Energy flow in ecosystem

Environmental Studies

Unit 2.2

Types of Flow models….

1. Single channel Models

2. Double channel Models (also called Y shaped Models.)

Grazing

Detritus

Single-channel energy models

• This model explains the unidirectional flow of energy.

• Whatever the energy captured by the autotrophs does not revert back to solar input. As it moves progressively through the various trophic levels, it is no longer available to the previous level.

• the system would collapse if the primary source, the sun, were cut off.

• there is a progressive decrease in energy level at each trophiclevel. So, shorter the food chain, greater would be the available food energy.

Photosynthesis

• It is a chemical process that converts carbon dioxide

into organic compounds, especially sugars, using the

energy from sunlight

The process occurs in two steps:

• First light energy is absorbed by chlorophyll to split a

molecule of water releasing hydrogen and oxygen.

• The second step uses the energy to convert carbon

dioxide to carbohydrates.

6CO2 + 12H2O ---> C6H12O6 + 6O2 + 6H2O

Respiration

While photosynthesis builds stored chemical energy in a

plant,

Respiration is the process of "burning" stored chemical

energy basically through oxidation, for maintaining

plant metabolism.

During plant respiration,

C6H12O6+6O2--->6CO2+6H2O+2830 kj

Autotrophs

(111 g/cm2/yr.)Herbivores

(15 g/cm2/yr.)

Carnivores

(3 g/cm2/yr.)

Solar radiation(118,872 g/cm2/yr.)

Autotrophs

(111 g/cm2/yr.)Herbivores

(15 g/cm2/yr.)

Decomposition-D(3)

Not utilized-NU(70)

Respiration-R(23)

D (0.5)

NU (7.0)

R (4.5)

D (trace)

NU (1.2)

R (1.8)

1

Y- shaped or 2-channel model

It is applicable to both terrestrial and aquatic ecosystems. In thisenergy model, one arm represents herbivore food chain and theother arm represents the decomposer (detritus) food chain.

The primary producers are entirely different for each arms. Thismodel also indicates that two food chains are infact, undernatural conditions, not completely isolated from one another.

(i) it confirms to the basic stratified structure of ecosystem.

(ii) it separates the grazing and detritus food chains in both time andspace, and

(iii) micro consumers and macro consumers differ greatly in size andmetabolic relations.

Sunlight

Plants

Herbivore

Detritus Consumer

Predator

Predator

2

Universal Model

• Proposed by Odum. It is applicable to any living component whether a plant, animal /microorganisms or individual/population or a trophic group. • These models depict the basic pattern of energy flow in ecosystem. Under natural conditions, these organisms are inter related in a way that several food chains become interlocked this results into a complex food web.• Complexity of food web depends on the length of the food chain. Thus in nature, there operate multi channel energy flows. But in these the channels belong to either of the two basic food chains - Grazing or Detritus.

IA

NU

S

E

GP

R

B

3

4

References/Sources

1. https://lh5.ggpht.com/2SZXkoyviYm84vNry1cdicBBu9US_EVYPfbQtr9Aes2YvshYG0Ks7Oofi54ieKITVSFmZLg=s139

2. https://lh4.ggpht.com/bgEnwIiNJwJIXDAoFgAjOKgNFuemonldH6FtEf0KSBnSDyJVbXNqbG6ZbUuqSUxybdckens=s170

3. https://lh4.ggpht.com/KOJi8OsE1nofIJ6oo6xFCn6ny2JND3Z-CWtjGXX_sRDUAFfzGxLz6SHGkQ-B14-cInb0yA=s122

4. https://lh5.ggpht.com/_TATKuvaEDDGRmnIO81eKJG4FNXEjD0-e4DY_zw8yT8gq9ECTrI-ybUnP1T0luBwbKXlmA=s90

Book/Web Resources

http://www.docstoc.com/docs/172268724/ecosystemppt