) Diaphragm(iv) Chest cavity
(c) Skin(i) Earthworm
(d) Leaves(v) Stomata
(e) Fish(ii) Gills
(f) Frog(vi) Lungs and skin

Question 7:

Mark ‘T’ if the statement is true and ‘F’ if it is false:

(i) During heavy exercise the breathing rate of a person slows down. (T/F)

(ii) Plants carry out photosynthesis only during the day and respiration only at night. (T/F)

(iii) Frogs breathe through their skins as well as their lungs. (T/F)

(iv) The fishes have lungs for respiration. (T/F)

(v) The size of the chest cavity increases during inhalation. (T/F)

Answer:

i) False

ii) False

iii) True

iv) False

v) True

Question 8:

Given below is a square of letters in which are hidden different words related to respiration in organisms. These words may be present in any direction — upwards, downwards, or along the diagonals. Find the words for your respiratory system. Clues about those words are given below the square.

Puzzle on respiration

(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

Answer:

(i) Trachea

(ii) Ribs

(iii) Diaphragm

(iv) Stomata

(v) Spiracles

(vi) Lungs

(vii) Nostrils

(viii) Yeast

(ix) Ant

Question 9:

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.

Answer:

(b) The amount of air available to a person is less than that available on the ground.

Science: Class 7th: Chapter 9: Soil

Question 1:

Tick the most suitable answer in questions 1 and 2.

1. In addition to the rock particles, the soil contains

(i) air and water

(ii) water and plants

(iii) minerals, organic matter, air and water

(iv) water, air and plants

Answer:

(iii) minerals, organic matter, air and water.

Question 2:

The water holding capacity is the highest in

(i) sandy soil

(ii) clayey soil

(iii) loamy soil

(iv) mixture of sand and loam

Answer:

(ii) clayey soil

Question 3:

Match the items in Column I with those in Column II:

Column IColumn 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

Answer:

Column IColumn II
(i) A home for living organisms(b) All kinds of soil
(ii) Upper layer of the soil(c) Dark in colour
(iii) Sandy soil(a) Large particles
(iv) Middle layer of the soil(e) Lesser amount of humus
(v) Clayey soil(d) Small particles and packed tight

Question 4:

Explain how soil is formed.

Answer:

Soil is formed due to the weathering of rocks. Weathering is a process in which physical breakdown and chemical decomposition of minerals takes place primarily by wind, water and climatic changes. In the weathering process, rocks are converted to small pieces which eventually turn to soil particles to form a layer of soil.

Question 5:

How is clayey soil useful for crops?

Answer:

Clayey soil is useful for crops for the following reasons

  • It has excellent water holding capacity
  • Clayey soil is rich in organic matter
  • Clayey and loamy soils are suitable for growing cereals like wheat.
  • Water holding-capacity of clayey soil supports the growth of crops like paddy which require more water to grow.

Question 6:

List the differences between clayey soil and sandy soil

Answer:

Clayey SoilSandy Soil
1. Particles are finerParticles are larger
2 Particles are tightly packedParticles are loosely packed
3. Holds a good amount of waterWater holding capacity is low
4. It is heavy in weightIt is light in weight
5. Rich in humus and organic nutrientsNot rich in humus and organic nutrients
6. Very little air is trapped between the particlesMore air is trapped between the particles

Question 7:

Sketch the cross-section of soil and label the various layers.

Answer:

Question 8:

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.

Answer:

Amount of water = 200 ml

Percolation time = 40 minutes

Percolation rate = calculation of water percolation rate

= percolation rate calculation

= 5ml/min

Question 9:

Explain how soil pollution and soil erosion could be prevented

Answer:

Soil pollution can be controlled by the following measures:

  • By reducing the use of plastics, we can reduce soil pollution.
  • By controlling the use of chemical fertilisers and pesticides, we can control soil pollution.

Soil erosion can be controlled by taking the following steps

  • Planting more and more trees will result in the reduction of soil erosion.
  • By stopping deforestation and avoiding overgrazing of animals.

Question 10:

Solve the following crossword puzzle with the clues given:

Across

2. Plantation prevents it.

5. Use should be banned to avoid soil pollution.

6. Type of soil used for making pottery.

7. Living organism in the soil.

Down

1. In desert soil erosion occurs through.

3. Clay and loam are suitable for cereals like.

4. This type of soil can hold very little water.

5. Collective name for layers of soil.

Puzzles on Soil

Answer:

Across:

2. Erosion

5. Polythene

6. Clay

7. Earthworm

Down:

1. Wind

3. Wheat

4. Sandy

5. Profile