Captions are on! Click CC at bottom right to turn off. 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!
