Species of plant, animal and microorganism.
A biosphere is the sum of all the ecosystems established on Earth. Levels of organization in an ecosystem To understand the levels of belonging in an ecosystem, let us consider the diagram below. Individual, Species, Organism: An individual is any living thing or organism. Individuals do not breed with individuals from other groups.  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. Ecosystems are controlled both by external and internal factors. External factors such as climate, the parent material which forms the soil and topography, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. For example, the cycling of elements is controlled in part by organisms, which store or transform elements, and in part by the chemistry and geology of the natural world. The term Biogeochemistry is defined as the study of how living systems influence, and are controlled by, the geology and chemistry of the earth. There are many food links and chains in an ecosystem, and we refer to all of these linkages as a food web. Food webs can be very complicated, where it appears that everything is connected to everything else, and it is important to understand what are the most important linkages in any particular food web. The carrying capacity is the maximum population size of a particular species that a given ecosystem can sustain. As the population size increase, the demand for resources such as food, water, shelter and space increases. Eventually, there will not be enough resources for each individual and stress will occur. A limiting factor is a factor that restricts the size of a population from reaching its full potential. The amount of food & water in a habitat is an example of a limiting factor. Other factors include geographical space, predation, climate, competition (for prey, food, mates) etc. An ecosystem’s biological community consists of populations of every species of plant, animal and microorganism in the ecosystem. People interact directly or indirectly with populations whenever they interact with ecosystems.  An ecosystem consists of the biological community that occurs in some locale, and the physical and chemical factors that make up its non-living or abiotic environment. There are many food links and chains in an ecosystem, and we refer to all of these linkages as a food web. Food webs can be very complicated, where it appears that everything is connected to everything else, and it is important to understand what are the most important linkages in any particular food web. * Populations of organisms can be categorized by the function they serve in an ecosystem: producers make their own food (plants), consumers obtain food by eating other organisms (animals), and decomposers consume waste materials and dead organisms (bacteria and fungi). * Energy from the sun flows through ecosystems.  Toxic Waste. Particularly important for organisms living in a small-enclosed ecosystem, a large population in a species means that the waste produced by them begins to come into play, as the waste increases the risk of disease, and reduces hygiene. The result is that ecosystem can no longer sustain the species' population size and they begin to die out until the population size is at a more sustainable level. Human intervention also has increasingly played a part in determining the population of species, either via domestication or consequence from our actions. Density Independent Factors. These factors occur regardless of a population size in a species. Usually these are environmental disasters, such as a forest fire, tidal wave etc that destroy the natural ecosystem that a species survives in. The result is that ecosystem can no longer sustain the species' population size and they begin to die out until the population size is at a more sustainable level. Human intervention also has increasingly played a part in determining the population of species, either via domestication or consequence from our actions. An ecosystem is comprised of all the non-living elements and living species in a specific local environment. Components of most ecosystems include water, air, sunlight, soil, plants, microorganisms, insects and animals. Ecosystems may be terrestrial -- that is, on land -- or aquatic. Sizes of ecosystems vary; they could entail a small puddle or an enormous swath of desert.
http://eschooltoday.com/ecosystems/levels-of-organisation-in-an-ecosystem.html https://en.wikipedia.org/wiki/Ecosystem http://www.globalchange.umich.edu/globalchange1/current/lectures/kling/ecosystem/ecosystem.html http://schoolworkhelper.net/biotic-and-abiotic-factors-influence-on-ecosystems/ http://gerrymarten.com/human-ecology/chapter02.html http://www.globalchange.umich.edu/globalchange1/current/lectures/kling/ecosystem/ecosystem.html http://www.learningscience.org/lsc2dpopulationsecosystems.htm http://www.biology-online.org/4/5_monitoring_populations.htm http://www.biology-online.org/4/5_monitoring_populations.htm http://classroom.synonym.com/10-examples-natural-ecosystem-7836.html
example of population in an ecosystem