SOIL

 NOTES

Soil is one of the most important natural resources. It is the uppermost layer of earth’s crust which is blackish-brown in colour. Major functions of the soil are:

• It supports plant growth by holding the roots firmly and supplying water and nutrients to the plants.
• It acts as a natural habitat for many organisms like an earthworm, fungi, bacteria, ants, etc.
• It is also essential for agriculture which provides us with food, clothing and shelter for all.
• It supplies water and nutrients to plants.
  Therefore, we can say that soil is an inseparable part of our life.

Soil Profile
Soil is formed by breaking down of rocks by the action of wind, water or climate by the process called weathering. During this process, the rocks are worn away to form small particles by long exposure to the elements of weather.

Soil Types
The weathering of rocks produces small particles of various materials, these include sand and clay. The relative amount of sand and clay depends upon the rock from which the particles were formed. The rock particles present in soil are of different sizes and chemical compositions. On the basis of sizes, the rock particles present in soil can be divided mainly into four major groups:
(i) Clay, These are formed by the smallest rock particles. These are so small that we cannot see a single clay particle and it feels smooth.

(ii) Silt These are made up of somewhat bigger rock particle than clay. It is not so smooth as clay. Silts are found deposited at river beds. Floods deposit the silt from rivers in the field.

(iii) Sand, These are made up of larger particles enough than that of silt and can be easily seen. These are coarse to touch due to their larger size.

(iv) Gravel These are the largest sized rock particles that are present in the soil. These are the tiny stones that are present in topsoil in very small quantity.

Soil Erosion
The removal of land surface by water wind or ice is known as erosion. The topsoil is very fertile and in the absence of it, the plants cannot grow.

Exercise Questions

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

Solution:

The answer is (iii) minerals, organic matter, air and water.

2. The water holding capacity is the highest in

(i) sandy soil

(ii) clayey soil

(iii) loamy soil

(iv) mixture of sand and loam

Solution:

The answer is (ii) clayey soil

3. 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

Solution:

Column I	Column 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

4. Explain how soil is formed.

Solution:

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.

5. How is clayey soil useful for crops?

Solution:

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

6. List the differences between clayey soil and sandy soil.

Solution:

Clayey Soil	Sandy Soil
1. Particles are finer	Particles are larger
2 Particles are tightly packed	Particles are loosely packed
3. Holds a good amount of water	Water holding capacity is low
4. It is heavy in weight	It is light in weight
5. Rich in humus and organic nutrients	Not rich in humus and organic nutrients
6. Very little air is trapped between the particles	More air is trapped between the particles

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

Solution:

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.

Solution:

Amount of water = 200 ml

Percolation time = 40 minutes

Percolation rate = 

= 

= 5ml/min

9. Explain how soil pollution and soil erosion could be prevented

Solution:

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.

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.

Solution:

Across:

2. Erosion

5. Polythene

6. Clay

7. Earthworm

Down:

1. Wind

3. Wheat

4. Sandy

5. Profile

REPRODUCTION IN PLANTS

 NOTES

Different organisms reproduce in a different way. In plants, there are two different methods of reproduction:

1. Asexual reproduction
2. Sexual reproduction

The term ‘sexual’ means involving the fusion of sex cells or gametes while ‘asexual’ means without involving the fusion of gametes.

Asexual Reproduction
The process in which only one parent is involved in the production of new individuals of the same kind is called asexual reproduction. In plants, asexual reproduction results in the formation of offsprings or new plants without seeds or spores.
Asexual reproduction in plants occurs through the following methods:

1. Vegetative propagation
2. Budding
3. Fragmentation
4. Spore formation

Types of Flower
On the basis of the type of reproductive organs present in a flower, the flowers are of following types:
(i) Unisexual flower: The flower which contains only one reproductive organ (i.e. either male or female) are called unisexual flowers. These are also called as an incomplete flower, e.g. papaya, watermelon, corn, cucumber, etc.

(ii) Bisexual flower: The flower that contains both reproductive parts (i.e. male and female) in a single flower are called a bisexual flower. These are also termed as hermaphrodites or complete flower, e.g. rose, mustard, Hibiscus, etc.

Function of a Flower
The function of a flower is to make male and female gametes and also to ensure that fertilisation would take place for the seed formation. During sexual reproduction male and female gametes fuse to form the zygote.

Pollination
The transfer of pollen grains from the anther of a stamen to the stigma of a pistil is called pollination. Pollination takes place in two different ways:
(i) Self-pollination: When the pollen grain from the anther of one flower reaches to the stigma of the same ‘ flower, it is called self-pollination. Self-pollination generally occurs in a bisexual flower.

(ii) Cross-pollination: When the pollen grains from the anther of a flower or of a plant are transferred to the stigma of a flower of the same plant or that of a different plant of the same kind the process is called cross-pollination. This transfer to another plant is mediated by insects, wind, water, animals, birds, etc.

Agents of Pollination
The process of pollination is carried out by some external agencies like wind, water, insects, birds, etc. These are called agents of pollination.

Fertilisation
The process in which the male gamete fuses with the female gamete to form a new cell (called zygote) is called fertilisation.

When the pollens are deposited on the stigma of the pistol, it begins to germinate. After some time, a long pollen tube is developed from the pollen grain which passes through the style towards the female gametes in the ovary. The male gametes move down the pollen tube and the tube enters the ovule present inside the ovary.

The tip of pollen tube bursts and the male gamete comes out of the pollen tube. Inside the ovary, the male gametes fuse with the female gametes present in the ovule to form a fertilised egg cell which is called zygote.
The zygote develops into an embryo which is a part of a seed that develops into a new plant.

Fruit and Seed Formation
After the fertilisation, the ovary grows into the fruit and the ovule develops into the seeds

Seed Dispersal
Seeds are developed from the ovule. Seeds contain an embryo enclosed in a protective seed coat. Plants produce a large number of seeds. When these seeds fall down, they start growing. If a large number of seeds falls on the same place, they will not get enough space for water and light, and will not develop into a healthy plant. Thus, the seeds are moved away by some external agencies to far off places.

The process by which the seeds are scattered to different places (far and wide from their parents) is called dispersal. The seeds and fruits are dispersed away through various agencies like wind, water, birds and some animals. Sometime seed dispersal takes place naturally by the explosion or bursting of fruits.

Exercise Questions
1. 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 _____________.
Solution:
(a) Production of new individuals from the vegetative part of parent is called vegetative propogation.
(b) A flower may have either male or female reproductive parts. Such a flower is called unisexual.
(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 Pollination.
(d) The fusion of male and female gametes is termed as fertilisation.
(e) Seed dispersal takes place by means of wind, water and animals.
2. Describe the different methods of asexual reproduction. Give examples.
Solution:
Asexual modes of reproduction are as follows
Vegetative propagation:
A plant can produce new plants from vegetative parts of the plant like roots, stems.
Budding:
It involves the formation of a new individual from a bulb-like projection called a bud.
Fragmentation:
New organisms are formed from the fragments of the parent body.
Spore formation:
Plants reproduce by the formation of spores.
3. Explain what you understand by sexual reproduction.
Solution:
Sexual reproduction is a method where male and female gametes fuse to form a new individual. In plants, stamens and pistils are male and female reproductive organs which bear the anthers and ovary respectively.
4. State the main difference between asexual and sexual reproduction.
Solution:

Asexual reproduction	Sexual reproduction
It requires only one parents	Requires a male and female parent
Daughter cells formed are identical to parents and to each other.	Newly formed offsprings show variations in comparision to the parents.
Special reproductive organs are not required	Special reproductive organs are required
Ex: Yeast, rose, jasmine	Ex: Insects, animals

5. Sketch the reproductive parts of a flower.
Solution:

6. Explain the difference between self-pollination and cross-pollination.
Solution:

Self-pollination	Cross-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.
Self-pollination occurs only in bi-sexual flowers	It occurs in both unisexual and bisexual flowers

7. How does the process of fertilisation take place in flowers?
Solution:
The process of fusion of male and female gametes (to form a zygote) is called fertilisation. The zygote develops into an embryo and embryo undergoes mitotic cell division to form seeds.
8. Describe the various ways by which seeds are dispersed.
Solution:
Seeds and fruits of plants are carried away by wind, water and animals. Winged seeds such as those of drumstick and maple, light seeds of grasses or hairy seeds of aak (Madar) and hairy fruit of sunflower, get blown off with the wind to faraway places. 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. 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. 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.
9. Match items in Column I with those in Column II: Column I 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

Solution:

Column-I	Column-II
(a) Bud	(iii) Yeast
(b) Eyes	(v) Potato
(c) Fragmentation	(ii) Spirogyra
(d) Wings	(i) Maple
(e) Spores	(iv) Bread mould

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 organism is
(i) rose (ii) bread mould (iii) potato (iv) ginger
(e) Bryophyllum can reproduce by its
(i) stem (ii) leaves (iii) roots (iv) flower
Solution:
a) (iv) flower
b) (i) fertilization
c) (iv) fruit
d) (ii) bread mould
e) (ii) leaves

TRANSPORTATION IN ANIMALS AND PLANTS

 NOTES

Circulatory System

The organ system of the body that is responsible for the transport of material throughout the body is called the circulatory system.

Blood

• Blood is a fluid tissue that transports nutrients and oxygen to the cells and carries away carbon dioxide and other waste products in our body.

RBC

• Red blood cells (RBC) present in the blood are responsible for the transport of oxygen throughout the body.
• They contain a red pigment called haemoglobin, which binds with the oxygen.
• The reddish colour of the blood is due to haemoglobin.

WBC

• The blood contains white blood cells (WBC), which are part of the immune system.
• They are like soldiers, which fight and kill germs that may enter the body.

Blood Platelets

• Platelets are the smallest cells in the blood.
• By clumping together, they form a blood clot, preventing loss of blood due to bleeding.
• They prevent excessive damage to the blood vessels by binding together at the site of damage.

Excretion

The process of removal of waste products from the cells of living organisms is called excretion.

• For human beings, the waste products are in the form of carbon dioxide, urine and faeces.

Kidneys

• Our body’s main excretory organs are the kidneys.
• There is a pair of kidneys present on either side of the spine.
• Each kidney is a bean-shaped organ, reddish in colour.
• It contains millions of tiny tubules that act as microscopic filters and filter out the useful and harmful substances from the blood.
• The useful substances are again reabsorbed back into the blood and only harmful substances are concentrated.
• These harmful substances are present in a dissolved state in water and now it is called as urine.
• Urine is excreted out of the body.
• Thus, kidneys act as filters of our body.

Dialysis

• Dialysis is the filtering of blood outside the human body using a machine, when both the kidneys fail.

Phloem

• Phloem is the plant tissue that transports the soluble organic material created during photosynthesis from the leaves to the other parts of the plant.

Xylem

• Xylem is the plant tissue that transports the water and other nutrients from the roots to other parts of the plant.

QUESTION ANSWERS 

Exercise Questions

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

Column- I	Column-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

Solution:

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

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 .

Solution:

(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 .

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

Solution:

a) i) Xylem

b) iii) under the fan

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

Solution:

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

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

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

Solution:

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

6. What are stomata? Give two functions of stomata.

Solution:

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.

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

Solution:

Transpiration serves the following functions 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.

8. What are the components of blood?

Solution:

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

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

Solution:

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.

10. What makes the blood look red?

Solution:

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

11. Describe the function of the heart.

Solution:

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 of 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.

12. Why is it necessary to excrete waste products?

Solution:

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

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

Solution:

 

FRICTION

 NOTES

Friction opposes the relative motion between two surfaces in contact. It acts on both the surfaces.

Factors Affecting Friction

• Friction depends on the nature of surfaces in contact.
• For a given pair of surfaces, friction depends upon the state of smoothness or roughness of those surfaces. It is less for smooth surfaces.
• Friction is independent of the area of contact.
• Friction depends on how hard the two surfaces pressed together

Friction is a must as well as evil:

• Friction produces heat when we vigorously rub our palms together for a few minutes.
• Friction is responsible for wear and tear of various parts of machines.
• Friction decreases the efficiency of machines as a part of the machine’s energy is lost in extra friction.
• Friction is responsible for writing, walking and transmitting energy.
• Friction is responsible for starting or stopping.
• Friction is used in gripping or holding an object with our hands.
  So, we can say friction is a must as well as evil.

Fluid Friction: Fluid exerts the force of friction on objects in motion through them.It is also called as drag.

nterlocking: Irregularities on two surfaces in contact may clasp with each other, increasing friction.

Lubricants: The substances which reduce friction are called lubricants.

Rolling Friction: When one body rolls over the surface of another body, the resistance to its motion is called the rolling friction.

Sliding Friction: When one surface is sliding over the other surface, sliding friction comes into play.

Static Friction: Static friction comes into play to counterbalance the applied force on the body..

ROLLING FRICTION IS LESS THAN THAT OF SLIDING FRICTION.

QUESTION ANSWERS AND EXCERCISE

Question 1.
Fill in the blanks.
(a) Friction opposes the ______ between the surfaces in contact with each other.
(b) Friction depends on the ______ of surfaces.
(c) Friction produces ______
(d) The sprinkling of powder on the carrom board _______ friction.
(e) Sliding friction is _______ than the static friction.
Solution:
(a) relative motion
(b) smoothness (or irregularities or nature)
(c) heat
(d) reduces
(e) less

Question 2.
Four children were asked to arrange forces due to rolling, static and sliding frictions in decreasing order. Their arrangements are given below. Choose the correct arrangement.
(a) rolling, static, sliding
(b) rolling, sliding, static
(c) static, sliding, rolling
(d) sliding, static, rolling
Solution:
(c) static, sliding, rolling.

Question 3.
Alida runs her toy car on a dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be
(a) wet marble floor, dry marble floor, newspaper and towel.
(b) newspaper, towel, dry marble floor, wet marble floor.
(c) towel, newspaper, dry marble floor, wet marble floor.
(d) wet marble floor, dry marble floor, towel, newspaper.
Answer:
(a) wet marble floor, dry marble floor, newspaper and towel.

QUESTION 4

Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.
Answer:
Frictional force will act upward, i.e., the direction opposite to that of sliding book.

Question 5.
You spill a bucket of soapy water on a marble floor accidentally. Would it make it easier or more difficult for you to walk on the floor? Why?
Answer:
The layer of soap makes the floor smooth due to which the friction is reduced. This makes the floor slippery and the foot cannot make a proper grip on the floor. Therefore it is difficult to walk on a soapy floor. We may slip on the floor.

QUESTION 6

Explain why sportsmen use shoes with spikes.

Answer:
Sportsmen use shoes with spikes to increase the friction between shoes and the surface. So the shoes with spikes do not slip while the sportsmen run and play.

Question 7.
Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?
Answer:
A heavy object produces more friction as it is pressed hard against the opposite surface. So Seema will have to apply a larger force.

QUESTION 8

Explain why sliding friction is less than static friction.
Answer:
The sliding friction is less than static friction because the sliding object get less time to interlock into the contact points on the floor. So it is somewhat easier to move an object already in motion than to get it started.

Question 9.
Give examples to show that friction is both a friend and a foe.
Answer:
Some points are given below which show that friction is both a friend and a foe:

1. Friction as a friend:
   • It allows us to grip and catch any object.
   • It helps us to walk comfortably on the floor.
   • It helps to minimise the speed or to stop any moving object.
   • It helps us to write.
2. Friction as a foe:
   • It causes wear and tears in objects.
   • It causes damage to the parts of machines and tools which further require money to get them repaired.
   • It reduces the speed of moving objects, so more force is required.
   • It produces hurdles in moving any object freely.

Question 10.
Explain why objects moving in fluids must have special shapes.
Answer:
The objects moving in fluids must have a special shape to overcome the fluid friction acting on them. Efforts are therefore made to minimise the friction, so objects are given special shape having pointed fronts with little broader middle portion which gets tapered at the back called streamlined.