LIFE PROCESSES

VERY SHORT ANSWER QUESTIONS

1. Name one accessory pigment and one essential pigment in
photosynthetic plants.
Ans. Accessory pigment – Carotene/Xanthophyll
Essential pigment – Chlorophyll
2. What advantage over an aquatic organism does a terrestrial organism
have with regard to obtaining oxygen for respiration?
Ans. Adaptation of terrestrial organism over aquatic organism for efficient
uptake of oxygen from air –
(i) Increased respiratory surface area.
(ii) Very fine and delicate surface for easy exchange of oxygen and carbon –
dioxide.
(iii) Placement of respiratory surface within the body for protection
(iv) Mechanism for moving the air in and out of respiratory surface where the
oxygen is absorbed.
3. Name the intermediate and the end products of glucose breakdown in
aerobic respiration.
Ans. Glucose —> Pyruvate — In presence of O2—> 6CO2 + 6H2O +38 ATP
4. What is villi? What are its functions?
Ans. Finger-like projections present in the inner lining of the small intestine are
called villi. They increase the surface area for the absorption of digested food in
the small intestine.
5. (i) Write the balanced chemical equation for the process of
photosynthesis,
(ii) When do the desert plants take up carbon dioxide and perform
photosynthesis ?
Ans.(i) Photosynthesis can be represented using a chemical equation. The
overall balanced equation is
6CO2 + 12H2O — Sunlight & Chlorophyll —> C6H12O6 + 6H2O + 6O2
(ii) Desert plants open up their stomata during night and take in CO2. Stomata
remains close during the day time to prevent the loss of water by i
transpiration. They store the CO2 in their cells until the sun comes out and they
can carry on with photosynthesis during the day time.
6. Give one reason why multicellular organisms require special organs for
exchange of gases between their body and their environment.
Ans. In unicellular organisms the entire body of the organism is in contact with
the environment\ hence exchange of materials can take place but, in
multicellular organisms the entire body of the organism is not in contact with
the environment and hence simple diffusion is not helpful.
 7. State two differences between arteries and veins.
Ans. Arteries: Arteries carry oxygenated blood away from the heart except
pulmonary artery. These are thick-walled, highly muscular except arteries of
cranium and vertebral column. Valves are absent. Blood in arteries moves with
pressure.
Veins: Veins carry deoxygenated blood, towards the heart except pulmonary
veins. These are thin-walled. Valves are present which provide unidirectional
flow of blood. Blood in veins moves under very low pressure.

SHORT ANSWER QUESTIONS

1. Draw a neat labelled diagram of the structure of a chloroplast.

2. Explain the process of nutrition in Amoeba.

Answer: Amoeba ingests food particles with the help of its pseudopodia. The
ingested food particle or phagosome fuses with lysosome to form food
vacuole. The digested food passes out of the vacuole into cytoplasm. The
undigested matter is thrown out.
3. Draw a diagram of human urinary system

4. (a) “The breathing cycle is rhythmic whereas exchange of gases is a

continuous process”. Justify this statement.
(b) What happens if the conducting tubes of the circulatory system develop a
leak? State in brief, how could this be avoided?
c) How does the opening and closing of stomata take place?
Answer: (a) The breathing cycle involves inhalation and exhalation of air due to
alternate expansion and contraction of thoracic cavity. Thus it is a rhythmic
process. But exchange of gases is a continuous process as it takes place
between the blood and each and every cell, by diffusion.
(b)The circulatory system will become inefficient if it develops a leak. This could
be avoided by maintaining a normal blood pressure.
(c) When water flows into the guard cells, the guard cells swell and the
stomatal pore opens up. When water moves out the guard cells shrinks and the
stomatal pore closes.
5. Name the respiratory organs of (i) fish (ii) mosquito (iii) earthworm.
Answer: Fish – gills, Mosquito – Trachea (air tubes), Earthworm – moist skin
LONG ANSWER QUESTIONS
1. State the role of the following in human digestive system :
(I) Digestive enzymes (II) Hydrochloric acid (III) villi
Answer: Digestive enzymes – Foods need to be broken into their small or
simpler molecules so that they can be absorbed into the bloodstream.
However, the physical breakdown of food is not enough. Enzymes are hence
needed for the chemical breakdown of food and speeding up the digestive
process. The products of digestion can hence be small enough to be absorbed.
Hydrochloric acid – Hydro chloric acid helps to kill the germs which might have
entered in to the system through food. It creates acidic medium for the pepsin
to act on food to breakdown proteins.
Villi – Villi are finger like projections in the small intestine. They help to increase
the surface area for absorption of the digested food. Villi are richly supplied
with blood vessel which help to absorb digested food in to the blood stream.
2. List the three steps in photosynthesis.
Answer: (i) Absorption of sun’s energy by Chlorophyll
(ii)Conversion of light energy into chemical energy; and, splitting of water into
hydrogen and oxygen using the light energy.
(iii) Reduction of carbon dioxide into carbohydrates like glucose using the
chemical energy.
3. What is the significance of Small Intestine in our body? (Any 3 points)
Answer: Significance of SI:
(i) The secretions of liver and pancreas are brought to the duodenum of SI. The
hepatic duct from liver and the pancreatic duct from pancreas join forming
hepato- pancreatic duct bring the secretions of both glands to duodenum
where these help in digestion of food.
(ii)There are some intestinal glands also in the first part of SI, which also
secrete enzymes. The process of digestion of food is completed here.
(iii) The fine finger-like structures called “Intestinal Villi” increase the surface
area for absorption of digestive end products.
(iv) The length of the SI ensures that food remains in it for a long time as it
travels through SI, thereby making it possible for maximum amount of
nutrients to be absorbed.

4. (a) Explain how does the exchange of gases occur in plants across the
surface of stems, roots and leaves.
(b) How are water and minerals transported in plants?

Answer. (a) In plants, there are tiny pores called stomata on leaves and lenticels
in stem which facilitate the exchange of gases. CO2 is taken in and O2 given out
(during photosynthesis) and vice- versa during respiration.

(b) Mechanism of Transport of Water and Minerals in a Plant

The vessels and tracheids of roots, stems and leaves in xylem tissue are
interconnected to form a continuous system of water-conducting channels
reaching all parts of the plant. The cells of the roots in contact with the soil
actively take up ions which creates a difference in the ion concentration
between the root and the soil. Thus, there is steady movement of water into
root xylem from the soil, creating a column of water that is pushed upwards.
Plant uses another strategy to move water in the xylem upwards to the highest
points of the plant body. The water which is lost through the stomata is
replaced by water from the xylem vessels in the leaf. Evaporation of water
molecules from the cells of a leaf creates a suction which pulls water from the
xylem cells of roots. This loss of water is transpiration which helps in the
absorption and upward movement of water and minerals dissolved in it from
roots to the leaves. Transpiration becomes the major driving force in
movement of water in the xylem during the day when the stomata are open.
This mechanism is also known as cohesion of water theory or transpiration
pull.

5. List any 3 functions of the major circulatory fluid of our body.

Answer: (i) Transport of O2 (from lungs to different parts of the body) and CO2
(from tissues/ organs, back to lungs).
(ii)Transport of digested food (glucose, amino acids, etc.) from Small Intestine
to various parts of the body.
(iii) Transport hormones from their site of production (endocrine organs) to the
site of action (target organs or tissues in different parts of the body).
(iv) Carry nitrogenous wastes of metabolism from various tissues/ organs, to
kidneys, to be removed as urine.
(v)Harmful substances or toxins are transported to the liver for detoxification.
(vi) Antibodies produced by the leucocytes provide immunity to the body.
(vii)Help maintain body temperature (thermoregulation) by the process of
sweating (perspiration)

HOW DO ORGANISMS REPRODUCE ?

Question 1: Why is DNA copying important in reproduction?
Answer 1. The information related to the inheritance of characteristics from
one parent to the next is stored in the DNA. The blueprint for body design is
produced as a result of DNA copying. The characteristic features to be
transmitted from one generation to the next are maintained by DNA copying.
The useful variations essential for species’ survival over time are related to DNA
copying.
Question 2: Variation is beneficial to the species, but it is not necessary for
the individual. Give the reason.
Answer 2. In species, many individuals of the same type are included. The
organisms of a species have a similar body design and are well adapted to their
niche and place. When the variation occurs in the individual, it is not beneficial
and may even lead to the individual’s death. But the variation may be helpful
when the species faces a drastically altered condition. The population may be
completely wiped out in this condition. Still, if the population can survive, it
increases the species’ chances of survival, and this variation proves beneficial.
For example, if the bacterial species survive in water that is neither too cold
nor too hot, and if there is a sudden rise in the temperature of the water, many
of the bacteria that live there die, but only those bacteria that are resistant to
heat can survive. But if this variation did not exist, then all the species of
bacteria would not have survived.
Question 3. Explain the difference between binary fission and multiple
fission.
Answer 3:

Binary fission Multiple fission

The parent division leads to the formation of The parent-child division may result in
nearly equal-sized daughter individuals. the formation of a large number of
small daughter individuals.

Two nuclei are formed. Several nuclei are formed.

For example: For example

Amoeba and Leishmania divide by binary Plasmodium and yeast divide by
fission. multiple fission.

Question 4: Mention the benefits of reproduction by spores.

Answer 4: The organisms reproducing through spore formation is beneficial in
several ways. They are:
  Spore formation are a simple and faster mode of reproduction.
 They can float in the air as they are light in weight, so the organisms may
be dispersed.
 The thick layer of the spore enables them to survive in the atmosphere,
which is unfavourable because of extreme temperatures and a lack of
food and water.
Question 5: Mention reasons why more complex organisms do not give rise
to new individuals through regeneration.
Answer 5. This is because of the following reasons:
 The entire body of simple organisms comprises similar types of cells, so
they reproduce through regeneration. The body of complex organisms
has a very high degree of organisation.
 The particular organs perform a specific function.
 Labour division occurs in the body of complex organisms.
 Specialised cells are present to carry out regeneration, which is absent in
complex organisms.
Question 6: Vegetative propagation is practised for growing some plants. Give
a reason and explain why vegetative propagation is important.
Answer 6: The plants that cannot produce seeds or those plants that have non-
viable seeds are preferred for vegetative propagation, like, for example,
bananas, potatoes, grapes, sugarcane, roses, oranges, etc. The advantages of
vegetative propagation are:
 The desired features of the parent plant can be easily replicated in the
new plants.
 Using this method, it is very quick and easy for flowers and fruits to be
grown in a shorter time
 Banana and rose are two examples of plants raised in this manner.
 The pathogen can eliminate any part of the plant using vegetative
propagation.

Question 7: What is the difference between fertilisation and pollination?

Explain.
Answer 7:
 Pollination Fertilisation

The transfer of pollen grains from Fertilisation is the fusion of male and female
the anther to the stigma of a flower gametes.
is known as pollination.

Pollination precedes fertilisation. Fertilisation can occur only after pollination,

when the pollen grains are germinated and
then sent by the male gametes to the ovule.

Pollination carries the male gamete Fertilisation brings about the fusion of
that produces the pollen grain to gametes.
the female sex organs.

Question 9. Define reproduction. Explain the types of reproduction. Mention

the characteristic features of asexual reproduction. What are the advantages
of sexual over asexual reproduction?
Answer 9:
The production of new organisms from the existing organisms of a species that
ensures the continuity of the population of that species is known as
reproduction. It is of two types:
 Asexual reproduction
 Sexual reproduction.
In asexual reproduction, the offspring is formed from a single parent, and
gametes are not fused. The various features of asexual reproduction are:
 Only one organism is involved.
 Different sexes are not involved.
 The cell division occurring is either mitotic or amitotic.
 The individuals produced are genetically identical to their parents. The
mode of multiplication is rapid.
 Gamete formation does not take place.
 Fertilisation does not take place.
The process of giving birth to a new offspring or individual through the fusion
of male and female gametes is known as sexual reproduction. A diploid zygote
is first formed, which develops into a mature organism.
The benefits of sexual reproduction over asexual reproduction are:
  The fusion of male and female gametes occurs between two sexually
distinct individuals, and the offspring produced has diverse
characteristics.
 Meiosis during gametogenesis provides opportunities for a new
combination of genes.
 Origin of new species
 Variation for evolution.
1. What happens to DNA when a cell reproduces?
2. what is the method by which the Plasmodium reproduces?
3. List four modes of asexual reproduction.
4. How does reproduction provide stability?
5. What is the method by which Spirogyra reproduces?
6. In which part of the Bryophyllum is the buds produced for vegetative
propagation?
7. What will happen when Planaria is cut into two pieces?
8. What happens when a mature Spirogyra filament attains considerable
length?
9. What is the method of reproduction of Hydra? Explain
10.Name two organisms which can regenerate.
11.Which organism causes “Kala-azar” disease, and what is the mode of
reproduction of that organism?
12.Which mode of reproduction is exhibited by Rhizopus?
Answer 11:
1. When DNA replication occurs, similar copies of DNA are formed.
2. Plasmodium’s reproduction method is called the multiple fission
method, an asexual reproduction method. The parent organism splits to
form many new organisms at the same time.
3. The four modes of asexual reproduction are budding, spore formation,
regeneration, and fragmentation.
4. The species’ population is stabilised by sexual reproduction. The transfer
of specific characters or body design features is essential for an
individual to survive in a population; this is possible through
reproduction. Variations that occur in the population due to
reproduction help the individual survive in a changing niche.
5. Spirogyra reproduces by fragmentation; it is a method of asexual
reproduction performed under favourable conditions by Spirogyra.
6. Bryophyllum reproduces vegetatively through buds produced on the
margins.7. Planaria undergo regeneration when they are cut into two
small pieces. This means that each fragment will grow into a
new Spirogyra.
 7. When a mature Spirogyra attains considerable length, it breaks into two
or more fragments, and each fragment grows into a new Spirogyra.
8. Hydra reproduces by budding, which is the method of asexual
reproduction. Hydra is a multicellular organism, and a small
protuberance arises from one side of the body. The protuberance grows
and gives rise to adult-like structures. At the free end, the hypostome
and tentacles are developed. It develops a basal disc at the point of
attachment with the parent organism and then gets detached to lead an
independent life.
9. Hydra and Planaria are the two organisms that can regenerate.
10.The causative agent of Kala-azar disease is Leishmania. It reproduces
asexually by binary fission.
11.The mode of reproduction for Rhizopus is spore formation. There are
three favourable conditions for the spore to germinate. They are
moisture, a suitable temperature, and food or nutrition.
Question 12. What happens when sporangia burst on maturation?
Answer 12: Many spores are released in the air when the sporangia burst on
maturation. When these spores fall on food or soil, and the conditions are
favourable, then these spores germinate into new individuals.
Question 13. What are the advantages of vegetative propagation?
Answer 13: This technique is useful for the propagation of those plants that are
seedless or do not produce viable seeds.
 For fruit trees and flowering bushes, grafting is a propagation method.
 We can obtain seedless plants by method of artificial vegetative
propagation.
 Grafting enables the combination of the most desirable characteristics of
two plants.
 Through stem cutting, certain plants, like roses, sugarcane, cacti, etc.,
can be propagated rapidly.
 Bananas and jasmine are the two plants grown through the vegetative
propagation method.
 The new plant produced by vegetative propagation is similar to the
parent plant, and the desired feature will be replicated in the new plants.
 Vegetative reproduction can propagate the orange plant that has lost the
ability to produce seeds.
Question 14. Explain in brief the following terms:
1. DNA
2. Reproduction
3. Multiple fission.
Answer 14:
 1. DNA is a polymer of many nucleotide units and is responsible for
carrying information from one generation to the next.
2. Reproduction is defined as the life process that helps in the
multiplication of an organism and the growth of its population.
3. Multiple fission is a form of asexual reproduction. In this, the parent
organism splits to form many new organisms simultaneously. An example
is Plasmodium.
Question 15. When DNA copying is ineffective, what effect does it have on
the reproduction process, and how does DNA remain constant through each
new generation?
Answer 15: Variation occurs when the copying of DNA is not accurate. This
allows a few individuals to survive in the altered niche, and in this way, it
becomes the basis of evolution. These are very useful for the survival of the
species. The combination of the DNA copies of two individuals, male and
female, occurs during the process of sexual reproduction. Meiosis is the
reduction division that occurs during gamete formation and halves the
chromosome number in both the male and female gametes. The two gametes
fuse during fertilisation, and the original number of chromosomes is restored in
the offspring as it was in the parent. In this way, the amount of DNA in every
generation remains constant.
Question 16. How do Leishmania and Plasmodium reproduce, and mention
the difference in their modes of reproduction?
Answer 16. Leishmania and Plasmodium reproduce by the process of fission,
and this is an asexual mode of reproduction.
Plasmodium reproduces by multiple fission and produces 1000 daughter cells,
while Leishmania reproduces by binary fission. The parent cell divides
longitudinally in a specific plane, involving the flagellum at its tip, giving rise to
the two daughter cells.
Question 17. What are the advantages of spore-forming organisms?
Answer 17: The advantages of spore-forming organisms are:
 It helps the organism survive in harsh environmental conditions.
 Thick walls cover the spores, so it provides them with protection.
 They come in contact with the moist surface and germinate.
 They are small and light.
 Wind, water, and animals can easily disperse it.