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Do you have a favorite animal?
I went through many favorite animals when I was a kid – the velvet ant, the sea pig,
silkie bantam chickens…okay that one might actually still be my favorite.
What I loved most, though, was collecting facts about different animals.
I mean, I REALLY enjoyed it.
I could tell you how much a silkie bantam chicken weighs (on average) or where you could
find a sea pig.
But, of course, one fact to always know about your favorite animal is what your favorite
animal eats.
Are they herbivores which means they eat plants?
Carnivores which means they eat meat?
Omnivores which means they eat meat and plants?
And there are more categories than this.
Even though all my favorite animals ate different things, they all had one thing in common.
They were all heterotrophs.
Generally, animals are heterotrophs which means that they consume organic matter.
It doesn’t matter whether they are eating plants, meat, or both---they are heterotrophs.
Also known as consumers.
Along with animals being heterotrophs, so are fungi.
Some protists are heterotrophs and some bacteria and some Archaea too.
But not everything on this planet is a heterotroph.
Do you have a favorite plant?
That may be less popular than having a favorite animal.
Plants are generally autotrophs which means they make their own food.
To be more specific, they make organic substances (such as glucose) from inorganic substances
(such as carbon dioxide).
If talking about plants, their source of energy to do this is light.
Plants are also known as producers.
Their “food” is glucose, an organic substance, which they produce in the process of photosynthesis
by using inorganic substances such as carbon dioxide.
Oh and even the plants known as carnivorous plants still produce their own food using
photosynthesis.
It’s just that carnivorous plants can also digest insects to obtain nitrogen.
Nitrogen is an important element that living organisms need, and it turns out that most
carnivorous plants live in areas where there is low nitrogen in the soil.
Along with plants, some protists are autotrophs.
Some bacteria and some Archaea are too.
Now, it’s also possible that an organism itself can be both an autotroph and a heterotroph.
In our protist video, we talk about Euglena.
Euglena can do photosynthesis as autotrophs, but they can also be heterotrophs and consume
organic matter in cases where light is not available.
So far, we’ve been pretty general with showing examples of heterotrophs and autotrophs.
But what if I told you that it can get a lot fancier?
And, we’re going to go into some more depth, but we want to point out that you can still
get into more depth than we’ll be getting into; check out the further reading details
for more.
And as always, there are some fascinating exceptions in biology that we can’t include
in such a short video.
So we gave a general description that autotrophs make their own food---that is---they make
organic substances from inorganic substances and heterotrophs instead must consume food---meaning
they must consume organic substances.
If you remember from our biomolecules video, the molecules that make up life---they all
have carbon.
So the source for carbon is important.
Autotrophs and heterotrophs obtain carbon differently---autotrophs generally use an
inorganic source of carbon to make their food.
Heterotrophs, instead, must get their carbon from organic sources that they consume.
But, there are also these other terms here.
Photo---meaning light and Chemo---meaning chemical.
Instead of the carbon sources, these terms refer to the organism’s energy source.
So, when we’ve been talking about plants?
Plants are an example of a photoautotroph, because they use light as their energy source.
But not all autotrophs use light as an energy source.
Have you ever head of the deep sea vents?
I’ll never forget learning about these when I was a kid.
I used to think, “How can anything live down there with the lack of light?”
Plus, the substances there like hydrogen sulfide, which is something that can be dangerous to
many other organisms, and the extreme temperatures.
Well, it turns out, there’s still life down there.
Bacteria that are chemoautotrophs are a great example.
They are autotrophs as they can make their own food, recall that is making organic substances
from inorganic substances.
But their energy source is chemical, hence the name chemoautotroph.
They can oxidize inorganic substances--- like that hydrogen sulfide we mentioned.
For chemoautotrophs, the chemical they use depends on the species.
But no light required.
So we know humans are heterotrophs.
Humans, as well as other animals, are examples of chemoheterotrophs.
Humans have to consume organic matter and it is also organic compounds that act as their
energy source.
Okay, that leaves one more right?
We had chemoheterotrophs, photoautotrophs, chemoautotrophs, and…ah, we’re missing
photoheterotrophs.
This one has always been a bit challenging for me to wrap my mind around.
They are heterotrophs which means they do consume organic matter.
But, that “photo” prefix means their energy source is light which they require.
This mode of nutrition is found in a few types of prokaryotes.
Now it’s important to mention that these organisms will do some form of cellular respiration
to further break down their food to generate ATP.
And by food, it can be food that was consumed (like heterotrophs) or food that they produced
themselves (like autotrophs).
However, cellular respiration processes can vary; the process may involve oxygen, no oxygen,
different electron acceptors, it’s exciting and it’s in some different videos.
Overall, the beauty of how organisms obtain what they need to survive just continues to
amaze us.
Well, that’s it for the Amoeba Sisters and we remind you to stay curious!