| Interactions
of Organisms
Learn
about how organisms interact with eachother and with the nonliving
parts of their environment and how these interactions result
in the flow of energy and cycling of matter throughout the
sytem.
Why
Organisms Interact
Organisms (including humans) interact with eachother all
the time, whether we know it or not. Most
of the interactions between species involve food:
- competing
for the same food supply
- eating
- avoiding
being eaten
Energy
and the Food Chain
A food chain does more than show who eats whom. Eating is
how an animal gets energy. A food chain charts this flow of
energy through the system.
The
Sun
The ultimate source of energy is the sun. Plants (producers)
use photosynthesis to use the energy from the sun to nourish
themselves. Everything else in the food chain is considered
a consumer. Some animals (primary consumers)
eat the plants. Some animals eat plant-eating animals (secondary
consumers). Their predators are called tertiary
consumers. The further away from the producers in the
food chain, the less energy is obtained from the sun. A
carnivore (an plant/animal that eats only meat) would be
the furthest away from the sun's energy.
The
Predator
A plant or animal that preys on other animals for food.
A nasty beast, we must say. Examples of predators include
polar bears, tigers, walruses, the venus flytrap and many,
many more.
The
Prey
The unlucky devil who gets eaten by the predator. They prey
of a polar bear, for example, includes seals, walruses,
small whales and others.
Scavenger
An animal that feeds on dead flesh or other decaying organic
matter. They serve the purpose of removing decaying remains.
Vultures are scavengers and feed on dead flesh.
Symbiosis
Symbiotic means, living together. This is a relationship in
which in which at least one of the species benefits:
- Mutual
- If both organisms benefit in a symbiotic relationship,
it is called mutualism.
- Commensal
- One of the organisms benefits, where the other was is
unaffected.
- Parasitic
- One of the organisms benefits, where the other one is
injured.
Mutual
Relationships
Mutual relationships between plants and fungi are common.
The fungus invades and lives in the cells of the host's roots.
The fungus then helps the host plant absorb minerals from
the soil.
Commensal
Relationships
Commensal means "at the table together." A common
example of a commensal relationship is that of barnacles to
other marine life. One tyep of barnical attaches itself to
the the the jaws of whales. Without the whale they could not
live, but the whale is not hurt by their presences. Another
example is the bacteria that live in our large intestines.
It is harmless, but it lives off of the food in our gut.
Parasitic
Relationships
Animals and plants can have parasites. Some may be living
and others (like viruses) can be nonliving. A parasite is
an organism that lives on or in the body of another organism,
from whose tissues it gets its nourishment, and to whom it
does some damage. Parasites can damage their host by either
causing tissue damage or delivering toxins.
Animal parasites can include:
- viruses
- bacteria
- fungi
- protozoans
- flatworms (tapeworms and flukes)
- nematodes
- insects (fleas, lice),
- and arachnids (mites).
Plant parasites can include:
- viruses
- bacteria
- fungi
- nematodes,
- and a few other plants
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