Life Processes NCERT Text Book Questions &
Answers
Question: 1: Why is diffusion insufficient to meet the
oxygen requirements of multicellular organisms like
humans?
Answers:- The size of the multicellular organisms is very
large compare to unicellular organisms. Diffusion is a
passive mode of transport of substances and can
transfer gases up to a very small distance only. This will
not be sufficient for multicellular organisms’ needs.
Question: 2. What criteria do we use to decide whether
something is alive?
Answer:- The main criteria to check for life, is the sign
of breathing and respiration. If there is no sign of
breathing or respirations then the given organism is not
alive.
Question: 3:- What are outside raw materials used for
by an organism?
Answer: Minerals and water and gases are outside raw
materials used by an organism.
Question: 4:- What processes would you consider
essential for maintaining life?
Answer: Processes essential for maintaining life are as
follows:
Nutrition
Respiration
Reproduction
Excretion
Locomotion or movement
Question: 5. What are the differences between
autotrophic nutrition and heterotrophic nutrition?
Answer: Autotrophic nutrition means that the organism
is preparing its own food and is not dependent on any
other organism for food. Green plants are autotrophs.
Heterotrophic nutrition means that the organism does
not prepare its own food and is dependent on other
organisms for food. All organisms which are not among
green plants are heterotrophic.
Question: 6. Where do plants get each of the raw
materials required for photosynthesis?
Answer:
Pic is given
Question: 7. What is the role of the acid in our
stomach?
Answer: The hydrochloric acid is found in our stomach.
It helps in killing harmful germs which may have come
along with food.
Question: 8. What is the function of digestive enzymes?
Answer: The function of digestive enzyme is to hasten
the process of breaking up of complex molecules into
simpler and absorbable molecules. This makes it easy
for the body to absorb food.
Question: 9. How is the small intestine designed to
absorb digested food?
Answer: In the small intestine the innermost layer is in
the shape of finger like structures. These are known as
villi. Several folds because of villi increase the absorbing
surface of small intestine. The blood capillaries in villi
absorb simpler molecules from food.
Question: 10. What advantage over an aquatic organism
does a terrestrial organism have with regard to
obtaining oxygen for respiration?
Answer: In the aquatic habitat the concentration of
oxygen is good up to a certain depth only. Moreover, as
oxygen is available as dissolved in water, so taking
oxygen from there is not a very efficient method to
that.
In terrestrial habitat oxygen is available in free form so
it is easier to absorb by organisms. This is more
efficient so terrestrial organisms can facilitate better
utilization of food by way of respiration.
Question: 11. What are the different ways in which
glucose is oxidised to provide energy in various
organisms?
Answer: There are two types of respiration for
oxidization of glucose.
(a) Aerobic respiration: This involves complete
oxidation of glucose hence optimum output of energy is
achieved. This happens in presence of oxygen.
(b) Anaerobic respiration: As the name suggests this
happens in the absence of oxygen hence complete
oxidation of glucose does not take place. Usually
bacteria show anaerobic respiration. Even sometimes in
our calf muscles anaerobic respiration takes place.
Question: 12. How is oxygen and carbon dioxide
transported in human beings?
Answer: Oxygen and carbon dioxide are transported in
human beings with a dedicated gas transportation
system. This system is mainly composed of following
parts:
Lungs: Lungs help in breathing in oxygen rich air and
breathing out carbon dioxide rich air.
Heart: Heart pumps deoxygenated blood to lungs for
oxygenation and pumps oxygenated blood to different
organs of body.
Veins: Veins usually carry deoxygenated blood from
different body parts to the heart. One exception is the
pulmonary vein which carries oxygenated blood from
lungs to heart.
Arteries: Arteries usually carry oxygenated blood from
heart to different parts of the body. One exception is
pulmonary artery which carries deoxygenated blood
from heart to lungs.
Question: 13. How are the lungs designed in human
beings to maximise the area for exchange of gases?
Answer: The bronchioles in lungs are finely branched
and end up in air sacs. The structure of air sac
increases the surface area inside lungs. This helps in
making a larger area for exchange of gases.
Question: 14. What are the components of the transport
system in human beings? What are the functions of
these components?
Answer: The transport system is mainly comprised of
following organs:
Heart: Heart is a pumping organ and pumps blood. As
blood carries gases and food and waste product along
with it so heart plays a major role in transportation.
Lungs: The main job of lungs is in facilitating transport
of oxygen and carbon dioxide to and from the body
respectively.
Liver: Food goes to liver after it is absorbed by small
intestine. From liver the food is distributed to different
parts of body. This system is also called as hepatic
portal system.
Question: 15. Why is it necessary to separate
oxygenated and deoxygenated blood in mammals and
birds?
Answer: Mammals and birds are warm blooded animals.
This means they can control their body temperature
and don’t have to depend on environment for their
body temperature regulation. Because of this birds and
mammals require optimum oxidization of glucose which
would be possible with good supply of oxygen. By
developing four chambered heart they have made it
possible to completely segregate the oxygenated and
deoxygenated blood in their bodies which is their need
because of their habit and habitat.
Question: 16. What are the components of the transport
system in highly organized plants?
Answer: The plant transport system in highly organized
plants contains following:
(a) Xylem: To transport water and minerals from roots
to other parts.
(b) Phloem: To transport food from leaves to other
parts.
Question: 17. How are water and minerals transported
in plants?
Answer: Water and minerals are transported from roots.
At the level of roots the root pressure helps in rise of
water and minerals up to some height. After that there
is complex mechanism at work. The transpiration taking
place in leaves creates a suction effect which pulls up
water in minerals to great heights.
Question: 18. How is food transported in plants?
Answer: Food is transported in plants through phloem.
The transport in phloem is an active process and
involves use of energy. The energy in the form of ATP
created osmotic gradient which results in transportation
of food through phloem.
Question: 19. Describe the structure and functioning of
nephrons.
Answer: The nephron is the functioning unit of kidneys.
Nephron consists of a capsule shaped structure called
Bowman’s capsule. The filtration of blood takes place in
Bowman’s capsule under very high pressure. After that
waste product goes to a network of collecting tubules
which finally meet in a common collecting duct. The
collecting duct meet in ureter which carries urine to the
urinary bladder.
Question: 20. What are the methods used by plants to
get rid of excretory products?
Answer: Plants get rid of carbon dioxide and oxygen
through diffusion. Old branches and leaves are shed off
when they become useless. Plants release some waste
products through roots also. Some waste products are
deposited near bark as raisins or gums.
Question: 21. How is the amount of urine produced
regulated?
Answer: The kidney has a mechanism to reabsorb water
from the filtrate. This depends on how much water is
left in the body and in the filtrate. The comparative
concentration of water gives a signal to the brain which
then takes the required corrective action of either
reabsorbing water or releasing more water. Thus the
amount of urine formation is regulated by kidneys.
Question: 22. The kidneys in human beings are a part of
the system for
(a) nutrition.
(b) respiration.
(c) excretion.
(d) transportation.
Answer: (c)
Question: 23. The xylem in plants are responsible for
(a) transport of water.
(b) transport of food.
(c) transport of amino acids.
(d) transport of oxygen.
Answer: (a)
Question: 24. The autotrophic mode of nutrition
requires
(a) carbon dioxide and water.
(b) chlorophyll.
(c) sunlight.
(d) all of the above.
Answer: (d)
Question: 25. The breakdown of pyruvate to give
carbon dioxide, water and energy takes place in
(a) cytoplasm.
(b) mitochondria.
(c) chloroplast.
(d) nucleus.
Answer: (b)
Question: 26. How are fats digested in our bodies?
Where does this process take place?
Answer: Fats are present in the intestine in the form of
large globules which makes it difficult for enzymes to
act on them. Bile salts break them down into smaller
globules increasing the efficiency of enzyme action. The
pancreas secretes pancreatic juice which contains
enzyme called lipase for breaking down emulsified fats.
The walls of the small intestine contain glands which
secrete intestinal juice. The enzymes present in it finally
convert fats into fatty acids and glycerol.
Question: 27. What is the role of saliva in the digestion
of food?
Answer: Saliva contains the enzyme amylase which
breaks complex molecules into sugar.
Question: 28. What are the necessary conditions for
autotrophic nutrition and what are its byproducts?
Answer: Conditions necessary for photosynthesis:
Sunlight, carbon dioxide and chlorophyll.
Byproduct of photosynthesis: Oxygen
Question: 29. What are the differences between aerobic
and anaerobic respiration? Name some organisms that
use the anaerobic mode of respiration.
Answer: In aerobic respiration there is complete
oxidation of glucose and the end product is water and
carbon dioxide.
In anaerobic respiration there is incomplete oxidation
of glucose and the end product is either lactic acid or
alcohol.
Yeast and bacteria use anaerobic mode of respiration.
Question: 30. How are the alveoli designed to maximise
the exchange of gases?
Answer: The wall of alveoli contains a fine network of
blood capillaries. This ensures maximum exchange of
gases.
Question: 31. What would be the consequences of a
deficiency of haemoglobin in our bodies?
Answer: Haemoglobin is the carrier of oxygen in blood.
Deficiency of haemoglobin will lead to less supply of
oxygen to different cells. This will, in turn lead
inefficient utilization of food by the body. Finally
person’s health will deteriorate.
Question: 32. Describe double circulation in human
beings. Why is it necessary?
Answer: In double circulation there is complete
segregation of oxygenated and deoxygenated blood.
Because of this the blood passes twice through the
heart in one cycle of circulation hence the name double
circulation.
This is necessary for optimum oxygen utilization as
humans are warm blooded animals and need extra
energy to maintain their body temperature.
Question: 33. What are the differences between the
transport of materials in xylem and phloem?
Answer: Transport in xylem: The transport in xylem is
from roots to upwards and takes place in only one
direction. This is a kind of passive transport as no
energy is required. Through xylem only water and
minerals are transported.
Transport in phloem: The transport in phloem is
bidirectional and food and some other products are
transported. The transport in phloem is an active
transport as it requires energy.
Question: 34. Compare the functioning of alveoli in the
lungs and nephrons in the kidneys with respect to their
structure and function.
Pic is given
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