(a) The differences between Grazing Food Chain (GFC) and Detritus Food Chain (DFC) are as follows

(b) The Detritus Food Chain (DFC) may be connected to the Grazing Food Chain (GFC) at same level in an ecosystem. It can be supported by the fact that certain organisms of the GFC are predators to certain animals of DFC.
For example, earthworms which are detritivores are eaten by small birds (DFC) which becomes prey to predators like vulture/kites or even small animals of the GFC.

(i) and (ii)
In grassland ecosystem, the number of producers (plants) is highest to support fewer herbivores (primary consumers) and carnivores (secondary and tertiary consumers). This can be understood by the following pyramid of number in a grassland ecosystem.

Only three top carnivores are supported in an ecosystem based on the production of nearly 60 lakh plants. As mentioned above, three tertiary consumers are supported by 60 lakh plants. Six tertiary consumers will be supported by 120 Lakh plants.

Effect of Oxygen : The decomposition of detritus is an energy requiring process. Most of the decomposers (bacteria and fungi) are aerobic organisms. They require Oxygen for their cellular activities while acting on dead organic matter.
Effect of Chemical : Composition Decomposition rate is slower, if detritus is rich in lignin and chitin. It is quicker if detritus is rich in nitrogen and water soluble substances like sugars.

(b) (i)  Since only 10% of energy is transferred from one trophic level to the next, the amount of energy keeps on decreasing as it travels to higher trophic levels.
(ii) Hence at higher trophic levels, the amount of energy is sufficient to sustain fewer organisms than the lower trophic levels.

Carbon cycle is the circulation of carbon between the abiotic and biotic components of the ecosystem with reservoir pool being carbonate rocks while the cycling pool consists of atmosphere and hydrosphere. Input. Carbon is being added to the cycling pool regularly by combustion of fossil fuels, respiration of organisms, volcano eruptions, hot springs, methane chimneys, weathering of carbonate rocks and industrial processing. Internal Cycling. Carbon present in the atmosphere (as CO₂) and hydrosphere (as bicarbonate and carbonic acid) is picked up by producers and changed into organic compounds in the process of photosynthesis. Annual carbon fixation is about 4 ×10 ¹³ kg. It produces about 170 billion tonnes (17×10 ¹³) of organic matter. Withdrawal of carbon by producers is called uptake. Part of organic matter synthesized by producers passes into higher trophic levels (herbivores, carnivores). It is called transfer. Wastes and dead bodies of organisms form detritus. Detritus is degraded by decomposers to release carbon locked in it. It enters the cycling pool for re-use by producers. Output. Some carbon is being taken out of cycling pool due to seepage of carbon rich water into interior of earth, skeletons and shells of animals and fossilisation.

(a) Healthy ecosystems are the base for a wide range of economic, environmental and aesthetic goods and services. The products of ecosystem processes are named as ecosystem services. For examples, healthy forest ecosystem purifies air and water, minimize droughts and floods, cycle nutrients, generates fertile soils, provides wildlife habitat, maintains biodiversity, pollinate crops, provid storage site for carbon and also provide aesthetic,cultural and spiritual values. Though value of such services of biodiversity is difficult to determine, it seems reasonable to think that biodiversity should carry a healthy price tag.
(b) Based on the nature of the habitat - whether it is water (or very wet areas) or it is on very dry areas- succession of plants is called hydrarch or xerarch, respectively.
Differences: Hydrarch succession takes place in wetter areas and the successional series progress from hydric to mesic conditions. As against this, xerarch succession takes place in dry areas and the series progress from xeric to mesic conditions.
Similarity: Both hydrarch and xerarch successions lead to medium water conditions (mesic), neither too dry (xeric) nor too wet (hydric).

Green plants are producers. They capture radiant energy of the sun during photosynthesis. Allother organisms depend upon plants directly (herbivores) or indirectly (carnivores) for their energy requirement. Thus the energy flows from producers to a number of consumers of various order in a unidirectional manner and it is neither created nor destroyed. In this way the first law of thermodynamics is satisfied in ecosystem functioning.

Earthworms are called farmer's friends because they bring about the fragmentation of detritus and loosening of soil. Humification is the process of formation of humus from detritus. Mineralization is the process of release of inorganic substances as both non-mineral and minerals from organic matter.

If the number of predators (tigers) get reduced, the number of prey (deer) population will increase. The prey population increases pressure on the vegetation. As a result, plant population decreases due to overgrazing.Little vegetation puts pressure on deer population and as a result deer population will decrease due to starvation, death or migration and ultimately more tigers (predators) will be affected.

(a)

(b)

(c)

(d)

(e)

(f)

(i) The species that invade a bare area called pioneer species.
(ii) In a xeric succession the pioneer species are usually lichens then bryophytes, which are succeeded by ferns and some other bigger plants.
Lichen produces lichen acid and carbonic acid which corrode rock surface and release minerals required for growth. The corroded rock accumulates soil particle by wind and provides substrate for bryophytes and ferns.

Sun is the endless source of energy, but the chemical materials of the environment are exhaustible.The producers fix solar energy into the chemical energy of organic compounds by utilizing inorganic substance (i.e., CO₂ and water). This stored energy is passed to consumers by repeated eating and being eaten.Decomposers act on dead decaying organic matter and return the locked inorganic substance back to the environment for their reuse by producers.Without this, all life will ultimately cease to exist and earth will be full of dead organisms and waste organic substances.

(a) Phytoplanktons
(b) Zooplanktons
(c) Oak tree
(d) lice and bugs

(i) Lichens are the pioneer species on a bare rock. They are resistant to desiccation and temperature extremes. They produce organic acids which corrode the rock surface. This produces depressions and releases minerals which facilitate their further growth. The dead lichens add organic matter to the forming soil. The next community develops on thismeagre soil formed.
(ii) The climax community will be trees.

All the regions of the world (atmosphere, lithosphere ad hydrosphere) where living organisms occur together with their abiotic environments from a biosphere. Main subdivisions of biosphere are atmosphere, lithosphere and hydrosphere.

An ecosystem may be defined as a structural and functional unit of the biosphere, comprising living organisms and their non-living environment that interact by means of food chains and chemical cycles resulting in energy flow, niotic diversity and material cycling to form a stable, self-supporting system. Few instances of an ecosystem are a pond, a lake, a grassland, a desert, a village, a forest etc,.

All organisms/animals which depend directly or indirectly on plants for their food are called consumers.
Consumers are of the following types:
(i) Primary consumers
They are the organisms/animals which depend directly on producers for their food;they are also called as herbivores,e.g. deer, rabbit, zooplanktons.
(ii)Secondary consumers
Secondary consumers are those animals which depend on the primary consumers for their food; they are primary carnivores, e.g frogs,hyena.
(iii)Tertiary consumers
Tertiary consumers are those animals which depend on the secondary consumers for their food;they are the secondary carnivores, e.g. lion, eagle, kite, etc.

Primary productivity is defined as the amount  of biomass or organic matter produced per unit area over a time period by the plants during photosynthesis.
It is also defined as the amount of biomass or  organic matter produced per unit area over a time period by the plants during photosynthesis.
Primary productivity depends on:
(i)The plant species inhabiting a particular area.
(ii)The environmental factors.
(iii) Available of nutrient.
(iv) Photosynthetic capacity of plants.