Populations in Balance

This unit introduces students to disturbances to the ecosystem. Some disturbances are natural; others are caused by human actions. Disturbances can harm an ecosystem; however there are times when an ecosystem benefits from a disturbance. Following a disturbance, there is usually a recovery. These recoveries can occur with or without human intervention. Students see how human intervention in some problems can cause unintended consequences. They consider the multiple perspectives of stakeholders as they make a decision about whether or not to intervene in a problem. Students argue the perspective of a particular stakeholder and consider the strengths of the arguments of others.

Activities

Scene: Snake Invaders

Elena, Rachel, and Miles learn about Guam's ecosystem from Rachel's cousin Rob.

Duration: Approximately 50 minutes

Lesson: Ecological Disturbances

In this activity centered around forest fires and other naturally occurring events, students consider whether ecological disturbances are good or bad.

Duration: Approximately 30 minutes

Lesson: A Chesapeake Bay Food Web

Through the story of the Chesapeake Bay oyster, students learn about its ecosystem's food web in this illustrated guide.

Duration: Approximately 30 minutes

Reading: Barnyard Backfire

Students explore human impact through the comic "Barnyard Backfire" and a related graphing exercise.

Duration: Approximately 120 minutes

Conversation: Town Hall Meeting

Students simulate a town hall meeting with presentations and careful observation of other viewpoints. During the simulation, students discuss the many different opinions about a new community rule.

Duration: Approximately 120 minutes

Writing: To Hunt or Not?

Students explore positions on a spectrum of opinion about hunting.

Duration: Approximately 120 minutes

Teacher Tune-ups

• What are ecological disturbances and recoveries? Are disturbances necessarily bad? Are people always involved?
• What is a food web with trophic levels?

Student View of Visuals and Activities

Some teachers prefer to have students view the slides and other visual assets in this unit directly instead of projecting them in class. Below is a web page to share with students with links to some of same items that are within in the teacher lesson plans, but without the explanatory text for the teacher.

 

• Student Links to Unit L1 Slides and Other Visuals

Original SciGen Unit

This unit has been adapted from "7.4 Populations in Balance" in the Word Generation program led by Catherine Snow (Harvard University) through a SERP collaboration with the Boston Public Schools and other districts in Massachusetts and Maryland.

PDFs of that earlier unit's teacher and student editions are available at the Science Generation Download Center.

native

adjective – originally from a place

The elderberry tree is native to Cape Cod in Massachusetts. Do you know of a native tree in your area?

population

noun – a group of animals or plants of the same species in an ecosystem

The population of brown tree snakes on Guam is increasing because of the lack of predators. What populations are declining?

interdependence

noun – when two or more parts depend on each other

The Chesapeake Bay oyster’s effect on other organisms in its habitat demonstrates interdependence.

disturbance

noun – an interruption in the normal way an ecosystem works

Are disturbances to ecosystems always bad?

recovery

noun – the process when an ecosystem returns to normal

Do you think recovery from the snake infestation on Guam is possible?

consumer

noun – an animal that eats other living things (like plants or other animals)

Do higher level consumers eat more plants or more animals?

producer

noun – a living thing that makes its own food through light and very simple substances

Seaweed is an example of a producer in an ocean ecosystem. What are some producers in a desert ecosystem?

predator

noun – an animal that preys on (hunts and eats) other animals

Eagles and ospreys are considered top predators in the Chesapeake Bay ecosystem. Why?

prey

noun – an animal that is hunted and killed for food by a predator

Can you think of some examples of prey that are larger than their predators?