Notes on Food chain, Food web and ecological pyramids (Functional aspect of ecosystem) | Grade 11 > Biology > Ecosystem | KULLABS.COM

Food chain, Food web and ecological pyramids (Functional aspect of ecosystem)

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Food chains

Food chains
source:www.tes.com
fig:Food chains

The transfer of food energy from one trophic level to another trophic level in an ecosystem by the repeated process of eating and being eaten is known as food chain. Generally, food chain starts with the organism which does not eat other organism and ends with the organism which is not eaten by the other organism.
Eg; Producer→ Primary consumer→ Secondary consumer→ Tertiary consumer

Types of food chain

There are three types of food chain they are;

  • Grazing food chain
  • DetrituS food chain
  • Parasitic food chain

Grazing food chain

Grazing food chain
source:www.slideshare.net
fig:Grazing food chain

This type of food chain starts from producers and ends to carnivores by passing through herbivores. This type of food chain directly depends on the radiate energy of the sun. Most of the ecosystem follow this type of chain.

Eg; Producer→ Primary consumer→ Secondary consumer→ Tertiary consumer

In grassland ecosystem,

Grasses→ Grasshopper→ Frog→ Snake→ Hawk

In pond ecosystem

Phytoplanktons→Zooplankton→ Small fish→ Large fish

Detritus food chain

Dentrial food chain
source:environmentandmanagement.blogspot.com
fig:Detritus food chain

The dead organic remains and metabolic wastes derive from producer and consumers are generally called detritus. The energy contained in a detritus serve as a source of energy for a group of organisms called detritivores. The main source of energy is the detritus. So, the food chain starts with detritus to detrivores and to their predators.

Eg; Detritus→Earthworm→ Birds

Parasitic food chain

Parasitic food chain
source:www.cram.com
fig:Parasitic food chain

It goes from large organisms to smaller ones without outright killing as in a case of predation.

Eg; Tree→herbivore bird→ parasites→ hyperparasites

Food web

Food web
source:www.teachengineering.org
fig:Food web

A food web can be defined as the natural interconnection of food chains and generally a graphical representation (usually an image) of what - eats - what in an ecological community.

Types of food web

  1. Terrestrial food web: It is the interlocking of various food chains in a terrestrial land.
  2. Aquatic food web: It is the interlocking of various food chains in the pond.

Productivity

The fixed amount of energy which passes from one trophic level to next trophic level is called productivity and the phenomenon is known as productivity. It is of two types:

  1. Primary productivity: Primary productivity is the rate at which energy is bound or organic material is synthesized by photosynthesis per unit area of earth's surface per unit time.
    The total solar energy captured in the food material by photosynthesis is known as gross primary productivity. It is utilized in respiration process in green plants. The amount of organic matter manufactured per unit area and time that is left after respiration of green plants is called net primary production.
    Net productivity of energy = Gross productivity - energy lost in respiration

  2. Secondary productivity:The rate at which the heterotrophic organisms remanufacture the energy supplying substances is known as secondary productivity.
    The total amount of energy stored in the tissues of heterotrophs (consumers and decomposers) is known as net secondary production.

Ecological Pyramids:

An ecological pyramid is defined as the graphical representation showing the relationship between the various trophic level of a community. There are three types of ecological pyramid which are as follows:

  1. Pyramid of Numbers:

    The pyramid of numbers shows the relationship in terms of a number of producers, herbivores, and carnivores at their successive trophic levels.
    There are two types of pyramid of numbers:

    Upright pyramid of number: It is found in the aquatic and grassland ecosystem, in these ecosystems, there are many small autotrophs which support lesser herbivores which in turn support the smaller number of carnivores. So, the pyramid is upright.

    The inverted pyramid of number; It is seen in the parasitic food chain where one primary producer supports numerous parasites which support more hyperparasites.

  2. Pyramid of biomass:

    Biomass can be defined as the total weight of dry matter or fixed energy present in the ecosystem at any one time. In this pyramid, there is a gradual decrease in the biomass from the producers to the higher trophic levels.
    There are two types of pyramid of biomass:

    Upright pyramid: It is seen in forest ecosystem as there is generally gradual decrease in biomass of organisms at successive levels from the producers to top carnivores.

    The inverted pyramid of biomass: This is found in the aquatic ecosystem. Here, the smaller weight of producers support consumers of large weight.

  3. Pyramid of energy:

    The energy pyramid describes the complete nature of the ecosystem. An upright pyramid will always be formed if the rate of energy utilized by different level is diagrammatically represented. There is always gradual decrease in the energy content at successive trophic levels from the producers to various consumers. At each trophic level, there is a successive loss of energy in the form of heat and respiration.



  • The transfer of materials and energy in the form of food from one trophic level to another trophic level by the repeated process of eating and being eaten is known as food chain.
  • Three types of the food chain are  grazing food chain, parasitic food chain, and detritus food chain.
  • The number of food chains is interconnected to each other forming a network is called food web.
  • Two type of food webs is terrestrial food web and aquatic food web.
  • The portion of fixed energy, a trophic level passes on to the next trophic level is called production.
  • The phenomenon of energy production is known as productivity.
  • An ecological pyramid can be defined as a graphical representation showing relationships between the various trophic levels of a community.

 

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