Five Kingdom Classification

What are Species?

• All individuals of a species can normally breed among themselves.

• Individuals of a particular species differ from all other living beings.

• All house cats of the world belong to one species; they may have some differences among themselves such as color, height, and the length of their tail, yet they can all interbreed.

• So, the house cat is one species {Felis domesticus).

• Similarly, there may be quite a few differences in the body features of people of different countries or races, yet there can be a marriage between them with normal children.

• So, all mankind today belongs to a single species {Homo sapiens).

• Similarly, all ‘peepal’ trees and all mango trees belong to their respective species.

  Horses and Donkeys are two different species, and both have numerous breeds.

• All breeds of horse and those of donkey can interbreed among themselves to produce fertile young ones but a cross between a horse and a donkey, though possible, does not produce a fertile “mule".

• Humans have been practicing producing mules for centuries, but several new types of crosses have been successfully tried in modern times.

Examples of a cross between different species:

• Zebra mated with a donkey produces “Zenkey" with ears and back like those of a donkey and striped legs and hips like the zebra.
• Zenkey is sterile
• A tiger mating with a female lion produces tigeon.

Genus:

• Similar species constitute the next higher category called genus (plural: genera). Let us take an example.
• We have crows around our homes.
• The hill crow is different from the crow found on the plains (the house crow) in many features—size, color, beak, etc.
• The hill crow and the house crow are two different species.
• They cannot interbreed; yet they are crows, easily made out from other birds.
• These two kinds of crows belong to the same genus Corvus.

Family:

• A group of genera with certain common characteristics form a family.
• Take an example. Lion (Panthera leo) and tiger (Panthera tigris) are different species but they belong to the same genus.
• This genus (Panthera) and another genus (Felis) which includes the domestic cat, also share some common characteristics.
• Therefore, there is the larger cat family (Felidae) which includes the genus of lion and tiger, and the genus of domestic cat.

Order

• A group of related families makes an order.
  • For example, the cat family Felidae (lions. tigers, and cats) and the dog family Canidae (dogs. foxes, jackals, etc.) possess some common features and so they make an order.
  • In the example cited here, the order is “Carnivora".

Class

• Related orders make a class.
  • For example, the orders of different animals like those of dogs, cats, bats, whales, monkeys, and even humans. etc., have some common features such as hairy skin and milk glands.
  • The particular class of animals mentioned here is “Mammalia"

Phylum

• A phylum is the largest division in the classification of plants and animals. Related classes constitute a phylum.
• For example, the classes of different animals like mammals, birds, and reptiles. frogs, fishes, etc., together have a notochord or a backbone.

Kingdom

• The kingdom is the largest division of living beings.

Drawbacks of Old 2-Kingdom Classification:

• According to the old classification as was given by Linnaeus (1707- 1778) the entire world of living organisms was divided into two kingdoms:
  • Kingdom Plantae (including all plants)
  • Kingdom Animalia (including all animals).
  • But this scheme had several drawbacks.
    • For example, how do we say that
    • “Bacteria and fungi are plants” — they have no chlorophyll and do not carry out photosynthesis.
    • Some single-celled organisms such as Euglena cannot be exclusively called plants or animals they have chloroplasts like plants, have cell mouths to feed like animals, and possess contractile vacuoles for excretion.
    • Bread mold, etc., are multicellular, but they have nothing like roots, stems, and leaves and they do not bear any flowers or seeds and they have no chlorophyll.
• So, the above three groups of organisms are now recognized as distinct kingdoms (Monera, Protista, and Fungi), and these together with the two other kingdoms, the plants (Plantae) and animals (Animalia), now constitute what is called the Five Kingdom classification, as is given below.

Five Kingdom Classification:

Kingdom Monera:

• It mainly includes bacteria, blue-green bacteria, and some unicellular algae.
• These are single-celled organisms
• They have no organized nucleus.
• The nuclear material DNA) is distributed in the cell with it being enclosed in a nuclear membrane.
• This condition of the cell is called prokaryotes
• They are also devoid of membrane-bound organelles like mitochondria and chloroplasts.

Kingdom Protista:

• These are single-celled organisms having a well-defined nucleus with a nuclear membrane (eukaryotic).
  • They include both the unicellular green autotrophic organisms (e, g. Chlamydomonas) as well as unicellular non-green heterotrophic organisms (e.g. Euglena, Amoeba, Paramecium), and also some of their multicellular photosynthetic descendants like Pandorina.

Kingdom Fungi:

• Most fungi are made up of thread-like hyphae rather than cells, and there are many nuclei distributed in the continuous cytoplasm.
  • Examples: Bread mold, Toadstool, Yeast, Penicillium

Kingdom Plantae:

• These are made of many cells (multicellular).
• They all have chlorophyll and they make their own food by photosynthesis (autotrophic i.e. self-nourishing).
• They include Thallophyta (algae), bryophytes (mosses), pteridophytes (ferns), gymnosperms (pine, etc), and angiosperms (flowering plants).

Thallophyta:

• Includes all algae e.g. Chlamydomonas, volvox, etc.
• Thallophytes are autotrophic as they contain chlorophyll.
• They have a thallus-like body, i.e. the plant body cannot be distinguished into roots, stems,s or leaves.
• They are primarily aquatic.

Bryophyta:

• Examples: mosses and liverworts plants belonging to this group have a plant body that has false root-like structures called rhizoids, and leaf-like structures.
• They are autotrophs.

Pteridophytes:

• Includes all ferns.
• Plants belonging to this group have a plant body that can be distinguished into root, stem, and leaves.
• The leaves are often made of leaflets bearing spores on the underside.
• They are non-flowering plants.

Gymnosperms:

• The plants belonging to this group bear naked seeds, i.e. the seeds are not enclosed in fruits.
• They may be either trees or shrubs.
• They bear both male and female flowers.
• They are of two types cycads and conifers.

Angiosperms:

• Includes all flowering plants.
• Plants belonging to this group have a highly developed plant body, which can be differentiated into root, stem, leaves, flowers, and fruits.
• The seeds are enclosed in a fruit. They are further divided into monocots and dicots.

Monocots:

• The plant belonging to this group bears seeds having only one cotyledon, the leaves have parallel venation, and the root system is fibrous.
• Examples: maize, rice, grass, etc.

Dicots:

• The plants belonging to this group bear seeds with two cotyledons, and the leaves have reticulate venation and a tap root system.
• Examples: peas, potato, apple, sunflower, rose, etc.

Kingdom Animalia:

• These are multicellular organisms without a cell wall and without chlorophyll. usually mobile, and obtaining food by eating or sucking, etc. (heterotrophic i.e., differently nourished).

Naming an Organism:

• In science, people from different countries with different languages have to read about each other’s research work.
• So, it was found necessary to eliminate any possible confusion in using local names by substituting them with names especially given in scientific language.
• The present practice is to use a no-part name for each species.
  • For example, our hill crow is Corvus macmrhynchos and the house crow is Corvus splendens.
• Scientific names are always written in the Roman script and when in print they are always in ’James. When hand-written they should always be underlined.
• The first letter of the genus name should be a Capital letter, while the species name ‹i.e. the second part) should begin with a small letter

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