Selina Class 7 ICSE Solutions

Selina Concise Biology Class 7 ICSE Solutions – Nervous System

by

Selina Concise Biology Class 7 ICSE Solutions – Nervous System

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 7 Biology. You can download the Selina Concise Biology ICSE Solutions for Class 7 with Free PDF download option. Selina Publishers Concise Biology for Class 7 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 7 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 7 Biology Chapter 6 Nervous System

Synopsis —

  • The interaction of these activities of a living being as per the needs of the body internally or externally is called coordination.
  • Nervous coordination is brought about by the nervous system which is made up of the brain, spinal cord, nerves and the sense organs.
  • Chemical coordination is brought about through chemical messengers called hormones.
  • The nervous system is made up of special cells called nerve cells or neurons.
  • The end of the axon terminates in a number of branches called terminal branches.
  • The terminal branches of the axon of one neuron lie very close to the dendrites of another neuron. This point of contact is called a synapse.
  • A nerve is formed of a bundle of axons (nerve fibres) enclosed in a tubular medullary sheath. There are three kind of nerves as describe
    1. sensory nerve
    2. motor nerve
    3. mixed nerve.
  • The nervous sytem of human beings consists of the following three systems:
    1. The central nervous system
    2. The peripheral nervous system
    3. The autonomic nervous system
  • The brain has three main parts:
    1. The cerebrum
    2. The cerebellum, and
    3. The medulla oblongata
  • The main functions of the spinal cord are:
    1. To control reflexes below the neck.
    2. To conduct messages from the skin and muscles to the brain.
    3. To conduct commands from the brain to muscles of the trunk and limbs.
  • The autonomic nervous system consists of a pair of chain of nerves and ganglia found on either side of the backbone.  This system controls the involuntary activities of the internal organs.
  • Stimulus: Any change in the environment that usually results in change in the activity of the body.
  • Response: The activity of the body in response to a received stimulus.
  • Impulse: A wave of electrical disturbance that runs through the nerves.
  • Receptors : These are sense organs which receives the stimulus.
  • Effector: Any muscle or gland where the response occurs.

Review Questions

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) Medulla oblongata controls
(i) Smelling
(ii) Beating of heart and respiratory movement
(iii) Intelligence and will power
(iv) Balancing the body

(b) Spinal cord is an extention of:
(i) Cerebellum
(ii) Cerebrum
(iii) Vertebral column
(iv) Medulla oblongata

(c) Body posture is mantained by:
(i) Cerebellum
(ii) Cerebrum
(iii) Medulla oblongata
(iv) Spinal cord

Short Answer Questions:

1. Write one word in the space provided to complete the second pair of the related words pertaining to nervous system.
Memory: cerebrum:: breathing:
Balance: cerebellum:: reasoning:
Answer:
Memory: cerebrum: beathing: medulla oblongata
Balance: cerebellum:: reasoning: cerebrum

2. (a) Name three major divisions of the human nervous system.
Answer:

  1. The central nervous system (brain and spinal cord)
  2. The peripheral nervous system
  3. The autonomic nervous system

(b) Name the three main parts of human brain.
Answer:

  1. Cerebrum
  2. Cerebellum
  3. Medulla oblongata

3. Given here is the diagram of a neuron. Name the parts numbered 1-6.
Selina Concise Biology Class 7 ICSE Solutions - Nervous System 1

Answer:

  1. dendrite
  2. dendrite (Terminal Arborization)
  3. nucleus
  4. axon (Nerve fibre)
  5. cell Body (cyton)
  6. node of ranvier
  7. sheath

Long answer questions

Question 1.
With the help of a suitable diagram describe the structure of a neuron.
Answer:
Selina Concise Biology Class 7 ICSE Solutions - Nervous System 2

Nervous system consists of special cells called nerve cells or neurons. It has a main cell body called cyton. It gives out many processes called dendrites. From it a very long process is given out. It is called axon or nerve fibre.

The cell body has a nucleus. The dendrites get the message from the organs and send this message to the axon through the cell body. Then the axon sends the message to muscles to contrast or to the gland for secretion.

The neurons make contact with one another through their processes. The axon at its end branches and meets the dendrites of another neuron. The meeting point is called synapse. The message is passed on from one axon to the dendrites of another neuron. How the message goes ? It is like this:
Organ → Message goes to dendrites →Cell body → Axon → Muscles or  glands

Question 2.
Briefly describe the structure of the cerebrum in human brain, and mention its functions.
Answer:
Brain consists of main three parts and lies in the cranial cavity of skull.

  1. The cerebrum
  2. The cerebellum
  3. The medulla oblongata

Cerebrum — It is very large and form two third of the whole brain. The two hemispheres are separated from each other by a deep longitudinal groove, the median fissure. The outer surface is folded with ridges and grooves. The hemispheres are hollow from inside and their walls have outer and inner portions. The outer portion has cell bodies of the neurons and it is called grey matter.
The wavery edges of the folded layer has large number of neurons to the extent of nine billion. The inner portion of the cerebrum has axons and it is called white matter.
Functions:

  1. It controls all the voluntary activities.
  2. It is the seat of intelligence, consciousness and will power.

Question 3.
Mention the three functions of spinal cord.
Answer:
Spinal cord has the following functions.

  1. It is the centre of reflex actions below the neck.
  2. It carries messages from the skin and muscles to the brain.
  3. All the stimuli and responses are passed from and to the brain through the spinal cord.

Question 4.
Describe three kinds of nerves, giving example of each.
Answer:
A nerve is formed by a group of nerve fibres (axons) encased
by tubular medullary sheath. The medullary sheath acts as insulation and do not allow mixing up of impulses of the neighbouring axons (nerve fibres) We have three kinds of nerves:

  1. Sensory nerve — It brings impulses from sense organs as these have sensory fibres. These nerve carry the impulses from the sense organs to the brain or to the spinal cord as optic nerve of the eye.
  2. Motor nerves—These carry impulses to muscles or glands from the brain or spinal cord. These nerves have only motor fibres as nerves to the muscles of the eye ball.
  3. Mixed nerve — It has both sensory and motors fibres as nerve going to the tongue.

Question 5.
What are voluntary and involuntary actions ? Which part of the nervous system controls them ?
Answer:
Voluntary action: When an action is produced with the involvement of thoughts, they are called the voluntary action. For example, writing an article jumping from heights. These actions are produced consciously by our body.
Involuntary action: Actions which take place without consciousness or willingness of an individual are called the involuntary action. Digestion, heart beating, sneezing, etc are few examples of involuntary actions.

  1. The cerebral cortex controls our voluntary actions like running and walking etc.
  2. Medulla helps in involuntary actions like hearbeat, breathing etc.

Additional Questions

I. Multiple choice questions. Tick (✓) the correct choice:

I. Nervous system in humans consists of
(a) brain and nerves
(b) brain and spinal cord
(c) brain, spinal cord and nerves
(d) none of the above.

II. Fill in the blanks:

  1. Basic structural unit of the nervous system is the neuron.
  2. Central nervous system consists of brain and spinal cord.
  3. A neuron consists of cell body, dendrite and axon.
  4. The neurons carrying impulses from the brain to the muscles are called motor or efferent neurons.
  5. Peripheral nervous system consists of nerves.
  6. The three main parts of the brain are cerebrum, cerebellum and medulla oblongata (brain stem).

III. State whether the following statements are true (T) or false (F):

1. Each neuron consists of three parts called cell body, cyton and axon.
 False. Each neuron consists of three parts called cell body, dendrite and axon.

2. The largest part of the brain is the cerebrum.
 True.

3. Cerebellum maintains balance of the body.
True.

4. There are 31 pairs of cranial nerves.
 False. There are 12 pairs of cranial nerves.

IV. Find the odd-one out, giving reasons:
Axon, cell body, dendrite, cerebellum
Ans. Cerebellum is the odd one out as it is a part of brain while rest three are parts of a neuron.

V. Define the following:
1. Reflex arc
2. Sensory neuron
3. Motor neuron
4. Neuron
Answer:

  1. Reflex arc: The path that an impulse takes in a reflex action is called a reflex arc.
  2. Sensory neuron: The neurons which carry impulses
    from the body parts to the spinal cord or the brain are called sensory or afferent neurons. For example, optic nerve of the eye.
  3. Motor neuron: The neurons which carry impulses from the brain or spinal cord to the body parts are called motor or efferent neurons.
  4. Neuron: A neuron or a nerve cell is the basic structural and functional unit of the nervous system.

VI. Answer the following:

Question 1.
 Describe the two parts of the nervous system.
Answer:
The nervous system of human has two parts:

  1. Central Nervous System (CNS): It consists of the brain and the spinal cord. The brain lies protected inside the skull while the spinal cord is protected within the vertebral column.
  2. Peripheral Nervous System (PNS): It consists of nerves arising from the spinal cord (spinal nerves) and the brain (cranial nerves). These nerves link the central nervous system with the various body organs.

Question 2.
What are nerves? Mention the types of nerves found in humans.
Answer:
A bundle of nerve fibres joined together as a tubular sheath that transmits impulses between brain or spinal cord and other body parts is called a nerve. The nerves constitute the peripheral nervous system.
Nerves are of two types in humans:

  1. Cranial nerves: They emerge from the brain. There are 12 pairs of cranial nerves.
  2. Spinal nerves: They emerge from the spinal cord. There are 31 pairs of spinal nerves.

Question 3.
Explain the structure of brain.
Answer:
The brain is the main control centre of the nervous system.
It is enclosed within the bony shell of cranium.
It consists ofthree main part:

    1. Cerebrum: It is the uppermost and largest part with many ridges and grooves. It is divided into right and left halves called cerebral hemispheres. It controls our thinking, reasoning, intelligence, memory and perception of pain, sound, touch, taste and smell.
    2. Cerebellum: It is located under the cerebrum at the back of the head. It maintains balance of the body and coordinates muscular activity.
    3. Brain stem (medulla oblongata): It joins the brain to the spinal cord. It controls the activity of internal organs like heartbeat and breathing.
      Selina Concise Biology Class 7 ICSE Solutions - Nervous System 3

Question 4.
Compare the nervous system and the endocrine system.
Answer:
Nervous system

  1. Messages are sent through nerve fibres.
  2. It consists of brain, spinal cord and nerves.
  3. No hormones are secreted. Messages are sent as impulses.
  4. Transmission of impulse is quick.

Endocrine system

  1. Messages are sent through blood in the form of hormones.
  2. It consists of endocrine glands.
  3. Hormones secreted by glands regulate the body activities. .
  4. Transmission takes time.

Selina Concise Chemistry Class 7 ICSE Solutions – Elements, Compounds and Mixtures

by

Selina Concise Chemistry Class 7 ICSE Solutions – Elements, Compounds and Mixtures

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 7 Chemistry. You can download the Selina Concise Chemistry ICSE Solutions for Class 7 with Free PDF download option. Selina Publishers Concise Chemistry Class 7 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 7 Chemistry ICSE SolutionsPhysicsBiologyMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 7 Chemistry Chapter 3 Elements, Compounds and Mixtures

Points to Remember :

  1. Every substance is made up of very tiny particles, called molecules. Molecules are formed from even smaller particles called atoms.
  2. Element— (a) Element is the simplest pure substance. It cannot be divided further into simpler substances by any chemical method, e.g. oxygen, hydrogen, sulphur, etc.
    (b) At present 116 elements are known, of which 92 are natural elements.
  3. Based on their properties, elements are classified into : metals, non-metals, metalloids, noble gases.
  4. Metals are ductile, malleable, good conductors of heat and electricity, high melting and boiling points. Metals are sonorous, e.g., Iron, Gold, Silver, etc.
  5. Non-metals are solids and brittle in nature, bad conductor of heat and electricity (exception Graphite) low melting and boiling points, e.g. sulphur, carbon, hydrogen, etc.
  6. Metalloids— These elements show properties of both metals and non-metals. They are hard solids, e.g. Boron, Silicon, Arsenic.
  7. Inert or noble gases— These elements do not react chemically with other elements or compounds are called noble (Inert) gases, e.g., helium, neon, argon, etc.
  8. Symbols of Elements— Each element is denoted by a symbol usually to first letter.
    Examples : Oxygen by O Hydrogen by H.
  9. Atom— “An Atom is the smallest particle of an element that can take part in a chemical reaction but may or may not have independent existence.”
    The atom of an element exhibits all the properties of that element.
  10. Molecule— A molecule is the smallest particle of a pure substance of element or compound which has independent existence. It exhibits all the properties of pure substance.
  11. Atomicity— The number of atoms of an element that join together to form a molecule of that element is known as the atomicity.
  12. Molecular Formula— of an element is the symbolic representation of its molecule. It indicates the number of atoms present in it. e.g. Magnesium oxide – MgO.

EXERCISE – I

Question 1.
Write the symbols of helium, silver, krypton, antimony, barium.
Answer:

Element                   Symbol
Helium                         He
Silver                            Ag
Krypton                       Kr
Antimony                    Sb
Barium                        Ba

Question 2.
Write the names of following elements Na, C, Kr, U, Ra, Fe, Co.
Answer:

Symbol           Element
Na                        Sodium
C                          Carbon
Kr                        Krypton
U                         Uranium
Ra                        Radium
Fe                           Iron
Co                        Cobalt

Question 3.
Define :

  1. Elements : An element is the basic form of matter that cannot be broken down into simpler substances by chemical reactions.
  2. Compounds : A compound is a pure substance formed by the chemical combination of two or more elements in a fixed ratio by mass.

Question 4.
Name the main metal present in the following :
Answer:

(a) Haemoglobin                                    Iron
(b) Chalk                                               Calcium
(c) Chlorophyll                                   Magnesium
(d) Chocolate wrappers                    Aluminium

Question 5.
Give four examples of non-metallic elements.
Answer:
Examples : Hydrogen, oxygen, nitrogen, carbon, chlorine, sulphur, phosphorus, etc.

Question 6.
What do you understand by :
Answer:

  1. Metalloids : Metalloids are those substances which have some properties of metals and some of non-metals e.g. boron, silicon.
  2. Noble gases : Noble gases are those which do not react chemically with other elements or compounds e.g. helium, neon, etc.

Question 7.
Select elements and compounds from the following list: Iron, plaster of paris, chalk, common salt, copper, aluminium, calcium oxide, cane sugar, carbon, silica, sodium sulphate, uranium, potassium carbonate, silver, carbon dioxide.
Answer:
Selina Concise ICSE Solutions for Class 7 Chemistry Chapter 3 Elements, Compounds and Mixtures-7

EXERCISE – II

Question 1.
State four difference between compounds and mixtures.
Answer:

CompoundMixture
1. A compound is a pure substance.1. A mixture is an impure substance.
2. Compounds are always homogeneous.2. Mixtures may be homogeneous or heterogeneous.
3. A compound has a fixed composition, i.e., it is formed when two or more pure substances chemically combine in a definite ratio by mass.3. A mixture has no fixed composition, i.e., it is formed by mixing two or more substances in any ratio without any chemical reaction.
4. Formation of a compound involves change in energy.4. Formation of a mixture does not involve any change in energy.
5. Compounds have specific set of properties.5. Mixtures do not have any specific set of properties.
6. Components of compounds can be separated only by complex chemical processes.6. Components of mixtures can be separated by simple physical methods.

 Question 2.
What are the characteristic properties of a pure substance? Why do we need them?
Answer:
Pure substance : Pure substances have a definite set of properties such as boiling point, melting point, density, etc. They are all homogeneous i.e., their composition is uniform throughout the bulk. Both elements and compounds are pure substances.
Pure substances are needed to :

  1. Manufacture medicines.
  2. To prepare chemicals in industry.
  3. For scientific purposes.
  4. To maintain the good health of human beings.

Question 3.
Give two examples for each of the following :
(a) Solid + Solid mixture
(b) Solid + Liquid mixture
(c) Liquid + Liquid mixture
Answer:
(a) Solid + Solid mixture :Sand and sugar,

  • Sand and stone,
  • sand and sugar.

(b) Solid + Liquid mixture :

  • Sand and water,
  • Charcoal and water.

(c) Liquid + Liquid mixture :

  • Oil in water,
  • Alcohol and water.

Question 4.
Define :

  1. Evaporation : Is the process ~of converting a liquid into its vapours state either by exposing it to air or by heating.
  2. Filtration : The process of separating solid particles from liquid by allowing it to pass through a filter paper is called filtration.
  3. Sublimation : The process in which a solid changes directly into its vapours on heating is called sublimation.
  4. Distillation : Distillation is the method of getting a pure liquid from a solution by evaporating and then condensing the vapours.
  5. Miscible liquids : Homogeneous liquid-liquid mixtures are called miscible liquids.
  6. Immiscible liquids : Heterogeneous liquid-liquid mixtures are called immiscible liquids.

Question 5.
Name the process by which the components of following mixtures can be separated.

  1. Iron and sulphur
  2. Ammonium chloride and sand
  3. Common salt from sea water
  4. Chaff and grain
  5. Water and mustard oil
  6. Sugar and water
  7. Cream from milk

Answer:

  1. Magnetic separation.
  2. Sublimation.
  3. Evaporation.
  4. Winnowing separates chaff (lighter) from heavier grains in two different heaps.
  5. Mustard oil and water is liquid-liquid immiscible mixture and is separated by separating funnel. Water being the heavier forms the lower layer.
  6. By evaporation in this process of converting a liquid into its vapour state by heating. Liquid is heated and water evaporate and sugar is obtained.
  7. Centrifugation.

Question 6.
How will you separate a mixture of common salt, chalk powder and powdered camphor? Explain.
Answer:
Comphor with sublimation. Chalk powder by Alteration then the residual left is common salt.

Question 7.
How is distillation more advantageous than evaporation?
Answer:
The advantage of distillation is that both components of the
solid and liquid mixture are obtained. Whereas in evaporation only solid is obtained.

Question 8.

  1. What is chromatography?
  2. Why is it named so?
  3. What are the advantages of chromatography?
  4. Name the simplest type of chromatography?
  5. On what principle is this method based?
  6. What is meant by stationary phase and mobile phase in chromatography?

Answer:

  1. The process of separating different dissolved constituents of a mixture by their absorption on an appropriate material is called chromatography.
  2. It is named so, because earlier it was used to separate mixtures containing coloured components only but these days this technique is applied to colourless substances too.
  3. Advantages of chromatography :
    (i) A very small quantity of the substance can be separated.
    (ii) Components with very similar physical and chemical properties can be separated.
    (iii) It identifies the different constituents of a mixture.
    (iv) lt also helps in quantitative estimation of components of a mixture.
  4. The simplest type of chromatography is “Paper chromatography”.
  5. Chromotography is based on differential affinities of compounds towards two phases i.e. stationary and mobile phase.
  6. The filter paper acts as “stationary phase” while the solvent act as “mobile phase”.

Question 9.
On what principle are the following methods of separation based? Give one example of a mixture for each of the methods mentioned in which they are used
Answer:

  1. Sublimation : Change of solid into vapours directly on heating and change of vapours into solid again on
    Example : Salt from ammonium chloride.
  2. Filtration : The process of separating insoluble solid particles from a liquid by allowing it to pass through a filter is called Alteration. These filters allow liquids to pass through them but not solids. The insoluble solid left on the filter is called the residue, while the liquid which passes through the filter is called the filtrate. Mixtures like chalk and water, clay and water, tea and tea leaves, sawdust and water, etc., are separated by this method.
  3. Sedimentation and decantation : The settling down of suspended, insoluble, heavy, solid particles in a solid- liquid mixture when left undistrubed is called sedimentation.
    The solid which settles at the bottom is called sediment while the clear liquid above it is called supernatant liquid.
    The process of pouring out the clear liquid, without disturbing the sediment, is called decantation.
    Example : A mixture of sand and water.
  4. Solvent extraction method : This method is used when one of the solid components is soluble in a liquid.
    Example : A mixture of sand and salt can be separated by this method. Salt gets dissolved in water while sand settles down in the container. The salt solution is then decanted. Salt is separated from the solution by evaporation. In this way, they can be separated.
  5. Magnetic separation : This method is used when one of the components of the mixture is iron. Iron gets attracted towards a magnet and hence can be separated. Mixtures of iron and sulphur, iron and sand, etc., can be separated by moving a magnet over them. Iron gets attached to the magnet and is separated.
  6. By using a separating funnel : It is a simple device used to separate the components of a liquid-liquid heterogeneous mixture.
    Example : Kerosene oil and water. The mixture is placed in a separating funnel and allowed to stand for sometime. The components form two clear layers. Water being heavier forms the lower layer and oil being lighter forms the upper layer. When the stopper of the funnel is opened, the heavier liquid trickles out slowly and is collected in a vessel. The stopper is closed when the bottom layer is entirely removed the funnel. In this way, the two liquids are separated.
  7. Fractional distillation : The process of distillation is used for separating the components of a homogeneous liquid-liquid mixture, like water and alcohol. This is based on the fact that alcohol boils at a lower temperature than water. The vapour of alcohol are collected and cooled while water is left behind in the original vessel. Thus, two liquids having different boiling points can be separated by distillation provided that difference in their boiling points must be 25 °C or more.

OBJECTIVE TYPE QUESTIONS

Question 1.
Fill in the blanks:
Answer:

  1. Elements are made up of same kind of atoms.
  2. Elements and compounds are pure substances.
  3. In a mixture the substances are not combined chemically.
  4. Clay is separated from water by the method called loading and decantation.
  5. Crystallisation is a process to obtain a very pure form of a solid dissolved in a liquid.
  6. Camphor and ammonium chloride can sublimate.

Question 2.
Give one word answers for the following :
Answer:

  1. The solid particles which remain on the filter paper after the filtration residue.
  2. The liquid which evaporates and then condenses during the process of distillation distillate.
  3. The process of transferring the clean liquid after the solid settles at the bottom of the container decantation.
  4. The process by which two miscible liquids are separated fractional distillation.

MULTIPLE CHOICE QUESTIONS

Select the correct alterative from the choices given for the following statements:
Question 1.
A pure liquid is obtained from a solution by :
Answer:

  1. evaporation
  2. distillation
  3. Alteration
  4.  crystallisation

Question 2.
Components of crude petroleum can be separated by :
Answer:

  1. distillation
  2. evaporation
  3. filtration
  4. fractional distillation

Question 3.
Example of a homogeneous mixture is :
Answer:

  1. tap water 
  2. distilled water
  3.  sand and water
  4. water and oil

Question 4.
In chromatography the filter paper is :
Answer:

  1.  stationary phase 
  2. mobile phase
  3. mixture
  4. none of the above

Question 5.
A set of mixture is :
Answer:

  1.  ink, honey, icecream, milk
  2. tapwater, gold, common salt, alloy
  3.  milk, brass, silver, honey
  4. butter, petroleum, tapwater, iron

 

Selina Concise Biology Class 7 ICSE Solutions – Allergy

by

Selina Concise Biology Class 7 ICSE Solutions – Allergy

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 7 Biology. You can download the Selina Concise Biology ICSE Solutions for Class 7 with Free PDF download option. Selina Publishers Concise Biology for Class 7 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 7 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 7 Biology Chapter 7 Allergy

Review Questions

Question 1.
Define the term “allergy”.
Answer:
Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to something in the environment that usually causes no adverse effects to most people. These diseases include hay fever, dermatities, asthma, food allergies, etc.

Question 2.
Name the inflammatory chemical released by the basophils causing skin reaction and construction of the bronchioles.
Answer:
The histamine causes inflammation, skin rash and constriction of the bronchioles (as in asthma).

Question 3.
How the allergy causing chemical is naturally removed from the body ?
Answer:
There are no permanent cure for an allergy. Medication for allergies do give relief. Those people prone to allergic reactions should be aware of the allergens that trigger these responses in their bodies and avoid them completely, especially food and medicines. Allergy shots are helpful to those with seasonal allergies like those caused by pollen.

4. Match the items given under column I with those given under column II.
column I                                         column II
Selina Concise Biology Class 7 ICSE Solutions - Allergy 1
Answer:
              column I                                         column II
Selina Concise Biology Class 7 ICSE Solutions - Allergy 2
Question 5.
Name any three routes of which allergens normally enter in our body.
Answer:

  1. Skin — Substances that come into contact with the skin, such as latex, are also common causes of allergic reactions, known as contact dermatitis or eczema.
  2. Mouth — A wide variety of foods can cause allergic reactions, but 90% of allergic responses to foods’are caused by cow’s milk, soy, eggs, wheat, peanuts, tree nuts, fish and shellfish.
  3. Nose — Pollen, spores, dust particles and certain chemicals find entry through the nose.

Question 6.
What are allergens ? Name any three allergens.
Answer:
The substances that cause allergies are called allergens.

  1. Dust particles
  2. Nuts
  3. Pollen

Question 7.
Name the two tests generally used to diagnose allergy and describe any one of them.
Answer:

  1. Prick Test—Skin prick test is also known as “puncture testing” or “prick testing” due to the series of tiny punctures or pricks made into the patients skin. A small plastic or metal device is used to puncture or prick the skin. Sometimes, the allergens are injected intradermally into the patients skin, with a needle and syringe. Small amounts of suspended allergens or their extracts (e.g., pollen grain, insect sting proteins, peanut extracts) are introduced to sites on the skin marked with pen or dye. Common areas for testing include the inside of forearm and the back.
  2. Blood Testing — A sample of the patient’s blood is sent to a laboratory for analysis. Multiple allergence can be detected with a single blood sample.
    The test measures the concentration of specific antibodies in the blood. The quantitative allergy blood result can help determine what a patient is allergic to, help predict and follow the disease development, estimate the risk of a severe reaction, and explain cross-reactivity.

Question 8.
Which test is mostly favoured for testing allergy, prick test or blood test ? Why ?
Answer:
Blood test is mostly favoured for testing allergy.

Blood Testing — A sample of the patient’s blood is sent to a laboratory for analysis. Multiple allergence can be detected with a single blood sample.
The test measures the concentration of specific antibodies in the blood. The quantitative allergy blood result can help determine what a patient is allergic to, help predict and follow the disease development, estimate the risk of a severe reaction, and explain cross-reactivity.