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We can know how safe our environment is if we monitor it:
measure the amount of toxins and other pollutants in our air, water, and
soil. This works, but we have to know which specific chemicals to
monitor. This is not always possible. Sometimes, we rely on biological
monitors. Ever hear of canaries in the coal mines? Canaries can act as
an early warning signal. They would die from toxic chemicals at much
lower concentrations than would humans. More recently, frogs are
attracting attention as sentinels. For example, male frog sexual
development is impaired by a weed killer (atrazine) at 1/30th of the
level thought to be safe for people. In the past decade, 200 frog
species have declined and 20 are thought to have become extinct.
But some things are obvious, right? You don't have to be the
class whiz to know that we probably ought to clean up dirty air, dirty
water, radioactive wastes, and other such obvious sources of
environmental hazards. Nor is there much debate over such
ecology-damaging events as soil erosion and chopping down forests and
jungle. A little common sense can help us know when we are not protecting the environment.
Below, we will remind you of some things that may not
be so obvious.
Fertilizer run-off
| Fertilizer that runs off into ponds and
lakes creates an environmental problem. Do you know why? If you look
at ponds and lakes that drain heavily fertilized farm fields, what
do you suppose you would see? You would see that the water was
greenish (like pea soup) or brown, that there was much plant
growth in it. If you looked at water samples under the microscope,
you would see many single-celled animals and a wide range of
insects and other invertebrates. These organisms fix the
nitrogen from the fertilizer. However, most plants cannot
use this nitrogen and excess nitrogen in the environment limits
species diversity. See
our water quality lesson on nitrates. Many fertilizers
also contain toxic chemicals than can cause accumulate in the
environment. |
The whole Florida Everglades has a fertilizer run-off problem.
Here a technician conducts studies on how to deal with the
problem. Click
here for more. |
Antibiotic Resistance
Technician smearing bacterial sample
on culture medium to test
for sensitivity to antibiotics |
How do we know if a given bacterium
has developed resistance to an antibiotic? The original technique
was to collect a sample of the bacterium. For example, if you have
a sore throat, the doctor might swab the back of your throat and
send that swab to a laboratory. A laboratory technician would gently
rub the swab on some growth medium in a round glass dish
and place little disks containing antibiotic on top of
the growth medium. When the glass dish is placed in a warm oven for a day or
so, the bacteria will grow all over the growth medium, EXCEPT near
the disks
that contain antibiotic that kills the bacteria. There will be a
clear zone, a halo, around each disk that has the kind of
antibiotic in it that prevents bacterial growth. In recent years,
this technique is showing that more and more kinds of antibiotics
have lost their effectiveness. |
 
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