A population is the number of individuals in a particular species, within a community
Ecosystems hold many species and within those species is a population, vast or minor. The greater the population of a species, the more sustainable and long-lasting the ecosystem is, overall. Biodiversity is known as the "variety of life" and is always changing.
An ecosystem is composed of abiotic and biotic organisms in a designated area. Abiotic organisms are non-living things, while biotic organisms are living. All the biotic organisms in an ecosystem are known as communities.
For instance, the forest is filled with biotic creatures, like mammals, and insects, like spiders. It also has many abiotic things like rocks, water, and soil.
An organism is an individual member of a species.
Animals can sustain themselves underwater too. Organisms that live underwater are known as Aquatic, along with water itself.
Squirrels and many other biotic organisms that live on land, and the land itself, are known as terrestrial. Animals sustain themselves, which means they can maintain at a certain level, for instance: the mammals maintain their lifestyle in the forest, by keeping their supplies ready when necessary, this is known as being sustainable.
Organisms like deer, use air, water, and land to live: the zone of air, water, and land are known as the Biosphere. These organisms, animals, and plants are particular species that inhabit ecological or environmental areas, which is known as a habitat.