std-vii transport and excretion · 2021. 1. 11. · std-vii transport and excretion answer these...
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Std-VII Transport and Excretion
Answer these questions:-
1. How do roots absorb water from the soil?
Ans:- Roots absorb water from the soil by the
process of 'osmosis' in which water passes
through a semi-permeable membrane from a
region of higher concentration of water to a
region of lower concentration of water.
2. How does water move up the stem against
the force of gravity?
Ans:- Water moves up the stem against the
force of gravity due to the phenomenon of
"TRANSPIRATION" which creates a suction
pressure in the Xylem so that the solution of
mineral and water called "sap" can take place
from the roots to the leaves.
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3. How is the food prepared in the leaves, move
to the rest of the plant?
Ans:- The food prepared in the leaves is carried
to the rest of the plant by a set of pipes called
the "Phloem" which also carries food to the
storage organs of plants, where extra food is
stored.
Q4. What are the components of blood?
Explain.
A4. The components of blood are as follows:-
(i) Plasma- The plasma is a straw-coloured
liquid containing about 90% water and is a
solution of minerals, wastes, digested food,
gases, enzymes, blood proteins and other
substances. The red blood cells, white blood
cells and platelets keep floating in this liquid.
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(ii) Red Blood cells:- Red blood cells (RBCs)
look like discs and can squeeze into very small
blood vessels. They owe their red colour to the
presence of haemoglobin, a protein present in
RBC that combines with oxygen and helps to
transport it from the lungs to the cells. RBCs
are made in the bone marrow.
(iii) White blood cells- The main function of
white blood cells (WBCs) to defend the body
against infections. They may be of different
shapes and lifespan.
(iv) Platelets- Platelets like RBCs are made in
the bone marrow but are much smaller and
have a lifespan of only about 10 days and help
in clotting of blood when one is injured.
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5. Explain with a block diagram, the functioning
of a human heart.
Ans-
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(i) The heart has four chambers and is divided
into two halves by a thick wall which prevents
the mixing of oxygenated and deoxygenated
blood.
(ii) Each half of the heart is divided into an
upper chamber called the 'Auricle' and a lower
chamber called the 'Ventricle'.
(iii) The right Auricle of the heart receives
deoxygenated blood from all over the body
through two major veins and then passes into
the right ventricle through a valve.
(iv) From the right ventricle, this deoxygenated
blood is carried by an artery, which carries it to
the lungs.
(v) In the lungs blood is purified i.e mixed with
oxygen after which this oxygenated blood is
carried by a vein to the 'Left Auricle' and then
into the 'Left Ventricle'.
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(vi) Finally the oxygenated blood is pumped
into the Aorta, whose branches carry the blood
to the rest part of the body.
6. Differentiate between Arteries and Veins.
Ans:- Differences between Arteries and Veins
are as follows:-
(I) ARTERIES carry blood from the heart to all
parts of the body while VEINS carry blood from
all parts of the body to heart.
(II) ARTERIES carry oxygenated blood while
VEINS carry deoxygenated blood.
(Exception : Pulmonary artery and pulmonary
vein carries deoxygenated and oxygenated
blood, respectively.).
(III) The blood carried by arteries is red in colour
while veins carry the blood which gets
purplered coloured due to impurities and CO2.
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(iv) ARTERIES are deeply seated and thick
walled whereas VEINS are superficial and thin
walled.
7. What does a doctor feel when he checks our
pulse?
Ans:- Everytime the heart contracts the blood
rushes into the arteries with pressure, making
them throb. It is this throbbing that a doctor
feels when he checks our pulse.
8.What is excretion? Why is excretion
essential?
Ans:- The process of removing waste from the
body is called 'Excretion'.
Excretion is essential for every organism
because if these wastes are not expelled, they
would poison the body of an organism.
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9. How does sweating help to maintain our
body temperature?
Ans:- Our sweat glands are present under the
skin. When we feel very hot, it is then that they
start producing sweat which comes at the
surface of the skin and absorb our body's heat
to evaporate and hence maintain our body
temperature by keeping us cool.
10. What do we excrete in the process of
sweating?
Ans:- In the process of sweating, we excrete out
water with salt and urea.
11. Name the organs that comprise the urinary
system.
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Ans:- It comprises of:-
(I) Two kidneys.
(II)Two ureters
(III)Urinary bladder.
(IV) Urethra
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12. How does the waste filtered by the
Nephrons reach the urinary bladder?
Ans:- Nephrons- These are the tubules in the
kidney that filter the waste and thus separate
the nitrogenous waste.
(I) A nephron has a small cup with a long tube
attached to it, called as BOWMANS CAPSULE.
(II) There is a mesh of capillaries,called
GLOMERULUS in each of these cups.
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(III) Water and waste like urea and salt filters
into the cup and flows into its tube.
(iv) This tube joins together with other such
tubes which ultimately join the ureters.
13. What is Dialysis? How is it carried out?
Ans:- Dialysis is a process of removing waste
from the blood artificially. It is carried out when
one is suffering from kidney failure.
(I) The patient's blood is taken out from an
artery and is allowed to pass through tubes
whose walls are semi- permeable.
(II) The tubes which are dipped in a solution
,act like a sieve.
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(III) It allows the smaller waste particles to pass
out of the blood into the solution through
osmosis.
(IV) The clean blood remains in the tube and is
then introduced into patient.
Std-VII Transport and Excretion