Introduction to Eukarya: Study with Video Lessons, Practice Problems & Examples

The domain Eukarya encompasses diverse eukaryotic organisms, including unicellular and multicellular forms. Key groups include fungi, which have chitin cell walls and obtain energy from organic materials; algae, photosynthetic organisms with cellulose walls; protozoa, unicellular and motile organisms without cell walls; and helminths, parasitic worms that can cause disease. Understanding these groups is essential for microbiology, as they play significant roles in ecosystems and human health.

Introduction to Eukarya

So now that we've introduced the prokaryotes, bacteria and archaea, in our previous lesson videos, in this video, we're going to begin our introduction to eukarya. And so it turns out that the term eukarya is actually the plural form of the word, and the singular form is actually eukaryote. And these are referring to organisms in one of the three domains of life. And so again, recall from our previous lesson videos that there are 3 domains of life, bacteria, archaea, and eukarya. Now the eukaryotic cells contain a membrane-bound nucleus, unlike the prokaryotic cells like bacteria and archaea that lack a membrane-bound nucleus. And eukaryotic cells can either be unicellular, meaning that they're just made up of 1 single cell, or eukaryotic organisms could be multicellular, meaning that they're made up of multiple cells. And it turns out that the domain eukarya includes the 4 eukaryotic kingdoms of plants, animals, fungi, and protists. And the protists include the algae and the protozoa. Now, even though the domain eukarya includes these 4 kingdoms, microbiologists tend to study only the microscopic eukaryotes. And so mainly, microbiologists will be focusing on the fungi, algae, protozoa, and helminths. And those are really the ones that are going to be the microscopic eukaryotes and the ones that are of main focus in the field of microbiology. And so if we take a look at our image down below, what you'll notice is that we're showing you the map of the microbial world. And already in our previous lesson videos, we've covered the prokaryote. So you can see that grayed out because we already covered it. And so moving forward here, we're gonna talk about the microscopic eukaryotes, which can be unicellular or multicellular, and they're going to have a membrane-bound nucleus. And so, when it comes to this domain, eukarya, notice that the microscopic eukaryotic organisms are gonna include the fungi, the protists which includes algae and protozoa, as well as helminths. And so moving forward, we'll talk about each of these groups and introduce them briefly. And then, what you can see is last but not least, we have the acellular infectious agents here which are not eukaryotes. These are not cellular organisms. They are acellular infectious agents. And again, we'll talk about those later in our course after we introduce the eukaryotes. And so this here concludes our introduction to the eukarya. And again, we'll talk more about these groups, fungi, protists and helminths as we move forward. So I'll see you all in our next video.

Fungi

This video, we're going to begin our introduction to fungi. And so fungi is actually a plural term, and the singular word is fungus. And so fungi are a diverse group of eukaryotes. They range from being unicellular yeasts that are made up of just one single cell, to multicellular filamentous molds, to even larger and more multicellular mushrooms. Unlike plants, fungi do not carry out photosynthesis. Also, unlike plants, which have cell walls made of a polysaccharide called cellulose, fungi have cell walls made of another polysaccharide called chitin. Now, fungi tend to harvest their energy from organic materials, and the term organic is referring to molecules that contain carbon and hydrogen. And so if we take a look at our image down below over here on the left-hand side, notice that we're showing you a snippet of our map of the lesson of the microbial world, focusing on the microscopic eukaryotes and mainly focusing on fungi here. Notice that fungi are a diverse group of eukaryotes. They range from being single-celled or unicellular, like Saccharomyces cerevisiae, which you can see the image of the yeast cells right here. They could be used for making wine, beer, and even bread as well, which is why we have these images at the top here. Fungi can also be multicellular filamentous molds like what you can see down here, like Penicillium rubens, for example, which is the first mold discovered to produce penicillin, an antibiotic that can kill bacteria. Over here we have an image of a petri dish that is growing mold and some bread that is also growing mold on it. Now, on the far right, what we have is even larger and more macroscopic, more multicellular mushrooms, which are also an example of fungi, such as Amanita muscaria, which is also known as fly agaric. As you can see here, fungi are a diverse group of organisms, and they are part of the eukaryotic domain. This here concludes our brief introduction to fungi, and we'll be able to talk about some of the other groups of eukaryotes as we move forward. I'll see you all in our next video.

Although plants and fungi are very similar, fungi do not have…

• A. Cell walls.
• B. The ability to perform photosynthesis.
• C. The ability to harvest energy from decaying matter.
• D. All of the above.

Protists:Algae

In this video, we're going to begin our introduction to protists, specifically algae. Now algae is actually the plural form of the word. The singular form is alga. And once again, algae are a diverse group of eukaryotes, but specifically, algae are photosynthetic eukaryotes, which means that they perform photosynthesis. And so they are also sometimes referred to as plant-like protists. And so, what you'll notice is that algae have a lot of similarities to plants in many ways. But one of the main differences between algae and plants is that algae can either be unicellular or, they can be multicellular, as well, and we'll be able to see some examples of that down below in our image. Now algae are a diverse group of eukaryotes. They have a wide variety of shapes as you can see down below in our image. They can reproduce either sexually or asexually, and they have cell walls that are made of cellulose, which is similar to how plants make their cell walls. Algae are usually found near the surface of either salt or freshwater or in moist terrestrial habitats. So they tend to like moisture and be in wet environments. So if we take a look at our image down below over here on the left-hand side, notice again we're showing you a little snippet of our map of the lesson on the microbial world, focusing on the microscopic eukaryotes. And notice once again that algae are one of the groups within protists. And so, over here, we have a bunch of different examples of algae, and you can see that they come in all different kinds of shapes and they can have different features as well, but they tend to be photosynthetic and very similar to plants. And so, notice up here at the top left, we have Odontella aurita. We have Urodina elegans, Uronema elegans. Then we have Macrocystis pyrifera, which is also known as brown algae. Then we have Dinobryon divergens, also known as golden algae, Volvox carteri, and Phacus spicis right here. And so there are a bunch these are just a small subset of some of the different types of algae. But for now, this here concludes our brief introduction to algae. And once again, we'll be able to learn a lot more about this group of organisms later in our course, and we'll be able to apply some of these concepts in our practice. So I'll see you all in our next video.

Plants and algae are very similar, however algae…

• A. Cannot perform photosynthesis.
• B. Do not have cell walls made of cellulose.
• C. Can only reproduce asexually.
• D. Can be either unicellular or multicellular.

Protists:Protozoa

This video, we're going to continue to talk about the protists, but more specifically introduce the protozoa. Protozoa is actually the plural form of the word, and the singular form is protozoan. These protozoa are, once again, a diverse group of eukaryotes, but their important distinguishing feature is that they are unicellular eukaryotes. They have a lot of similarities to animals, and so sometimes they're referred to as animal-like protists. Now, these protozoa, once again, they are a diverse group, and so they have a wide variety of different shapes as you can see down below in our image. They can also reproduce sexually or asexually. But unlike algae, fungi, and plants, these protozoa do not have cell walls. Most protozoa are going to be motile, which means that they are able to move around within their environments. They ingest organic materials or materials that contain carbon and hydrogen as a food source. If we take a look at our image down below over here on the left hand side, notice once again, we're showing you the little snippet of our map of the lesson on the microbial world. We're focusing on the microscopic eukaryotes, specifically the protozoa in this video. Notice over here on the right, we have a bunch of images of examples of protozoa, including Giardia duodenalis, Blepharisma japonicum, Trypanosoma cruzi, Centropyxis aculeata, Plasmodium vivax, which is the cause of malaria, and Amoeba proteus. You can see that the protozoa are, once again, a diverse group of eukaryotes, but they are all single-celled. They're all unicellular. This here concludes our brief introduction to the protozoa, and once again, we'll be able to talk more about this group later in our course. But for now, this concludes this introduction, and I'll see you in our next video.

Helminths

In this video, we're going to begin our introduction to helminths. And so helminths are yet another group of eukaryotes. More specifically, they are eukaryotic parasitic worms that will live at the expense of a host, which means that they tend to harm the host and tend to cause disease within the host that they infect. Now helminths are not technically microorganisms because some of them can be quite large. However, their eggs and their larvae are microscopic. And so that's why helminths can be a focus within the field of microbiology. Now helminths include flatworms and roundworms and tapeworms as well, and we'll show you some examples of helminths down below in our image. Now over here on the left-hand side, notice once again that we're showing you a little snippet of our map of the lesson on the microbial world, and we're focusing on the microscopic eukaryotes, specifically the helminths here in this video. And so we're showing you a bunch of different examples of helminths over here on the right-hand side, including Ancylostoma duodenale, Enterobius vermicularis, Trichuris trichiura, Dipylidium caninum, Trichinella spiralis, and Schistosoma mansoni. And so these are all different examples of helminths. And so you can see that they are tapeworms and pinworms and whipworms and things of that nature. And so this here concludes our brief introduction to helminths. And once again, we'll be able to talk more about this group of organisms later in our course. But for now, I'll see you all in our next video.

Which of these answers about helminths is true?

• A. Helminths are parasitic protozoans that infect many animal species.
• B. Helminths are parasitic, microscopic animals that infect many other animals species.
• C. Helminths are parasitic animals with microscopic eggs that infect many other animals species.
• D. None of the above.

Why do many microbiologists study helminths if they are technically not microscopic?

• A. The eggs and larva of these parasites are microscopic and we require microscopic equipment to see them.
• B. They can also cause bacterial infections to occur in humans.
• C. The damage they cause to humans is microscopic.
• D. Generally, microbiologists do not study these animals because they are not microscopic.

Here’s what students ask on this topic:

What are the main differences between prokaryotic and eukaryotic cells?

Prokaryotic cells, such as bacteria and archaea, lack a membrane-bound nucleus and other membrane-bound organelles. Their DNA is located in a nucleoid region. In contrast, eukaryotic cells, which include organisms in the domain Eukarya, have a membrane-bound nucleus that houses their DNA. Eukaryotic cells also contain various membrane-bound organelles, such as mitochondria, endoplasmic reticulum, and Golgi apparatus, which compartmentalize cellular functions. Additionally, eukaryotic cells can be either unicellular or multicellular, whereas prokaryotic cells are typically unicellular.

What are the four kingdoms included in the domain Eukarya?

The domain Eukarya includes four kingdoms: plants, animals, fungi, and protists. Plants are multicellular and perform photosynthesis. Animals are multicellular and obtain energy by consuming other organisms. Fungi can be unicellular or multicellular and obtain energy from organic materials. Protists are a diverse group that includes both unicellular and multicellular organisms, such as algae (photosynthetic) and protozoa (animal-like and motile).

How do fungi differ from plants?

Fungi differ from plants in several key ways. Unlike plants, fungi do not perform photosynthesis. Instead, they obtain energy by decomposing organic materials. Fungi have cell walls made of chitin, whereas plant cell walls are made of cellulose. Additionally, fungi can be unicellular (e.g., yeasts) or multicellular (e.g., molds and mushrooms), while plants are primarily multicellular.

What are the characteristics of protozoa?

Protozoa are unicellular eukaryotes that are often motile, meaning they can move around in their environment. They are similar to animals in that they ingest organic materials for energy, which is why they are sometimes referred to as animal-like protists. Unlike algae and fungi, protozoa do not have cell walls. They can reproduce sexually or asexually and exhibit a wide variety of shapes and forms.

Why are helminths studied in microbiology if they are not microorganisms?

Helminths, which include parasitic worms like flatworms, roundworms, and tapeworms, are studied in microbiology because their eggs and larvae are microscopic. These stages are crucial for understanding their life cycles and the diseases they cause. Helminths live at the expense of their hosts, often causing significant health issues, making them important subjects in the study of infectious diseases and parasitology.