|
Activities: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10
Activity One
Aliens Among Us
Objectives
Students will become familiar with the impact of exotic species on ecosystems
(with application to purple loosestrife) by investigating a local school
yard plant's biotic potential and environmental resistance, creating
an imaginary exotic plant to compete for the local plant's niche and
evaluating the possible results.
Science Curriculum Framework Objectives
Constructing objectives: 13, 19, 20
Reflecting
objectives: 11
Using objectives: LEC 13, 15, 16, 18
Method
In groups of two, students will discover
and apply information about a schoolyard plant's biotic potential and
environmental resistance. Students will chart the information and predict
results of the introduction of an imaginary invader species and apply
this learning to the problem of purple loosestrife.
Terms
Biotic, abiotic, biotic potential, environmental
resistance, indigenous species, nonindigenous species, exotic species.
Background
Each organism in an ecosystem survives
in relationship to other organisms (biotics) in the ecosystem. Each
organism is also effected by its physical non-living environment (abiotics).
The organism's push toward growth is its biotic potential. Some of the
factors that increase the organism's biotic potential (increasing likelihood
of survival) are its reproductive and growth rate, its ability to migrate
and invade new habitats, defense mechanisms, heartiness and ability
to cope with adverse conditions. Factors that offer environmental resistance
(limiting factors decreasing likelihood of survival) are insufficient
water, nutrients, suitable habitat, adverse weather conditions, predators,
disease, and competition for environmental features. At all times, the
biotic and abiotic factors in the environment limit growth of the individual
organism, and its kin - its total population - is under the influence
of biotic and abiotic features in the environment. As ecosystems evolve
and become more diverse and more stable, the organisms within the ecosystem
achieve a dynamic balance - each is connected and dependent on the others.
Each organism's biotic potential and environmental resistance interact
to keep the populations balanced. This balance is dynamic; it changes
over time. If some of the interaction between species is lost, if the
balance is upset, the web of connections may begin to unravel. As people
have traveled from place to place, they have altered the environment
and carried along (sometimes purposefully and sometimes accidentally)
species of plants and animals not indigenous to the area. Those which
are introduced and begin to thrive are called nonindigenous species.
Many introduced species never become established and their populations
simply collapse within a generation or two. Successful invaders have
upset the balance of native ecosystems by permanently altering the biotic
potential and environmental resistance. When an exotic species invades
an ecosystem, it often has a much greater biotic potential and little
environmental resistance compared to native species. If it is able to
out-compete the indigenous organisms for space, nutrients, water, etc.
it may be able to out-reproduce the local species. To maintain the health
of native ecosystems, to make informed personal and community choices,
it is important to be aware of the impact of exotic species such as
purple loosestrife, zebra mussels, sea lamprey, spotted knapweed and
the goby fish to name a few.
Materials
Plant identification books, clipboards, plain paper (for extension:
soil moisture, ph, weather data, more).
Procedure
- In the classroom, introduce the concept of
dynamic balance between biotic potential and environmental resistance
relative to population growth. Take a mini field trip outside in the
school yard. Ask students, in groups of two, to identify plants growing
in the school yard and choose one for further investigation.
- Create a chart to list the biotic potential
and environmental resistance for the chosen schoolyard plant using
plant books, encyclopedias, the Internet, and field observation.
Example: QUACKGRASS
BIOTIC POTENTIAL -- ENVIRONMENTAL RESISTANCE
REPRODUCTION - grows by runners
COMPETITORS - dandelions, and seeds crabgrass,
etc.
GROWTH - rapid
WATER - tolerant of wide variation
MIGRATION - people spread it
PREDATORS - few visible signs of predation.
Mowed by people
COPING - hardy, thrives in most soil
DISEASE - few signs of disease
- Discuss limiting factors and predict the chosen
plant's population growth in the schoolyard.
- Ask the same groups of two students to create
an imaginary exotic plant species; chart biotic and abiotic limits
to growth, biotic potential and environmental resistance. Draw a picture
of the exotic plant. Draw a web for the chosen plant with other organisms
observed in its ecosystem.Predict the population
growth of the chose plant relative to other organisms in the web.
- Describe how the imaginary species would get
into the chosen plant's ecosystem, and based on its biotic potential
and environmental resistance, discuss ways people could control its
spread.
- Hand out a reading on purple loosestrife. Read
and discuss how it arrived and spread. Create a class chart for purple
loosestrife. Draw a web for the purple loosestrife with other wetland organisms. Predict the population growth of loosestrife relative to
other organisms in the web.
- Create several hypotheses about the impact of
purple loosestrife on an ecosystem. Defend the hypotheses with information
about biotic potential and environmental resistance. Compare to the
scenarios developed by the class for school yard plants.
Extensions
As
a scientist, if you were to observe an increase in purple loosestrife
over the next several years, what inferences could you make? Using the
Internet, gather information on the spread of purple loosestrife over
the last 100 years. Describe how your inferences compare to the historical
record.
Interview people living in the area where there
is a purple loosestrife infestation. Find out what they remember about
the plant. How long has it been there? How fast have the numbers increased?
Evaluation
Student
presentations to class of their local plant research and imaginary exotic
species including prediction of population growth of both in relationship
to each other. Teacher observation of understanding of concepts of biotic
potential and environmental resistance and the effects on the populations.
Activities: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10
|
