Kingdom Monera, Protista and Fungi

Classification, Functions and Characteristics of Kingdom Monera, Protista and Fungi

Kingdom Monera:

Kingdom Monera comprises of the bacteria and cyanobacteria that are usually known as blue-green algae. While only bacteria are prokaryotic which lack a true nucleus, (which means without a nuclear membrane). The only prokaryotic plant kingdom is Monera. Bacteria were the first cellular organisms to develop on the earth since afterlife initiated around 3.5 billion years ago and they are the single cellular organisms on the planet earth for about the next two billion years. 

Most bacteria are unicellular or single-celled but some cyanobacteria and actinomycetes are multicellular and filamentous in which filaments might be branched. Monerans are also the most abundant of all living cellular organisms. 

Bacterial cell structure:

The bacterium which is a single-celled has a cell wall made of peptidoglycan compound enclosing the cell membrane and a single circular chromosome. The cell contains ribosomes, but it lacks membrane-bound organelles. 

Parts of a bacterium:

Cell wall: It is the outermost covering of a cell. The prokaryotes possess a rigid cell wall that gives shape and protects the cell wall. The cell wall is made up of a chemical called peptidoglycan which is unique to lipids, bacteria, polysaccharides and some proteins.

Pili: They are a thin and short thread-like tubular compositions projecting out from the cell wall in some of the bacteria.
Flagella: Flagella are present in some bacteria that help them in moving. They are thicker and longer than pili. Flagella of prokaryote’s structure will be different than that of the eukaryotes.

Plasma membrane: It is located below the cell wall. It surrounds the cytoplasm and other cell contents. Similar to that of the eukaryotes, the plasma membrane is made up of proteins and lipids. 

Genetic material:

One whole circular chromosome is made up of a double helical molecule of DNA. It is situated in nucleoid, a region of the cytoplasm. The bacteria called prokaryotes because the chromosome doesn't have a true nucleus. So, Monera is the prokaryotic kingdom. Other than the bacteria, there are many other species of bacteria that possess one or more additional rings of DNA called plasmids. They replicate along with the bacterial chromosome and allow genes for antibiotic resistance and operate as the F-factor or sex factor giving the property of male sex to the cell that has the F-factor or the sex factor. 

Cell organelles:

Membrane-bound organelles such as mitochondria; endoplasmic reticulum, Golgi complex, and chloroplast are not present. Here, only 70s ribosomes that are different from the eukaryotes are present.

General body functions of Monera:

  • • Nutrition:

  • There are four nutritional categories that are found in bacteria. They are:

  • a. Autotrophs are those who produce their own organic food.

  • b. Saprotrophs are those who feed on dead organic matter.

  • c. Symbionts are those which utilize food from other life forms which they are coupled for mutual benefit.

  • d. Parasites are those that absorb food from living beings and harm them.

  • • Respiration:

  • Respiration in bacteria can be in two forms. They are:

  • a. Aerobic respiration- which is done using oxygen or

  • b. Anaerobic respiration- that is done in the absence of oxygen

  • Breakdown of food or cellular respiration to release energy happens in mesosomes that are the cell membrane’s inner extensions.

  • • Reproduction:

  • a. Asexual reproduction:

  • Using binary fission, bacteria reproduce asexually. It takes nearly 20 minutes for one bacterium cell to divide into two by the binary fission, under the favorable conditions.

    Binary fission in bacteria
  • b. Sexual recombination:

  • Sexual recombination is also known as genetic recombination. Primitive mode of sexual reproduction is shown by some kind of bacteria. It differs from that of the sexual reproduction happening in higher life forms. 

  • i. Two bacteria that lie very close for gene transfer (conjugating bacteria) are held jointly by pili.

  • ii. Here, a segment of the DNA strand is transferred from F-factor (fertility factor) i.e male donor cell to the female recipient cell.

  • Kingdom Protista:

    Protista is called as unicellular eukaryotes. They comprise of Diatoms, protozoa, and unicellular algae. They have membrane-bound organelles like nucleus with chromosomes covered in the nuclear membrane, chloroplast (only in photosynthetic protists), mitochondria, and endoplasmic reticulum and Golgi bodies. Here, the respiratory organelles are mitochondria. 

    Protista is parasitic, photosynthetic or saprotrophic.

    Unlike bacteria, Protista would have flagella or cilia having 9 + 2 microtubules which consist of only one spirally protein (flagellin). They can reproduce both sexually and asexually. Some protists are harmful and some are beneficial to human beings.

    Classification of Protista:

    The kingdom Protista consists of:

  • 1. Phylum Protozoa: It has the following four classes:

  • a. Rhizopoda

  • b. Flagellate

  • c. Ciliata

  • d. Sporozoa

  • The protistan algae fit in to:

  • • Phylum Bacillariophyta

  • • Phylum Chlorophyta

  • 2. The Diatoms:

  • The diatoms are present in both salt and fresh water and in moist soil too. Thousands of species of diatoms performs as food for the aquatic animals. Diatoms can be colonial, unicellular or filamentous and arise in a wide range of shapes.

    Each cell here has a single major plastid and nucleus. They produce cell walls containing silica.

  • 3. Other Algae:

  • Algae can be either unicellular or multicellular. Since they contain chlorophyll, the algae can prepare their own food by photosynthesis. Some algae have other pigments like brown pigment (Fucoxanthin), red pigment (Phycoerythrin) or blue pigment (phycocyanin). The algae can be brown, blue or red in color depending on the pigment present. 

    The algae have a definite nucleus, cell wall, cell membrane, chloroplast, and cytoplasm. The chloroplast is ribbon-shaped in Spirogyra and cup-shaped in Chlamydomonas. The starch-containing bodies such as Pyrenoids are an integral part of the chloroplasts in the green algae.

    Kingdom Fungi:

    During the warm humid season, chapati, bread slices, leather shoes, and belts, develop a dusty layer on them. In flower beds and lawns, mushrooms pop out and these are called as fungi.

    Characteristics of fungi:

  • • Fungi are heterotrophic multicellular or unicellular eukaryotes.

  • • Fungi survive as a slender thread like filaments called hyphae. Hypha could be single-celled or multi-celled ones and has one or more nuclei. Yeast is single-celled and uninucleate.

  • • A hypha would be divided into cells by partitions called septa. They have pores and cytoplasm streams freely through it. Mycelium is the name for a group of hyphae forming a network.

  • • Mycelia spread out on the ground or on the substrate and also extend up to several kilometers. They don’t have chlorophyll. Their nutrition is done by absorption or feeding on dead organic matter.

  • • Aquatic fungi have flagellate spores or flagellate gametes. At any stage of the life cycle, higher fungi don't have a flagellum.

  • • Reproduction in fungi can be both sexual by means of conjugation and asexual by flagellate or non-flagellate spores.

  • Main kinds of fungi:

    The fungi can be classified into five main kinds. They are:

  • • Myxomycetes, the slime molds that have an irregular shape. They have a creeping multinucleate mass of protoplasm sometimes enclosing up to several square meters.

  • • Phycomycetes, unicellular, branched and filamentous. Example: Phytophthora and Rhizopus.

  • • Ascomycetes, single celled or multicellular. Example: Penicillium, Aspergillus and Neurospora.

  • • Basidiomycetes, multicellular, branched and are characterized by smuts, rusts, toadstools, and mushrooms that are large enough so that they can be viewed through naked eyes.

  • • Deuteromycetes, multicellular filamentous branched fungi reproduce by asexual means alone. Example: Alternaria.

  • • Mycorrhizae and lichens exist in symbiotic relationships. Lichens are the combination of definite fungus and a blue-green or green alga that prepares food while the fungus aids in protection and absorbs minerals and water from the neighboring places.