Introduction to Taxonomy - Online Tutor, Practice Problems & Exam Prep

Taxonomy classifies living organisms into eight categories: domain, kingdom, phylum, class, order, family, genus, and species. The three domains of life are Bacteria, Archaea, and Eukarya, with Bacteria and Archaea being prokaryotic, lacking a nucleus, while Eukarya includes both unicellular and multicellular eukaryotic organisms. The Eukarya domain is further divided into four kingdoms: Animalia, Plantae, Fungi, and Protista. Organisms can also be categorized based on energy acquisition as producers (autotrophs), consumers (heterotrophs), and decomposers, emphasizing the sun's role in energy flow.

Introduction to Taxonomy

In this video, we're going to begin our introduction to taxonomy. Taxonomy is defined as the branch of science that classifies, identifies, and names all living organisms. There are actually 8 categories used to classify all life. Notice that in our image shown below, we present all 8 categories used to classify all living organisms from the most inclusive category on the far left, which is the domain, through to the least inclusive category of species on the right. The species only includes one single type of organism. The 8 categories of life, from most inclusive to least inclusive, are domain, kingdom, phylum, class, order, family, genus, and species.

One way to remember the 8 categories that classify all living organisms from most inclusive to least inclusive is by using this mnemonic device: "Dear King Philip came over for great soup." Each first letter of these categories corresponds to a word in the mnemonic, thus helping us remember the sequence from most inclusive to least inclusive. Pictured here is an image of "King Philip" who came over for some great soup. If you can recall "Dear King Philip came over for great soup," you'll be able to place these 8 categories in the correct order from most inclusive to least inclusive.

This concludes our brief introduction to taxonomy, and I'll see you guys in our next video.

Which branch of biology is concerned with the naming and classifying of organisms?

• A. Bioinformatics.
• B. Taxonomy.
• C. Genomics.
• D. Evolution.
• E. Biology.

3 Domains of Life

So from our last lesson video, we know that there are 8 categories of life used to classify all living organisms. And the most inclusive of those eight categories is the domain. But really, there are 3 domains of life, and that's the focus of this video. So, once again, the broadest and most inclusive categories of life are the 3 domains, which we have numbered down below. And so the first domain of life is domain bacteria. The second domain of life is domain archaea. And the third and final domain of life is domain eukarya.

Now domain bacteria and domain archaea can be grouped together because they both consist of what are known as prokaryotic cells. Now, later in our course, we'll talk more about these prokaryotic cells, but for now, what you guys should know is that these prokaryotic cells lack an organelle called the nucleus. Now, the eukaryote domain, on the other hand, consists of eukaryotic cells. And once again, we'll talk more about eukaryotic cells later in our course, but for now you should know, that eukaryotic cells actually contain a nucleus. So, you could think of them much as being the opposite of prokaryotic cells, which lack the nucleus.

Now, if you take a look at our image down below, what you'll notice is we are showing you the 3 domains here, domain bacteria, domain archaea, and domain eukarya. And this portion right here of the image, scientists will refer to as a phylogenetic tree. But for our purposes here in this video, you can just think of it as the tree of life. And it's showing us where all organisms, all living organisms, where they fall and how they can be categorized. And so, on this horizontal axis here, what we have is time. And so, the further to the left you are on the axis, the further in the past you are. And as you make your way towards the right of the image, you make your way towards the present. And in today's present time, there are these 3 domains, domain bacteria, archaea, and eukarya. However, if you go way back into the past, there is evidence that suggests that all life came from a common ancestor. And this is just a theory, so, it can never be proven true, but there is lots of evidence that supports this idea.

And so, what you'll notice is that the theory shows that life came from a single common ancestor, but over time as we make our way to the right, notice that through natural selection and evolution, these three different branches of life came to exist, the 3 different domains. Now, once again, domain bacteria and domain archaea can be grouped together, which is why we have these brackets around them, and they can be grouped together because they both consist of prokaryotic cells. So, they can be called prokaryotes. And as we mentioned above, prokaryotic cells lack an organelle called a nucleus. But, also, prokaryotic cells are unicellular, meaning that they're only made up of just one single cell.

Whereas down here, what you'll notice is with the domain eukaryote, this is where humans fall, like ourselves. And, these are going to be consisted of eukaryotic cells, so they're referred to as eukaryotes as well. Now, eukaryotes, although you may think of humans as being multicellular, eukaryotes can either be unicellular or multicellular. And so it includes all multicellular organisms that you can think of, but it also includes some unicellular organisms as well. And so that's something important to keep in mind. But once again, later in our course, we’ll talk even more about these prokaryotes and eukaryotes. For now, you should focus on the 3 domains of life, domain bacteria, domain archaea, and domain eukarya. And so this here concludes our introduction to the 3 domains of life. And as we move forward in our course, we'll be able to get a little bit of practice with this idea. So I’ll see you guys in our next video.

Introduction to Taxonomy Example 1

Alright. So here we have an example problem that wants us to fill in the 2 blanks here in this sentence using one of these 4 potential answer options down below. And the example problem says, according to the diagram over here, A is blank, whereas B is blank. And so when we take a look at this diagram over here, notice that on one end what we have is A, and on the opposite end of the diagram, what we have are the 3 domains of life: domain bacteria, archaea, and eukarya. And so, notice that A is right here at this position and B is specifically pointing to this position right here. And so when we take a look at option A here it says, that A is the most recent species to evolve on Earth. But, of course, we know from our last lesson video that when we see a diagram like this one, that it's actually based on time and, furthest to the right, what we have is the present. So this represents the present. And, as you go backwards, we're actually going into the past. And so, the three domains of life are what we have in today's present world. However, going backwards into the past, this is where we started. And so what we're saying is that, A, by saying that it is the most recent species to evolve on Earth, it's not really recent at all if it's way back in the past. A is in the past and, the most recent species to evolve are going to be in the present, somewhere towards the right of the diagram. And so what that means is we can eliminate answer option A and answer option B since both of them say that for this first blank A is the most recent species to evolve on Earth, and we know that's not right. Instead, we know that A is going to be the common ancestor of all life, so it's either going to be option C or option D. That's the correct answer for this problem. And since both C and D have the same thing for the first blank, we need to take a look at what it says for option B. So, B is, this option here says, the common ancestor of bacteria and archaea. And, this option here says that B is the last common ancestor of archaea and eukarya. And so when we take a look at B, again, it's pointing to this specific location right here. And so, this is referring to the closest relationship between archaea and eukarya. The closest relationship between archaea and bacteria would be up here. So if you were to trace this back, this is the closest place that they meet. And so, what that means is we can eliminate answer option C because it says that B is, the common ancestor of bacteria and archaea, but that's not true of B. That would actually be up here. And so that only leaves answer option D here as the correct answer. And so, B is going to be the last common ancestor of archaea and eukarya. That's where they connect most recently right here. And so D here is going to be the correct answer for this example problem, and that concludes this example solve. See you guys in our next video.

Kingdoms of the Eukarya Domain

In this video, we're going to introduce the kingdoms of the Eukarya domain, and so we need to recall from some of our previous lesson videos that organisms in each domain can be further subdivided into kingdoms. It is important to note that the other domains, including Bacteria and Archaea, also have their own respective kingdoms, but in this video, we're focusing specifically on the kingdoms of the Eukarya domain. Domain Eukarya actually has 4 kingdoms, and you can see these 4 kingdoms down below with these 4 boxes in our image. The first kingdom is going to be Kingdom Animalia, which includes tigers, lions, elephants, insects, and of course, humans. These organisms are going to be multicellular and fall within Kingdom Animalia.

The next kingdom we have is Kingdom Plantae, which, as its name implies, includes all different types of flowers, plants, trees, and other similar organisms. These are also going to be multicellular. The next kingdom is Kingdom Fungi, which includes fungi such as mushrooms, as you can see here. These are mostly multicellular, but there are some unicellular examples.

The fourth and final kingdom of the Eukarya domain is the Protista, or the protists, which are going to be either unicellular or multicellular. Therefore, there are examples of both unicellular and multicellular protists. Domain Eukarya, as you can see here, includes multicellular organisms but can also include some unicellular organisms as well. This concludes our brief introduction to the kingdoms of the Eukarya domain, and we'll be able to get some practice applying these concepts as we move forward. So, I'll see you all in our next video.

Introduction to Taxonomy Example 2

So here we have an example problem that's asking which of the following kingdoms is not part of the eukaryotic domain. And we've got these 4 potential answer options down below. Now, of course, we know from our previous lesson video that kingdom Plantae certainly is one of the kingdoms of the eukarya domain. So because it is and we're looking for the one that is not, we can cross off option a. And the same goes for option b, kingdom Protista, we know for sure is going to be one of the kingdoms of the eukaryote domain from our last lesson video. So we can also cross off option b. And once again, option c, kingdom Fungi, we also know is one of the 4 kingdoms within the eukarya domain. So we can cross off option c.

So then, of course, this leaves option d here, kingdom Eubacteria, bacteria in it, which we know is an entirely separate domain from the eukaryotic domain. And so, option d here is the only one that is not part of the eukaryotic domain. And notice that there are 3 domains here that are listed that are part of the eukaryotic domain. And the 4th one that is not listed here is kingdom Animalia, which is the one that you and I, as humans, fall into. But for now, option d here is the correct answer for this example problem, so I'll see you guys in our next video.

The proposal that one type of organism can change into another type over a long period of time is known as:

• A. Creativity.
• B. Evolution.
• C. Natural history.
• D. Preconception.
• E. Preservation.

Categorizing Life Based on Energy Acquisition

In this video, we're going to introduce yet another way that scientists can classify living organisms, and that is through categorizing life based on energy acquisition. Scientists can categorize living organisms into 3 classes just based on how those organisms acquire their energy. Below, we have the 3 classes that group organisms based on how they acquire their energy.

The first class is the Producers, also sometimes referred to as autotrophs. As their name implies, these producers are organisms that acquire their energy by producing or making their own food. The root "auto" in autotrophs means "self", so they make the food themselves.

The second class is the Consumers, also referred to as heterotrophs. As their name implies, these consumers are organisms that acquire their energy by consuming or eating other living organisms. The root "hetero" in heterotroph means "different", so they acquire their energy by eating different organisms.

The third class is the Decomposers. As their name implies, these decomposers are organisms that acquire their energy by decomposing other organisms and acquiring energy from the waste and the dead organisms as well, obtaining energy from dying or dead organisms.

When we get to our image below, we will distinguish between these 3 different categories of organisms based on how they acquire their energy. It is important to note that most of the energy that's utilized by living organisms originates from the sun. Also, it's crucial to note that with every single energy transfer, or with every transfer of energy, some of that energy is going to be lost as heat. This is an idea that we'll explore more later in our course when discussing the laws of thermodynamics.

Notice in our image, we show you that the sun, which is about 93,000,000 miles from the earth, is going to have sunlight that travels all the way to our planet where there are organisms capable of capturing the energy from the sun and using it to create their own food. This represents the producers, sometimes referred to as autotrophs.

You'll notice that the yellow arrows in this diagram represent energy, and the green arrows represent matter. As the energy is transferred from the sun to the producers, there is a loss of energy as heat. These producers can be consumed by consumers. Here we have a bunny rabbit representing our consumers, who obtain their energy by eating other organisms. This bunny rabbit will eat the grass to obtain its energy. Notice that energy and matter are both being transferred from the producers to the consumers, and heat is being lost as well, which occurs with every transfer of energy.

Eventually, this bunny rabbit will pass away, and when it does, there are decomposers capable of acquiring energy from the dying organisms. Here, we show fungi serving as decomposers, acquiring energy and matter from the dying consumers as well as from the dying producers. Notice that when these decomposers die, they release nutrients into the soil, and the nutrients in the soil can be utilized by other living producers, completing the cycle of matter and energy.

This concludes our brief lesson on how living organisms can be categorized based on their energy acquisition. We'll be able to get some practice applying these concepts as we move forward. I'll see you all in our next video.

Introduction to Taxonomy Example 3

Alright. So here we have an example problem that wants us to complete the sentence here using one of these 4 potential answer options down below. And the example problem says autotrophs are also called either consumers, synthesizers, producers, or carnivores. Now, of course, what we need to recall from our last lesson video is that autotrophs are going to be organisms that are going to create their own food. And so they're able to create their own food using nonliving things. And so, you can see this auto prefix here, is one that means self. And so when it has autotroph, it's basically saying it can create their own food on their own by themselves, for instance. So another name for autotrophs, of course, we know from our previous lesson video, is going to be producers, and that's because producers produce or create their own food. So the correct answer is going to be option C for this example problem. Now recall that consumers are going to have to consume their food by eating other living organisms. Synthesizers is not really the term that we use to refer to these. And then carnivores are going to be organisms that eat meat. And so, we did also did not really talk about this in our previous lesson video, so we should have been able to eliminate that one. Once again, autotrophs are also called producers, and that concludes this example. So I'll see you all in our next video.

Biologists can divide living organisms into two groups: autotrophs and heterotrophs, which differ in _________.

• A. Their method of obtaining energy.
• B. The characteristics of life.
• C. Their mode of inheritance.
• D. The way that they generate ATP.