BY

RASUL KHAN
HAZRATH SEYYID MADANI ENGLISH MEDIUM SCHOOL, ULLAL.

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S.N TOPIC EXAM PAGE.NO

I-SEMESTER

1 FA -1 3 - 15
LIFE PROCESS

2 FA -2 15 - 22
CONTROL AND COORDINATION

II - S E M E S T E R

FA – 3 23 - 33
3 HUMAN REPRODUCTION

4 FA – 4 34 - 40
HEREDITY

FA – 4 41 - 46
5 OUR ENVIRONMENT

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 LIFE PROCESS

NUTRITION
What are the differences between autotrophic nutrition and heterotrophic
nutrition?
Autotrophic nutrition Heterotrophic nutrition
In which organic food is obtained
1 In which organic food is manufactured.
from various sources.
chlorophyll is required chlorophyll is Not required
Food is generally prepared during day
Food can be prepared at all times
time.
Ex : green plants and some bacteria Ex :All animals and fungi
Write Equation of Photosynthesis?

Write the event occurs during Photosynthesis?

 Absorption of light energy by chlorophyll.
3  Conversion of light energy to chemical energy.
 Splitting of water molecules into hydrogen and oxygen.
 Reduction of carbon dioxide to carbohydrates.
What are the necessary conditions for autotrophic nutrition and what are
its by-products?
4
Conditions: absorption of solar energy, and take CO2 and water.
By products : Glucose, O2 and water
What are Stomata? Write its function.
Tiny pores present on the surface of the leaves.
5 Functions:
 Exchange of gases O2/CO2
 Helps in transpiration.
Explain the function of guard cell?
 The opening and closing of the pore is a function of the guard cells.
6  The guard cells swell when water flows into them, causing the stomata
pore to open.
 Similarly the pore closes if the guard cells shrink.

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 Observe the given below figures :

7
a) Which figure indicates the massive amount of exchange of gases? Why?
b) Name the parts X and Y. What is the function of other part X?
a) Fig. (i) : because the stomata pore is open
b) X — Guard cell, Y — Stomata pore.
Function of guard cell: Regulates opening and closing of stomata pore.
Explain the process of exchange of gases that take place through stomata in
plants.
 In plants the large intercellular spaces and all the cells are oftenly in contact
8
with air;
 Due to this CO2 and oxygen are exchanged by diffusion.
 This means Gases can go into cells and away from them and out into the air.
Draw the diagram showing the open stomata pore. Label the following parts:

i) Chloroplast ii) Guard cell.

Note :
 Carbohydrates are utilised for providing energy to the plant.
 The carbohydrates which are not used immediately are stored in the form of
10
starch,
 Nitrogen is an essential element used in the synthesis of proteins and other
compounds.

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 TRANSPORTATION
What are the components of the transport system in highly organised
plants?
11
 Xylem : transports water and mineral ions.
 Phloem: conducts food from leaves to other parts of plants.
Write the difference between Xylem and Phloem? (June 2023)

Xylem Phloem
Conducts water and minerals Transport food
12
Transport only in Upward direction Transport Both upward and
downward directions.
Works by suction pressure Works by Osmotic pressure
What is Transpiration?
13 The loss of water in the form of vapour from the aerial parts of the plant is
known as transpiration.
How does transportation of water take place over the heights in a plant?
 At the roots, cells in contact with the soil actively take up ions.

 This creates a difference in the concentration of ions between the root

and the soil.

14
 Water moves into the root from the soil to eliminate this difference.

 There is a steady movement of water into root xylem.

 Evaporation of water molecules from the leaves creates a suction

which pulls water from xylem cells of root.

Explain the advantages of transpiration in plants?

 Transpiration helps in the absorption and upward movement of water
15
and minerals from roots to the leaves.
 It also helps in temperature regulation.
How does transpiration help in upward movement of water from roots to

leaves?
16
 Evaporation of water molecules from the cells of a leaf creates a

suction force which pulls water from the xylem cells.

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 What is Translocation?
17
Transport of soluble products of photosynthesis is called translocation.
Explain the transportation (Translocation) of food (product of photosynthesis)
takes place in phloem.

 Translocation takes place in sieve tube, with the help of companion

cell, both in upward and downward directions.
18  Sucrose is transferred into phloem using energy from ATP.
 This increases the osmotic pressure of the tissue causing water to
move into it.
 It helps to move the materials from phloem to other tissues of having
low pressure.

EXCRETION
What are the methods used by plants to get rid of excretory products?
 Excess of water removed by transpiration.
 Remove oxygen and carbon dioxide gases through stomata.
19
 Resins and gums get store in old xylem.
 Diffusing certain wastes into surrounding soil.
 Leaves fall off that store waste products in them.

NUTRITION

What is the role of saliva in the digestion of food?

20  The saliva contains an enzyme called salivary amylase that breakdown starch
which is complex molecule to give simple sugar.
What is the function of digestive enzymes?
The digestive enzymes convert
21  proteins to amino acids
 complex carbohydrates into Glucose
 Fat into fatty acids and glycerol.
Which enzymes of pancreas help in efficient digestion of protein?
22
Trypsin and chymotrypsin.

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 Explain the digestion of food materials in stomach and small intestine.
Stomach :

 Gastric glands present in the wall of the stomach release hydrochloric acid,
pepsin and mucus.
 Hydrochloric acid creates an acidic medium which facilitates the action of
pepsin.

23  Pepsin digests protein.

 The mucus protects the inner lining of the stomach from the action of the acid
under normal conditions.

Small intestine :

 It receives pancreatic juice and bile juice. Bile juice makes the food alkaline.
 Bile salts emulsify the fats in the small intestine.
 Trypsin helps to digest the proteins.
Name the two glands, which secretes Amylase enzyme.
24
Salivary glands and pancreas.
Why does herbivores have longer, small intestine than carnivores?
25  Herbivores need a longer small intestine to digest cellulose.
 Meat is easier to digest; hence carnivores have a shorter small intestine.
How are fats digested in our bodies? Where does this process take place?
 Fats are digested in the small intestine.
 The small intestine gets bile juice and pancreatic juice.
26
 The bile salts break down the large fat globules into smaller globules.
 This is referred to as emulsification of fats.
 It takes place in the small intestine.
Bile juice does not have any digestive enzyme but still plays a significant
role in the process of digestion. Justify the statement.
 Bile juice makes the acidic food coming from the stomach alkaline for the
27
action of pancreatic enzymes.
 Bile salts break the large globules of fat in the intestine to smaller globules
increasing the efficiency of enzyme action.
What is the role of the following enzymes in human alimentary canal?
28 i) Trypsin: Digests proteins present in food.
ii) Lipase: Breaks down emulsified fats.

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 What are villi? Write its function.
 The inner lining of the small intestine has numerous finger-like projections
called Villi.
29
 It increases the surface area for absorption.
 The villi are richly supplied with blood vessels which take the absorbed food to
each and every cell of the body.
What is emulsification? What are its significations?
 The process of breakdown of larger fat droplets into smaller droplets of fat with
30
the help of bile salts present in bile juice.
 It helps to increase the surface area for enzyme action.

RESPIRATION
What are the differences between aerobic and anaerobic respiration
Aerobic respiration Anaerobic respiration
It takes place in the presence of O2 It takes place in the absence of O2.
31
Energy released is more Energy released is less
Produce carbon dioxide, water, and Produce ethanol, carbon dioxide and
energy are energy.
What are the different ways in which glucose is oxidised to provide energy in
various organisms?
Answer :
 Absence of oxygen ( An aerobic respiration):

→ →

32  Presence of oxygen ( aerobic respiration):

→ →

 Lack of oxygen :

→ →

Which molecule is formed during the first step of cellular respiration by the
33 breakdown of glucose molecule in cytoplasm?
Pyruvate.
Which acid responsible for the cramping of muscles?
34
Lactic acid.

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 What is Pyruvate? Where this process does takes place?
35 The break-down of glucose, a six-carbon molecule, into a three-carbon molecule
called pyruvate. This process takes place in the cytoplasm.
The rate of breathing in aquatic organisms is much faster than that seen in
terrestrial organisms. Give reason.
36
The amount of dissolved oxygen is fairly low compared to the amount of oxygen in
the air.
What advantage over an aquatic organism does a terrestrial organism have
with regard to obtaining oxygen for respiration?
 Terrestrial animals can breathe the oxygen in the atmosphere,
37  But aquatic animals need to use the oxygen dissolved in water.
 This oxygen is absorbed by different organs in different animals.
 All these organs have a structure that increases the surface area which is in
contact with the oxygen-rich atmosphere.
Why is it advisable to breathe through nose?
38 There are fine hair and mucus gland in the inner lining of nose which filter the
incoming air of germs and dust.
Rings of cartilage are present in the throat. Give reason?
39
These ensure that the air-passage does not collapse.
Explain the structure and function of alveoli.
Structure of alveoli:
 These are balloon like structures.
40  The walls of the alveoli contain an extensive network of blood-vessels.
Function:
 Alveoli absorb oxygen and give up carbon dioxide.
 These provide a surface where the exchange of gases can take place.
How are the lungs designed in human beings to maximise the area for
exchange of gases?
 Alveoli are the site for exchange of gases.
 The alveoli provide a surface where the exchange of gases can take place.
41
 The air that is rushed inside the lungs fills the numerous alveoli present in
the lungs.
 These numerous alveoli increase the surface area for gaseous exchange
making the process of respiration more efficient.

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 How is oxygen and carbon dioxide transported in human beings?
 The respiratory pigment is haemoglobin which has a very high affinity for
oxygen.
42
 This pigment is present in the red blood corpuscles.
 Carbon dioxide is more soluble in water than oxygen.
 Hence is mostly transported in the dissolved form in our blood.
Name the respiratory pigment in human beings? What is its role?
OR Explain briefly the role of haemoglobin pigments present in our blood.
43
 Haemoglobin is present in red blood cells.
 Haemoglobin has affinity for O2 thus helping in its transport.

TRANSPORTATION

What is Plasma? Write its functions.

 Blood consists of fluid medium called plasma.
44
 Plasma transports food, carbon dioxide and nitrogenous wastes in dissolved
form.
Write the important components and their functions of blood.
i) Plasma: Plasma transports food, carbon dioxide and nitrogenous wastes in
dissolved form..
ii) Red blood corpuscles: helps in the transportation of oxygen and carbon
45
dioxide.
iii) White blood corpuscles: helps in protection by destroying disease causing
micro organisms
iv) Blood platelets: helps in the clotting of blood.
In humans, how is the digested food absorbed by the blood?
46
 Absorbed by finger like projections Villi present in small intestine.
What is double circulation of blood in human beings?
47 Blood goes through the heart twice during each cycle. This is called double
circulation of blood.
Mention the importance of double circulation in our body.

 It ensures efficient supply of oxygen to the body.

48  Helpful to supply more energy.
 To maintain body temperature.

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 Draw the diagram showing the schematic sectional view of the human heart.
Label the following parts.

49

Explain the stages of „double circulation‟ of the blood in humans.

Transportation of blood in heart :
i) Oxygen-rich blood from the lungs comes to the left atrium.

ii) When the left atrium relaxes and contracts then blood gets transferred to left

ventricle

50 iii) When the left ventricle contracts the blood is pumped out to the body through

aorta.

iv) De-oxygenated blood comes from the body to the right atrium.

v) As the right atrium contracts the blood get transferred to the right ventricle.

vi) On contraction of right ventricle the blood go to the lungs for oxygenation.

Oxygenated and deoxygenated bloods are separate in the heart of mammals

51 and birds. Why?
Since they need more energy to maintain their body temperature constant.
What would be the consequences of deficiency of haemoglobin in our
52 bodies?
Ans: Anaemia.

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 Give reasons.
 Ventricles of the human heart have thick wall.
Since ventricles have to pump blood into various organs.
53  Arteries are thick walled and elastic?
Arteries receive the blood pumped by heart with lots of pressure.
 Veins do not required thick walls.
Because the blood is no longer under pressure
“The body temperature of frogs and lizards depend on temperature in the
environment.” Justify.
 Both frogs and lizards have three chambered heart
54
 Oxygenated and deoxygenated blood mix in the heart.
 Production of energy became slightly less.
 This energy cannot be used for maintaining constant temperature.
How the functions of arteries, veins and capillaries are interrelated in the
circulation of blood?
 Arteries carry blood away from the heart to various organs of the body.
55  Exchange of material between the blood and surrounding takes place
across the thin wall of smallest vessels, the capillaries.
 The capillaries then join together to form veins.
 Veins collect the blood from different organs and bring it back to the heart.
What is Lymph?
56 Lymph is the colourless fluid containing lymphocyte, which fights against
infections
Write the difference between blood and lymph?
Blood Lymph
57 Blood transports oxygen It removes waste from the system.
red in colour and colourless
contains more protein contains less protein
Write the functions of Lymph?
58  Lymph carries digested and absorbed fat from intestine.
 It helps in production of antibodies.
What is the function of valves in human heart?
59 Valves ensure that blood does not flow backwards when the atria or ventricles contract.

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 List out any three differences between arteries and veins.
Arteries Veins
60 Carry oxygen-rich blood away from the Carry deoxygenated blood towards
heart except pulmonary artery. The heart except pulmonary vein.
Have thick, elastic walls Thin walled
Write one function each of the following components of the transport
system in human beings i) blood vessels ii)blood platelets iii) Lymph
iv)Heart
61 a. Blood vessels: transport of blood.
b. Blood platelets: clotting of blood
c. Lymph: carries digested fats
d. Heart: pumps blood to all parts.
How is the structure of human heart supportive in transporting oxygenated
blood and deoxygenated blood? Explain. (June 2023)
Human heart:
 Has different chambers
62
 The valves present in between the chambers prevent backward flow of blood
 Separated by dividing wall septum
 Septum is responsible for creating separate pathways to transport oxygenated
and deoxygenated blood.
Schematic representation of blood circulation in the mammals is given
below :

63

i) Name the blood vesseles „x‟ and „y‟ (MARCH 2024)

ii) Which blood vessel has valves?
Ans. : i) Artery Vein
ii) Vein has valves

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 EXCRETION
What is excretion?
64 The biological process involved in the removal of these harmful metabolic wastes
from the body is called excretion.
Name the organs that are part of the human excretory system.
 a pair of kidneys
65  a pair of ureters
 a urinary bladder
 a urethra.
Where are the kidneys located in the human body?
66
Kidneys are located in the abdomen, one on either side of the backbone.
Which of the following shows the correct path of urine flow in humans?
67
Kidneys → Ureters → Urinary bladder → Urethra
What is the composition of urine?
68
The urine contains mainly water, various salts, urea and uric acid.
What is Nephron?
69
Structural and functional unit of a kidney is called Nephron.
Briefly explain the formation of urine in nephrons.
 Filtration of blood from capillaries present in cuplike structure of nephron
70  Re-absorption of glucose, amino acids, salts and excess of water by long
tubule of nephron from filtrated fluids.
 Formation of urine by remaining water and salts.
Nephrons are called fundamental functional units of excretory system.
71 Kidney consists of large number of nephrons which filter nitrogenous waste such
as urea or uric acid from blood.
Explain the structure and function of nephron?
 Structure of Nephrons:
Each kidney has large numbers of filtration units called nephrons packed
close together.
72 Function:
 Blood is reaching kidneys by renal artery.
 Here filtration takes place.
 By this glucose, Amino acid and salts are reabsorbed.

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 Draw the diagram to show the structure of nephron.

73

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ANIMALS-NERVOUS SYSTEM

1 What is synapse?
A small gap between two adjacent neurons is called synapse.
2 What is Neuron?
It is the structural and functional unit of nervous system
3 Explain the Structure and function of Neuron :
Dendrite: Acquires information.
Cell body: Acquired information travels as an electrical impulse.
Axon: It transmits electrical impulse from cell body to dendrite of next neuron.
4 The correct path of movement of electrical impulse in a neuron is
Ans. : (A) Dendrite → Cell body → Axon → nerve end
WHAT HAPPENS IN REFLEX ACTIONS?

5 “A person immediately starts running soon after observing a snake.” The

correct transmission path of reflex impulse in this situation is
Receptor → Sensory neuron → Spinal cord → Relay neuron → Motor neuron →
Effector
6 What is reflex action? Which is the centre of reflex action?
An automatic and rapid response to a stimulus is called reflex action. It is
controlled by spinal cord.
7 What is reflex arc?
The pathway taken by nerve impulses in a reflex action is called reflex.
8 Which signals will get disrupted in case of a spinal cord injury?
Reflex actions will be disturbed
9 “We withdraw our leg when stepped on thorn unknowingly.”
(a) Trace the sequences of events which occur in this action.
(b) Which part of human nervous system controls this action?
 Receptors receive the stimulus of pain
 Messages reach spinal cord through sensory neuron.
 Then it goes to brain.
 Brain sends the impulse to the motor neuron in which muscles withdraw
the leg.
(b) Spinal cord / reflex arc.

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10 Trace the sequence of events which occur in our body when a bright light
is focussed on your eyes.
 The receptor cell receives the stimulus and an impulse is generated.
 This impulse is passed on to sensory neuron,
 Then it goes to brain,
 Brain sends the impulse to the motor neuron which contracts the pupil.
11 Name the given structure. What is its general function? Mention the
function of the parts labelled as A and B. These structures in animals are
said to be efficient ways to give quick responses. Why ?

 Reflex arc.
 It gives sudden action in response to the event happening in the
environment.
 A) Sensory neuron : It conducts the impulse of stimulus from receptor to
 B) Effectors: This shows the sudden visible response.
 Reflex arcs have evolved in animals because the thinking process of brain is
not fast enough in many animals.
 Meanwhile many animals have very little of the complex neuron network
needed for thinking.
 So it can function in the absence of true thought process and increase the
chance of survival.
12 „Reflex arcs are considered as more efficient for quick responses.‟ Justify.
The thinking process of the brain is not fast enough. As the response by the
reflex arc is very quick it’s functioning is more efficient.
13 Compare and contrast nervous and hormonal mechanisms for control and
coordination in animals.
Nervous mechanism Hormonal mechanism

It is a fast process. It is a slow process.

Growth is not affected. Growth is affected.

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14 What is the difference between a reflex action and walking?

Reflex action Walking

It is an involuntary action. It is a voluntary action

It is controlled and coordinated by Brain instructs and controls leg

spinal cord. muscles to move.
15 How are involuntary actions and reflex actions different from each other ?

Involuntary action Reflex action

actions which occur immediately it is an immediate response to an

without any thinking event which does not require any
processing by brain.
It is controlled by mid and hind Reflex actions are controlled by
brain. spinal cord.

HUMAN BRAIN
16

17 Which part of the human brain controls the following activities?

i) Involuntary activities : Medulla
ii) Thinking process : Cerebrum
iii) Posture and balance of the body : Cerebellum

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18 List the functions of the following parts of the brain:
Cerebrum (Fore brain)
1) It is the main thinking part of brain.
2) It is responsible for reasoning, speech intelligence, sight, and hearing.
Medulla (Hind brain)
1) It controls involuntary actions such as breathing, blood pressure,etc.
2) It regulates reflex responses like salivation and vomiting
Cerebellum
 It maintains posture and equilibrium of the body
 It is responsible for the precision of voluntary actions.
19 Imagine the following situations:
(i) Clapping at the end of a programme
(ii) Fluctuating blood pressure in the body.
How these situations are functionally different? Give reason.
(i) Voluntary action :
 Based on deciding what to do next.
 Controlled by forebrain.
(ii) Involuntary action :
 Action without thinking control
 Controlled by hind brain.
20 How muscle cells respond for a nerve impulse?
 Muscle cells receive nerve impulses from neurons.
 Muscle cells convert received electric impulses into chemical signals.
 Then the special proteins in the muscle cells change their shape and
arrangement
 Due to this new arrangement of proteins the muscle cells either elongate or
become short.
21 Compare the protective structures of the brain and the spinal cord.
 The brain sits inside a bony box.
 Inside the box, the brain is contained in a fluid-filled balloon which
provides further shock absorption.
 Spinal cord is protected by the vertebral column.

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 COORDINATION IN PLANTS

22 What are phytohormones? Name phytohormone that promote growth and

inhibits the growth.
Chemical compounds that help to coordinate growth, development and
responses to the environment.
Phytohormones that promote growth :
 Auxins
 Gibberellins
 Cytokines.
Phytohormones that inhibits the growth :
Abscissic acid
23 What is meant by tropic movements?
Directional movements of specific part of a plant in response to external stimuli

MOVEMENT DUE TO GROWTH

24 Define the following terms:

1) Phototropism: The movement of plant parts in response to light.

2) Geotropism: The movement of plant parts in response to gravity.

3) Hydrotropism: The growth of the plant in response to water

4) Chemotropism: The growth of plant in response to chemical stimulus.

Ex: Growth of pollen tube towards ovules during fertilization.

25 Write one example each of the following tropic movements:

(i) Positive phototropism: Growth of the shoot towards light.

(ii)Negative phototropism: Growth of the root away from light.

(iii) Positive geotropism: Growth of the roots towards earth.

(iv)Negative geotropism: shoots growing away from the earth.

(v) Hydrotropism: Growth of the roots towards water.

(vi)Chemotropism: growth of pollen tubes towards the ovules.

26 The folding up of leaves of sensitive plant (touch-me-not plant) on

touching with a finger is not a tropism. Why?
Ans: This movement is independent of growth and non-directional.

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27 List the functions of the following plant hormones.
1 Auxins: - It helps cells to grow longer.

- It helps in the bending of stem towards light.

2 Gibberellins: - It helps in the growth of stem.

3 Cytokines: - It promotes cell division

- It helps in rapid cell division in fruits & seeds.

4 Abscissic acid: - It inhibits the growth including wilting of leaves

28 How do auxins promote the growth of a tendril around a support?

 When the tip of a tendril touches a support, the auxins present in it move to
that side of tip which is away from the support.
 Auxins promote growth.
 Due to more auxins in it, the side of tendril away from the support grows
rapidly.
 It makes the tendril twirl (or bend) around the support.
29 When a plant receives light from one direction then the plant appears to
bend towards the direction of light. Analyse the reason for this response.
 When growing plants detect light, a hormone called auxins, synthesized at
the shoot tip, helps the cells to grow longer.
 When light is coming from one side of the plant, auxins diffuses towards
the shady side of the shoot.
 This concentration of auxins stimulates the cells to grow longer on the side
of the shoot which is away from light.
 Thus, the plant appears to bend towards light.
30 As the growth advances in a climbing plant (creeper) that appears as the
plant is moving towards a particular direction. How?
 For a touch, when the tendrils of creeper plants come in contact with a
support, the plant circles around it and grows faster.
 When tendrils get attached to a support then, tips of the plant synthesise
auxins hormone at higher concentration and stimulates the elongation of
cells.
 Then the plant shows growth towards light.

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31 How does „touch-me-not‟ plant respond to touch? Explain.
 The parts of the plants that are being touched use electro-chemical
impulses for a movement.
 For this movement plant cells change their shape by changing the amount
of water in them.
 As a result of this change plant cells either swells or shrinks and therefore
change the shape of leaves.

HORMONES IN ANIMALS

32 Why hormones are called chemical messengers?

The hormones secreted from endocrine glands reach the target organs through
the blood And stimulate particular function. Hence, hormones are called
chemical messengers.
33 List the important hormones and functions of the following glands.

Hormones Endocrine gland Functions

Growth hormone Pituitary gland Stimulates growth in all organs
Thyroxin Thyroid gland It regulates metabolism in the body.
Insulin Pancreas: Function: regulates the blood sugar
level.
Testosterone Testis Functions: It helps in growth of
secondary sexual characters in
male.
Helps in the formation of sperms
Oestrogen Ovaries: It controls menstrual cycle.

Adrenaline Adrenal gland: Preparing the body to face

emergency situation
34 Why iodized salt is advisable?
Because iodine mineral is essential part of thyroxin hormone secreted by
thyroid gland. Its deficiency causes a disease called goitre.
35 What is Diabetes? How is it caused? How it can be cured?
 Disease in which blood sugar level increase.
 Cause: Due to the deficiency of insulin hormone.
 it can be controlled by injecting insulin hormone

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36 A person‟s face has become pale and his breathing rate has increased due
to fear. Analyse the process which enables the person to deal with this
situation.
 Adrenaline is directly secreted into the blood. The blood to the skin is
reduced due to contraction of muscles around small arteries.
 The breathing rate increases because of the contractions of the
diaphragm and the rib muscles.
 The heart beats faster, resulting in supply of more oxygen to the muscles
37 Note :
If there is a deficiency of growth hormone in childhood, it leads to dwarfism.
38 Name the mineral required for the production of thyroxin hormone. What
are the functions of this hormone?
 Iodine
 For the production of required quantity of thyroxin by thyroid glands.
 Thus, to control the possibility of having goitre disease
 To regulate metabolic activities
 To provide a best balance for body growth.
39 a) Which hormone is produced by having iodine rich salt in our diet ?
Mention the gland that secretes this hormone.
b) Which disease is caused due to the deficiency of iodine in our diet ?
Write one symptom of this disease.
a) Thyroxin.
Gland — Thyroid
b) Goitre
Symptom : Swollen neck, reduced rate of metabolism
40 How does our body respond when adrenaline is secreted into the blood?
 The heart beats faster, resulting in supply of more oxygen to our muscles. 2
 The blood to the digestive system and skin will be reduced due to the
contraction of muscles around small arteries in these organs.
 This diverts the blood to our skeletal muscles.
 The breathing rate also increases because of the contractions of the
diaphragm and the rib muscles.

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 DO ORGANISMS CREATE EXACT COPIES THEMSELVES?
1 What is the basic event of reproduction?
Creation of a DNA copy.
2 When a cell reproduces, what happens to its DNA?
DNA replication occurs which forms two similar copies of DNA.
3 What is DNA replication?
The process of giving rise to new DNA from the DNA of mother cell during
interphase of cell division.
4 How does re-establishment of chromosome number occur in sexual
reproduction?
 Chromosome number is reduced to half by meiotic cell division in sex cells.
 During sexual reproduction when male and female gametes fuse, the original
number of chromosomes will be re-established.
5 What is the importance of DNA copying in reproduction?
 It maintains the characteristics of species.
 It maintains the continuity of life.
 It produces variations.
6 Why is variation beneficial to the species but not necessarily for the
individual?
 It lets a species adapt to the changing environment.
 Variations make differences in generation which leads to evolution.
 Variations at individual level will not help in evolving, but would result in
ageing.
 So variation from any source in an individual can be harmful.
7 Newly formed DNA copies may not be identical at times. Give one reason.
Because the process of copying the DNA leads to some variations each time.
8 What is DNA copying?
DNA copying is the production of similar copies of DNA present in a cell using
various chemical reactions.

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9 “The consistency in DNA replication during reproduction is very
important.” Justify.
 The consistency of DNA copying during reproduction is important for
maintenance of body design features that allow the organism to use that
particular niche [area where organisms live].
 Reproduction is linked to the stability of population of species.
10 List two ways due to which variations arise in a population.
1. Errors in DNA copying mechanism
2. Sexual reproduction
11 State the importance of variation.
1. Helps a species to survive
2. Helps an organism to adapt to the changing environment
3. Forms the basis of evolution
12 How can DNA copying be decided as one of the ways of reproduction in
lower organisms?
Two genetically identical daughter cells are produced by the division of nucleus.

MODES OF REPRODUCTION USED BY SINGLE ORGANISMS

13 Write the difference between sexual reproduction and asexual reproduction.
Sexual Reproduction Asexual Reproduction
Two parents (male and female) involved Only one parent involved
Gametes are formed Gametes are not formed
Zygote is formed Zygote is not formed.
14 What is asexual reproduction? Name the type of asexual reproduction that
takes place in the following.
Answer :
 Production of young ones without fusion of gametes.
 Binary fission : Amoeba, Paramecium, Leishmania.
 Multiple fission : Plasmodium
 Fragmentation : Spirogyra
 Regeneration : Planaria
 Budding : Hydra and Bryophyllum
 Spore formation : Rhizopus

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15 What is fission?
The parent cell divides into two or more daughter cells.
16 Write the difference between binary fission and Multiple fission.
Binary Fission Multiple Fission
One cell splits into two equal One cell divides into many daughter
halves cells simultaneously
Generally seen during favourable Generally occurs in unfavourable
conditions conditions or in parasitic forms
Ex: Amoeba, Paramecium Ex : Plasmodium (malarial parasite)

17 Name the causative agent of the disease “kala- azar” and its mode of
asexual reproduction.
 Leishmania.
 It reproduces asexually by binary fission.
18 What is fragmentation? Give an example.
The organism breaks-up into smaller pieces upon maturation, each piece
develops into new individual. E.g., Spirogyra
19 What is Regeneration? Give an example.
If organism is somehow cut or broken into many pieces, each piece grows into a
complete organism. E.g., Planaria, Hydra.
20 Explain the process of reproduction in hydra.
 Reproduction is by budding.
 A bud develops as an outgrowth due to repeated cell division at one specific
site.
 The bud develops into an independent individual.
21 What happens to the bud once it becomes fully mature?
It detaches from the parent body and becomes a new independent individual.
22 What is vegetative reproduction? What are its advantages?
The development of new plants from the parts like root, stem and leaves under
appropriate conditions are called vegetative propagation.
Advantages
 These plants can bear flowers and fruits earlier than those produced from
seeds.
 Plants are genetically similar to the parent plant.

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23 „Regeneration is not reproduction‟. Justify this statement with reason.
When a piece is cut from an organism, it grows into complete organisms.
Regeneration is carried out by specialized cells. It is not reproduction since
most organisms would not be able to grow through pieces.
24 How the process of budding in hydra is different from Bryophyllum?
 In hydra, a bud develops at one specific site.
 These buds when fully mature detach from the parent body and become new
independent individuals.
 In Bryophyllum, buds are produced in the notches along the leaf margin.
 These buds fall on the soil and develop into new plants.
25 Name an organism which reproduces by spore formation.
Rhizopus reproduces by the method of spore formation.
26 Describe reproduction by spores in Rhizopus.
 Rhizopus reproduces by spore formation.
 During the growth of Rhizopus, small rounded, bulb-like structures develop
at the top of the erect hyphae. Such structures are called sporangia.
 Sporangia contain cells, or spores, that can eventually develop into new
Rhizopus individuals.
27 Name the reproductive and Non-reproductive part of Rhizopus .
Reproductive part – Sporangia
Non-reproductive part – Hypha/Hyphae

SEXUAL REPRODUCTION
28 Part of a flower in the plant that develops into fruit is
Ans. : — ovary
29 Write the function of the following parts of a bisexual flower : (1) stigma (2)
pollen tube and (3) anther
(1) Stigma: To trap pollen grains.
(2) Pollen tube: To transfer male gamete to female gamete.
(3) Anther: To produce pollen grains.

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30 Name the (1) future shoot and (2) future root of a germinating seed.
(1) Plumule (2) Radicle
31 Name the parts of the flower that develop into (1) seed and (2) fruit after
fertilization.
(1) Ovule (2) Ovary
32 Name a part of the flower which
(i) Persists even after a fruit is formed. Answer :Sepals
(ii) Attracts insects for pollination. Answer : Petals
(iii) produces pollen grains and Answer : Anther
(iv) Changes into seed after fertilisation. Answer : Ovule.
33 After pollination, how does a male germ cell reach the ovary ?
Mention the significance of this event
• Through the pollen tube.
• Male germ cell fuses with female germ cell to produce a zygote.
34 Which specific part of the plant is used for sexual and asexual means of
propagation to produce a new plant?
Sexual – Seed
Asexual - Roots/stem/leaves.
35 Give one example of (i) a flower, and (ii) a fruit grown by vegetative
propagation.
(i) Rose/Jasmine
(ii) Grapes/orange/banana
36 Draw the diagram showing the germination of pollen on stigma.

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37 In the given figure of Cotyledon the parts labelled as A and B respectively are

Ans. : primary shoot, primary root

38 Differentiate between self-pollination and cross pollination.
 Transfer of pollen on the stigma of same flower is self-pollination.
 If the pollen is transferred from one flower to another, it is known as
crosspollination.
39 Observe the figures of flowers given below.

Name the types of pollination that can occur in these two flowers.
 Flower A : Self-pollination.
 Flower B : Cross pollination
40 How is the process of pollination different from fertilisation?
Pollination Fertilization
It is the transfer of pollen grain from It is the fusion of male gamete with

the anther to the stigma of flower female gamete (egg).

It leads to fertilization It leads to formation of seeds

It is an external process It is an internal process.

41 Write the difference between two types of flower.

Bisexual flower Unisexual flower
It contain both stamens and pistil It contains either stamens or pistil

Self-pollination Cross Pollination

E.g., Hibiscus, mustard. Ex: Papaya, watermelon.

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42 What are the changes that occur in flower after fertilization?(Seed formation)
 Pollen tube grows out of the pollen grain and travels through the style to reach
the ovary.
 Fertilisation takes place to produce zygote.
 The zygote divides several times to form an embryo within the ovule.
 The ovule develops a tough coat and is gradually converted into a seed.
 The ovary grows rapidly and ripens to form a fruit.
 The petals, sepals, stamens, style and stigma may shrivel and fall off.
REPRODUCTION IN HUMAN BEINGS
43 “Reaching to sexual maturation is an essential event with respect to
mammals like humans.” Substantiate this statement.
In males
 Development of testes helps to produce sperm.
 To have secondary sexual characters.
In females
 To cause menstrual cycle
 For the production and release of ovum
44 Give reason why:
(i) Testes are located outside the abdominal cavity.
Sperm formation requires a lower temperature than the normal body temperature
(ii) lining of the uterus becomes thick every month
To receive, nurture and nourish the growing embryo.
45 Explain the significant function of each structure in human male
reproductive system.
i) Testis:
• Formation of sperms.
• Secretion of testosterone.
ii) Scrotum:
They regulate temperature necessary for production of sperms.
iii) Urethra and vas deferens:
Transport sperm from testis.
iv) Prostate gland and seminal vesicle:
They add their secretion to make the sperm transport easier and provide nutrition.
v) Penis: Delivers the sperms to the site of ferliziation.

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46 In sustaining reproductive fertility of a person,
(a) position of the testis in the body
(b) secretion of the testosterone
(c) Secretion of the prostate gland are supplementary to each other. Explain
scientifically.
(a) Sperm formation requires a lower temperature than body temperature.
(b) Testosterone regulates the formation of sperm.
(c) Secretion of Prostate gland makes the transportation of sperm easier.
47 Name the glands which add their secretions to the sperms. List two functions
of these secretions.
 Prostate gland and seminal vesicle
 It provides nutrition to the sperms
 It makes the transport of sperms easier through the fluid medium.
48 How does uterus prepare to receive the fertilized egg in woman? What
happens if egg does not fertilise? Explain.
 Uterus prepares itself every month to receive fertilized egg.
 It makes its inner layer thick and spongy.
 If the egg is not fertilized, it lives for about one day.
 If fertilization doesn’t occur the lining slowly breaks and comes out through
the vagina as blood and mucous. ( Menstruation occurs )

49 What is the function of ovary and fallopian tube in human female

reproductive system?
Ovary :

 Formation of female germ cells or eggs.

 Secretion of Oestrogen.

Fallopian tube :

 Egg is carried from ovary to womb

50 How does a fertilized egg in the uterus develop into an embryo?

 The fertilised egg (Zygote ) starts dividing and forms an embryo.

 The embryo is implanted in the lining of the uterus.

 It continues to grow and develop organs to become foetus.

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51 Explain the structure and important role of placenta during gestation period
of woman. OR How does this embryo get nourishment in the mother‟s womb
? Explain. OR What is placenta? Write its function.
 Disc like tissue which is embedded in the uterine wall is called placenta.
 It supplies nutrients to developing embryo from mother’s blood.
 Removes the wastes generated from the embryo and drained into mother’s blood
52 Roles of the „uterus‟ and „placenta‟ are complementary to each other in the
development of a child. How ? Explain.
 Uterus is an elastic bag like structure where the embryo is implanted and
continues to grow and develop organs to become foetus.
 During pregnancy period the embryo gets nutrition from the mother’s blood
with help of disc shaped special tissue embedded in the uterine wall is called
placenta.
53 In humans, how the surgical contraceptive methods can be used to prevent
pregnancy?
 If the vas deferens in the man is blocked, sperm transfer will be prevented.
Fertilisation will not take place.
 If the fallopian tube in the woman is blocked, the egg will not be able to reach
the uterus. Fertilisation will not take place
54 Name the Sexually Transmitted Diseases (STDs):
Bacterial: Gonorrhoea and syphilis
Viral: Warts and HIV-AIDS
55 What is contraception? Explain the different methods of contraception.
Avoiding unwanted pregnancy is called contraception.
Methods of contraception
(a) Physical barrier
• Use of condoms, cervical caps and diaphragm.
(b) Chemical methods
• Use of oral pills
(c) Intrauterine contraceptive device (IUCD)
• Copper-T or loop is placed in uterus to prevent pregnancy.
(d) Surgical methods
• In males the vas deferens is blocked to prevent sperm transfer called vasectomy.
• In females, the fallopian tube is blocked to prevent egg transfer called tubectomy.

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56 Surgical method of contraception is better than oral method of
contraception. Why?
Since oral method change hormonal balances, they can cause side-effects. But
surgical methods are safe in the long run.
57 A woman is using a copper-T. Will it help in protecting her from sexually
transmitted diseases?
 Copper-T is a contraceptive method which prevents implantation of the zygote
inside the uterus.
 It cannot prevent a woman from sexually transmitted diseases.
58 Name the part of the human female reproductive system where
(i) fertilisation occurs and
(ii) Implantation of zygote takes place.
(i) Oviduct / Fallopian Tube
(ii) Uterus
59 Name the parts in the human female reproductive system where the following
functions take place :
(1) Maturation of eggs : Ovary
(2) Fusion of the egg and the sperm : Fallopian tube
(3) Implantation of the zygote : Lining of the uterus

EXERCISES
60 Asexual reproduction takes place through budding in
Answer: (b) Yeast
61 Which of the following is not a part of the female reproductive system in
human beings?
(a) Ovary (b) Uterus (c) Vas deferens (d) Fallopian tube
Answer: (c) Vas deferens
62 The anther contains
(a) sepals (b) ovules (c) carpel (d) pollen grains
Answer: (d) Pollen grains
63 What are the advantages of sexual reproduction over asexual reproduction?
 The offspring has the characters of both the parents.
 The survival of the species is ensured as there are more variations.
 The offspring can easily adapt to environmental changes.
 It also improves the health of humans.

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64 How are the modes for reproduction different in unicellular and
multicellular organisms?
Reproduction mode in unicellular Reproduction mode in multicellular
organisms organisms
Asexual reproduction takes place in Sexual reproduction takes place in
unicellular organisms. multicellular organisms.
Only one organism is required in this A male and a female both are required in
method. this method.
No special cells are present for
Special cells are present for reproduction.
reproduction.
65 How does reproduction help in providing stability to populations of
species?
 The introduction of variations during reproduction provides stability to the
populations of various species by preventing them from getting wiped out
during adverse conditions.
 Reproduction also helps to generate copies of individuals which are suited to
a particular environment.

ACCUMULATION OF VARIATION DURING REPRODUCTION

1 If a trait A exists in 10% of a population of an asexually reproducing species
and a trait B exists in 60% of the same population, which trait is likely to
have arisen earlier?
 Trait B, Because it is present in more members of the population.
2 How does the creation of variations in a species promote survival?
 The variations provide stability to the population of various species by
preventing them from getting wiped out during adverse conditions.
 The natural environment also changes, and variations in species which become
suited to the environment help it to survive.
3 Which of the processes, sexual reproduction or asexual reproduction, bring
about maximum variations in the offspring‟s?
Sexual reproduction.
4 Name one variation in humans connected with ears.
Free earlobes and attached earlobes.

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 HEREDITY
5 What is Heredity?
Transfer of traits from generation to generation is called heredity.
6 How do Mendel‟s experiments show that traits may be dominant or recessive?
 Mendel took pea plants with different characteristics – a tall plant and a short
plant.
 On cross pollination, he got all tall plants in first generation (F1).
 But by the self-pollination of F1 tall plants, the plants of second generation
consisted of tall and short pants in the ratio of 3: 1.
 On the basis of these experiments, the characteristics appeared in first
generation were called dominant.
 And the characteristics that did not appear were called recessive.
7 The information source for making proteins in the cells is _____
Ans. : DNA
8 According to Mendel what are dominant traits and recessive traits?
 The traits that appear in the organisms are dominant traits.
 The traits that are invisible or less appearing are called recessive traits.
9 How do Mendel‟s experiments show that traits are inherited independently?
 Mendel took pea plants showing two different characteristics and carried out
dihybrid cross.
 The traits appeared in first generation were termed as dominant.
 When he used F1 progeny to generate F2 by self-pollination plants of different
types were produced in the ratio 9:3:3:1.
 In some plants both the traits were dominant, while in some plants both were
recessive and some plants exhibited mixed traits.
 This indicates that traits are inherited independently.
10 What is dihybrid cross? Write the ratio of the plants obtained in the F2
generation in Mendel‟s hybridisation experiment.
 If parents showing two different characteristics are crossed then it is called
dihybrid cross. Ratio: 9 : 3 : 3 : 1.
11 What is monohybrid cross? Write the ratio of the plants obtained in the F2
generation in Mendel‟s hybridisation experiment.
 Cross between single characters of parents are called monohybrid cross.
 Ratio: 3 : 1.

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12 A man with blood group A marries a woman with blood group O and their
daughter has blood group O. Is this information enough to tell you which of
the traits – blood group A or O – is dominant? Why or why not?
 This information is not enough.
 This is because each individual is carrying two alleles.
 The recessive trait can occur only when two alleles are similar.
 If blood group A is dominant and O is recessive, then daughter can have blood
group O only when both recessive alleles occur together in mother, and father
has one allele of O and other of A.
13 The gene for brown coloured hair is recessive that of gene for black coloured
hair. What is the hair colour of a person who has inherited a gene for brown
coloured hair from mother and black coloured hair from father?
Ans. : Black coloured hair
14 Mendel crossed plants bearing red flowers ( RR ) with the plants bearing
White flowers (rr) and produced progeny from them. The plants with red
flowers obtained in F1 generation were different from the plants with red
Flowers of parental generation. Why? Explain with reasons.
 Plant bearing red flowers has both the dominant traits RR.
 Plant bearing white flowers has both the recessive traits rr.
 F1 generation plant inherits one copy of dominant trait (red) and one copy of
recessive trait (white) from the parental plants R r. But only the dominant trait
(Red) is expressed.

15 What is the law of dominance of traits? Explain with an example.

a) Law of dominance of traits: -In a cross between a pair of contrasting characters,
only one parental character will be expressed in F1 generation which is called
dominant trait and the other is called recessive trait.
For example

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16 Differentiate between F1 generation and F2 generation in context of Mendel‟s
experiment.
F1 Generation F2 generation
first generation plants second generation plants
Obtained by Cross pollination Obtained by self-pollination of F1
generation
Only dominant traits appear Both dominant and recessive traits are
present.
17 Is it possible that a trait gets inherited, but not expressed? Give an example
to justify your answer.
• Yes
• When pure tall pea plants (TT) are crossed with pure short pea plants (tt) only tall
pea plants (Tt) are obtained in F1 generation of pea plants.
• On self-pollinating tall pea plants (Tt) of F1, both tall and short pea plants are
obtained in F2 generation of pea plants.
• Reappearance of the short pea plants in F2 generation shows that the short trait
of pea plants was present in the individuals of F1 but it could not get expressed.

SEX DETERMINATION
18 Sex of the child determined by the father. How? OR
“Chromosomes inherited from the father determines the sex of a
Child.” Explain.
 In father the sex chromosomes are odd pair called ‘X’ and ‘Y’.
 But in mother both chromosomes are in a perfect pair called ‘XX’
 So, if the child gets ‘X’ chromosome inherited by father, the sex of a child will
be female (XX). ]
 If the child gets inherited by ‘Y’ chromosome, the sex of a child will be male.
19 What is the probability of a male child or a female child being born in case of
human beings?
• Probability of male child is 50% and female child born is 50% in human beings.
20 How is the sex of male child be determined in humans ?
If zygote received Y chromosome from the father then the zygote develops into a
male child.

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 CHECKER BOARD
21 NOTE :

DOMINENT RECESSIVE
Tall (TT) Short (tt)
Round seed (RR) Wrinkle seed (rr)
Yellow coloured seed (YY) Green coloured seed (yy)

 Monohybrids cross: a cross between single contrasting characters.

Phenotypic ratio : 3 : 1
Genotypic ratio : 1 : 2 : 1

 Dihybrid Cross: cross between two different contrasting characters.

Genotypic ratio : 9 : 3 : 3 : 1
 F1 generation : plants are cross pollinated
 F2 generation : plants are self-pollinated
22 Round seed (RR) producing pea plant is hybridised with wrinkled seed (rr)
producing plant. Mention the result obtained in F2 generation with the help
of checker board. Write the genotypic ratios of plant types.

(Round seed ) - F1 generation

- F2 generation

R r

R RR Rr

r Rr rr

Genotypic ratios : 1 : 2 : 1

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23 The plant bearing round green coloured (RRyy) seed are crossed with wrinkle
yellow coloured (rrYY) the same plant. Represent the result obtained in the
F2 generation of dihybrid cross with the help of a checker board. Mention
the varieties of plants obtained in F2 generation.

Ry rY

RrYy - F1 Generation

The plants obtained are

Round yellow — 9
Round green — 3
Wrinkled yellow — 3
Wrinkled green — 1
Genotypic ratio : 9 : 3 : 3 : 1
24 Red flowering (RR) 4 O‟clock plant is crossed with white flowering (WW) 4
O‟clock plant. There are 25% red flowering, 25% white flowering and 50%
hybrids are obtained in F2 generation. Then,
i) What are the characteristics of plants of F1 generation?
ii) Show the results of F2 generation with the help of a checker board and
mention the genotypic ratio.
iii) Determine the trait that can be considered either as „dominant‟ or

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 „recessive‟ by analysing the results of both F1 and F2 generations.

Genotype ratio ; 1 : 2 : 1
iii) In F1 -generation 100% hybrids In F2 -generation 50% hybrids
So, that neither red colour nor, white colour is dominant / recessive.
25 Tall pea plant producing red flowers ( TT RR ) is crossed with short pea plant
producing white flowers ( tt rr ).
i) Mention the type of plants produced from these plants in the F1
generation. ii) Write the ratio of plants obtained in the F2 generation by
crossing the plants of F1 generation and name the varieties of plants
obtained.

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 EXERCISE
1 A Mendelian experiment consisted of breeding tall pea plants bearing violet
flowers with short pea plants bearing white flowers. The progeny all bore
violet flowers, but almost half of them were short. This suggests that the
genetic make-up of the tall parent can be depicted as
(a) TTWW (b) TTww (c) TtWW (d) TtWw
Answer:
(c) TtWW
2 A study found that children with light-coloured eyes are likely to have
parents with light-coloured eyes. On this basis, can we say anything about
whether the light eye colour trait is dominant or recessive? Why or why
not?
Answer:
We can say that light eye colour trait is dominant because only dominant traits
are expressed in the first generation.
3 Outline a project which aims to find the dominant coat colour in dogs.
Answer:
Suppose a black homozygous male is mated with a white homozygous female. If
the progeny has all black dogs then the dominant coat colour is black.
4 How is the equal genetic contribution of male and female parents ensured
in the progeny?
 When the gametes from male and female parent combine during sexual
reproduction to form zygote, they contribute equal amount of DNA(half each).
 The normal body cells of human contain 46 chromosomes each.
 Human sperm cells and egg cells both have 23 chromosomes .
 So the combination of these 23 chromosomes from male and female each
during sexual reproduction ensures equal genetic contribution to progeny

5 Pea plants with round seeds ( RR ) are crossed with pea plants with
wrinkled seeds ( rr ). The percentage of plants that are having RR genetic
makeup in F2 generation is,
(A) 25% (B) 50% (C) 30% (D) 75%
Ans. : (A) 25%

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 ECO-SYSTEM – WHAT ARE ITS COMPONENTS
1 Write two examples each for natural and artificial ecosystems.
 Natural ecosystem — forest, pond, lake.
 Artificial ecosystem — aquarium, garden, crop-field.
2 What is an eco-system?
An ecosystem is defined as a structural and functional unit of the biosphere
comprising of living organisms and non-living environment.
3 We do not clean ponds or lakes but an aquarium needs to be cleaned
regularly. Why?
Ponds or lakes being natural ecosystems are self-sufficient and do not need to be
maintained regularly. On the other hand, aquarium being an artificial ecosystem
needs to be cleaned and maintained regularly because the producers and
decomposers are absent in aquarium.

FOOD CHAINS AND WEBS

4 “As energy moves progressively through various trophic levels of food chain
it is no longer available to the previous level.” Give reasons.
OR
Flow of energy in an ecosystem is always unidirectional. Why? Explain.
 The flow of energy in the food chain is unidirectional.
 The energy that is captured by autotrophs does not revert back to the solar
input.
 The energy which passes to the herbivores does not come back to
autotrophs.
 The energy available at each trophic level gets diminished progressively due
to loss of energy at each level.
5 Give reason: Food chains generally consist of only three or four steps.
Very little energy is available ( 10% ) for the next level of consumers.
6 What is trophic level?
Each step or level of a food chain is called Trophic levels.
7 Primary consumers in any food chain are always
Herbivores

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8 What is „biological magnification‟?
Ans.: Process that involves magnification (increase) of the harmful chemicals at
different trophic levels of ecosystem.
9 Construct a terrestrial food chain with trophic levels.
Grass → Rabbit → Wild cat → Tiger
10 Consider the following food chain which occurs in a forest:
Grass → Deer → Lion
If 10000 J of solar energy is available to the grass, how much energy would
be available to the deer to transfer it to the lion?
The energy available to the deer is 1000 J to transfer it to the lion. This can be
depicted as follows:

→ →

11 What will happen if we kill all organisms in one trophic level?

 It will always adversely affect the ecosystem.
 Only 10% of the energy is received by the next trophic level.
12 “The number of organisms decreases by reaching higher trophic level of a
food chain in an ecosystem.” Why ?
Because as reaching to high trophic level of food chain, the amount of available
energy goes on decreasing.
13 What is a food chain?
A series of organisms feeding on one another at various trophic levels.
14 A Food chain in a polluted aquatic eco system is given. Observe it and
answer the following questions.

(i) Which organisms are disturbed more due to bio magnification? Why?
(ii) This ecosystem will destroy gradually due to bio magnification. Why?
Answer :(i)
 Birds are disturbed more due to bio magnification.
 As the birds occupy the top most level in the given food chain.
Answer (ii)
 As the chemicals are non-degradable
 This leads to gradual destruction of the ecosystem.
15 Producers of aquatic eco-system are
Ans. : (A) algae

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16 Explain with the help of a terrestrial food chain how some harmful
chemicals enter our bodies through the food chain. Why is the concentration
of these harmful chemicals found to be maximum in human beings?
 Plants → Goat → Human Being
 Pesticides are washed down into the soil and water bodies.
 From the soil pesticides are absorbed by crop plants and enter the food chain.
 These chemicals are non-biodegradable
 Get accumulated progressively at each trophic level.
 As human beings occupy the top level in any food chain.
 The maximum concentration of these chemicals gets accumulated in our
bodies.
17 In an ecosystem, the amount of energy of sunlight captured by green plants
to convert it into food energy is :
(A) 90% (B) 99% (C) 1% (D) 10%
Answer : (C) 1%
18 Write an aquatic food chain with four tropic levels. Name the primary and
tertiary consumer present in this food chain.

• Primary Consumer: - Zooplankton

• Tertiary Consumer: - Large fish
19 Explain why a garden is called an ecosystem.
Because garden contain both biotic components which interact with each other
and with abiotic components for their growth, reproduction and other activities.
20 The number of Trophic levels in a food chain is limited.give an example to
justify this statement.
• Grass → Grasshopper → Frog → Snake → Eagle
(10,000 J) (1000 J) (100 J) (10 J) (1 J)
• Justification: Only 10% of the energy present at one trophic level is transferred
to the next higher trophic level. The loss of energy at each step is so great that
very little usable energy remains after 4-5 trophic levels.
21
→ →

In the given food chain, what will be the impact of removing all the
organisms of second trophic level on the first and third trophic level? Will
the impact be the same for the organisms of the third trophic level in the

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 above food chain if they were present in a food web? Justify
• Number of plants/organisms of first trophic level will increase.
• Number of lions/ organisms of third trophic level will decrease.
• No
• Food web is more stable where other animals as prey may be available.
22 Observe the given food chain and answer the following questions :

i) What is the amount of energy do green plants have if the energy available
to the tiger is 700 kJ?
ii) The organism of which trophic level has the maximum accumulation of
harmful chemicals? Why?
i) Green plants are having the amount of energy – 70000 kJ ( Law of 10% )
ii) Tiger.
 These chemicals are not degradable
 Get accumulated at each trophic level.
 Hence the top level in any food chain the maximum concentration of these
chemicals is accumulated.
23 In an aquatic eco-system the organisms such as fishes, birds, insect larvae
and diatoms are found. Construct a food chain using these organisms. If 10
calories of energy is available to the tertiary consumers in this food chain,
what amount of energy was produced in the first trophic level ?
Ans. :
Food Chain :
Diatoms → Insect larvae → Fishes → Birds
Producer’s → Pry. Consumer → Sec. Consumer → Ter. Consumer ↓
10,000 calories → 1000 calories → 100 calories → 10 calories
Organisms in the first trophic level that produced the energy was 10,000 calories.

OZONE LAYER AND HOW IT IS GETTING DEPLETED

24 Briefly explain the formation of ozone in the atmosphere.

 The higher energy UV radiations split apart some molecular oxygen [ O2 ]
into free oxygen [ O ] atoms.
 These atoms then combine with molecular oxygen to form ozone.

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25 Give reason: Protecting of ozone layer is necessary.
OR
„„Ozone, although a deadly poison, performs an essential function for the life
on the earth.‟‟ Justify this statement.
Ozone layer shields the surface of the earth from ultraviolet radiation from the
sun. This radiation is highly damaging to organisms.
26 Nowadays Chlorofluorocarbon (CFC) free refrigerators are being
manufactured. Why?
CFC’s are responsible for the decrease in the amount of ozone layer which
protects the earth from ultraviolet rays of sun.
27 The depletion of ozone layer is a cause of concern. Why?
Ozone layer acts as a protective shield by preventing harmful UV radiations from
entering the Earth surface. Hence, the depletion of ozone layer is a cause of
concern.
28 Explain how ozone affects an ecosystem.
 Incidences of skin cancer and herpes.
 Incidences of cataract in eyes.
 Global warming.
29 A gas „X‟ which is a deadly poison is found at the higher levels of
atmosphere and performs an essential function. Name the gas and write the
functions performed by this gas in the atmosphere. Which chemical is linked
to the decrease in the level of this gas? What measure have been taken by
an international organisation to check the depletion of the layer containing
this gas?
• Gas ‘X’ is Ozone
• Ozone shields the surface of the earth from ultra-violet radiations from the sun.
• CFCs (Chlorofluorocarbons)
• Manufacturing of CFC free refrigerators

MANAGING THE GARBAGE WE PRODUCE

30 Give reason :
Decomposers play an important role in an ecosystem.
Decomposers breakdown the dead remains and waste products of organisms.
These substances are used up once more by the plants.

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31 What is the role of decomposers in an ecosystem?
Decompose dead wastes of plants and animals thus keep surroundings clean
and maintain ecological balance
32 Mention any two effects of non-biodegradable substances on the
environment
 These substances do not undergo natural recycling
 It may cause ‘Biological magnification’.
 Cause environmental pollution.
33 State with reason any two possible consequences of elimination of
decomposers from the earth.
 The food chains will get affected.
 The dead bodies of plants and animals will go on accumulating
 Polluting the environment.
34 What are decomposers? Explain how the decomposers
(i) Keep the environment clean, and also (ii) replenish the soil nutrients.
 The micro-organisms that breakdown complex organic matter into simpler
substances.
• (i) by decomposing the garbage.
(ii) Recycle the nutrients that enter the soil and are used up again by plants.
35 Differences between biodegradable and non- biodegradable wastes.
Biodegradable Wastes Non-biodegradable Wastes
Degraded by microorganisms Cannot be degraded by micro-organisms.

Less harmful More harmful.

Cause less pollution Cause more pollution

Example :
Example : Glass, plastic
Peel of fruits, leaves, remaining food

36 How can you help in reducing the problem of waste disposal? Give any two
methods?
1. By changing our lifestyle and change in attitude will reduce disposable
waste.
2. Reducing packaging.
3. Recycling of waste.
4. Preparing compost of biodegradable waste.

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