Page: 95
1. Why is diffusion insufficient to meet the oxygen
requirements of multicellular organisms like humans?
Answer:
In
multicellular organisms, all the body cells are not in direct contact with the
surrounding environment. So, every cell of the body will not get enough oxygen
by the process of diffusion from the environment.
2. What criteria do we use to decide whether something is
alive?
Answer:
Growth,
reproduction, metabolism, consciousness etc.
3. What are outside raw materials used by an organism?
Answer:
Organisms use
organic molecules as raw material. Heterotrophs use food and autotrophs use CO2,
minerals, water. Organisms receive oxygen for respiration.
4. What processes would you consider essential for
maintaining life?
Answer:
Nutrition, Respiration,
Transportation, Excretion etc.
Page: 101
1. What are the differences between autotrophic nutrition and
heterotrophic nutrition?
Answer:
· Autotrophic nutrition: Here, organisms synthesize its own food. They do not depend on
other organisms.
They use simple inorganic
materials and synthesise their food in presence of sunlight. E.g., All green
plants.
· Heterotrophic nutrition: Here, organisms cannot synthesize its own food. They
depend on other organisms for their food.
E.g., All the animals, most
bacteria and fungi.
2. Where do plants get each of the raw materials required for
photosynthesis?
Answer:
· Carbon dioxide: It
is absorbed from environment/ atmosphere through stomata.
· Water: It is
absorbed from the soil through roots and transport to leaves.
· Sunlight: From
the sun.
· Chlorophyll:
It is present in chloroplasts found in green leaves.
3. What is the role of the acid in our stomach?
Answer:
· To make acidic medium which is necessary for the
activation of the enzyme pepsin.
· To kill bacteria present in the food.
4. What is the function of digestive enzymes?
Answer:
Digestive
enzymes break down complex molecules in the food into smaller simpler molecules
so that they can be absorbed by the intestinal wall.
5. How is the small intestine designed to absorb digested
food?
Answer:
The small
intestine is very long and highly coiled. Also, its inner lining has numerous
finger-like structures called villi. All these features increase the surface
area for maximum absorption of digested food. The villi has numerous blood
vessels which take the absorbed food.
Page: 105
1. What advantage over an aquatic organism does a terrestrial
organism have with regard to obtaining oxygen for respiration?
Answer:
Aquatic
organisms use oxygen dissolved in surrounding water. Concentration of dissolved
oxygen is very low. So the breathing rate in aquatic organisms very high.
Terrestrial
organisms get oxygen from the oxygen-rich atmosphere. Hence, they have less
breathing rate than aquatic organisms.
2. What are the different ways in which glucose is oxidised
to provide energy in various organisms?
Answer:
In all
organisms, glucose (6 carbon) molecules are breakdown yielding pyruvate (3-carbon
molecule). It takes place in the cytoplasm.
Further break
down of pyruvate occurs in different ways in different organisms. It is
represented below:
3. How is oxygen and carbon dioxide transported in human
beings?
Answer:
· Oxygen Transport:
Haemoglobin present in the blood takes up the oxygen from the air in the lungs
and carries to all tissues.
· Carbon dioxide Transport: CO2 is more soluble in water. Therefore, it is
mostly transported from tissues in the dissolved form in blood plasma to lungs.
Then it diffuses from blood to air in the lungs.
4. How are the lungs designed in human beings to maximise the
area for exchange of gases?
Answer:
In the lungs,
the air passage divides into smaller and smaller branches called bronchi. They
again divided into fine branches called bronchioles. The bronchioles terminate
in balloon-like and thin-walled structures called alveoli. The alveoli provide
maximum surface area for gas exchange.
Page: 110
1. What are the components of the transport system in human
beings? What are the functions of these components?
Answer:
Heart, blood
and blood vessels.
· Function of heart: It
receives deoxygenated blood from the body parts and pumps to lungs for oxygenation.
It receives purified blood from lungs and pumps to various body parts.
· Function of blood: It
transports oxygen, CO2, nutrients, hormones and nitrogenous wastes.
It also protects the body from diseases and regulates body temperature.
· Function of blood vessels: They carry blood from heart to body parts and vice versa.
2. Why is it necessary to separate oxygenated and
deoxygenated blood in mammals and birds?
Answer:
Mammals and
birds need constant supply of oxygen to get energy to maintain their body
temperature. Separation of oxygenated and deoxygenated blood allows sufficient
supply of oxygen to the body.
3. What are the components of the transport system in highly
organised plants?
Answer:
There are two
conducting tissues called xylem and phloem.
· Xylem: Consists of
vessels, tracheids and other xylem tissues. The interconnected vessels and
tracheids form a continuous system of water conducting channels reaching all
parts of the plant. Xylem carries water and minerals.
· Phloem: Conducts
products of photosynthesis from leaves to different plant parts.
4. How are water and minerals transport in plants?
Answer:
In xylem
tissue, vessels & tracheids of the roots, stems and leaves are
interconnected to form a water-conducting channels reaching all parts.
At the roots,
cells actively take up ions from soil. This creates a difference in the
concentration of ions between root and soil. So, water moves into the root from
the soil. Thus there is steady movement of water into root xylem.
The water is
lost from the leaves as vapour through stomata. It is called transpiration.
This loss is replaced by water from the xylem vessels in the leaf.
Transpiration
creates a suction which pulls water from the xylem cells of roots. Thus,
transpiration helps in the absorption and upward movement of water &
minerals from roots to the leaves.
5. How is food transported in plants?
Answer:
Transport of
soluble products of photosynthesis (food) from leaves to other parts through phloem
is called translocation. It needs energy.
These
substances are delivered to the storage organs of roots, fruits and seeds and
to growing organs.
Translocation
takes place in the sieve tubes with the help of adjacent companion cells both
in upward and downward directions.
Material like
sucrose is transferred into phloem using energy from ATP. This increases the
osmotic pressure of the tissue causing water to move into it. This pressure
moves the material in the phloem to tissues.
Page: 112
1. Describe the structure and functions of nephrons.
Answer:
Each kidney
has large numbers of filtration units called nephrons.
Structure: At the end of each nephron, a cup-shaped structure called
Bowman’s capsule is seen. It encloses a cluster of very thin-walled blood
capillaries called glomerulus. There is a long and coiled tubular part in
nephron starting from the Bowman’s capsule.
Function: In glomerulus, blood is filtered and the Bowman’s capsule
collects the filtrate.
Glucose,
amino acids, salts & major amount of water in the initial filtrate are selectively
reabsorbed in tubular part. The remaining filtrate is excreted as the urine.
2. What are the methods used by plants to get rid of
excretory products?
Answer:
· Gaseous products are removed through stomata in leaves and
lenticels in stems.
· Solid and liquid wastes are removed by the shedding off
leaves, peeling off bark and felling off fruits.
· Secretion of wastes the form of gums and resins.
3. How is the amount of urine produced regulated?
Answer:
The amount of
urine is regulated by kidney. It is based on amount of excess water in the body and
amount of dissolved waste is to be excreted.
When water is excess, large quantities of dilute urine is excreted out. When water is less, a small quantity of concentrate urine is excreted.
When there are more dissolved wastes in the body, more quantity of water is required to excrete them. Therefore, the amount of urine produced increases.