| |
| |
Except
for a few
exceptions, all of the energy for all life and human technology comes
from the SUN.
Animals and humans can't eat sunshine. Plants
are the first level in the food chain. They convert sunlight to food
for animals (though the plants may not look at it that way).
|
|
 |
|
|
|
| |
The
Mysterious Everything
flows in bite sized chunks (literally) through life, from one living thing to
another living thing to another 
living thing, and so on and so on, but not forever. ("Energy's
One Way Trip"). Matter
also flows through life, but in this section we are only talking about energy.
This flow of energy is transported through
the animals by a system biologists call the food chain. A food
chain in a given ecosystem is usually very complicated but it is useful to think
of the food chain in the four simple steps or levels described below.
The drawing below only shows three steps. Which
one is missing?
Scroll
down to read about the 4 food chain steps...
|
|
|
|
|
|
|
| |
The flow of energy through life is not an endless cycle. The energy
doesn't go round and round getting used over and over again and never wearing
out. Its passage through the food chain can better be described as
in and out.
As energy moves up the food chain there is less
and less of it to go around. That's the main reason there aren't very many
big fierce predators compared to the herbivores. Not enough energy for them! We'll
talk about this in detail in another section, but a brief explanation goes something
like the following:
Most of the solar energy that falls
on the earth is not used by plants. It bounces back to space or heats the air,
oceans, and ground, and makes weather, among other things.
Sooo....
The plants only get a little bit of the solar
energy that hits the earth.
And....
The herbivores only get a little bit of the
energy that hits the plants.
And....
The carnivores and decomposers only
get a little bit of the energy that was eaten by the herbivores.
(Most of the plant energy that
is consumed by a herbivore is used by that herbivore to keep itself eating, breathing,
walking, and staying warm. Only a little bit is left over for the carnivore or
decomposer that eats the herbivore.)
Sooo...
At the end of the chain there isn't much of that original
solar energy left.
Therefore....
We need fresh sunshine everday and new plants have
to keep growing. Otherwise the whole amazing system would quickly run out
of energy and everything alive would come to a "dead"
stop.
|
|
|
|
|
Energy
above flows (or jumps in bites?) from sun to primary producers (plant) to primary
consumers (mouse) to secondary consumers (coyote) to decomposers (bacteria, etc.)
|
Picture of a Food Chain
Energy flows from the sun
to the plants to the plant eaters to the meat eaters. 
1) Primary Producers -- Green
plants and certain types of bacteria and 
algae are the primary producers because
they are the ones that produce usable energy for the rest of the living organisms
on earth. They use energy from the sun to make sucrose, glucose,
and other compounds that other life forms can eat and "burn" for energy.
In each one of those sugar molecules a little bit of the sun's energy is
stored in a form that we can call chemical energy. But it might better be called
"potential energy" since it is a sort of "doing-nothing-for-now-waiting-to-happen"
kind of energy (for more on this visit Energy
Changes).
2) Herbivores - Herbivores
are the plant eaters. They have the ability to digest the plants
they eat and release the energy stored in the plant cells for their own use. Some
examples of animals in this group are deer, cows, elephants, rabbits, elks, zebras,
most insects, and birds that eat fruit and seeds. Sometimes scientists call this
level of the food chain the Primary Consumers
(sounds like Economics class).
3)
Carnivores - These
guys are the meat eaters. Predators and scavengers are in
this group. Sometimes this level in the food chain is
refered to as the Secondary Consumers. They
eat the guys that eat the plants and sometimes they eat each other. Most of these
animals can't eat plants at all. They would starve to death if it weren't
for the Herbivores digesting the plants first. They've got the glamour
job but they're really pretty helpless without all the boring plants and herbivores.
Cats
and dogs, killer whales, sharks, spiders, snakes, wolves, vultures, hawks, eagles,
crocodiles, and many other fierce predators that for some reason we are especially
fascinated with, are in this group.
4) Decomposers
- These are not the guys that sit around unwriting songs
and symphonies (get it? The opposite of composers?). They are the guys that
eat up dead bodies - both plant and animal. And aren't we glad they do.
This group of useful critters are mostly bacteria
and fungus, but also, according to our sources, includes maggots, dung
beetles, earth worms, sow bugs (shown below), and many other eaters of dead organic
matter. Without them there would be a lot of dead bodies lying around.
 They're
like carnivores and herbivores, because they also have to get their energy from
the cells of animals or plants. The difference is they prefer their food dead
- very dead.
What do you think? Are maggots decomposers
or carnivores (or just yucky little things we'd rather not think about)? |
|
|
| |
| |
Hamburgers are for Omnivores
Some
animals can eat plants and other animals. So you could say they are both
a herbivore and a carnivore. That's the way humans are. We can eat
plants and we can eat meat. Well, la tee da.
It must have been too difficult for biologists
to say herbicarnivore or carniherbivore, so they decided to call humans, and others
like us, omnivores. It means we'll eat
just about anything we can get our amazing opposable thumbed hands on.
Black bears and brown bears are in our omnivorous
club. And pigs we think. Can you think of any others?
I can't think of anything better than being an omnivore.
We can be either primary or secondary consumers. It's
so empowering!
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
| |
Its been estimated that one large maple tree, with 500 pounds of leaves (fun
raking in the fall), can make two tons of simple carbohydrates (sugar) during
one nice sunny day!
How many tons would that be in a month of sunny days? |
|
|
|
|
|
| |
|
|
| |
It starts with the sun. The Mysterious
Everything, that makes everything happen on Earth, flows continuously
from the sun to the earth.
All life needs energy to live, and the energy we need comes
from the sun. Unfortunately, we crawlers, slitherers, walkers, and flyers,
can't get nourishment from the sun without some help.
We can stand in the sun all day, get warmed by it,
even get a good sunburn, but we won't get nourished.
|
|
 |
|
|
|
|
| |
What
do green plants, blue-green algae, and a few types of bacteria,
have in common?
They are the only organisms that can turn sunlight into
the little energy storage packages that we call sugar. If it wasn't
for them the rest of us would go hungry because we can't live without those little
sugar molecules that only they can provide.
Do plants seem a little boring? Sitting in one spot
all day long, growing ever so slowly. Like watching grass grow, they say.
Well they aren't moving fast, but they are busy. When
the sun is shining, they're doing photosynthesis,
furiously turning sunlight into stored energy that all the non-plants need for
survival. Every day they turn the sun's energy into millions of tons of
sugar. |
|
|
|
|
|
|
|
| |
"Energy,
energy, everywhere, nor any drop to eat". (with apologies to Samuel
Coleridge).
Our mostly stationary green friends come to the rescue.
They take a little sunshine from the sky, a little carbon dioxide from the
air around them, a little water from the surroundings, and they turn those basic
ingredients into little parts of themselves that we call plant cells. This
process is called photosynthesis. (They
also make and release a useful little gas called oxygen during photosynthesis.)
Each one of those plant cells contain little packets,
or molecules, of stored energy that we call carbohydrates.
Some of the most important
and simple types of carbohydrates are called sugars. One of the most important
sugars for animals and humans is glucose.
|
|
|
|
|
|
|
| |
| |
|
The
educational content of this website is freely available to anyone anywhere in
the world.
|
|
|
|
|
| |
|
 |
|
|
|
|
|
|
|
|
|
|
|
