An Overview On The Characteristics of Five Kingdom Classification

Evolution is one of the Biology Topics that has been debated and studied for centuries, exploring the process by which species change over time.

Five Kingdom Classification: Kingdoms, Features and Examples

Characteristics and Classification of Monera

The kingdom Prokaryotae is divided into two sub-kingdoms: Archaebacteria (Archaea) and Eubacteria (Bacteria). Of the two sub-kingdoms, the Archaebacteria is more ancient.

(i) Archaebacteria
Most archaebacteria are autotrophs and only a few, photosynthesize. Archaebacteria derive the energy for their metabolic activities, from the oxidation of chemical energy sources, such as the reduced gases – ammonia (NH₃), methane (CH₄), or hydrogen sulphide (H₂S). In the presence of one of these chemicals, archaebacteria can manufacture their own amino acids and proteins.

The environments where these chemical energy sources are found are often harsh for most other kinds of organisms. Archaebacteria are divided into the following three groups:

• Methanogens: As their name implies, methanogens manufacture methane as the result of their metabolic activities. Methanogens die in the presence of oxygen. Thus, they are found in swamps and marshes, in which all the oxygen has been consumed by the other organisms living in those environments. The methane smell characteristic of swamps and marshes is courtesy of methanogens.
• Thermoacidophiles: These archaea favour extremely hot and acidic environments, such as hot springs. Many thermoacidophiles use hydrogen sulphide as their energy source.
• Halophiles: These archaea grow in very salty environments, such as the Great Salt Lake and the Dead Sea. These environments are extremely alkaline.

(ii) Eubacteria
Prokaryotic cells of bacteria have an outer cell wall that surrounds the plasma membrane, which in turn surrounds a non-compartmentalized cytoplasm dotted with ribosomes. They generally lack membrane-enclosed organelles such as nuclei, chloroplasts, and mitochondria. A circular strand of DNA usually coiled into one region of the cell, the nucleoid, serves as a single chromosome. Metabolic activities, such as electron transport (a function of mitochondria) and photosynthesis, take place on the plasma membrane, which sometimes folds inwards into the cell’s interior.

Nearly all bacteria are encased in a porous but rigid cell wall that protects them from osmotic rupture in watery environments and gives different types of bacteria their characteristic shapes. The most common bacterial shapes are rodlike bacilli (singular, bacillus), spheres called cocci (singular, coccus), and the corkscrew-shaped spirilla (singular, spirillum). The cell wall of bacteria contains a unique material called peptidoglycan. Peptidoglycan is composed of chains of sugars cross-linked by peptides (short chains of amino acids).

The Gram-staining technique distinguishes two types of cell-wall construction in bacteria, enabling us to classify them as gram-positive or gram-negative. Gram stain causes gram-positive bacteria to stain red. The cell wall of gram-negative bacteria contains an additional outer membrane resembling a plasma membrane in structure. The antibiotic penicillin works best on gram-positive bacteria. Another antibiotic streptomycin works best on gram-negative bacteria.

Gram staining technique is one of the first procedures a microbiologist will perform on a newly found or unfamiliar bacterial species; it is important because it suggests the types of antibiotics that might be effective in fighting a pathogenic (disease-producing) bacterium. An antibiotic is a chemical made by one microorganism (e.g., fungi, bacteria) that can slow the growth or kill another microorganism.

Many bacteria are motile (e.g., Escherichia coli) and contain one or more flagella. The flagella are made of a protein, called flagellin and tend to rotate like the propeller of a ship. Some bacteria also contain very fine, short appendages on the cell surface. They are called pili and help in the sexual reproduction of bacteria and in the attachment of pathogenic bacteria to their hosts.

The eight groups of eubacteria with their typical examples and key characteristics have been tabulated in the Table.

Main Groups of Eubacteria

Kingdom Protista – Characteristics and Classification of Protists

This group includes many kinds of unicellular eukaryotic organisms such as unicellular algae, protozoans, and unicellular fungi (Oomycota and slime molds). Some of these organisms use appendages, such as hair-like cilia (e.g., Paramecium) or whip-like flagellum (e.g., Euglena). Their mode of nutrition can be autotrophic (e.g., unicellular algae, diatoms) or heterotrophic (e.g., protozoans)

Examples: Unicellular algae; Chlorella, Chlamydomonas; diatoms, and protozoans.

Phylum Protozoa (Gr., protos – first; zoon – animals; early animals)

• Unicellular (one-celled or single-celled), mostly aquatic (freshwater or marine) animals.
• Solitary or colonial, free living or parasitic or symbiotic.
• Body naked or covered by pellicle or hard shells.
• Body shape may be irregular, spherical, oval, elongated or flattended.
• Cytoplasm is differentiated into outer ectoplasm and inner endoplasm.
• Uninucleate, binucleate, or multinucleate.
• Locomotion using finger-like pseudopodia, flagella or cilia.
• Nutrition is mostly heterotrophic.
• Asexual reproduction by binary fission, multiple fission, and sexual reproduction by conjugation. Phylum

Protozoa are divided into the following five classes:
Class 1. Mastigophora: Locomotory organs are flagella.
Examples: Euglena, Noctiluca, Trypanosoma (causes sleeping sickness), Giardia (causes dysentery), Leishmania (causes kala-azar), Volvox.

Class 2. Sarcodina (Rhizopoda): Pseudopodia are chief organelles of locomotion and food catching.
Examples: Amoeba, Entamoeba (causes dysentery), Polystomella, Arcella.

Class 3. Sporozoa:
1. Lack locomotary organelles.
2. All are parasites.
Examples: Plasmodium (causes malaria), Monocystis.

Class 4. Ciliata: Cilia chief locomotory and food-catching organelles.
Examples: Paramecium, Opalina, Nyctotherus, Vorticella.

Class 5. Suctoria: Adult without any locomotory organelles.
Example: Ephelota

Kingdom Fungi – Structure, Characteristics & Classification

Fungi (Lfungus – a mushroom)
1. Simple non-green plants which are not photosynthetic. They are heterotrophic and eukaryotic organisms. Some fungi, such as Puccinia, Albugo, Ustilago, etc., are parasites and draw their nutrients from the living cells of their host plants. Some fungi, such as Mucor, Rhizopus, Penicillium, and Agaricus, are decomposers (hence fungi form a kingdom of multicellular decomposers), saprophytes or saprobionts, deriving their nourishment from the dead remains of plants and animals.

2. They may be unicellular (yeast) or filamentous (most fungi). The body of a multicellular and filamentous fungus is called a mycelium and is composed of several thread-like structures, termed hyphae.

3. Fungi have a cell wall containing a mixture of chitin and cellulose. Chitin is a tough complex sugar.

4. The reserve food is glycogen.
Examples: Bread mold (Rhizopus, Mucor); yeast (Saccharomyces); pink bread mold (Neurospora); green mould (Penicillium); cup fungus (Peiziza); morel, guchi or sponge fungus or gill fungus (Morchella); mushroom or gill fungus (Agaricus); rust (Puccinia); smut (Ustilago) and Aspergillus.

Lichens

• Lichens grow as the slow-growing coloured patches on rocks, the bark of tree trunks, and even on the ground. They are very hardy.
• In lichens, blue-green algae or cyanobacteria and fungi live in symbiosis (mutualism), i.e., they co-exist for mutual benefit.
• The algal component of the lichen is known as phycobiont and the fungal component is mycobiont.
• The fungus absorbs water and mineral matter and supplies it to the algae. The algae, in turn, prepares food and supplies it to the fungus.

Lichens can tolerate prolonged drought and drastic variations in temperature. They occur in hostile habitats such as barren rocks, walls, tree trunks, and icy regions where they can be seen as slow-growing large coloured patches. Lichens are sensitive to air pollution. They are a source of essences, dhup, and havan samagri, and some medicines and dyes (e.g., orcein (a biological stain), orchil (violet dye), and litmus).

Examples: Crustose lichens (e.g., Rhizocarbon, Graphic); foliose lichens (e.g., Parmelia, Collema), and fruticose lichens (e.g., Alectoria, Usnea).

Kingdom Plantae – Biological Classification

• Plantae includes multicellular organisms except for some primitive relatives of algae.
• They are eukaryotes, that is, each cell has a nucleus and membrane bound cellular organelles.
• Cellulose-containing cell wall occurs around the cell.
• A mature plant commonly possesses a single large central vacuole bound by tonoplast (membrane).
• The reserve food of plants is starch and lipids (oil/fat).
• In all plant cells occur double membrane covered cell organelles, called plastids.
• Some plastids possess photosynthetic pigments (chlorophylls). They are called chloroplasts.
• The nutrition of plants is the autotrophic type with the help of chlorophyll present in chloroplasts, plants are able to perform photosynthesis.
• Growth in plants is generally indefinite due to presence of growing points.
• The body form of the plants is irregular due to the presence of branches.

Classification of Animal Kingdom (Animalia)

• Animals have wall-less eukaryotic cells.
• Animals’ heterotrophic nutrition is of holozoic (= ingestive) type. An internal alimentary canal is present for extra-cellular or intracellular digestion and absorption of food in most animals. Digestion is intracellular in primitive animals. The undigested matter is thrown out.
• The growth of animals is limited and stops after reaching maturity.
• Animals generally possess a definite shape, size and symmetry. Exceptions occur in some lower forms.
• Most animals are mobile (locomotary). Locomotion is required for obtaining food and other necessities (e.g., dwelling, mate).
• Sponges and cnidarians (e.g., Hydra, Obelia, corals), however, are mobile (e.g., tentacles in Hydra and flagella of choanocytes in sponges).
• Movements occur in animals with the help of a muscular system.
• Information is conveyed to different parts of the body by the nervous system which also provides stimulus to muscles for contraction.
• Animals have organisation at the cellular, tissue, organs, and organ system level.