Question

model of energy flow in ecosystem
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Answer 1

Answer:

1.  Single Channel Energy Flow Models

2. Y-shaped Energy Flow Models:

Explanation:

1. Single-Channel Energy Models:

• The principle of food chains and the working of the two laws of thermodynamics can be better made clear by means of, energy
• The flow of energy takes place in a unidirectional manner through a single channel of green plants to herbivores and carnivores. The energy which is passed to the next trophic level is never reverted back to the lower level.
• there occurs a progressive decrease in energy level at each trophic level. This is accounted largely by the energy dissipated as heat in metabolic activities and measured here as respiration coupled, with un-utilized energy.
• Energy inflows balance outflows as required by the first law of thermodynamics, and energy transfer is accompanied by dispersion of energy into unavailable heat (i.e. respiration) as required by the second law. Figure 1. 4 presents a very simplified energy flow model of three tropic levels, from which it becomes evident that the energy flow is greatly reduced at each successive trophic level from producers to herbivores and then to carnivores.
• Thus at each transfer of energy from one level to another, major part of energy is lost as heat or other form. There is a successive reduction in energy flow whether we consider it in terms of total flow (i.e. total energy input and total assimilation) or secondary production and respiration components. Thus, of the 3,000 Kcal of total light falling upon the green plants, approximately 50 per cent (1500Kcal) is absorbed, of which only 1 per cent (15 Kcal) is converted at first trophic level.

2. Y-shaped Energy Flow Models:

• The Y-shaped model further indicates that the two food chains namely the grazing food chain and detritus food chain are in fact, under natural conditions, not completely isolated from one another.
• The grazing food chain beginning with green plant base going to herbivores and the detritus food chain beginning with dead organic matter acted by microbes, then passing to detritivores and their consumers.
• The important point in Y-shaped model is that the two food chains are not isolated from each other. This Y- shaped model is more realistic and practical working model than the single-channel model because,

• it confirms to stratified structure of ecosystems,
• it separates the grazing and detritus chains (direct consumption of living plants and utilization of dead organic matter respectively) in both time and space, and
• that the micro-consumers (absorptive bacteria, fungi) and the macro-consumers (phagotrophic animals) differ greatly size-metabolism relations.
• It must however, be remembered that these models depict the basic pattern of energy flow in ecosystem. In practice, under natural conditions, the organisms are interrelated in a way that several food chains become interlocked results into a complex food web. We have already referred to food webs in grassland and in pond ecosystems. The complexity of food web depends on the length of the food chains.
• Thus in nature there operates multi-channel energy flows, but in these the channels belong to either of the two basic food chains i.e., will be either a grazing or a detritus food chain. Interlocking pattern of such several chains in food web of an ecosystem would lead to a multi-channel flow of energy. Thus in practice, under field conditions, we might face difficulties in measuring energetic of ecosystem.

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Answer 2

Answer:

It is also called double channel model, given by H. T. Odum. In nature, both grazing and detritus food chains operate in the same ecosystem. However, sometimes grazing food chain (open sea ecosystem) or detritus food chain (in forestecosystem) predominates.

Explanation:

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