Two to Five Kingdom Classification

Explain the Two to Five kingdom classification.

MODIFICATION OF OLD CLASSIFICATION:

Two to Five Kingdom Classification Systems:

Different classification systems recognize Two to five kingdoms

For centuries, the living organisms have been classified into Two kingdoms, plants and animals.

(1) Kingdom (Plante):

Plant can prepare their own food from simple inorganic material and store energy (autotroph), while.

(2) Kingdom (Animalia):

Animals cannot synthesize their own food from simple inorganic material and depend for their food either on autotrophs or on decaying organic matter (heterotrophs).

Objection in Old Classification:

Bacteria were included in plants.

Many biologist found this system satisfactory, while other found it unworkable for many unicellular organisms like.

Euglena that have both plant like (presence of chlorophyll) and animal like (lack of cell wall) characters and also because it.

Ignores the differences between Prokaryotic and Eukaryotic cells.

(3) Kingdom (Protista):

In 1866, Ernst Hackel proposed a third kingdom PROTISTA to accommodate Euglena like organisms and bacterial.

In 1937, E-Chatton suggested differentiating terms:

Procariotique (from Greek pro, meaning before, and karyon, meaning nucleus) used to describe bacterial and blue-green algae, and Eu-caritique (from Greek eu, mean true) to describe animal and plant cells.

(4) Kingdom (Fungi):

Some biologists also disagree about the classification of FUNGI, such as bread mold, yeast and mushrooms, which, Resemble plants in many ways but are not autotrophs.

Fungi are special forms of heterotrophs that obtain energy and structural material by breaking down (decomposing) and absorbing food substances from the surroundings, and possess chitin as a major structural component in their cell walls.

(5) Kingdom (Monera):

Robert Whittaker (1969):

A relatively recent system of classification, the five kingdom system, was proposed by Robert Whittaker (1969).

This system of classification is based on three different levels of cellular organization associated with three principal modes of nutrition.

(i) Photosynthesis.

(ii) Absorption and

(iii) Ingestion.

The Five Kingdoms Proposed:

(i) (MONERA) the prokaryotic unicellular organisms such as bacterial,

(ii) (PROTISTA) the Eukaryotic predominantly unicellular organisms such as Euglena and Amoeba

(iii) (PLANTAE) the Eukaryotic multicellular Autotrophs

(iv) (FUNGI) the Eukaryotic multicellular Reducers: (mushrooms)

(v) (ANIMALIA) the Eukaryotic multicellular Consumers

PLANTS are autotrophic in nutritional mode, making their own food by photosynthesis such as mosses, ferns, flowering plants.

FUNGI are heterotrophic organisms that are absorptive in their nutritional mode.

Most fungi are decomposers that live on organic material.

Secrete digestive enzymes and absorb small organic molecules which are produced by digestion.

ANIMALS live mostly by ingesting food and digesting it within specialized cavities.

They lack cellulose and show movements for example birds, reptile.

In five kingdom classification all eukaryotes that did not fit the definition of plants, fungi, or animalia were included in Protista.

Most Protists are Unicellular forms, but this kingdom also includes relatively simple multicellular organisms that are believed to be direct descendants of unicellular protists.

Modification of 5 Kingdom System:

Lynn Margulis and Karlene Schwartz (1988) modified five kingdom classification of Whittaker by considering

(a) Cellular organization

(b) Mode of nutrition

(d) Organelles of Symbiotic origin (Beneficial relationship Mitochondria, Chloroplast)

These five kingdom are in modified forms:

(i) Prokaryotae (Monera),

(ii) Protoctistsa (Protists),

(iii) Plantae,

(iv) Animalia and

(v) Fungi