Answer:
Three types of blood vessels are
connected to form a closed system in human body.
(i) Arteries These are wide,
thick elastic walled vassels, which carry blood from heart to all body parts.
Arteries carry oxygenated blood except pulmonary artery, which carries deoxygenated
blood from heart to lungs.
(ii) Capillaries Arteries keep
dividing further into smaller vessels and finally for the smallest vessels
called capillaries. These have permeable wall and exchange gases, nutrients and
waste products across the tissues.
(1)
(iii) Veins The capillaries
combine together to form thin walled vessels called veins. Veins carry
deoxygenated blood from body organs to the heart. Pulmonary vein carries
oxygenated blood from lungs to the heart.
Or
The mechanism of transport of
water and minerals in plants is as follows
(i) The xylem forms an
interconnected network of vascular tissues, which create a continuous channel
from root tracheids to all plant parts. (1)
(ii) The cells of root hair in contact
with soil take up ions, which create an ion concentration gradient between root
and soil. (1)
(iii) The water flows into root
from soil due to osmosis. (1)
(iv) Stomata loose water to the
surroundings through transpiration. This creates a suction force, which pulls
water upwards to heights. (1)
(v) The steady movement of water
into the root from the soil pushes water upwards. (1)
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