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FIBRE TO FABRIC class 7 science important questions

FIBRE TO FABRIC class 7 important questions

Q.1. What are natural fibres?

Ans. The fibres which we get from the nature are called natural fibres. Two types of natural fibres are animal fibre and plant fibre. Fibres such as cotton, jute and flax are obtained from plants and are called plant fibres and fibres such as wool and silk are obtained from animals and are called animal fibres.

Q.2. Name some animals which are a source of wool.

Ans. Some animals which are a source of wool are sheep, goat, camel, yak, Llama, alpaca and vicuna etc.

Note: Yak reared in Tibet and Ladakh.

Angora goats and sheep reared in Kashmir.

Camels, reared in Rajasthan.

Llama, alpaca and vicuna reared in South America.

Q.3. Why do some animals have thick coat of hair?

Ans. Some animals have thick coat of hair because hair trap a lot of air. Air being a poor conductor of heat, acts as an insulator and does not allow the heat energy of their bodies to escape. So, the thick coat of hair keeps these animals warm.

Q.4. What do you mean by the term ‘breeding of sheep’?

Ans. The sheep having thick coat of hair in their body in large quantity are multiplied to get more number of sheep, so that good quality of wool will be obtained. This is called breeding of sheep.

Q.5. The different steps involved in the processing of fleece to wool are

a) Shearing: The fleece of the sheep along with a thin layer of skin is removed from its body. This process of removing fleece from the body of the sheep is known as shearing. Machines similar to those used by barbers are used to shear off fleece from the body of the sheep.

b) Scouring: The sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt. This process of removing grease, dust and dirt from the sheared skin is known as scouring. In the old days it is done manually, but now a day it is done by machines.

c) Sorting: After scouring, sorting is done. The hairy skin is sent to factory where hair of different textures are separated or sorted. This process of separation of wool is known as sorting.

d) Dyeing: The natural fleece of sheep and goats being black, brown or white, the fibres are dyed in various colours. This process is known as dyeing.

e) Rolling: The process by which fibres are straightened, combed and rolled into yarn is called Rolling. .The longer fibres are made into wool for sweaters and the shorter fibres are spun and woven into woolen clothes.

Q.6. What is sericulture?

Ans. The rearing of silkworms for obtaining silk is called sericulture. In this process farmers take care of the silkworms, keep their eggs under hygienic conditions and suitable condition of temperature and humidity. It is a very old occupation in India.

Q.7. Explain the life history of silk moth ?

Ans. The life history of silk moth passes through four different stages. They are egg, larva pupa and adult moth.

Egg: The female silk moth is larger than the male silk moth. It lays hundreds of eggs on the underside of the fresh mulberry leaves which stick to it because of some gummy material.

Larva: In due course of time these eggs hatch to form white larva, commonly known as silk worm or caterpillar. They eat mulberry leaves day and night for 4 to 6 weeks and grow in size.

Pupa: The third stage in the life cycle of silk moth is pupa. The grown up silk worm or larva stops eating and secrets a sticky fluid, a protein called fibroin from its salivary gland which hardens on exposure to air and becomes silk fibre.. This silk fibre is wrapped around its body to form a ball-like structure called cocoon. At this stage, the larva becomes a pupa.

Adult: Further development of pupa stage takes place within the cocoon. It develops into adult silk moth. At this stage the silk moth cuts the cocoon around it and emerges out to start a new life cycle.

Q.8. Explain about the processing of silk from cocoon.

Ans. The two main process involved are:-

a) Rearing of the silk worms

b) Processing of the silkworms.

a) Rearing of the silk worms: A female silk moth lays hundreds of eggs at a time. The eggs are stored carefully on strips of clothes or paper and sold to silkworm farmers. The eggs are kept under hygienic conditions and suitable conditions of temperature and humidity. Then the larvae hatch out from the eggs. Then they eat mulberry leaves and forms into a pupa. The outer covering of the pupa is known as cocoon. Then when it is fully developed into a silk moth, it comes out and leaves the cocoon.

b) Processing silk: A pile of cocoons is taken. They are kept under sun or boiled or exposed to steam. The silk fibres are separated out. The process of taking out threads from the cocoon is known as reeling the silk. It is done in special machines which unwind the threads or fibres of silk from the cocoons. Silk fibres are then spun into silk threads, which are woven into silk cloth by weavers.

AMEND EDUCATION ACADEMY CLASS 10 SCIENCE OUR ENVIRONMENT NCERT Notes

AMEND EDUCATION ACADEMY  CLASS 10 SCIENCE OUR ENVIRONMENT

An ecosystem consists of biotic components including living organisms and abiotic components, the physical factors like temperature, rainfall, wind, soil and minerals.
       •  An ecosystem can be natural or artificial. Organisms in the ecosystem can be categorised into producers, consumers and decomposers.

Producers are the organisms that produce their own food without the help of any other organism.FOR EXAMPLE PLANTS

       •  They are also known as autotrophs.
       •  They make their food from inorganic substances through a process called photosynthesis.
       •  Autotrophs are green plants, phytoplankton and blue green algae.

Consumers are the organisms which cannot produce food but depend on producers for the same.

       •  These are also called as called heterotrophs.
       •  Heterotrophs are the animals can be classified into herbivores, omnivores, carnivores and parasites based on their food pattern.

Decomposers are the organisms which feed on dead and decaying matter.

       •  Decomposers break down the complex organic compounds present in dead animals and plants, which are then used by other members of the ecosystem.
       •  Decomposers like bacteria and fungi are known as saprobes.

Food chains describe the feeding relationship between the organisms of an ecosystem.

       •  The flow of energy from one species to another at various biotic levels forms a food chain.
       •  The successive levels in the food chains of a community are called as trophic levels.
       •  Various trophic levels in a food chain include producers, primary consumers, secondary consumers and tertiary consumers.
       •  A web of cross-linked food chains is called a food web.

Ozone is molecule formed by the combination of three oxygen atoms. There is a layer of ozone in the stratosphere. It acts as a natural sun-block and shields us from the UV radiations of the sun which are dangerous to living organisms.Ozone depletion is the sharp reduction of ozone in the stratosphere due to chlorofluorocarbons (CFC’s) used as refrigerants and in fire extinguishers.

Increased use of non-biodegradable items have left the environment polluted with them.

Important Definitions

1) ECOLOGY – The study of the interaction of living organisms with each other and their surroundings is called ecology.

2) ENVIRONMENT – Everything that surrounds organisms and influences its life.

a) Biotic components of environment --- The living organisms .e.g. Plants and animals.

b) Abiotic components of environment --- The nonliving components  like water, air, light, etc.

It is the sum total of all external conditions and influences that affect the life and the development of organisms i.e.,it includes all the biotic and abiotic factors.

3) ECOSYSTEM – All interacting organisms in an area together with the nonliving constituents of environment. (Functional unit of an environment)

Functions of ecosystem:-

a) Flow of energy         b) Cycling of nutrients(bio-geo chemical cycles).

4) PRODUCERS --- They make the energy from sunlight available to the rest of the ecosystem.

5) CONSUMERS --- Animals can not manufacture their own food. They are called consumers.

6) BIODEGRABLE ---- Substances that are broken down by the action of bacteria or other saprophytes. e.g. – Paper.

7) NONBIODEGRABLE --- Substances that are not broken down by the action of bacteria or saprophytes. e. g. Plastic.

8) FOOD CHAIN -The process of one organism eating the other. 

GRASS-- > GRASSHOPPER-- >; FROG -> SNAKE

Importance of food chain

1.It helps in transfer of food energy from one organism to another.

2.It is a pathway for the flow of energy.

3. It helps in understanding the interdependence amongst different organisms.

Trophic levels are the various steps in the food chain .

Producers --- first trophic level                   Herbivores --- second trophic levels

Carnivores --- third trophic level               Top carnivores --- fourth trophic level

9) FOODWEB ----- It is a network of food links between populations in a community.

10) FLOW OF ENERGY -Ten percent law Energy available at each successive trophic level is 10 % of the previous level. (Lindeman 1942)

The law states that, “ only a 10 % amount of the total available energy is transferred from one trophic level to the next. The rest 90% of energy is used up or lost to the surrounding.”

11) BIOLOGICAL MAGNIFICATION --- Progressive accumulation of non- biodegradable waste at various trophic levels of food chain.

12. Differences between food chain & food web 

Food chain

1. The process of eating & being eaten to transfer food energy.  2. It forms a part of food web.

3. It has limited populations.

Food web

1. It is a system of interconnected food chains. 2. It contains many food chains.

3. It has several populations of different species.

13. HOW DO OUR ACTIVITIES AFFECT THE ENVIRONMENT?

Two major problems:-

a) Depletion of ozone layer

b) Disposal of waste

Good ozone and bad ozone

The thick blanket of ozone layer in the atmosphere which forms a protective cover & prevents UV radiation from reaching the earth‘s surface. This is called good ozone and is found in the stratosphere.

Ozone when present in the troposphere act as a pollutant . This harmful ozone is called bad ozone.

14. Depletion of ozone layer : The ozone layer protects all the organisms from the harmful ultra violet rays.

Ozone depleting substances: CFCs, N2O, CH4 , CCl4

These chlorine containing compounds are used in:  Aerosols, solvents, refrigerants and fire extinguishers.  Ozone hole developed over Antarctica.

Important Question/Answers

1.      Why are some substances biodegradable and some non-biodegradable?

Answer Substances are classified as biodegradable and non-biodegradable because some substances can be decomposed by microorganisms and some cannot.
Substances that are broken down into simple soluble forms are called biodegradable substances and the substances that are not decomposed by microorganisms into harmless substances are called non biodegradable substances.

2.      Give any two ways in which biodegradable substances would affect the environment.

Answer: Biodegradable substances can affect the environment in following ways:

By recycling the raw materials in nature.

By improving the humus content in soil.

3.      . Give any two ways in which non-biodegradable substances would affect the environment.

(i) They contaminate soil and water resources as they cannot be decomposed by micro-organisms.

(ii) These substances, when accidentally eaten by stray animals, can harm them and can even cause their death.

1.    What are trophic levels? Give an example of a food chain and state the different trophic levels in it.

A trophic level is the level of species in an ecosystem on the basis of the source of nutrition such as producers, primary consumers, secondary consumers, etc.
The producers form the first trophic level as they manufacture food. The primary consumers form the second trophic level, the secondary consumers form the third, and the tertiary consumers form the fourth trophic level.

2.    What is the role of decomposers in the ecosystem?

Decomposers include micro-organisms such as bacteria and fungi that obtain nutrients by breaking down the remains of dead plants and animals. They help in the breakdown of organic matter or biomass from the body of dead plants and animals into simple inorganic raw materials, such as CO₂, H₂O, and some nutrients.

3.    What is ozone and how does it affect any ecosystem?

Ozone is a colourless gas that acts as a screen for ultraviolet radiation. It is continuously formed at the higher levels of the atmosphere due to the action of UV rays on molecular oxygen. The high energy UV radiations break down O₂ molecules into nascent oxygen.

How can you help in reducing the problem of waste disposal? Give any two methods.

The problem of waste disposal can be solved by proper waste management including the collection, transport, processing, and disposal of the waste materials.

The problem of waste management can be solved by the following given measures:

·        Use separate bins (blue and green) for disposing non-biodegradable and biodegradable wastes.

o   Reduce the usage of non-biodegradable products such as plastics.

4.    What will happen if we kill all the organisms in one trophic level?

If all the organisms of any one trophic level are killed, then it will disrupt the entire food chain.

For example, in a food chain, if all the plants are killed, then all the deer will die due to lack of food. If all the deer are dead, then soon the tigers will also die. Due to the death of these animals, the decomposer’s population will rise in that area.

This is just an example of one food chain. However, in nature, food chains are not isolated. They are interconnected in the form of food web. Therefore, killing all the plants of an area will not only affect the deer, it will also affect other herbivores such as goat, cattle, sheep, etc.

5.    What is ozone and how does it affect any ecosystem?

Answer: Ozone is a form of oxygen. Ozone is a triatomic molecule while oxygen is a diatomic molecule. Ozone forms the ozone layer in our atmosphere. Ozone plays an important role in the ecosystem. The ozone layer wards off harmful ultraviolet radiations from the sun and thus protects the living beings.

6.    Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?

Answer: Ozone layer works like a protective shield for living beings. The ozone layers wards off harmful ultraviolet radiations from the sun. Damage to the ozone layer can result in increased level of ultraviolet radiations in our atmosphere. This would be very dangerous for all life forms.

In 1987, the UNEP (United Nations Environment Programme) succeeded in forging an agreement among different nations to freeze the CFC production at 1986 level. Later, an agreement was signed among different nations to phase out CFCs. It is important to note that CFC is used in refrigerators and aerosol spray. India is also a signatory of that agreement and thanks to the efforts by the United Nations and different environmentalists, the CFC emission has been put under some control.

Class 7 NCERT Science Transportation

The heart has four chambers: two atria and two ventricles. The right atrium receives oxygen-poor blood from the body and pumps it to the right ventricle. The right ventricle pumps the oxygen-poor blood to the lungs. The left atrium receives oxygen-rich blood from the lungs and pumps it to the left ventricle

 

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

Answer: The cells of plants and animals need various substances to carry out important metabolic activities. Further, many waste products are created during these metabolic activities. Transport of materials is necessary to supply the various substances and to remove the waste products.

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

Answer: Clotting is necessary to prevent blood loss. Platelets are responsible for clotting of blood. If there are no platelets, the blood would not clot in case of an injury. This will lead to excess blood loss and finally in death of the person.

3 - What are stomata? Give two functions of stomata.

Answer: The innumerable very small pores on the surface of leaf are called stomata. Transpiration and exchange of gases (carbon dioxide and oxygen) are some of the functions of stomata.

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

Answer: Transpiration serves important functions in plants. Transpiration creates the transpiration pull; which is responsible for the rise of water to great heights in tall plants and other trees.

5 - What are the components of blood?

Answer: The main components of blood are: Plasma, Blood Cells and Platelets.

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

Answer: Blood acts as a carrier of various substances. Every part of the body needs certain substances to perform its functions. Additionally, every part creates some waste products. Blood is needed by all parts of the body so that various substances can be supplied to them and waste can be removed from them.

7 - What makes the blood look red?

Answer: Blood is red because of the presence of a pigment; called haemoglobin.

8 - Describe the function of the heart.

Answer: The heart is a pumping organ which pumps the blood. The heart pumps the deoxygenated blood to the lungs; for oxygenation. Moreover, the heart pumps the oxygenated blood to different parts of the body.

9 - Why is it necessary to excrete waste products?

Answer: Waste products can prove lethal if not removed in time. Hence, it is necessary to excrete the waste products.

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

Answer