This document discusses life processes and how organisms reproduce. It contains questions and answers about photosynthesis, plant nutrition and transport, human excretory system, control and coordination in humans, and sexually transmitted diseases. Some key points: - Photosynthesis involves the absorption of light energy by chlorophyll, conversion of light energy to chemical energy, and production of carbohydrates from carbon dioxide and water. - The human digestive system breaks down food, absorbs nutrients, and removes waste. Hormones and nerves help control and coordinate various body functions. - Reproduction requires DNA copying to generate similar copies that can direct cell functioning and pass on traits to offspring. Sexually transmitted diseases are infections spread through sexual contact

1. LIFE PROCESSES
Q 1. Enumerate three events that occur during photosynthesis.
Ans. 1. During photosynthesis the following events occur .
(I) Absorption of light energy by the chlorophyll pigment.
(ii) Conversion of light energy into chemical energy and splitting of water molecules into
hydrogen
and oxygen.
(iii) Reduction of carbon dioxide into carbohydrates.
Q 2. (a) Draw a labelled diagram of cross-section of leaf lamina to show chloroplasts.
(b) How will you prove that chlorophyll is essential for photosynthesis?
Ans. 2.(a) Refer fig.6.1 of page no.96 of NCERT Science Text Book.
(b) The following activity can prove that chlorophyll is essential for photosynthesis. Refer
Activity
6.1 page no.96 NCERT Science Text Book.
Q 3. (a) Write major functions of stomata.
(b) Stomata remain closed during the day in desert plants. How do they get carbon dioxide
for photosynthesis?
Ans. 3. (a) i. Exchange of gases
ii. Transpiration.
(b) In deserts, temperature is very high so stomata are closed to reduce the loss of water due to
transpiration. Therefore, desert plants are adapted to take up carbon dioxide at night when stomata are
open. This carbon dioxide taken up in night, prepare an intermediate compound. This intermediate
compound is acted upon by energy absorbed by the chlorophyll during the day to prepare food.
Q 4. Explain the process of nutrition in Amoeba with help of labelled diagrams.
Ans. 4. Refer diagrams of Fig.6.5 page no.98 NCERT Science text Book.
Q 5. Draw a diagram of human alimentary canal and label the following.
(a) Part in which digestion of starch starts.
(b) Part in which bile is stored.
(c ) Part in which digested food is absorbed.
Ans. 5. (a) Mouth/Buccal cavity (b ) Gall bladder (c ) Walls of small intestine/Villi. Refer Fig. 6.6
page no.99 of NCERT Science Text Book.

2. Q 6. Explain the significance of peristaltic movements that occur all along the gut during digestion.
Justify the statement “ Bile does not contain any enzyme, but it is essential for digestion”.
Ans. 6. The lining of the digestive canal has muscles that contract rhythmically in order to push the food
forward. This movement is called peristaltic movement which occurs all along the gut.
Bile does not contain any enzyme, but it makes the medium alkaline in small intestine, so that trypsin
acts on proteins in this medium. It emulsifies fat; means breaks large globules of fat into smaller ones
for increasing the efficiency of enzyme action.
Q 7. Which is the internal energy reserve in plants? Do the animals have same energy reserve? Justify
your answer.
Ans. 7. Carbohydrates are utilized for providing energy to the plant and are stored in the form of starch,
which serves as the internal energy reserve to be used as and when required by the plant.
In animals, carbohydrates are reserved in the form of glycogen, as internal energy reserve. The
carbohydrates like starch(in plants) and glycogen(in animals) serve as internal energy reserve because
they are polymer of glucose and their hydrolysis provide glucose molecules to provide energy at the
time of need.
Q 8. State three modes of heterotrophic nutrition by giving suitable examples.
Ans. 8. (i) Saprophytic –Break down the food out side the body and then absorb it. Example: Bread
mould, Yeast and Mushroom.
(ii) Holozoic – Take in whole food material and break down into simple/smaller substances
inside the body Ex. Humans, Rabbit and Fish
(iii) Parasitic – Derive nutrition from plants and animals without killing them. Example: Cuscuta, and
Tapeworm.
Q 9. List the role of each of the following in our digestive system.(a) Saliva (b) Mucus (c) Hydrochloric
acid.
Ans. 9. (a) Saliva contains an enzyme salivary amylase that breaks down starch into sugar.
(b) Mucus protects the inner lining of the stomach.
(c) Hydrochloric acid creates an acidic medium which facilitates the action of enzyme pepsin.
Q 10. Explain the breakdown of glucose in a cell in the presence and absence of oxygen.
Ans. 10. Refer Fig 6.8 Page no.102 of NCERT Science Text Book.

3. 11. Why should we breathe only through our nose though we can breathe very well breathe through
mouth?
Ans: 1.The air we inhale contains dust particles. The air passing through nostrils is filtered by fine hairs
that line the passage.
2. The passage is also lined with mucus which helps in this process to filter air.
3. If we inhale the air through mouth, there is a chance for the air to enter the lungs without
filtration.
So we need to breathe through our nose.
12. Why are respiratory pigments needed for higher animals?
Ans: 1.When the body size of animals is large, the diffusion pressure alone cannot take care of oxygen
delivery to all parts of the body. Instead, respiratory pigments take up oxygen from the air in the lungs
and carry it to tissues which are deficient in oxygen before releasing it.
2. In higher animals, ie., in human beings the respiratory pigment is haemoglobin which has a very
high affinity for oxygen. This pigment is present in the red bold corpuscles. The pigment having high
affinity for oxygen, meets the requirement of oxygen in higher animals.
13. Describe the role of nephron in the purification of blood.
Ans: Each kidney has filtration units called nephrons packed closed together .Some substances in the
initial filtrate, such as glucose, amino acids ,salts and a major amount of water are selectively re-
absorbed as the urine flows along the tube. Thus the nephron takes up the job of filtration of only liquid
wastes from our body.
14. What is called excretion? Draw and label the diagram of human excretory system.
Ans: Removal of harmful nitrogenous metabolic waste material from the body is called excretion. Neat
labeled diagram 6.13 from NCERT text book for class X Page No. 110.
15. How are wastes are formed in plants? Mention how plants excrete some of these wastes and store
them for various purposes.
Ans: 1.In plants wastes are formed due to metabolism and during photosynthesis
2. They get rid excess water during transpiration
3. Many dead cells help the plant for mechanical support.
4. Waste products may be stored in leaves that fall off.
5. Some plants store the waste products as resins and gums, especially in old xylem.
6. Plants also excrete some waste substances into soil around them.
7. Many plant waste products are stored in cellular vacuoles.(any six points)
16. Why do aquatic animals breathe faster compared to terrestrial animals?
Ans: Terrestrial animals can breathe the oxygen in the atmosphere,but animals that live in water need to
use the oxygen dissolved in water. Since the amount of dissolved oxygen is fairly low compared to the
amount of oxygen in the air, the rate of breathing in aquatic organisms is much faster than that seen in
terrestrial organisms.
17. What is the role of alveoli in human respiratory system to meet the requirement of oxygen to our
body?
Ans: The alveoli provide a surface where exchange of gases can take place. The walls of the alveoli
contain an extensive network of bold-vessels for the exchange of gases.
18. Draw the schematic diagram showing the various ways through which energy is released through
break down of digested carbohydrates at cellular level.

4. Ans: Figure 6.8 from NCERT text book for class X Page No. 102.
19.. a. Define translocation.
b. When does water rise upward in plants?
Ans. A. Transport of soluble products of photosynthesis
b. When
1. transpiration creates suction in xylem.
2. Root pressure is generated in xylem cells of root
20.a. What do you mean by Double circulation?
b . Write the functions of lymph.
Ans. a. passing of blood through the heart twice in one cycle.
b.1. transportation of digested and absorbed fats from the small intestine.
2. Drains excess fluid from inter cellular spaces back in the blood.
21.a. What are blood vessels?
b. Find the differences between arteries and viens.
Ans. .a . thin cylindrical tube like structures which carry the blood.
b. arteries veins
1.thick elastic wall. thin walled
2.deep in between bone and musles superficial below the skin
3.carry blood away from the heart carry blood from organs to heart
4.carry oxygenated blood except pulmonary artery carry deoxygenated blood except pulmonary
vein
5.valves absent valves present
6.blood flows with pressure blood is not under pressure
22.a. Which is the tissue responsible for transportation of materials in our body?
b. Name the components of it and mention one use of the each component.
Ans. a. connective tissue called blood.
b. it has
1.plasma ----- fluid medium transports food, CO2, nitrogenous wastes in dissolved form.
2.RBC ----------- carries oxygen, makes blood red
3.WBC ----- develops immunity, kill germs

5. 4.platelets ---------- stops bleeding/ blood clotting
23. Briefly describe the functioning of human heart with the help of a neat labeled diagram.
Ans. Diagram , page no 106, fig 6.10
1. O2 rich blood from lungs comes to left atrium and deoxygenated blood from body parts comes to
right atrium when atria are vat relaxed state.
2. Left and atria starts contracting and blood is transferred to expanding left and right ventricles
3. Left ventricle is with oxygenated blood and right is with deoxygenated blood.
4. When ventricles contract, oxygenated blood is transferred to body parts through aorta and
deoxygenated blood is sent to lungs through pulmonary artery for oxygenation.
CONTROL AND CO-ORDINATION
1. (a) Draw the structure of neuron and label cell body and axon.
(b) Name the part of neuron:
(i) Where information is acquired?
(ii) Through which information travels as an electrical
impulse.
Ans. (a) 7.1 (a) Page. No 115 NCERT Science class X.
(b) (i) Dendrite.
(ii) Axon.
2. What is a reflex action? Describe the steps involved in a reflex action.
Ans. Reflex action is an unconscious, involuntary and automatic response to a stimulus.
These actions are mainly formed from the spinal cord.
Steps involved in a reflex action:
(i) Receptor organ like skin receives the stimulus and activates a sensory nerve impulse.
(ii) Sensory neuron sends nerve impulse to neurons of spinal cord.
(iii) The neurons of spinal cord transmit the sensory nerve impulse to motor neuron.
(iv) Motor neuron sends these impulses to the effectors like leg muscles which produces the desired
response.
3. (a) Name the plant hormone which promotes cell division.
(b) Write the function of Auxin and Abscisic acid.
Ans. (a) Cytokinins.
(b) Function of Auxin :Synthesized at the shoot tip, helps the cells to grow longer.
Function of Abscisic acid: Inhibits growth, Wilting of the leaves.

6. 4. Write the functions of the following hormones:
(a) Thyroxine. (b) Insulin. (c) Growth hormone.
(d) Oestrogen. (e) Adrenalin (f) Testosterone.
Ans. (a) Thyroxin: Regulates carbohydrate, protein and fat metabolism in the body.
(b) Insulin: Helps in regulating blood sugar levels.
(c) Growth hormone: Regulates growth and development of the body.
(d) Oestrogen: The changes associated with puberty in females are because of Oestrogen.
(e) Adrenalin: Controls heart beat, breathing rate and diverts blood to our skeletal muscles.
(f) Testosterone: The changes associated with puberty in males are because of testosterone.
5. Write one example each of the following tropic movements:
(a) Phototropism. (b) Geotropism. (c) Chemotropism.
Ans. Phototropism: Shoots respond by bending towards light.
Geotropism: The downward growth of roots, in response to the gravity.
Chemotropism: The growth of the pollen tubes towards ovules.
6. Write the functions of Forebrain, Medulla and Cerebellum of human brain.
Ans. Forebrain: The main thinking part of the brain specialized for hearing, smell, sight and so on.
Medulla: All the involuntary actions including blood pressure, salivation and vomiting are
controlled by the medulla in the hind -brain.
Cerebellum: It is responsible for precision of voluntary actions like picking up a pencil, riding a
bicycle and maintaining posture and balance of the body.
7 Draw neat diagram of human brain and label the following parts
a)mid-brain b)pituitary gland c)cerebrum d)cerebellum
Ans 7
8.What is synapse? In a neuron cell how is an electrical impulse created and what is the role of synapse
in this context?

7. Ans 8) Synapse is the junction between two adjacent neuron or nerve cell i.e. between axon ending of
one and the dendrite of the next.
Transmission Of Nerve Impulse ;- 1.The information acquired at the end of the dendrite tip of a neuron
creates an electrical impulse.
2.This impulse travels from the dendrite to the cell body along the axon to its end.
3.At the end of the axon , the electrical impulse set off the release of some chemicals , which cross the
synapse and state a similar electrical impulse in a dendrite of the next neuron. In this way nerve
impulses travel in the body.
Synapse helps in transmitting impulses from on neuron to another.
9 a) State the function of gustatory receptor and olfactory receptor
b) Why is it advised to use iodized salt in our diet?
c) Name one gland in human body which secretes digestive enzymes as well as hormones.
Ans 9 a) Gustatory Receptors ;- It detects taste.
Olfactory Receptors ;- It detects smell .
(b)1. Iodised salt contains iodine which is necessary for the thyroid gland to synthesize thyroxine
hormone.
2.Thyroxine regulates carbohydrates, proteins, and fat metabolism in the body to provide growth
balance.
(c) Pancreas.
10 What is phototropism? How does it occur in plants?
Ans 10) PHOTOTROPISM ;- Bending of shoot towards light.
PHOTOTROPISM IN PLANTS ;- Plants bend towards light when they are exposed to it.
When light is coming from one side of the plant, growth hormone auxins diffuses towards the shady
side of the shoot.
Concentration of auxins stimulates the cells to grow longer on the shady side. Thus plant appear to bend
towards light.
11 a)What are plant hormones
b) how do auxins promote the growth of a tendril around a support?
Ans 11) (a) PLANT HORMONES ;-A plant hormone is a chemical substance which is produced
naturally in the plant and regulates growth and physiological process to bring about control and
coordination of various activities in plants.

8. b) Tendril are sensitive to touch or contact of other objects. When a tendril touches a support the
hormone auxin from the tip of the tendril diffuses towards the side of the tendril that is not in contact
with the support. As a result, the side that is not in contact with the support grows faster than the side
which is in contact with the support. This leads to the bending of tendril towards the support.
12 a) How does our body respond when adrenaline is secreted into the blood?
b) why are some patients of diabetes treated by giving insulin injections
Ans 12) (a) Adrenal gland secretes hormone adrenaline which is called emergency hormone. This
hormone is rapidly secreted in response to stress or during emergency situations. This hormone speeds
up heart beats, rate of respiration, and raise glucose level in the blood, so that we can get a lot of energy
quickly to fight or flight from the emergency situation.
(b) Insulin helps in regulating blood sugars levels, if insulin secretion is reduced. Insulin injection is
given to such patients to compensate for reduced insulin secretion.
HOW DO ORGANISMS REPRODUCE?
1. What is DNA copying? Sate its importance.
ANS:
DNA in the cell nucleus is the information source for making the proteins and different proteins
lead to different body designs. During reproduction, similar copy of DNA is generated and the
process is called DNA Copying.
IMPORTANCE: 1. DNA copying provides cellular apparatus in the daughter cell.
2. DNA in daughter cell will be able to control the functioning of the
daughter cells.
3. DNA Copies will retain the trait.
2. In the human body, what is the role of (a) seminal vesicles and (b) prostate gland. List two
functions performed by testis in human beings.
ANS:
(a) Seminal Vesicles: They produce seminal plasma which is in the form of fluid which makes
the transport of the sperms smooth and also provide nourishment to them.
(b) Prostate gland: It secrets the prostatic fluid, that keeps the sperms alive and helps them to
swim vigorously.
FUNCTIONS OF THE TESTIS: 1. Formation of the sperms
2. Secrets the hormone testosterone.
3. What are sexually transmitted diseases? List two examples of each disease caused due to
bacterial infection and viral infection. Which device may be used to prevent the spread of such
diseases?
ANS: STDs are diseases which spread by sexual contact from an infected person to a healthy
person.
a. Gonorrhoea and syphilis are caused by bacterial infection.
b. AIDS and Genital wards are caused by viral infection.

9. PREVENTION: 1. By avoiding sexual contact with infected person.
2. Using condom during sexual act.
4. (a) List any four reasons for adopting the contraceptive methods.
(b) If a woman is using Copper-T, will it help protecting her from sexually transmitted
diseases? Why?
ANS:
(a) Four reasons for adopting the contraceptive methods are
(i) to increase the gap between two children
(ii) To prevent unwanted pregnancy.
(iii) To prevent transmission of STD.
(iv)To control population growth
(b) If a woman is using a Copper – T, it will not help in protecting her from sexually
transmitted diseases. It prevents only implantation in the uterus.
5. In human females, what happens when (a) egg is fertilized (b) egg is not fertilized?
ANS: (a) If the egg is fertilized, it moves up to uterus and get implanted on uterus.
The uterine wall thins and richly supplied with blood. The region between embryo
and uterine wall goes into placenta which provides nourishment and oxygen
to the embryo.
(b) If the egg is not fertilized, the thick and nourishing line of the uterus breaks
and comes out through vagina as blood and mucus which is called menstruation.
6. Differentiate between the modes of pollination in flowering plants.
Describe double fertilization in plants.
ANS:
During the fertilization in the plants, the following events take place:
(a) One of the male gamete fuses with the female gamete present in the
embryo sac.
(b) The other male gamete fuses with the two polar nuclei in the embryo sac.
(c) The first fusion forms zygote , while the second one forms the endosperms. The
process of fusion occurring twice in the embryo sac is called double fertilization.
7 .(i)What is fertilization? Distinguish between internal fertilization and external fertilization.
(ii) What is the site of fertilization in human beings?
Sl. No. Self-Pollination Cross-Pollination
1 It occurs within a flower or between two
flowers of the same plant.
It occurs between two flowers borne
On different plants of the same species
2 Pollen grains are produced in small no. Pollen grains are produced in large no.

10. Ans: (i) Fertilisation is defined as the fusion of male gamete (sperm) and female gamate(ovum) to form
a zygote during sexual reproduction.
8. Define the terms unisexual and bisexual plant giving one example of each.
Ans: Unisexual is the plant whose flowers contain either stamen or carpel but not both. Example:
Papaya,Watermelon. Bisexual is the plant whose flowers contain both stamens and carpels. Example:
Hibiscus, Mustard.
9. Illuatrate with the help of suitable diagram: (i) Regeneration in Planaria. (ii) Budding in Hydra.
Regeneration in Planaria
(ii)
Budding in Hydra
10. Illustrate with the help of suitable diagram: (i) Binary Fission in Amoeba. (ii) Multiple Fission in
Plasmodium.
Ans:
(i)
Sl.
No.
External Fertilisation Internal fertilization
1 The fusion of male and female gamete occurs outside
the body
The fusion of gametes occur inside the
body.
2 Gametes are released outside the body Gamete are released inside the body
3 Development occurs outside the body Development occurs inside the body
4 Example: Frog Example: human,brirds,cattles

11. (ii)
Multiple Fission in Plasmodium
11. Draw a diagram of germination of pollen in stigma of a flower and label pollen garin, male germ
cell,pollen tube,female germ cell.
Ans:
12. Explain vegetative propagation with the help of two examples. List
any two advantages of vegetative propagation.
Ans: In vegetative propagation, new plants are obtained from the parts of
parent plant like stem, roots and leaves, without the help of any
reproductive organ. Example: (i) leaves of Bryophyllum bear
adventitious buds along margins. (ii) Grafting to improve variety of
mango , guava atc.
Advantages of Vegetative Propagation are:
(a) it is cheaper, easier and more rapid method of propagation in plants
than growing plants from seeds.
(b) vegetative propagation make possible the propagation of plants such as Banana, Orange, rose,
Jasmine that have lost ability to produce seeds.
(c) plants produced by Vegetative Propagation are genetically similar to the parent plant.

12. HERIDITY AND EVOLUTION
1.How does the natural selection directs the evolution of new population. Explain with an example.
(or) What is the relationship between natural selection and the theory of evolution?
Ans. Evolution is the process by which species come to possess genetic adaptations to the
environment. Its working mechanism is natural selection. The mechanism of natural selection acts
through individuals as it determines which individuals have the best adaptations for reproductive
success.
2. In an experiment the tails of mice are removed by a surgery to produce the next generation as tailless
progeny. Do they succeeded in this case? Explain with reason.
(or)
3.An individual cannot pass on its progeny the experiences of its lifetime. Justify the statement with the
help of an example and also give reason for the same.
Ans. (1) They are acquired traits.
(2) Changes in non-reproductive cells , i.e., somatic cells cannot give rise to inheritance
of characters to the progeny.
example : when a tail of mice is cut off during its life time , its progeny do not bring a mice
without tail at birth.
4. Describe briefly four ways in which Speciation occurs.
Ans. Traits arise due to variations which occur due to sexual reproduction of inaccuracies during
DNA copying or environmental factors. Now, the individuals with a particular trait may increase in a
population due to the following factors :
(i) Natural selection: Those variations which give survival advantage to an organism are selected in
nature and such traits increase in population.
(ii) Genetic drift: It occurs due to change in gene frequency due to accumulation of particular type of
genes.
(iii) Geographical isolation: It leads to change in gene frequency leading to expression of one type of
traits in a geographically isolated population.
(iv) Migration: It leads to flow of a particular type of gene in a specified population.
5. Can the wing of a butterfly and the wing of a bat be regarded as homologous. Why?
Ans. No, the wing of a butterfly and the wing of a bat cannot be considered homologous organs
because they both perform the same function of flying but their origin and structure is not similar.
6. “Variation useful for the survival of a species”, Justify.
Ans. Variation is useful for the survival of species over time. If a population of reproducing
organisms were suited to a particular environment and if the environment were drastically altered, the
population could be wiped out. However, if some variations were to be present in a few individuals in
these populations, there may be some chance of their survival.

13. E.g. : If the temperature of water increases by global warming, most bacteria would die. But a
population of heat resistant bacteria could survive here. These few variants would be resistant to the heat
and would survive and grow further.
7. Explain the following terms : a) Heredity b) Trait c) Evolution.
Ans.a) Heredity is the passing of traits from parent or ancestors to their offsprings. Or This is the
process by which an offspring cell or organism acquires the characteristics of its parent cell or
organism.
b) A trait is a distinct type of characteristic of an organism. For example, eye color is a character of an
organism, while blue, brown and black are its traits.
c) Evolution is the change in the characteristics of a species over several generations and it depends
upon the process of natural selection. For example, man evolved from apes.
8. Briefly explain with the help of a cross the process of sex determination in human beings.
Ans. Sex in human beings is determined genetically which means that chromosomes inherited
from parents decide whether we will be boys or girls.
We inherit (22+X) chromosomes from mother and (22 +X) or (22 + Y) from the father. If an offspring
inherits X chromosomes from each parent then she will be a girl. But if an offspring inherits one Y
chromosome from the father, then he will be a boy as shown below in the diagram.
9. Name the plant on which Mendel conducted his experiments and briefly explain the concept of
variations.
Ans. Mendel conducted his experiments on garden pea plant ( Pisum Sativum).
Variations: Any differences between, individual organisms, or groups of organisms of any species are
known as variations. /differences between offspring of sameparents

14. Types: Variations maybe caused
1. by genetic differences.
2. or by the effect of environmental factors.
10. What are genes? Where are they located and what is their function?
Ans. A gene is a small portion of the DNA which provides information for a protein. It is the
functional unit of DNA. It is responsible for the transmission of the hereditary characters from the
parents to the offsprings.
Location : Gene's are present on the DNA (Deoxyribonucleic Acid)
Functions of genes: 1. They provide instructions for making proteins.
2. They are responsible for the transmission of characteristics from parents to the offsprings.
3. They control structure and function of cells.
11. a) What are Fossils?
b) How can we estimate the age of fossils?
c) Explain the importance of fossils in deciding evolutionary relationships.
Ans: a. Fossils are the remains of dead organisms of the existing past. They are preserved
traces of living organisms.
b. The age of fossils can be estimated by
i.Carbon dating( using radioactive C-14 isotope)
ii. Digging the soil ( deeper the fossil older it is)
c. They reveal the evolutionary history of life forms which have existed earlier do not exist today
which indicate that the living forms are ever changing( evolving).
12. Explain the terms homologous and analogous organs with examples.
Ans : Homologous Organs :- These are the organs that have same basic structural design and
origin but having different function.
Ex: 1.Fore limbs of man and fore limbs of horse,
2. Wings of birds and flippers of whale.
Analogous Organs:- These are the organs that perform same function but have different origin
and structural plan.
Ex:- 1. Wings of bat and wings of bird,
2. Fins of fish and flippers of whale.

15. 13. (a) “Evolution cannot be said to progressive”. Explain.
(b) Can we say which among bacteria, spiders, fish and chimpanzees have a better body design.
Why or why not?
Ans. a)
 There is no real progress in the idea of evolution. It cannot always be equated with progress or
better body designs.
 Evolution causes generation of diversity and the shaping of diversity by environmental
selection. Due to evolution, more and more complex body designs have emerged over time.
 However this does not mean that the simple body designs are inefficient.
b)
 Infact, bacteria having simple body design are still the most cosmopolitan in distribution on
the earth. Therefore bacteria spider, fish and chimpanzees are all different branches of
evolution. So that evolution does not processed as “ladder of progress but” occurs as
branches of tree.
14. How are the areas of study-Evolution and classification interlinked?
Ans:-
Classification of organisms is a reflection of their evolutionary relationship.
 Classification of organisms based on relative similarities and differences among organisms.
 Resemblances in organisms are because they have arisen from a common ancestor and
differences in them are due to adaptations to different types of environment.
 As organisms can be graded in order of increasing complexity from generation to generation,
the variations make organisms more different than their ancestors it indicates at the concept
of evolution.
15. a) What are analogous organs?
b) A list of examples are given below. Identify the analogous organs and homologous organs.
Wings of bird and wings of bat Forelimbs of frog and Human
Potato and Sweet Potato Carrot and Beetroot
Ans:- a) Analogous Organs:- These are the organs that perform same function but have different
origin and structural plan.
b)Analogous Organs:- Wings of bird and Wings of bat, Potato and Sweet Potato
Homologous Organs:- Forelimbs of frog and Human, Carrot and Beetroot.

16. OUR ENVIRONMENT
1. Why forests are considered biodiversity hot spots? List two ways in which an individual can
effectively contribute to the management of forests and wild life.
Ans .Biodiversity is measured by the number of different life forms found in an area in a forest,
various species exist which include bacteria, fungi, ferns, plants, nematodes, insects, birds,
reptiles and mammals. Forests are therefore considered as biodiversity hot spots.
An individual can contribute in the management of forests and wildlife by:
1. Avoiding cutting down of forests and killing of wildlife.
2. Educating people about the importance of forests and wildlife in our life.
2. What is the role of decomposers in the ecosystem?
Ans. various roles played by decomposers in the ecosystem are:
 They decompose biodegradable substances into useful substance.
 They release nutrients into soil by decomposing dead and decaying matter, thus
making the soil fertile.
 They maintain the nutrient pool by returning back the nutrients in the pool.
3. What is ozone and how does it affect any ecosystem?
ans )Ozone ( O3) is a molecule, made up of three atoms of oxygen.
Ozone ( O3) forms a layer in the upper atmosphere , it is very essential for the life of this planet. It
shields the surface of the earth from ultra – violet radiation (UV) coming from sun as these radiations
are very harmful causing skin cancer and cataract in humans. It also does harm to the crops.
4. What will happen if we kill all the organisms in one trophic level?
ans.If we kill all the organisms of one trophic level it will create an imbalance in the ecosystem. As
an Example, In a food chain Grass  Dear  Lion, if we remove all lions then population of deer will
increase which will cause over – grazing. This will lead to deforestation. It may even lead to soil
erosion causing further conversion of fertile land into barren desert.
5. What is biological magnification? Will the levels of this magnification be different at different
levels of the ecosystem?
Ans . Biological magnification is defined as the phenomena of accumulation of increase in the
concentration of some toxic substances at each trophic level.
The levels of biomagnification will be different at different trophic levels. For example, in a pond of
water, DDT was sprayed and the producers were found to have 0.04 ppm concentration of DDT. Since
manytypes of planktons are eaten by some fishes and clams, their body accumulates 0.23 ppm of DDT.
Sea gull that feeds on clams accumulates more DDT as one sea gull eats many clams. Hawk, the top
carnivore, has the highest concentration of DDT.

17. MANAGEMENT OF NATURAL RESOURCES:
1.Why forests are considered biodiversity hot spots? List two ways in which an individual can
effectively contribute to the management of forests and wild life.
Ans .Biodiversity is measured by the number of different life forms found in an area in a forest,
various species exist which include bacteria, fungi, ferns, plants, nematodes, insects, birds,
reptiles and mammals. Forests are therefore considered as biodiversity hot spots.
An individual can contribute in the management of forests and wildlife by:
3. Avoiding cutting down of forests and killing of wildlife.
4. Educating people about the importance of forests and wildlife in our life.
2.Name any four categories of people who depend on the forest resources, mentioning major needs of
each category.
Ans.
1. Local people who live around forests: They use forests for grazing their cattle’s, collecting
fruits, firewood, bamboo and thatch.
2. Industrialists: theycollect raw materials from forests for their industries.
3. Tourists: They visit forests for recreation.
4. Forests department of Government: They control the resources of forests.
3. a)List any four characteristics of a good fuel.
b) Give two examples each of the following:
1. Renewable sources of energy
2. Non – renewable sources of energy
Ans.a) 1.Higher calorific value.
2. Lesser pollution
3. Sustainable for longer period
4. Easily transportable.
b)1. Geothermal energy, wind energy
2. Coal, petroleum
4. List four advantages of water stored in the ground?
Ans. Four advantages of storing water in the ground are
1. It does not evaporate
2. It is relatively protected from contamination by human and animal wastes.
3. It does not provide breeding ground for mosquitoes.
4. It provides moisture for vegetation.
5. Mention disadvantages of Dams.
a. Deforestation: it causes loss of biological diversity (plants, animals, and microbes) leads to many
environmental problems like water logging, earth quakes etc.
b. Displacement: Displacement of large number of peasants and tribal without enough
compensation or habitation lead to many social problems.
c. Water- logging and salinization – canals drawn out from dams causes the problems of water
logging and salinization within years in dry and half dry sandy areas.
6. a)What is the role of decomposers in the ecosystem?
b) B. In a food chain, 10,000 joules of energy is available to the producer. How much energy will be
available to the secondary consumer to transfer it to the tertiary consumer?
Ans. a) Role of decomposers in the environment:
1. They return the nutrients to the nutrient pool.
2. They help in completing the different bio-geochemical cycles, thus they maintain the balance in
the ecosystem.
3. Control over large scale nuclear explosions and limited use of supersonic planes.
b) 10 J will be available to the secondary consumer to transfer to the tertiary consumer.