Functional aspect of ecosystems

Functional aspect of ecosystems:
1. Trophic level:
The arrangements of producers and consumers in an ecosystem is called trophic structure where each level is called trophic level.
- The first trophic level is made up of green plants which directly derive their energy from the sun
- The energy from plants is passed into herbivores (primary consumers) thus they constitute second trophic level
- The herbivores i.e. the primary consumers are passed their energy into primary carnivores thus secondary consumer or primary carnivores constitute the third trophic level
- The tertiary consumer derive their energy from secondary consumers thu constitute the fourth trophic level
- The decomposer forms the last trophic level
- Some organisms derive their energy from more than one trophic level e.g. omnivorous mammals feed upon both producers as well as consumers e.g. human

2. Food chain 
The transfer of food energy from the producers through a series of organisms with repeated process of eating and being eaten is called food chain.
- The concept of food chain was introduced by Charles Elton
- It forms a simple linear chain of eating and being eaten.
- It is three types

A. Grazing or predatory food chain 
I. In pond
It starts from phytoplankton in pond ecosystem from which food energy moves smaller to larger animals.
- It is the longest food chain of natural ecosystem
Phytoplankton  ➞  Larvae      ➞    small fishes  ➞  Larger fishes
                             Zooplankton         pri. Cons.          Sec.cons
II. Grassland ecosystem 
         Plant    ➞   Larvae and   ➔  Frog   ➞   Snakes 
                              Insects
Ist trophic             II                       III               IV
level
-  It starts from plant and energy goes from smaller to larger animals

B. Detritus or saprophytic food chain
- The dead bodies of plants and animals are partially decomposed by bacteria and fungi into organic matters called detritus.
- The energy coontained in this detritus is not totally lost in the ecosystem but serves as a source of energy for other groups of animals called detritivorous.
- It starts from detritus and energy goes from smaller to larger animals
I. In pond 
Detritus of Phytoplankton ➞Larvae of  ➞   Smaller ➞ Larger fishes
and macrophytes                    insects          fishes
                                                (Detritivorous)

II. In grassland 
Detritus of   ➙ Millipeds, Larvae    ➞ Frog  ➞  Snakes
Plant                  insects
                            (Detritivorous)

C. Parasitic food chain 
-- The primary source of food and energy is parasism
-  It starts from plant and energy goes from larger to smaller animals
- It is the shortest food chain of natural ecosystem
Plants  ➞  Sheep  ➞ Liverfluke  ➔Protozoans


3. Food web:
- The interconnected food chain is called food web.
- No food chain is independent thus hardly there is a linear food chain in nature
- Thus in an ecosystems, various food chain are interconnected together and forms acomplex network.
- Food web in nature is generally made up of three types of food chains i.e grazing, detritus and parasitic food chain.
- In natural ecosystem same organism may be eaten by several organism of higher trophic level.
- It provides alternative pathways of food availability and makes the ecosystem stable stable.


                     Grasshopper  ⟶    Lizard
                  ↗                                      ↘

      Grass          →       Rabbit         ⟶   Hawk
                  ↘                                       ↗
                        Mouse     →    Snakes
            Fig: Food web in grassland ecosystem


Ecological pyramids:
- The graphical representation of ecological parameters such as number, biomass and energy at each trophic level is called ecological pyramids.
- Accordingly ecological pyramids are of three types i.e. pyramid of number, pyramid of biomass and pyramid of energy.
- The concept of ecological pyramids was introduced by Charles Elton.
- In ecological pyramids, the base is always occupied by producers whereas successive level by higher consumers.

Fig:  Ecological pyramid

A. Pyramids of number:
- The graphical representation of the arrangements of number of individuals of different trophic level in food chain of natural ecosystem in called pyramids of number.
- The number of plants (producers) are always larger in grassland and pond ecosystem and numbers of consumers decrease from bottom to top thus it has upright pyramids.
- The producers are always larger in number whereas top carnivores are least in number.

Fig: Pyramids of number in pond & grassland
B. Pyramids of biomass:
- It is the graphical representation of the biomass present in different trophic level in an ecosystems.
- It is upright in terrestrial ecosystems where biomass is maximum at producers level and gradually decreas in biomass from lower to higher trophic level.
- The  shape of pyramid of biomass in terrestrial ecosystems are due to transfer of only 10% biomass from lower to the next higher trophic level.
- In aquatic ecosystems pyramids of biomass are inverted or spindle shaped because here biomass depends upon reproductive potential and longevity of life.

Fig: Pyramids of biomass in pond & grassland
C. Pyramid of energy:
- It is the graphical representation of the amount of energy trapped perunit time and area in different trophic level of an ecosystem.
- Pyramids of energy are always upright this is due to gradual decrease in energy in successive trophic levels.
- According to a rule only 10% energy is transferred from a trophic level to the next higher trophic level.

Fig: Pyramids of energy