1. (c) excretion

2. (a) transport of water

3. (d) all of the above

4. (b) mitochondria

5. Digestion of fats takes place in small intestine. Fats entering in intestine are in the
form of large globules. Bile juice breaks down these large globules into smaller
globules. Afterwards fat digesting enzyme lipase present in pancreatic juice and
intestinal juice converts it into fatty acids and glycerol.

6. The saliva contains an enzyme called salivary amylase that breaks down starch
which is complex molecule into glucose.

7. Conditions necessary for autotrophic nutrition are:
 (i) Light (ii) Chlorophyll
 (iii) Water and (iv) Carbon dioxide
 By-products are:
(i) Oxygen and (ii) Water

8. Difference between aerobic and anaerobic respiration:
(i) Takes place in presence of oxygen.
(ii) Complete oxidation of glucose
(iii) More energy is produced.
(i) Takes place in absence of oxygen
(ii) Incomplete oxidation of glucose
(iii) Less energy is produced

9. The walls of the alveoli is folded and has large surface areas. It contain an extensive
network of blood vessels which provide a surface where the exchange of gases can
take place.

10. Haemoglobin is a pigment present in RBC. It has a high affinity for oxygen. It carries
oxygen from lungs to various tissues which are deficient in oxygen. Presence of less
hemoglobin will result in less supply of oxygen to tissues. A person having less
hemoglobin will get tired soon and will have a pale look.

11. In mammals and birds the blood goes through the heart twice during each cycle. This
is known as double circulation.
Deoxygenated blood which enters right auricle and then it enters the right ventricle
from where it is pumped to lungs for oxygenation. From lungs after oxygenation it
comes to left auricle and then enters left ventricle from where it is pumped to
various parts of body.
Such system of circulation does not allow mixing of oxygenated and deoxygenated
blood which allows efficient supply of oxygen to the body.

12. Difference between transport in xylem and phloem:

a. Xylem transport minerals and
water from root to leaves.
b. Transport is unidirectional.
c. Xylem consists of trachieds and
a. Phloem transport food from leaves to
root and storage organs.
b. Transport is bidirectional.
c. Phloem consists of sieve tubes and
companion cells.

13. Comparison between alveoli and nephron:

They have thin-walled balloon-like
structure. The alveoli provide a surface
extensively supplied with blood
capillaries for exchange of gases in lungs.
Carbon dioxide released in the cavity of
alveoli and oxygen is taken by
hemoglobin present in RBC of blood.
Nephron is a cluster of very thin
walled blood capillaries found in
kidney. Each capillaries cluster
remains associated with the cupshaped
end of a tube called Bowman’s
capsule that collects the filtered urine,
at the same time the useful substance
are reabsorbed.

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