Life Processes NCERT Text Book Questions & Answers
Question: 1: Why is
diffusion insufficient to meet the oxygen requirements of multicellular
organisms like humans?
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?
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
Question: 3:- What
are outside raw materials used for by an organism?
Minerals and water and gases are outside raw materials used by an organism.
Question: 4:- What
processes would you consider essential for maintaining life?
Processes essential for maintaining life are as follows:
Question: 5. What
are the differences between autotrophic nutrition and heterotrophic nutrition?
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.
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
Question: 6. Where
do plants get each of the raw materials required for photosynthesis?
Question: 7. What is
the role of the acid in our stomach?
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?
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?
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?
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.
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
There are two types of respiration for oxidization of glucose.
respiration: This involves complete oxidation of glucose hence optimum output of
energy is achieved. This happens in presence of oxygen.
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
Question: 12. How is
oxygen and carbon dioxide transported in human beings?
Oxygen and carbon dioxide are transported in human beings with a dedicated gas
transportation system. This system is mainly composed of following parts:
help in breathing in oxygen rich air and breathing out carbon dioxide rich air.
pumps deoxygenated blood to lungs for oxygenation and pumps oxygenated blood to
different organs of body.
usually carry deoxygenated blood from different body parts to the heart. One
exception is the pulmonary vein which carries oxygenated blood from lungs to
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
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?
The transport system is mainly comprised of following organs:
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.
main job of lungs is in facilitating transport of oxygen and carbon dioxide to
and from the body respectively.
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
Question: 15. Why is
it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
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?
The plant transport system in highly organized plants contains following:
(a) Xylem: To
transport water and minerals from roots to other parts.
To transport food from leaves to other parts.
Question: 17. How
are water and minerals transported in plants?
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?
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.
Describe the structure and functioning of nephrons.
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?
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
Question: 21. How is
the amount of urine produced regulated?
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
Question: 23. The
xylem in plants are responsible for
of amino acids.
Question: 24. The
autotrophic mode of nutrition requires
dioxide and water.
(d) all of
Question: 25. The
breakdown of pyruvate to give carbon dioxide, water and energy takes place in
Question: 26. How
are fats digested in our bodies? Where does this process take place?
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?
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
Conditions necessary for photosynthesis:
carbon dioxide and chlorophyll.
Question: 29. What
are the differences between aerobic and anaerobic respiration? Name some
organisms that use the anaerobic mode of respiration.
In aerobic respiration there is complete oxidation of glucose and the end
product is water and carbon dioxide.
respiration there is incomplete oxidation of glucose and the end product is
either lactic acid or alcohol.
bacteria use anaerobic mode of respiration.
Question: 30. How
are the alveoli designed to maximise the exchange of gases?
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?
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
Describe double circulation in human beings. Why is it necessary?
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.
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?
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.
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
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with
respect to their structure and functioning.