Lesson Video: Kingdom Monera | Nagwa Lesson Video: Kingdom Monera | Nagwa

Lesson Video: Kingdom Monera Biology • First Year of Secondary School

In this video, we will learn how to describe the characteristics of organisms belonging to the kingdom Monera, recall the divisions of kingdom Monera as Eubacteria and Archaebacteria, and apply knowledge of these kingdoms to classify given organisms correctly.

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Video Transcript

In this video, we will learn to describe the characteristics common to organisms in the kingdom Monera. We will learn about the differences between eubacteria and archaea. And then we’ll practice classifying organisms based on what we’ve learnt.

A kingdom is a very general classification containing many different species. However, all organisms within a particular kingdom have some traits in common. Kingdom Monera was originally created to classify organisms which are prokaryotes. The main difference between prokaryotic cells and eukaryotic cells is that prokaryotic cells do not contain a nucleus. In eukaryotic cells, the genetic material, or DNA, is in several long strands called chromosomes. And the chromosomes are stored and protected within a nucleus.

In contrast, prokaryotic cells have their genetic material in a chromosomal loop. And this loop of DNA is suspended in the cytoplasm of the cell. In addition to not possessing a nucleus, all prokaryotes reproduce asexually through a process called binary fission. Prokaryotic organisms are also all unicellular, although some of them can link together into strands or form colonies. The organisms within kingdom Monera can be further classified based on other traits into various phyla. These phyla can be further divided into classes, classes into orders, orders into families, families into genera, and genera into individual species. Remember that all of the members of kingdom Monera possess the traits that we already described because they’re all prokaryotes.

Let’s look at some additional characteristics within kingdom Monera. The word part “karyote” means kernel or nucleus, and the prefix pro- in this word means before. In contrast, the eu- in eukaryote means true. Prokaryotic organisms evolved on Earth before eukaryotic organisms. Some students find it helpful to remember that pro- means no nucleus. In addition to not possessing a nucleus, prokaryotic cells also do not possess other membrane-bound organelles, such as mitochondria. Organisms within kingdom Monera may be autotrophs, heterotrophs, or a mixture of both.

The difference between autotrophs and heterotrophs is how they get the nutrients that they need to produce cellular energy. Heterotrophic organisms must absorb organic matter or consume other organisms in order to get the nutrients that they need. On the other hand, autotrophic organisms convert inorganic materials into the nutrients that they need to produce cellular energy. They can do this using a process called photosynthesis, which utilizes the energy found in sunlight, or through chemosynthesis, which uses other sources of energy, such as heat. Auto- is a word part that means self, which can help you remember that autotrophs make nutrients by themselves.

Another feature of prokaryotic cells is that they possess a cell wall. The chemicals found in the cell walls of different organisms is sometimes used as a key to their classification. Members of the plant kingdom have cell walls made of cellulose, and members of the fungus kingdom have cell walls made of chitin. But what about the cell walls of monerans? Well, some monerans have a cell wall made of a chemical called peptidoglycan, and some do not. For this reason and several others, the moneran kingdom has more recently been divided into two separate kingdoms, Bacteria and Archaea.

Archaea and bacteria have different evolutionary histories and relationships, which give them different characteristics, even though they’re both types of prokaryotes. Bacteria are sometimes called eubacteria, which means true bacteria. These are the types of prokaryotes that you’re most likely already familiar with. They exist everywhere and even sometimes cause infections and illness. Archaea is a word that means old, and they’re also sometimes referred to as archaebacteria. Archaebacteria got this name because they were first found living in extreme environments similar to those thought to have existed on Earth long, long ago. We call these organisms extremophiles.

While archaea may most commonly be found in environments like thermal vents, hot springs, or stomach acid, which has an extremely low pH, scientists have since learnt that they also exist all throughout nature. The cell walls of bacterial cells are made of peptidoglycan, while the cell walls of archaea are made of other related molecules. Archaea also differ from bacteria in the structure of their RNA as well as certain aspects of their genetic makeup.

Now that we’ve learnt about kingdom Monera, what a prokaryote is, and the difference between bacteria and archaea, let’s try a practice question.

Which of the following is a characteristic of an organism belonging to kingdom Monera? (A) Most of these organisms are large and multicellular. (B) The cells of these organisms contain a cellulose cell wall. (C) These organisms only reproduce sexually. Or (D) the cells of these organisms do not contain a membrane-bound nucleus.

In order to answer this question, we’ll recall what we know about the characteristics of the five kingdoms of life. And then we’ll use this information to determine which of the answer choices is specific to kingdom Monera. The American botanist Robert Whittaker is credited with developing the five-kingdom system. The five kingdoms into which he divided all living organisms are Monera, Plant, Animal, Fungus, and Protist.

The main difference that sets members of kingdom Monera apart from the other four is that all monerans are prokaryotic organisms, meaning that their cells do not possess a nucleus or other membrane-bound organelles. All of the organisms in the other four kingdoms of life are eukaryotic, meaning that their cells possess a nucleus in which the genetic material, or DNA, is stored. If you’re able to remember that monerans are prokaryotic and that pro- means no nucleus, then you have enough information to answer this question. But we’ll investigate further and determine why each of the other answer choices is incorrect.

All prokaryotic organisms are unicellular, although some join together to form strands or colonies. This rules out the answer choice that says these organisms are large and multicellular. The cell walls of monerans are made of peptidoglycan or other similar molecules. The cell walls of plant cells are made of cellulose, and the cell walls of fungal cells are made of chitin. So, we know that organisms belonging to kingdom Monera do not possess a cellulose cell wall. Finally, prokaryotic organisms reproduce through a process called binary fission.

In binary fission, one parent cell replicates its genetic material and then reproduces into two identical daughter cells. Since only one parent is involved, this is a method of asexual reproduction. This allows us to eliminate the answer choice that says that these organisms reproduce sexually. The answer choice that describes a characteristic of an organism belonging to kingdom Monera is the cells of these organisms do not contain a membrane-bound nucleus.

Let’s try another practice question.

A unicellular organism has been discovered. The organism is adapted to survive in hot springs that have very high temperatures and low pH levels. Which kingdom, Archaebacteria or Eubacteria, is this organism most likely to belong to?

This question describes some of the characteristics of an unidentified unicellular organism. And then it asks us which of two kingdoms, Archaebacteria or Eubacteria, is this organism most likely to belong to. In order to answer this question, we’ll recall the characteristics of organisms that are classified as archaebacteria and organisms that are classified as eubacteria. And then we’ll use the information about the mystery organism to determine which of the two groups it most likely belongs to.

In order to best organize what we know about these two kingdoms, I’ve made a Venn diagram. There’s one section for eubacteria, one section for archaebacteria, and where the two circles overlap represents information that’s true about both. Organisms that belong to kingdom Eubacteria as well as organisms that belong to kingdom Archaebacteria can be described as prokaryotic. Prokaryotic organisms are unicellular, they’re asexual, and they have cells that do not possess a membrane-bound nucleus.

The word eubacteria means true bacteria. These are the bacteria that you’re likely already familiar with. Eubacteria exist nearly everywhere on Earth, and they possess a cell wall made of a chemical called peptidoglycan. The word archaebacteria means ancient bacteria. These organisms got their name because they were first discovered existing in extreme environments. These environments are similar to ones that were much more common on Earth a long, long time ago. Another distinguishing characteristic of archaebacteria is that their cell walls are not made of peptidoglycan.

We’ve determined the characteristics of archaebacteria and eubacteria. So, now we need to review the characteristics of our mystery organism and figure out which kingdom it belongs to. We’re first told that our organism is unicellular, but that’s a characteristic of both archaebacteria and eubacteria. So, being unicellular doesn’t help us to figure out which of the two kingdoms our organism belongs to.

We are also told that this organism exists where temperatures are very high and pH is very low. While extremely high temperature and low pH would kill most eubacteria, archaebacteria are known for existing in extreme environments. A hot spring is a good example of an extreme environment. So, we can conclude that the kingdom that this unicellular organism is most likely to belong to is Archaebacteria.

Let’s wrap up our lesson by taking a moment to review what we’ve learnt. In this video, we learnt about the kingdom Monera. We learnt that all of the organisms in the kingdom Monera are prokaryotic. Prokaryotic organisms are unicellular, their cells do not possess a nucleus, and they reproduce asexually. We also learnt that, more recently, the kingdom Monera has been divided into two kingdoms, Bacteria and Archaea. The members of the Bacteria kingdom can be found living nearly everywhere on Earth, and they have cell walls made of a chemical called peptidoglycan. In contrast, archaea tend to live in extreme environments, and they have a cell wall that is not made of peptidoglycan.

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