An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system. These biotic and abiotic components are regarded as linked together through nutrient cycles and energy flows. As ecosystems are defined by the network of interactions among organisms, and between organisms and their environment, they can be of any size but usually encompass specific, limited spaces(although some scientists say that the entire planet is an ecosystem).
Energy, water, nitrogen and soil minerals are other essential abotic components of an ecosystem.The energy that flows through ecosystems is obtained primarily from the sun. It generally enters the system through photosynthesis, a process that also captures carbon from the atmosphere. By feeding on plants and on one another, animals play an important role in the movement of matter and energy through the system. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes

Sparrow Also Play An Important Role In Ecosystem

Sparrows are generally associates with human beings.Sparrows are found in the places where human are densely populated. Sparrows eat food grains like wheat, oat etc and larvae of mosquitoes and insects.

The some major importance of sparrow are :

Ecological Balance : Every animal and plants in this world has its significance. The sparrow is a member of many food chain and food web. So as you know if you harm any food chain it will affect complete food web. So if you will not save sparrow it will disturb ecological balance.

Pollination in many plants : Sparrow helps in pollination in many plants. Pollination is a
process by which the pollen grain of one flower reaches to stigma of other flower in sexual reproduction. So Sparrow helps in sexual reproduction in plants.

Reduce many diseases : Sparrow eats larvae of many insects and mosquitoes which causes many diseases like malaria, dengue etc. So sparrows protect us from many diseases which are life threatened.

Brings prosperity : Sparrows bring prosperity for us. We like to watch this small and lovable bird. Our children always want to observe this bird and always sing songs related to this bird to entertain themselves.

Reasons of declining

Loss of tree cover : The deforestation is also a reason of decline of sparrows population. We are constructing modern buildings, malls, big bazaar, industries etc by destroying forest and plants.

Pollution : Pollution is the most important reasons of declining the numbers of sparrows. Different types of pollution like water pollution, soil pollution, noise pollution, etc adversely affect sparrows.

Loss of habitat : Due to modern technology old spacious buildings have been changed to the shapes where sparrow do not find their habitat. It is the most important reason of decline of population.