(i) Ramesh suffered from attitude sickness because he could'nt get sufficient oxygen due to low atmospheric pressure at a high attitude.
(ii) His friend advised him to take rest for some time because he thought that after a short rest period his body would get acclimatized to the atmospheric conditions prevailing at the high attitude
(iii) Values exhibited by Ramesh's friend-awareness and helpful nature.

(i) Mycorrhizae
(ii) In this association, fungi help the plants in absorption of nutrients, while plants provide food for the fungus.
(iii) (a) It optimises the use of fertilisers, especially phosphorus
(b) It increases crop yield and plant tolerance to saline environments.
(iv) Students are curious towards science and biological aspects.

(i)Smaller animals are rarely found in polar regions because such animals have surface area relative to their volume and they tend to loose heat very fast when it is cold outside. This is they are rarely found in polar regions
(ii) Animals that live in polar regions are adaptable to polar environments by features like the presence of thick skin coat, tendency to change colour or camouflage to white in snow and high metabolic rate. These features allow animals to adapt in colder environments.
(iii) Chief characteristics of polar region animals are:
(a) large sizes
(b) hairy skin
(c) lipid layer beneath the skin
(iv) Himani showed curiosity and eagerness for learning new things

The chemical composition and pH of water are important to affect the animals.
Some animals can tolerate only a narrow range of salinity and are called stenohaline.
Some animals can tolerate a wide range of salinity and are called euryhaline.
Many freshwater fishes can not live for long in sea water and vice versa, because of the osmotic problems, they would face in such waters.
(b) (i) The leaves are reduced to spines.
(ii) The stem is green, flattened, spongy and takes over the function of photosynthesis .
(iii) A thick cuticle prevents loss of water.
(iv) They have a special photosynthetic mechanism (CAM), that enables their stomata to remain closed during day and open during night.
(c) Water is the most precious resource, use it judiciously and think of programs for its conservation.

(a) The factors include
(i) The rotation of the earth around the sun and the tilt of its axis cause annual variation in the intensity and duration of temperature, which affects distinct reasons.
(ii) Annual variation in precipitation.
(b) (i) Scorching deserts of Rajasthan.
(ii) Rain-soaked Meghalaya forests
(iii) Deep ocean trenches.
(iv) Tropical rain forests
(v) High mountain tops. (any four)
(c) Interactions are necessary; they should be beneficial to all.