Populations, Communities, and Ecosystems Help

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By — McGraw-Hill Professional
Updated on Aug 30, 2011

Introduction to Populations, Communities, and Ecosystems

Life does not stop with the individual body. There are still several levels of biological organization lying beyond the organism (but including it).


Of course, male and female organisms of the same species ( SPEE -sheez) or “kind” can breed with one another. The result of such breeding is a population. A population consists of a group of individuals of the same species that live together in the same place. A population of human beings, for example, consists of individuals of the species Homo sapiens ( HOH -moh SAY -pea- enz ) – literally “men” ( Homo ) who are “wise” ( sapiens ), living and breeding together.


Found above the population level is the community level. A community consists of all the organisms (including those of different species) living and potentially interacting with each other in the same area. An interacting group of Homo sapiens and various species of plants, animals, birds, and insects, for instance, could make up a particular forest community.


Perched at the peak of the Pyramid of Life is the ecosystem. An ecosystem includes both the living organisms in a biological community as well as the non-living factors present in their physical environment. A forest community like the one just described, for example, could include rivers, waterfalls, and scenic gorges.


We have now defined and discussed all 12 levels of biological organization. And when we talk about biological organization, we essentially mean Biological Order. Each of the 12 levels in the Pyramid of Life, then, represents a particular pattern and complexity of Biological Order. If one of these levels becomes disturbed, such that its pattern is broken, then many other levels in the Pyramid may also become disturbed. Consequently, Biological Disorder may first occur within only a single level of biological organization. But this initial state of disorder may eventually disturb either higher or lower levels within the Pyramid. Therefore, Biological Disorder can rapidly spread through many levels, like a series of falling dominoes. The result – sickness or death of the organism!


Practice problems for these concepts can be found at: Patterns of Life Test

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