(i) The sequential inter-linking of organisms involving the transfer of food energy from the producers, through a series of organisms with repeated eating and being eaten is referred to as the food chain.
(ii) It is defined as a structural and functional unit of the biosphere, compressing living organisms and their non living environment that interact by means of food chains and chemical cycles resulting in energy flow, biotic diversity and material cycling to form a stable, self-supporting system.
(iii) Genesh's father wanted to enhance his son's interest in environmental science.

(i) Healthy forest ecosystem purifies air and water, mitigate droughts and floods, cycle nutrients, generates fertile soils, provides wildlife habitat, maintains biodiversity, pollinate crops, provides storage site for carbon and also provides aesthetic, cultural and spiritual values.
(iii) Out of cost of various ecosystem services, soil formation accounts for 50% and contribution of other services like recreation and nutrient cycling are less then 10% each. The cost of climate regulation and habitat for wildlife are about 6% each.
(iv) Values shown by Avinash are awareness towards ecosystem and environment.

(i) Earthworms are known as detritivores as they breakdown  detritus(dead remains of plants and animals) into smaller particles. Earthworms are often called farmer's friend.
(ii) Fragmentation is the first step in the process of decomposition. It is the process by which detritivores (e.g. earthworm) breakdown detritus in smaller particles.
(iii) The steps involved in decomposition are fragmentation, leaching, catabolism, humification and mineralisation.
(iv) Arun is very alert, curious and had scientific attitude.

(i) Food chain is the sequence of populations or organisms of an ecosystem through which food and its contained energy passes with each member and become food of later member of a sequence. It is a feeding chain of organisms in an ecosystem.
(ii) Grass is the producer which captures the solar energy and feeds the energy into food chain through photosynthesis.Goat is the primary consumer while man is secondary consumer.
(iii) There are mainly two types of food chain :
(a) Grazing Food Chain (GFC) - Begins with producers.
(b) Detritus Food Chain(DFC) - Begins with dead organic matter and decomposers.
(iv) Jeremy is keen and vigilant towards his studies practical applications.

(i) He occupies three trophic levels in three different food chains.
(ii) (a)Plants(vegetables) ->Pragyan
(b)Plants->Insects->Hen->Egg->Pragyan
(c)Plants->Hen->Egg->Pragyan.
(iii) Food chain (a) gives him maximum energy. This is because plants are autotrophs, i.e. they produce food through the process of photosynthesis and according to 10% law only 10% energy is passed on to next trophic level.
(iv) Pragyan is a sincere child, who possess scientific attitude towards his daily life.