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The Environment, Levels of Ecology and Ecosystems

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  1. 1:54 Organismal Ecology
  2. 2:18 Population Ecology
  3. 3:07 Community Ecology
  4. 3:49 Ecosystem Ecology
  5. 4:10 Biosphere Ecology
  6. 4:34 Lesson Summary
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Taught by

Joshua Anderson

Do you know the difference between an environment and an ecosystem? In this lesson, you'll find out what makes an environment, and what makes an ecosystem. You'll also learn what ecology is and some of the ways that scientists study ecology using organisms, populations, communities, ecosystems and even the entire biosphere.

Principles of Ecology

Ecology is the study of the interactions between organisms and the environment they live in, which brings us to another important term that's used frequently in ecology: the environment, which is the set of conditions that surround an organism. Environmental factors include temperature, light, water, air, soil and nutrients that surround an organism. An environment can be very large and even refer to the entire Earth. An environment can also be very small. For example, the environment of an intracellular parasite can be as small as a single host cell. In most cases, when the term environment is used in the context of ecology, it refers to all the abiotic factors or nonliving environmental factors that surround an organism. However, in the case of organisms that live inside other organisms, we can't really be strict about this particular definition because the tissue surrounding these organisms is living, but that still doesn't exclude the tissue from being a part of the environment nonetheless.

Ecology covers a wide array of interactions that are observed on a microscopic scale all the way up to a global scale. Ecology looks at how organisms interact with each other, how they are affected by their environment, and how they, in turn, affect the environment that they live in. Humans, in particular, have had a huge impact on many different ecosystems, and these changes have affected, not only, other species but the global environment as a whole. But before we get to all that, let's talk about the different levels of organization within ecology and touch on a few ways in which these different levels are studied by biologists.

Organismal Ecology

Here, we have a monkey, which is an example of an organism or an individual living thing that is capable of responding to stimuli, growing, reproducing, and maintaining homeostasis. The interactions that an individual organism has with its environment can be referred to as organismal ecology and is the lowest level of ecology that can be studied.

Population Ecology

All organisms in a particular geographic area that belong to the same species make up a population. Population ecology studies the interactions between a particular population and the environment. Population studies are the type of ecological study most likely to be talked about by the general public and have been a rich source of data for ecologists over the years. A population gives an ecologist a well-defined group of subjects to study whose numbers can, usually, be reasonably estimated, which gives a scientist a way to quantify their results. If population studies are done in a geographic area with a large enough number of populations, ecologists can then begin piecing together the larger ecological picture, which brings us to the next level of ecology: community ecology.

Community Ecology

A community is composed of all organisms of all species in a geographic area. A community consists of all plants, animals, fungi, and single-celled organisms in whatever geographical area is being studied. Communities are comprised of so many different species of organisms that community studies are difficult to execute all at once, which is why most ecologists tend to focus on population studies. Then, when population studies from enough representative organisms are available for a particular location, the different population studies can be combined to answer questions about the community as a whole.

Ecosytem Ecology

An ecosystem is composed of the community and all abiotic factors like weather, water, soil, and elevation within a geographic location. Ecosystem ecology is often used when studying energy flow. In addition, pollution studies often focus on the effects that various types of pollution have on specific ecosystems.

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