MARINE
ECOLOGY
Ecology hmmm, a popular word.
What is ecology? Is ecology collecting paper and aluminum cans? Is it the
balance of nature? Is it something to be "for" or
"against"? Maybe we can tell by looking at the word itself. "Ecology" comes from two Greek
words "oikos" which means "house"
and "logic" which means the "science or study of". Isn't that a big help? Ecology means the"study of house". Well, not quite but, maybe
so.... Ecology is the study of the relationships that occur in our
house, the earth. Ecology is the study of three general types of
relationships that we see in nature: (1) relationships among organisms of the
same kind; (2) relationships among organisms of different kinds; and (3)
relationships between organisms and the nonliving environment..
RELATIONSHIPS
Same
kinds different
kinds
non-living
Ecologists then study these three types of
relationships as they occur in a particular volume of space called an
ecosystem. An ecosystem is all of the living and nonliving factors in a given
space. We could look at the oceans as an
ecosystem.
Since
we define the boundaries of the ecosystem, we would also call a particular bay
or inlet an "ecosystem. The
ecosystem concept lets us look at a particular area in detail. It is important to remember, however, that
ecosystem boundaries are
man-made.
The real world is one single ecosystem in which all the nonliving and living
factors affect each other to one degree or another.
1. What
is "ecology"?
2. What
is an ecosystem?
How could we study an ecosystem? Let's make one in
a 10 gallon jar and see.
The
Boundaries of Our Ecosystem
What kinds of things would we need to make a
sealed ecosystem that could exist for an extended period of time? Lets look at the components
of the ecosystem. Think of the ecosystem
as composed of two major parts: The nonliving environment or surroundings and
the living environment or the biological community. The nonliving environment
provides the energy, nutrients, and living space that the members of the
biological community require for their existence.
3. What are the two major parts of an
ecosystem?
4. How could we call the 10 gallon jar part of the
nonliving environment of our ecosystem? What does it provide?
Let's add 10 gallons of seawater and a couple of
inches of beach sand to our jar to provide nutrients for the living organisms
we'll need. But what
about the energy? Lucky for us the jar is made of clear glass! The
energy can shine right in ...sunlight! Sunlight is the initial energy source
for all of the ecosystems of the world. 
Our ecosystem is now ready for us to add the
biological community. What shall we add? One way of looking at the components
of the biological community is to divide them into two major groups of organisms:
The autotrophs and the heterotrophs.
Autotrophs (auto-self + troph=food)
are organisms capable of manufacturing their own "food" from simple
inorganic molecules like carbon dioxide (C02) and water (H02). Most autotrophs are green plants. Heterotrophs
(hetero=other + troph=food)
are organisms that
cannot manufacture their own food. Heterotrophs obtain their food by feeding on other
organisms or on particulate (small separate particles) organic matter such as a
piece of seaweed that has washed up on the shore.
5. (a) What is a major
difference between autotrophs and heterotrophs?
(b) Circle the autotrophs.
sea
lettuce shark kelp periwinkle snail
seaweed oysters floating
microscopic green plants
Okay... let's add our autotrophs.
This might present a bit of a challenge since there are two large groups of autotrophs: photoautotrophs and chemoautotrophs.
Wow! That's a mouthful. Photoautotrophs use the energy from the sun to manufacture
food from simple inorganic molecules. (Photo=light + auto=self + troph=food).
Incidentally, the process of using light energy to manufacture food from
the simple inorganic molecules, carbon dioxide and water, is called
photosynthesis (photo=light + synthesis=place together). What can we add for
our photoautotroph? Let's add a couple of eel grass plants. 
6.
Use your knowledge of word parts to define “chemoautotrophic”.
Biologists often ignore chemoautotrophs. Chemoautotrophs
manufacture the food they need with energy derived from special kinds of
chemical reactions (chem.=with chemicals + auto=self +
troph=food.) Chemoautotrophs are generally microscopic bacteria that use
sulfur and nitrogen to make protein molecules.
These protein molecules can find their way back into the living system
as the bacteria are eaten by larger organisms.
Since these bacteria can live in areas with little or no oxygen, they
are sometimes very important in ocean areas with sandy or muddy bottoms. How can we add chemoautorophs
to our ecosystem? The bacteria are too
small to see with our beach sand (hitchhikers) and will establish themselves
just fine.
- What
do chemoautotrophs use as raw materials from
which they manufacture food?
So, now we have an ecosystem with a non-living
environment and a living environment.
Are we finished? Well, we could
be. Our system would maintain itself for
a while. The autotrophs could continue to grow until
they ran out of raw materials. Can we add anything else that might make our
mini-sea more interesting? Sure, we’ve
neglected a whole group of organisms, the heterotrophs.
- What
are heterotrophs?
“Hetero” is the Greek
prefix meaning “other or different”.
Heterotrophs
are organisms that obtain their food from other sources; they cannot make their
own food. Since there are so many different organisms that fit into the heterotroph category, ecologists have divided heterotrophs into three groups: herbivores, carnivores, and
decomposers. Each group has its own special way to obtain the energy-and
nutrients needed for maintenance, growth and reproduction. Herbivores are plant
eaters. Carnivores eat meat in the form of plant eaters or other carnivores.
Decomposers are organisms that use dead plant and animal materials as food.
Decomposers play an important role in recycling nutrients. They break down
organic substances, and use the energy and some of the nutrients stored in the
"food". They return the remaining nutrients to the environment where
they are available for use by other organism.
9.
"Omni" is from a Latin word meaning "all". What do you
suppose omnivores, eat?
Can
we add some heterotrophs to our ecosystem? Sure.
Let's add some periwinkle snails which feed on the eel grass surface.
To make things more interesting let's add an oyster drill that feeds on
periwinkle snails. Now we have a complete
system except for the decomposers. Many decomposers are bacteria. Ahal We've already added our decomposers
with the sand. If we've picked the proper number of organisms, we could have a
self sustaining ecosystem that would maintain itself for long periods.
10.
In our mini-ecosystem, what is the role of the
periwinkle? Of the oyster drill?
11. The members of the biological community are
listed below. Connect the members by drawing arrows that show who eats whom. Be sure your arrows point from the eaten to
the eater.
eel
grass periwinkle snail oyster
drill decomposers
(b) Why might you want to draw an arrow from the
decomposers to the eel grass?
(c) Your diagram above shows something called a
"food chain". Use your knowledge of other marine plants and animals
to create another food chain.
Now that you've built your ecosystem, let's take a
look at the way in which it functions.
It is important to realize that the ecosystem operates as a whole unit.
What does this mean? Damage to one ecosystem component will inevitably cause
other changes in the ecosystem. Since man is in the business of changing
ecosystems, it is critical that we have as such knowledge about the anticipated
change as possible. We can then
be sure that the other ecosystem changes that follow the original change are
minor and do not threaten the continued existence of the ecosystem as a stable
unit. Nowhere is it more critical to understand the changes than in the marine
ecosystem. Unfortunately, there is much we don't know. There is, however, much
we can learn that is known.
12. Eel grass blight has been introduced into our
system with the sand. What will happen to each of the other members of the
living community if the blight kills all of the eel grass?
a.
chemoautotrophs b.
periwinkle snails c.
oyster drill d. decomposers
13.
Which organism or group will feel the effect more rapidly?
Before we leave' our ecosystem we need to look at
two ecological processes
which lie at the heart of ecosystem structure and dynamics: 1)
energy flow and 2) nutrient movement. Both energy and nutrients move from one
member of the biological community to another as food. What is the difference
between the two?
Energy flows while nutrients or matter cycles.
What does this imply? Energy enters a system and passes through that system.
Once energy passes through an ecosystem, it is lost forever; not-so with
nutrients. They are recycled from one system to another. Nutrients are almost
never lost to the biological community as a whole.
14.
What is the ultimate source of all the energy that ecosystems use?
15.
Since nutrients-cycle from one ecosystem to another, is it possible that some
of the nutrients that make up your body were in a cow in the state of
Real world
ecosystems are much more complex than the one we just built. The principals are
the same but as you add more and more components, the number of possible
interactions increases dramatically. It is almost impossible to know all the
things that will happen when one changes an ecosystem. The more we know the
less the chance of making irreversible changes. In all of our decision making, we should
strive to avoid making are irreversible decisions.
16. Why should we avoid making irreversible
decisions?
ECOGRAM
Use the clues given below to find the words to
fill the thirteen lines. The correct answer will have the same number of
letters as there are blanks in the ecogram. When you
have filled is all of the lines correctly, as important ecological term will
appear as if by magic!
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