Curriculum
Connections
Photo courtesy of Ginter Park Elementary |
And
Around it Goes: The Water Cycle
Since water
formed on the planet, it’s been traveling endlessly through
the processes of evaporation, precipitation, and runoff.
Observations of your pond’s fluctuating water levels due to
rain or evaporation
offer the opportunity for students to puzzle out and understand
that all water on Earth is connected through the water cycle.
Ask, The water we used to fill our pond: where did it
come from, and where did it go? List and talk about
their answers, then introduce an illustration of the water
cycle for discussion.
Once you’ve assessed that students understand the general
cycle, challenge them to make a connection between it and
the source
water for your school pond. If you filled it with water from
a spigot or hydrant, you might invite a worker from the town’s
water utility to come in to field questions from students,
or have a hydrologist come in and talk about how the school’s
artesian well draws water from an underground reservoir.
Ultimately, they should be able to see how their pond is
part of the cycle,
and that the water there is constantly in motion, even when
it looks like it’s just sitting there!
Water
Cycle Diagrams:
Third
Grade Web Quest (animated diagram)
USGS:
Water Science for Schools
Biosphere
in a Bottle
 Observations
of a humble jar of pondwater can help students appreciate the
role of plants in transforming light energy
from the sun into the food energy that sustains all life on
Earth. Water containing producers (mainly algae and higher
plants), consumers (tiny animals) and decomposers (bacteria
and fungi), and placed under a light source, can act as a model
of any living system! Carbon, oxygen, and other important elements
cycle through the minibiosphere, as in the larger world, through
processes of photosynthesis, respiration, and decomposition.
This
project is easily accessible to a range of grade levels.
Younger kids may simply observe and describe changes over
time and wonder at the diversity of emerging life.
Older students
can do more quantitative measuring and identification of
life forms.
Minibiospheres
can provide an engaging focus for long term observations;
an understanding that systems cycle and change
over time; and a glimpse into the tremendous diversity
of life teeming in even a small jarful of pondwater.
Making observations
for
at least six weeks gives students a sense of the pace and
type of changes that occur over a season. You might want
to keep
one or two of your biospheres indefinitely: many can reach
some state of equilibrium and remain healthy for months
or even years.
Consider breaking into small groups, with each group of
students setting up several minibiosphere jars.
Photo
courtesy of Austin Independent School District |
Biosphere Setup
Step 1. For each minibiosphere, obtain
a clean pint or quart jar with a screw-top lid. Because
too
much
organic matter in the jars can cause a gas buildup
and potential explosion,
use a nail to poke a hole in each lid and seal the
hole with melted wax. This will act as a pressure-release
valve.
Step 2. Collect pondwater and mud. Add
mud to the jar, providing a 1/2- to 1-1/2-inch-deep base;
add pondwater to fill the jar 2/3 to 3/4 full. Make a
point
of collecting some visible primary producers (algae and
plants) and consumers (snails
and insects). Don't
include large animals or plants since it's such a small
habitat.
(Make your pondwater collections at any time of the
year. One instructor reports that her students were
awestruck
as tiny
green plants and baby snails "hatched" from
seemingly lifeless mud and water collected during the
winter.)
Step 3. Before sealing the jars, have
students make careful observations of the contents. Use
hand lenses
and microscopes,
if available,
to explore the pondwater. Suggest that students also
observe and use crayons or pencils to record the color
of the water,
or the amount of light passing through. The density
of the green color is an indicator of the quantity of
producers
present, which will change during the experiments.
Step 4. Allow the biospheres to sit
for a week in a brightly lit room out of direct sun,
or under
growlights, before
beginning
experiments. Have students repeat and record observations,
noting changes in the abundance of different organisms,
color changes, odor, and so on.
Although, ideally, these systems should remain closed
once they've been set up, student interest will be higher
if
they can open them briefly on a regular basis and remove
a small
quantity of water for closer observation.
 Simulating Environmental Changes
Minibiospheres also provide an opportunity to set up
experiments to test the effects of simulated environmental
changes
on the system. To spur inquiry, ask your students to
hypothesize what
might happen if something in the environment stimulated
changes
in their school pond. What if we let a tree grow
up and shade the pond? What if salt used to melt ice
on the
sidewalk, or fertilizer used on the playground turf
washed
into it? Have
students use their imaginations to come up with their
own ideas. Compile their ideas and ask how
they would set up an experiment
to test
such changes in the pondwater biospheres.
Have small
groups of students set up several minibiosphere jars. Be
sure to keep one jar as the control and experiment
with the others. Groups might each test the same
variables, or different concentrations or degrees of a single
variable. Here are some suggestions:
-
24
hours of light vs. natural (12-14 hours)
-
low
pH versus actual pond pH (simulated acid rainfall)
-
no
light (cover with black paper)
-
addition
of small quantities of fertilizer (simulated fertilizer
runoff)
-
cold
versus warmer temperatures
-
addition
of salt (simulated road salt runoff)
-
addition
of commercial phosphate detergent (simulated pollution)
-
colored
cellophane around jars (growth under different light
colors)
Once
you’ve recorded results from some of these experiments, extend
them into a discussion or study
of how human activities stimulate analogous environmental
changes in your region (e.g., eutrophication
in local water bodies
from nutrient pollution; sterilization of lakes
and waterways due to acid rain; salinization of
water supplies) and what is being done
to help restore
health to these bodies of water. Oh,
the Webs They Weave
Photo
courtesy of Austin Independent School District |
Have your
eager observers take stock of the species that live in and
around their pond, on both the macro (and, if appropriate),
the micro scale. Since water is a key element of all habitats,
they likely have seen animals drinking or birds hunting pond
insects. Create a master list from this survey, and assign
small groups to each sort the plants and creatures into different
categories of their choosing. For younger students, there might
be just two — plants and animals — but older kids might recall
the three types of plants required for a healthy pond, and
classify plants as emergent, submergent, or floating, and sort
animals into lists of amphibian, insect, and so on.
Using their
lists, have
groups draw simple food chains, beginning with the sun, using
arrows to indicate how each plant or animal provides
energy to the next in line. Next, have them
re-draw two or more chains and consider how they connect
to one another
to form
food webs. They might use different
colored pencils or crayons
to indicate the different relationships — predator-prey,
producer-consumer
(plant-animal), producer-decomposer, consumer-decomposer.
This will help you assess students' grasp of the concepts
they have explored.
To celebrate
their new understanding, have students combine their webs
into a colorful poster bulletin board display, complete with
drawings,
photos,
or images cut from magazines.
As observations reveal more inhabitants,
or a shifting of
species
over the seasons, adapt the poster to reflect the current
residents of the habitat.
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More
Pond Investigations
- Challenge
students to figure out how to determine their pond's
volume (in milliliters, liters, and/or gallons).
- Estimate
population numbers of selected plants and animals,
then create a graph. Note population changes over
time.
- Explore
pond organisms up close using hand lenses or microscopes.
Have students draw and describe them, noting their
methods of movement (or how they are rooted), food
sources, life cycle changes, and so on. What types
of features might help pond life adapt, compete,
or survive?
- Write
a story of the life history of a pond, following
the process of succession. Helpful links: Four
Stages of Pond Succession and descriptive
images.
- Spend
some quiet observation time at your pond, then have
students write, draw, or paint freely about something
that inspired them during that period.
- Learn
about invasive exotic water plants in your area,
such as Eurasian milfoil, hydrilla, and purple loosetrife.
Explore the problems they cause, what is being
done to combat them, and how your class can help.
- Get
to know the insect species considered indicators
of water quality in your area, keep track of what
shows up in your pond, and consider what this says
about
the purity of the water. For a sample list of insects,
visit the Hamilton Heights Elementary School Web
site.
- Use
ponds and other waterways as a means of studying
the geography and history of your region. Were waterways
important travel routes for native people and early
explorers, for commercial fishing or transport, or
for wartime naval activity?
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