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.

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.

(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.

5. Explain with a block diagram, the functioning

of a human heart.

Ans-

(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'.

(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.

(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.

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.

Ans:- It comprises of:-

(I) Two kidneys.

(II)Two ureters

(III)Urinary bladder.

(IV) Urethra

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.

(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.

(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