Ecological pyramid and ecological succession

 Ecological pyramids:-

1) Pyramid shape is such that base of a pyramid is broad and narrows down towards the apex. 

2) the base of each pyramid represents the producers or the first trophic level whereas The Apex or tip represents tertiary or top level consumer. 

3) the usually studied types of pyramids are

Pyramid of number

Pyramid of biomass 

1. pyramid of energy
2. Any species can occupy more than 1 position in trophic level in some ecosystem at the same time.
3. Example of sparrow
4.  inmost ecosystems all the pyramids of number, Biomass and energy are more while herbivores are list and carnivores very less . And energy of lower level is higher as that of higher level.
5.  Exception is tree and insects while Biomass of sea is also inverted. 
6. Pyramid of energy is always upright and can't be inverted because energy is always gets loosed from one tropical level to other and to other
7. While energy lost is of heat. 
8. Each bar represents energy of pyramid the amount of energy present at is tropical level in a given time Or annually per unit area. 

Limitations:-

Certain organisms are at Two Or more trophic level this can't get explained. 

It is assumed that food chain is simple which never exist in nature. 

Saprophytes are not get any position although they are very important. 

Ecological succession:-

 

1. An important characteristic of all communities is that their composition and structure changes constantly in response to the changing environmental conditions.
2.  The change in orderly and sequential and parallel with the changes in the physical environment.This lead finally to community that is in equilibrium with the environment and that is called a climax community. 
3.  The gradual and fairly predictable change in the species composition of a given area is called ecological succession. 
4. During succession same species colonies or inhabit and area and whereas population of the species decline and even disappear. 
5. The entire sequence of communities that successively change in a given area are called sere. 
6. Individual transitional communities are seral stages or seral communities. 
7. The present day communities come into existence because of ecological succession that happened over millions of years since life started on earth. 
8. Actual succession and evolution would have been parallel processes at that time. 
9. Examples Areas where primary succession occurs are newly cooled Lava , bare rock, newly created pond or reservoir. 
10. Secondary succession begins in areas where natural biotic communities have been destroyed switches in abandoned farm lands, burn Or cut forests,  land that have been flooded.
11.  Secondary succession is faster than primary succession.
12. Man made activities as deforestation or fire eliminate some species and abandon some species aur convert some seral stage of succession to an earlier stage. 

Succession of plants:-

1. Based on natural habitat it is very weight or dry areas succession of plant is called Hydrarch Or xerarch. 
2. Hydrarch succession takes place in water abundant wetter areas and successional series progress from hydric to the meric condition. 
3. Hence both hydrarch and Siraj stations lead to the medium water mesic condition that is neither too dry (xeric) nor too wet hydric. 
4. The species which invade a base area call Pioneer species. 
5. In primary succession on rocks lichen secrete acids to dissolve rock helping weathering and soil formation. 
6. Later bryophytes which are able to hold some small amount of soil
7. After sometime big plants and ultimately stable forest community is formed. 
8. This climate community remains stable as long as environmental conditions remains an unchanged. 
9. The time the xerophytic habit that gets converted into a mesophytic one. 
10. In primary succession in water The pioneer are the small phytoplanktons, which are replaced with time by rooted or submerged plants rooted floating angiosperms followed by free floating angiosperms, followed by free floating plants, then Reed swamp, scrub and finally the trees. climax is land. 
11. In secondary succession the species that invade depends on the condition of the soil, availqability of water also helps propagules present. Since the soil is there, rate of succession is high and faster climax is also reached more quickly. 
12. Primary session is very slow process taking thousands of years for the climax  to be reached.