Producers: Organisms that make their own food, they don’t need to eat. Another term for
producers is Autotroph.
Photosynthetic Autotrophs:
Algae- both single celled
Ferns
Grasses and
Flowering Plants
and multi-cellular
and Mosses
Photosynthetic Autotrophs are
Organisms that make their own food from Sunlight, Carbon Dioxide (CO2) and Water (H2O) with
chlorophyll in the chloroplasts. Sunlight gives enough energy to the chloroplasts to break the
hydrogen bonds in water. The energy released is used to drive the rest of photosynthesis, using
the carbon in carbon dioxide to produce glucose and other carbohydrates.
The point is that by using the energy in sunlight, and some simple chemicals in the environment,
these producers are able to make their own food. They do not have to eat other living things to
survive. These producers are at the base of nearly every food chain and provide the food energy
needed by the consumers in ecosystems.
Chemosynthetic producers are bacteria and algae that make their food using Sulfur (in H2S) instead
of Oxygen (in H2O) .
We call this Chemo-synthesis (building with chemicals) instead of Photo-synthesis (building with
light). Instead of light energy, these organisms use heat energy to help power the chemical
reactions they use to make their own food.
Two places with lots of Chemosynthesis are;
Hot Springs where hot, sulfur rich water leaves the Earth
Hot Springs with Bacteria, Yellowstone National Park
And in the deep ocean at the mid-ocean ridges where hot water leaves the Earth’s crust at black
smoker or white smoker vents. Here, bacteria living inside the gills of giant tube worms are the
base of a whole ecosystem that never sees sunlight.
Again, these bacteria
are producers, or
autotrophs, organisms
that never need to eat
because they can
produce their own food
from chemical and heat
energy.
So, how do scientists use this to organize the living things in ecosystems?
This is called an Energy Pyramid or Trophic Pyramid
A Trophic Pyramid shows how
energy flows through ecosystems.
The reason it is in the shape of a
pyramid is that a lot of energy is lost
between each trophic level
(remember troph means nourish) or
feeding level.
As we discussed, the base of any
ecosystem are its producers. Then
come primary consumers, the plant
eaters or herbivores. Animals that
eat the herbivores, the next level up
are called secondary consumers,
and so on.
Each level in the energy or trophic pyramid contains less food energy, fewer calories, than the one
below. This is because so much energy is used at each level to stay alive. A roadrunner must
spend energy chasing the horned lizard, spend energy eating and digesting it, spend energy
keeping its body temperature stable at 104F, spend energy avoiding its enemies. All of this energy
is subtracted from what was in the level below. Only the energy that is used to grow and reproduce
is included in the Third level consumer box of this pyramid.
Of course it can’t be that simple.
Dead material needs to be broken down into the nutrients that plants need (along with water and
CO2) to build their bodies. These nutrients are released into the ecosystem by detritivores (break
down parts of living things like leaves, skin) and decomposers.
Detritivores and decomposers include- bacteria, fungi, many insects, and also many single celled
animals.
Important nutrients they return to the ecosystem include Carbon, Hydrogen, Oxygen, Nitrogen,
Phosphorous, Calcium, Sulfur and other elements that help build living things.
Food Webs: Way more complicated,
but way more accurate as a model
for how the organisms in a
community interact.
The difference between a food web
and a food chain is that the food
chain shows all of the connections
between consumers in the
community. This means that for any
animal, there may be several pathsdifferent food chains, through which
it can get its energy.
The most important thing to learn
about food web is that they can be
used to predict how and ecosystem
might change if a species in the food
web is disturbed.
For example in this food web, if the
Adelie Penguins were to die out, the
leopard seals that eat them would
need to replace them in its diet by
eating more of something else,
perhaps more squid or Emperor
penguins. Eating more squid might reduce the squid population and make it harder for Elephant
seals to find food, reducing their population size and affecting the Killer whales that have already
lost a food source, since they too had been eating the Adelie Penguins. Also because there are no
more Adelie Penguins, and fewer squid, the populations of plankton and the fish that eat them
should increase as the feeding pressure on them is less.
As you can see, there are many connections in a food web, and the ecosystem it represents, and
the consequences of changing it can be very hard to predict.