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Microbes
Helpful or Harmful?
Microbes Defined
• A Microbe:
– Is a very tiny form of life
– Includes:
•
•
•
•
Viruses
Bacteria
Fungi
Protozoans
– Is best seen under the microscope
Misconceptions
• As you already know, every organism in an
ecosystem serves a function, even those we are afraid
of.
• When most people think of microbes, they tend to
think only of the more harmful disease causing
microbes such as viruses and bacteria.
• However, harmful microbes are not all that exist.
• A number of the microbes that are found on Earth are
actually highly beneficial to humans.
Helpful & Harmful Microbes
Microbe
Harmful
Helpful
Viruses
Small Pox, HIV, Polio
Tulip Virus
Bacteria
Black Death, Strep
Throat, Gangrene
Probiotics Bacteria,
Lactic Acid Bacteria
Protozoans
Malaria, Sleeping
Sickness
Simply for Study
Fungus
Ringworm, Moulds,
Plant Rust
Penicillin, Mushrooms
Microbes in the Environment
• In addition to the small scale ways in which microbes
affect humans, there are also much larger scale
instances in which microbes affect the balance of
entire ecosystems.
• Two such instances include:
– Microbes and Food
– Microbes and Disease
Microbes and Recycling
• As you are already aware, all nutrients in the
environment must be recycled.
• This recycling process takes place when upper level
organisms consume lower level organisms in a food
chain, better known as the cycling of matter.
• However, upper level organisms consuming other
lower level organisms alone, does not complete this
cycle.
• Instead, smaller, more discrete organisms are needed
to complete the necessary decomposition process.
Microbes and Food
• These essential organisms are microbes, such as
fungi, and bacteria.
• In a food chain, once an organism is consumed, the
nutrients in its body are returned to the soil via its
remains, as well as through the expulsion of waste
from the consumer.
• However, when these remains and waste are
deposited on the soil, they require additional
assistance to be broken down into basic nutrients so
they can then seep into the soil and serve as food for
plant life.
• It is at this point that microbes step in.
Microbes and Food Cont’d
• Microbes such as bacteria and fungus feed off the
remains and wastes, breaking them down into small
molecules which are then able to sink into the soil
and in turn, be absorbed by the plant life, to start the
matter cycle over again.
• If these microbes did not exist however, the entire
ecosystem would collapse, as the remains of
organisms would simply stay as wastes on the surface
of the soil rather than become nutrients within it.
• Gradually plants, starved of nutrients, would die,
leaving herbivores with no food and therefore causing
the total collapse of the food chain.
Scavenger
4th Trophic
Level
Radiant
Energy
1st Trophic
Level
Producers
(Plants)
Tertiary
Consumers
2nd Trophic
Level
3rd Trophic
Level
Primary
Consumers
Secondary
Consumers
(Herbivores) (Carnivores)
Decomposers
( Top
Carnivores)
Microbes and Disease
• Imagine what would happen if all organisms in an
ecosystem were completely healthy and never died…
• What would happen to the ecosystem?
Microbes and Disease Cont’d
• What occurs is overcrowding and eventual collapse of
the entire ecosystem.
• This is where microbes step in.
• When microbes cause disease among populations of
organisms, it is a means of regulating population.
• This regulation prevents overpopulation of an area
and the eventual collapse of the entire ecosystem.
Microbes and Disease Cont’d
• For example:
– If deer in Cape Breton never
died, they would eventually
overpopulate the area and run
out of resources to survive
(food, shelter, etc.), thus all of
them would be wiped out.
– If however, some of them
became infected by a
microbial disease and died,
their population would be
reduced and allow all of the
deer that remained, the
opportunity to obtain the
resources necessary for
survival.
In Conclusion
• Microbes are both Helpful and Harmful!
• They are a necessary “evil” of an ecosystem.