ShareLife on Earth - To Live or Die ... That Is The Question
This marvelous Earth we call home, provides us with everything we need to live, with just one exception. Our Sun provides energy to fuel the food chains on which we depend and to keep Earth from freezing. Only a very small amount of matter comes to Earth, and an even smaller amount leaves Earth permanently. Thinking of Earth in this way allows us to see it as a closed set of ecosystems and biomes that scientists call the biosphere.
With fantastic tolerance for changes in both abiotic and biotic factors, Earth's systems stay amazingly stable over long periods of time. Viewing this apparent stability in Earth's biosphere, one might think that everything, both living and nonliving, could remain forever. Why is it then, that species go extinct? Today, humans have a large impact on living things in areas where we choose to build our farms and cities. We have many choices to make regarding the value of wild lands versus lands that are managed for human use. While it is true that human activity can cause the extinction of species, we are not the only influence that can do so.
Throughout Earth's history, species have evolved and then disappeared leaving evidence of their existence in the fossil record. Curious scientists have studied and theorized about the reasons why species have become extinct.
Purpose:
In order to understand large-scale extinction, you need
to study the factors that govern the survival of organisms. This activity
will provide you with a chance to do just that by attempting to create
a self-sustaining ecosystem similar to those shown here.
Materials:
- Container
- These two-quart rectangular glass canisters shown above were purchased at a local superstore.
- Glass jars would work just as well and would cost less.
- Containers with large openings are easier to work with than soda bottles. An Internet search with the words "bottle biology" will yield some excellent ideas on how to create an aquarium or a terrarium with soda bottles.
- Abiotic Factors:
- Soil
- Rocks
- Sand
- Water
- Biotic Factors (Organisms):
- Plants
- Small animals
- Arthropods
- Fish
- Please do not use amphibians or mammals unless you have a very large ecosystem. You are not to open this system to feed an organism.
- A light source
- Sunny window
- Artificial light
Things to Consider:
Like Earth's biosphere, a self-contained ecosystem should
provide all of the matter for living things to survive. The energy will
need to be supplied in the form of light. It is best to use very small
animals in your system. A mouse would not do well in a sealed jar. Small
fish, insects, brine shrimp or even microorganisms would be better choices.
Self-sustaining ecosystems have been known to last for up to a decade
when designed properly. Most small ecosystem models will change drastically
or see the extinction of major species in much shorter time periods.
An Internet search with the words "self-sustaining ecosystem"
or "ecosphere" will provide a wealth of interesting information
that may help you.
Procedure:
- Design a self-contained ecosystem.
- List the abiotic and biotic items you would like to include in your ecosystem.
- Share your design with a teacher, family, friends, or classmates to see if they have any suggestions.
- Construct your ecosystem.
- Draw or photograph your ecosystem and write a journal entry describing what you think will happen in the ecosystem.
- If you expect changes to take place, predict when and why they will happen.
- If you think your ecosystem will remain stable, explain what factors will contribute to its stability.
- Make an estimate regarding the length of time you think your ecosystem will survive and explain your basis for this estimate.
- Observe your ecosystem weekly for at least six weeks. Make detailed observations of the biotic and abiotic changes you may observe.
- Do your best to keep track of the major species in your ecosystem, and discuss what you see happening to them.
Analysis:
- What species went extinct during your activity?
- What changes were you not expecting to occur?
- Scientists consider habitat descruction, introduction of non-native species, overharvesting and pollution to be major causes of extinction today. Do any of these relate to what you saw happen in your ecosystem?
- Compare your ecosystem's survival to that of a friend's ecosystem..
- How were they similar?
- How were they different?
- Summarize the changes and stable parts of your ecosystem over this period of time. In your summary, explain as many factors as you can that might contribute to the extinction of species on Earth.
- Share your observations with a parent or guardian, teacher, friends, and/or classmates.
