Question 1.
What processes would you consider essential for maintaining life?
Answer.
Nutrition, respiration, transportation and
excretion.
Question 2.
Why is diffusion insufficient to meet the
oxygen requirements of multicellular organisms like humans?
Answer.
In multicellular organisms, only the cells
present in the surface layer are in direct contact with the surrounding
environment, whereas other cells are not. Therefore, diffusion is insufficient
to meet the oxygen requirements of multicellular organisms like humans.
Question 3.
What criteria do we use to decide whether
something is alive?
Answer.
Growth, movement or locomotion, response
to, stimuli and ability to reproduce are the criteria that we use to decide
whether something is alive.
Question 4.
What are outside raw materials used for by
an organism?
Answer.
The outside raw materials used for by an
organism are:
(a) Food for
obtaining energy.
(b) Oxygen to
use it in the process of breakdown of food sources for cellular needs.
Question 5.
Where do plants get each of the raw
materials required for photosynthesis?
Answer.
Plants get carbon dioxide from atmosphere.
It gets water and minerals from the soil.
Question 6.
What is the role of the acid in our
stomach?
Answer.
The acid (hydrochloric acid) formed in our
stomach helps in killing unwanted harmful germs which may have gained entry
along with the food. It is secreted by the gastric glands creates an acidic
medium which facilitates the action of the pepsin enzyme.
Question 7.
What is the function of digestive enzymes?
Answer.
The function of digestive enzymes is to
hasten the process of digestion in which complex
molecules break down into simpler molecules
which are then easily absorbed by the body.
Question 8.
What are the differences between
autotrophic nutrition and heterotrophic nutrition?
Answer.
| Autotrophic nutrition | Heterotrophic nutrition |
| 1. The organism prepares its own food. | 1. The organism does not prepares its own food. |
| 2. It is not dependent on any other organism for their food. Example: Green plants. | 2. It is dependent on other organisms for food. Examples: Man, dogs, lions snakes, etc. |
Question 9.
What advantage over an aquatic organism
does a terrestrial organism have with regard to obtaining oxygen for
respiration?
Answer.
The water has oxygen dissolved in it. On
the other hand, the air has oxygen gas present freely. Beside this, the
concentration of oxygen is more in the atmosphere than water. Hence, the
aquatic organisms have to breathe quite fast to get the required oxygen. The
terrestrial animals can easily get oxygen from the atmosphere.
Question 10.
How is the small intestine designed to
absorb digested food?
Answer.
The small intestine has several folds in
its inner mucous layer called villi. The presence of folds increases the
surface area and thereby increases the absorption area. The blood capillaries
present in the villi absorb simple molecules from the food.
Question 11.
How is oxygen and carbon dioxide
transported in human beings?
Answer.
Oxygen and carbon dioxide are transported
in human beings with the help of ‘transportation system’.
Transport of oxygen: The air present in the alveolar sacs have high concentration of oxygen,
while the blood capillaries surrounding the alveolar sacs are deficient in
oxygen. Oxygen diffuses from the alveoli to the blood capillaries where it
combines with the haemoglobin to form oxyhaemoglobin. Then the blood reaches
the tissues where oxyhaemoglobin breaks into haemoglobin and oxygen. This
oxygen enters the cells.
Transport of carbon dioxide: The tissues have high concentration of carbon dioxide than the blood
entering them. Therefore, carbon dioxide diffuses from the tissues into the
blood. Then it reaches the lungs where it diffuses into the alveoli, and
expelled out into the atmosphere through the respiratory tract.
Question 12.
How are the lungs designed in human beings
to maximise the area for exchange of gases?
Answer.
The lungs have special air sacs called
‘alveoli’. The presence of air sac increases the surface area inside the
lungs. Alveoli are the places where exchange of gases takes place. There are
about 300-350 millions of alveoli in each lung. The alveoli are filled with
air and they swell up. During inspiration, the ribs move up and diaphragm
flattens which increases the surface area. The increased surface area helps in
maximum exchange of gases to take place.
Question 13.
What are the components of the transport
system in human beings? What are the functions of these components?
Answer.
The components along with functions of
transport system in human beings are as:
Heart: It is
a muscular pumping organ that helps to pump blood around the body.
Blood: The
blood is a fluid connective tissue. It consists of a watery fluid called
plasma, and three types of cells: red blood cells, white blood cells and
platelets. Plasma helps in transporting food, carbon dioxide, salts and
nitrogenous wastes in dissolved form. Red blood cells carry oxygen. White
blood cells engulf bacteria and produce antibodies, which provide immunity
against various disease-causing pathogens. Platelets help to clot the blood at
the site of injury.
Blood vessels: There are three types of blood vessels. They are: arteries, veins and
capillaries. These vessels help in transporting the blood in the body.
Lymph: It
carries digested and absorbed fats from intestine and transports them to the
blood. It also drains excess fluid from extra-cellular space back into the
blood.
Question 14.
Why is it necessary to separate oxygenated
and deoxygenated blood in mammals and birds?
Answer.
Separation of oxygenated and deoxygenated
blood allows a highly efficient supply of oxygen to the body. Since mammals
and birds have high energy needs to maintain their body temperature,
therefore, it is necessary to separate oxygenated and deoxygenated blood in
them.
Question 15.
What are the components of the transport
system in highly organised plants?
Answer.
The transport systems of highly organised
plants are:
(a) Xylem: This tissue helps in transportation of water and dissolved minerals
from roots to other parts of the plant.
(b) Phloem: This tissue helps in transportation of prepared food from leaves to
other parts of the plant.
Question 16.
How are water and minerals transported in
plants?
Answer.
Water and minerals are transported in
plants through the xylem tissues, which consist of interconnected vessels and
tracheids stretching from the roots to the leaves. Root hairs are in contact
to the soil containing water and mineral salts. They take up mineral ions by
active transport. This creates a difference in concentration of these ions
between the root and soil. Therefore, water moves into the root hairs to
eliminate this difference. Then water diffuses into the cortical cells. After
that the water (containing dissolved minerals) reaches the endodermis by
osmosis and then into the root xylem. From the root xylem the water reaches
the stem xylem and then conducted to other parts through the branched xylem
tissues.
The pressure with which water is
pushed into the xylem of the root is called root pressure.
This pressure cannot make up for the water
lost by transpiration in tall trees. The loss of water due to transpiration
creates a force called transpiration pull which pulls water up through the
xylem vessels to the highest point of the plant body.
Question 17.
How is food transported in plants?
Answer.
The food is transported in plants both in ‘
upward and downward direction through
phloem tissues, which consist of sieve
tubes and companion cells. The translocation in
phloem occurs with the expenditure of
energy. Sucrose is the main form of carbohydrate which is transferred into the
phloem tissues using energy from ATP. When sucrose is synthesised in the leaf
cells, the osmotic pressure of the cells increases causing water to move into
it. This causes translocation of sucrose in the form of solution from the
point of synthesis to the points having less pressure. This allows the phloem
to move material according to the plants needs.
Question 18.
Describe the structure and functioning of
nephrons.
Answer.
The nephron is the basic filtering unit of
kidneys. Each kidney has 1-1.5 million nephrons in it.
The filtration of blood takes place in
Bowman’s capsule under a very high pressure. Finally, the waste products go to
a network of collecting tubules which finally meet in a common collecting
duct. This collecting duct joins the ureter which carries urine to the urinary
bladder for excretion.
Structure and functioning of nephrons
- Bowman’s capsule: The Bowman’s Capsule is a cup-shaped structure which houses the ‘glomerulus’. For this reason, it is also known as the ‘glomerular capsule’. Fluids flowing through the glomerulus are removed from larger particles.
- Proximal convoluted tubule or proximal tubule: This is the first twisted region after the Bowman’s capsule. It lies in the cortex. The reabsorption of essential substances takes place here. This is known as tubular reabsorption.
- Loop of Henle: The long, hairpin loop after the proximal tubule is called ‘loop of Henle’. It is extended from the cortex down into the medulla and back.
- Distal convoluted tubule or distal tubule: This is the second twisted portion of the nephron after the loop of Henle. It is located in the cortex.
- Collecting duct: This is the long straight portion after the distal tubule. The distal convoluted tubule is the most distal (distant) portion of the nephron and is responsible for the reabsorption of sodium, and water.
Question 19.
What are the methods used by plants to get
rid of excretory products?
Answer.
- Plants get rid of the oxygen produced during photosynthesis by its diffusion through stomata and lenticels.
- They get rid of excess water by transpiration.
- Many waste products are stored in cell vacuoles.
- Some wastes are removed in the falling leaves.
- Other, wastes are stored as resins and gums, especially in old xylem.
- Plants also get rid of some waste products by excreting into the surrounding soil.
Question 20.
How is the amount of urine produced
regulated?
Answer.
The kidney has an effective mechanism to .
control the,.urine production. They can reabsorb water from the glomerulus
filtrate when the water level of the body is low. Similarly, if water level in
the body is significantly high, the kidneys allow more water to get
eliminated.
Question 21.
What are the different ways in which
glucose is oxidised to provide energy in various organisms?
Answer.
Glucose is oxidised either aerobically,
i.e. in the presence of oxygen or anareobically, i.e. in the absence of oxygen
to provide energy in various living organisms. In organisms like yeast,
glucose is oxidised anareobically to give ethanol, carbon dioxide and energy.
Aerobically, glucose is oxidised to give carbon dioxide, water and energy.
Chapter End Questions
Question 1.
The kidneys in human beings are a part of
the system for
(a) nutrition
(b) respiration
(c) excretion
(d) transportation
Answer.
(c) excretion
Question 2.
The xylem in plants responsible for
(a) transport
of water
(b) transport
of food
(c) transport
of amino acids
(d) transport
of oxygen
Answer.
(a) transport
of water
Question 3.
The autotrophic mode of nutrition requires
(a) carbon
dioxide and water
(b) chlorophyll
(c) sunlight
(d) all of
the above
Answer.
(d) all of
the above
Question 4.
The breakdown of pyruvate to give carbon
dioxide, water and energy take place in
(a) cytoplasm
(b) mitochondria
(c) chloroplast
(d) nucleus
Answer.
(a) cytoplasm
Question 5.
What would be the consequences of a
deficiency of haemoglobin in our bodies?
Answer.
Haemoglobin is the carrier of oxygen. If
the haemoglobin becomes deficient, the cells of our body would not be able to
obtain sufficient oxygen for respiration. We may get tired easily. Deficiency
of haemoglobin also causes anaemia.
Question 6.
How are fat digested in our bodies? Where
does this process take place?
Answer.
In our bodies, most of the fat digested in
small intestine. Here, fat is first emulsified with the help of bile salts.
The emulsification of fat converts it into small fat droplets which are then
acted upon by the pancreatic and intestinal lipase. The lipase breaks the fat
into fatty acids and glycerol.
Question 7.
What is the role of saliva in the digestion
of food?
Answer.
Saliva is secreted by the salivary glands
present in the cavity of mouth for:
- Moistening and softening of food for easy crushing by the teeth.
- The action of enzyme salivary amylase which converts starch into maltose.
- Converting the food into slippery bolus for easy swallowing.
Question 8.
What are the necessary conditions for
auto-trophic nutrition and what are its by-products?
Answer.
The conditions necessary for autotrophic
nutrition are:
(a) Sufficient amounts of carbon dioxide
(b) Presence
of chlorophyll
(c) Sunlight
(d) Water
(e) Optimum
temperature
The by-products are: glucose
and oxygen gas.
Question 9.
How does aerobic respiration differ from
anaerobic respiration?
Answer.
| Aerobic respiration | Anaerobic respiration |
|
1. This process takes place in the presence of oxygen.
|
1. This process takes place in the absence of oxygen.
|
|
2. It involves complete oxidation of glucose.
|
2. It involves incomplete oxidation of glucose.
|
|
3. The end products of this process are carbon dioxide and water.
|
3. The end products of this process are ethanol and cabondioxide, or lactic acid..
|
|
4. Large amount of energy is released during this process.
|
4. comparatively less amount of energy is released during this process.
|
|
5. This process takes place in the cytoplasm as well as in mitochondria of the cell.
|
5. This process takes place in the cytoplasm of the cell.
|
- Anaerobic mode of respiration is used by yeasts and some bacteria.
Question 10.
Compare the functioning of alveoli in the
lungs and nephrons in the kidneys with respect to their structure and
functioning.
Answer.
Comparison with respect to structure: Both
alveoli and nephrons possess a network of blood capillaries.
Comparison with respect to functioning:
Alveoli provide a surface for gaseous exchange while nephrons help in
purifying blood by filtering waste products in the form of urine.
Question 11.
What are the differences between the
transport of materials in xylem and phloem?
Answer.
(i) Xylem
helps in transporting water and minerals whereas phloem helps in transporting
products of photosynthesis, amino acids and other substances.
(ii) Xylem
helps in upward movement of substances whereas phloem helps in movement of
substances both in upward and downward directions.
Question 12.
Describe double circulation in human
beings. Why is it necessary?
Answer.
Double circulation means that the blood
flows twice through the heart to complete one circuit in the body. It has two
parts:
- The pulmonary circulation in which deoxygenated blood flows from the heart to the lungs, where it gets oxygenated, and again comes back to the heart via pulmonary vein.
- The systemic circulation in which the oxygenated blood flows from the heart to all the organs of the body except lungs, and then back again to the heart via vena cava.
Double circulation is necessary to prevent
intermixing of deoxygenated and oxygenated blood. It is also required to
provide a highly efficient supply of oxygen to the body.
Question 13.
How are the alveoli designed to maximise
the exchange of gases?
Answer.
Within a human lung about 300 million
alveoli of various sizes are present which provide total alveolar surface of
75 to 80 square metres. The walls of the alveoli are thin to a single layer of
epithelium. Moreover, they are closely wrapped in an extensive network of
blood vessels called capillaries.