566: When the bark of a tree is removed in a circular fashion all around near its base, it gradually dries up and dies because
(a) Water from soil cannot rise to aerial parts
(b) Roots are starved of energy
(c) Tree is infected by soil microbes
(d) Roots do not receive oxygen for respiration
Explanation:
When the bark of a tree is removed in a circular fashion all around near its base, it gradually dries up an dies due to the reason that the phloem layer of tissue just below the bark is responsible for carrying food produced in the leaves by photosynthesis to the roots. Without this food, the roots ultimately die and cease sending water and minerals to the leaves. Then the leaves die.
Plants need water to photosynthesize. To summaarise a fairly complex process, photosynthesis is the synthesis of sugar (energy) from light, carbon dioxide and water, with oxygen as a by-product. Take away any of those factors, and the plant won't grow. It has no energy.
567: In a bisexual flower, if androecium and gynaecium mature at different times, the phenomenon is know as
(a) Dichogamy
(b) Herkogamy
(c) Heterogamy
(d) Monogamy
Explanation:
Dichogamy is maturation of androecium and gynoecium at different times. It is of 2 types protandry and protogyny. When androecium (stamens) matures earlier than gynoecium it is called protandry and the vice versa is protogyny.
568: In the context of mitigating the impending global warming due to anthropogenic emissions of carbon dioxide, which of the following can be the potential sites for carbon sequestration?
1. Abandoned and uneconomic coal seams
2. Depleted oil and gas reservoirs
3. Subterranean deep saline formations
Select the correct answer using the code given below:
(a) 1 and 2 only
(b) 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
569: Ultrafiltering units of kidney are known as:
(a) Nephron
(b) Glomerulus
(c) Vena Cava
(d) Tubule
570: It is possible to produce algae based biofuels, but what is/are the likely limitation(s) of developing countries in promoting this industry?
1. Production of algae based biofuels is possible in seas only and not on continents.
2. Setting up and engineering the algae based biofuel production requires high level of expertise/technology until the construction is completed.
3. Economically viable production necessitates the setting up of large scale facilities which may raise ecological and social concerns.
Select the correct answer using the code given below:
a. 1 and 2 only
b. 2 and 3 only
c. 3 only
d. 1, 2 and 3