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Community Ecology

Activity Description

This lesson is the third in the general ecology “unit.”  It focuses on community ecology and ecosystems ecology.  It is mainly lecture but there is a food web activity where the students draw their own urban food web (in groups or as a class on the board) and compare it to some sample “forest” food webs.

It will probably come up that many things in community ecology are hard to fit into the given categories.  This will also occur throughout ecosystem ecology (is a dead animal abiotic or biotic?).  As discussed in the species concept lesson, categories are human constructs, so they are never perfect.  We use them only as long as they are useful to us, and if you are working in a system where they are not useful, then new tools can be developed.


Estimated Time of Activity: 1.5 hrs

Activity Objectives

Students will be able do the following as a result of the activity:

  • Understand the main relationships between species
    • Predation, competition, mutualism, and commensalisms
    • Be able to decide on how two species interact
  • Understand the difference between the biotic and abiotic components of a system
  • Understand the main differences between urban ecosystems and other ecosystems:
    • Energy comes primarily from external sources
    • Low richness, often very high abundances of a few species
    • Many invasive/exotic species
  • Understand types of pollution and its impact on populations, and some solutions to this problem

Activity Prerequisites

Prior pop bio lesson, 9th grade biology content knowledge of food webs and community interactions

Activity Instructions

  1. Lecture is via powerpoint.  There are a few assessment moments within the lecture.
  2. The first is when the students ID the type of relationships between the displayed organisms.  Some relationships are vague (esp. commensalisms/mutualism or commensalism/ammensalism/parasitism in some cases).  This is fine, students should be free to argue/discuss their ideas.  The teacher should point out that it is the job of the biologist to figure out which it is (by studying the two organisms).  If you have a question you go out and collect data to answer it.
  3. The second is during the ecosystem ecology section, when food webs are first brought up.  Food webs are technically diagrams of the community, but it is possible (and important) to also talk about the ultimate source of energy (the sun) and the structural characteristics of a city which give it its unique ecology.  Many of these things are results of human behavior but might be abiotic factors (alterations to the landscape, etc.).
  4. During the food web section, the class should make a urban food web.  I have done this simply as a class discussion where students call out names of species and the teacher draws the food web on the board with student direction.  However, a larger class project can be made of this activity where student groups make their own food webs.  This activity can also be saved for after the students have fleshed out their urban wildlife field guides in the next unit.
  5. The last section of the lecture is on pollution and other types of anthropogenic modifications to the ecosystem.  I did not include land-use changes as that is covered in the Urban Wildlife Management unit.
  6. The end of the class can be used to show some entertaining movie clips that deal with species interactions.  The students should ID what interactions are going on

Lions and Hyaenas – this is a youtube mix of a nature special detailing the competitive interactions between two social predators.  There is a pride of lions and a large clan of hyaenas that regularly compete for food and have grown to “hate” each other.  The first half of the clip shows the hyaenas ambushing the female lions at night and harassing them and stealing their kill.  The male lion shows up and kills the alpha female (hyaenas are a matriarchal species) and then kills her daughter the next day.

Bushmen hunting party – This movie is particularly good in my opinion.  Shows bushmen hunting in the African desert.  This movie can start a useful discussion on where one draws the line in human behavior between “ok” and “bad” environmental impacts (eg, why might people say the bushmen hunting the eland is ok, but logging is not).  This could bring up a discussion on sustainability. 

It also can bring up a discussion of hunting and why or why not it may be unethical (eg, if students express disdain at the killing of the eland, the teacher may want to point out that most schoolchildren do eat meat, they just pay to have it killed rather than doing it themselves). 

Ant-Fungus parasitism – A fungus infects and ant and controls its behavior

Dung Beetle  - this is a short film showing a dung beetle handling a piece of elephant dung.  This could be an example of commensalism.  The narrator then mentions the flies that live on the dung beetle clean it of parasites (so in this film there is parasitism, mutualism, and predation as well as the obvious commensalism).

Venus Fly Trap – A predatory plant


You can give a short writing, poster, or powerpoint assignment where students research a type of pollution or environmental problem.  They should describe the issue, describe its effects on the food web and the ecosystem (including humans and urban centers), what is being done about it and what individuals can do about it, and what remaining questions scientists are currently investigating about it.  This can be done in groups and can be as small as a 1-page essay or turned into a larger project.  Larger projects can also be done in groups.


Powerpoint (link coming soon)

poster materials if food webs will be done by group

Community Ecology movies (available on dropbox)

Lions and Hyaenas

Bushmen Hunting

Ant-Fungus Parasitism

Dung Beetle

Venus Fly-Trap

Instructor’s Notes

In this class, but in this lesson in particular, I suggest the teacher present the effects of humans on the landscape as neutral (humans acting as a keystone species), rather than categorically negative (“human activity is causing the extinction of species”) as is often the case.  While there are many clear examples of humans acting irresponsibly, there are also many gray areas where I think humans are simply operating in their interconnected ecosystem just like any other heterotroph. 

I believe that the students should make up their own minds about the ethical value of different human endeavors.  Debate about these issues is a huge part of wildlife and ecosystem management and should be encouraged in this class.


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