materials are either ejected by defecation or regurgitated in pellets of
indigested remains.
Assimilated energy (that is not lost through respiration or excretion)
is available for the synthesis of new biomass through growth and
reproduction. Organisms lose some biomass by death, disease or annual
leaf-drop, where they enter the detritus pathways of the food chain i.e.,
after the death and decomposition of organisms the materials flow back
into the environment. The remaining biomass is eventually consumed by
herbivores or predators and its energy there by enters the next higher trophic
level in the ecosystem.
The materials keep on cycling i.e. entering the living beings and through
death and decay returning to the soil and atmosphere Such a flow of
materials between organisms and their environment is called Cycling of
materials or mineral circulation or Biogeochemical cycles (You have
learnt in class IX )
Energy enters the producers in the ecosystem from the sun in the form
of solar energy or solar radiation. No other organisms except green plants
and Photosynthetic bacteria due to the presence of chlorophyll are capable
of absorbing solar energy and converting it into chemical energy (food)
From the producers, the chemical energy passes to the consumers
from one tropic level to the next through food. At each trophic level,
organisms use most of the food energy that they assimilate into their bodies
to fulfill their metabolic requirements- performance of work, growth and
reproduction. Because biological energy transformations are inefficient,
a substantial proportion of metabolized food energy is lost, unused as
heat. Hence pyramid of energy is always upright.
Only a small fraction goes to the eater at next trophic level. Organisms
are no different from man-made machines in this respect. Most of the
energy in gasoline is lost as heat in a car’s engine rather than being
transformed into the energy of motion. In natural communities, energy
used to perform work or dissipated as heat cannot be consumed by other
organism and is forever lost to the ecosystem.
