Do you like to organize things? One of us is very organized. Maybe a little bit too much. As for Pinky, it's more like she lost a game of Jumanji.
But scientists, they are often trying to classify and organize different organisms based on shared characteristics. It's very important to have tools to differentiate among different organisms. So in this particular clip, we are going to use a tool called a dichotomous key to identify five different organisms that each happen to be from five different taxonomic groups. So what's a dichotomous key?
Well, it allows you to identify organisms based on a series of statements that are typically organized in pairs. We are going to use the dichotomous key to determine scientific names for five mystery organisms. So what's a scientific name?
Often scientific names have Latin or Greek roots, and they can be used across different languages by scientists all over the world. This unification in the naming system is important because common names vary by language and location. They're often far less reliable.
For example, this scientific name has a lot of common names, such as mountain lion, Texas panther, puma, or cougar. Although those were fun to say. OK, so let's go ahead and get started. Here are our mystery organisms with clues. We're going to use this dichotomous key.
Now, we're going to point out that this dichotomous key has been created for use with these five specific organisms in the chart and only these specific organisms. So let's start with mystery organism A, an amoeba. With a dichotomous key, you always want to start with number one. And if you look at the clues, you notice this organism contains a nucleus.
A reminder from our prokaryote eukaryote video, this means it is a eukaryote. And this tells us to go to number three. So is this organism a autotroph or a heterotroph? Well, autotrophs make their own food. An example is a photosynthetic organism making food from light energy.
But heterotrophs must rely on external food sources. So since our clue states that this organism feeds on other organisms, it must be a heterotroph. And this tells us to go to number four. Now, in number four, we have to think about this. There's actually a lot of different species of amoeba, and we don't know what kind it is.
But it mentions that this specimen is small, because it's saying its size is measured in this unit, micrometers. And if you're wondering what that means, well, it takes one... thousand micrometers to be equal to one millimeter.
And this particular specimen is definitely microscopic, meaning you need a microscope to see it well. Now not all microscopic organisms are necessarily single-celled, but if you look at our organism here, this is one cell. A single-celled organism is unicellular, which means it only has one cell.
Therefore, 4b is more appropriate, meaning that our organism is this. Now this one kind of had a giveaway because the scientific name had amoeba in it, didn't it? But be careful, as you will find that's not always the case. One thing about unicellular and multicellular.
Generally organisms that are large enough for you to see easily with the naked eye, with a few exceptions, are multicellular. Organisms that can be seen easily with the naked eye, they tend to have structures that are made of many cells. Think of plants, animals, mushrooms. For the purpose of this exercise, we have illustrations to hopefully make it very clear. But if you're ever unsure, you can always research online.
Okay, let's do one more. Mystery organism B, a plant. Again, always start with number one.
The details mention nuclei. Remember, that's the plural of nucleus, because you don't say nucleuses, you say nuclei. Well, this organism is made up of many cells that all have a nucleus.
Like the previous example. Well, that makes it a eukaryote. So that takes us to number three. Are plants autotrophs or heterotrophs?
Well, they make their own food from the sun by photosynthesis. That makes them autotrophs because they're making their own food. That means, according to this key, this is the scientific name of this plant. Just a fun fact, the common name for this plant is a spider plant. But the scientific name is much more fancy.
So now you can try with the other mystery organisms on our handout that goes with this. A few big things we want to remind you. Number one, remember to always start with number one on the key. And so you'll start with number one for every organism.
And number two, you have to be careful not to just pick out random phrases in the dichotomous key. You may think you're taking a shortcut, but there are no shortcuts. You need to go through the sequence. For example, there's more than one organism on this chart that is unicellular in that phrase 4b.
So if you just picked out that phrase, you'd have more than one organism in that category. Our handout also includes a challenge. This dichotomous key is really only useful with these five organisms. So, if we add in another organism, like this cat here, will it still work? Well, here's its scientific name.
But now if you notice, our key is not going to work correctly. Your challenge is to redesign the dichotomous key so that it would also work if including this cat. You may just need a few revisions or additions. On our handout, we have room for you to create the modified dichotomous key so that the cat's included.
And last thing, when making a dichotomous key, you need to use clues that an observer would have access to. If we started putting habitat information in the dichotomous key, for example, you wouldn't necessarily know that information unless it was included. So just something to keep in mind.
Well, that's it for the Amoeba Sisters, and we remind you to stay curious.