Need for classification
For keeping books completely different subjects a different almirah are employed in an honest library in order that after we would like a specific book of geographies, English, History, Physics, Chemistry, biology or the zoological science etc.
We will at once do away with that book from that section or an almirah.
If these books don't seem to be unbroken in such systematic means we have a tendency to cannot do away with needed a book out of the assemblage of thousands of books.
A simmilarly inspire of a good diversity amongst the animals, the kingdom is well organized and is incredibly systematic.
For the systematic study animals are divided into minor and major teams on the premise of similarities and variations.
Every cluster has been given a specific name relying upon their characteristics.
As an example completely different sorts of birds are enclosed in a class supported their structural and physiological similarities.
Within the same means lizards, snakes and tortoises are enclosed in a class Reptilia.
There are estimated 10-15 million living organisms in the earth of which 1.7 million has been studied.
This suggests there are enormous varieties of animal, plants and other organisms.
These organisms show great diversity in morphological, structural, functional and genetic features.
To study such enormous diversity of organisms on this planet, one would naturally free the necessity of classifying them into groups and subgroups on the basis of their similarities and differences.
Several systems of classification have been proposed by scientist.
Two kingdom classification
Carolus Linnaeus categorized organisms into two kingdoms.
1. Kingdom Plantae
The Kingdom Plantae is characterized by the presence of cell wall
They are autotrophs making its own food by the process of photosynthesis.
Most of them except some lower aquatic forms are non-mortile.
They are relatively less sensitive to the external stimuli and respond very slowly.
2. Kingdom Animalia
the other hand animal cell lack cell wall, having only cell membrane as the outer covering of the cell.
They are not the autotrophs. They collect their food from plants and depended on them for food.
Furthermore, They are motile having different locomotive organs.
Furthermore, They are highly sensitive to the external stimuli and show a quick response to it.
Demerits of two kingdom classification
-This two kingdom classification did not clearly defined the place of bacteria having prokaryotic cells.
-Algae like Chlamydomonas has flagella and shows locomotion which is animal character but placed in kingdom plantae due to being autotrophs.
— Fungi, which are non-chlorophyllous and heterotrophic have included in the plant kingdom for its structural similarity.
— Viruses, which lack cell wall, protoplasm and are living only inside the host cell have been placed in kingdom plantae.
— The two kingdom did not identified the evolutionary relationship between them.
Thus, the two kingdom classification failed to classify all the organisms according to their characters.
Three kingdom classification
To overcome the problems with two kingdom classification, Ernst H. Hackel created a kingdom Protista.
The kingdom Protista includes all the simpler forms of the life.
He putted bacteria, algae, fungi and sponges on the kingdom Protista.
Thus, it formed three kingdom classification having kingdom Protista, kingdom plantae and kingdom Animalia.
Four kingdom classification
In 1956, Lynn Margulies and H. F. Vopeland proposed a four kingdom classification system
1. Kingdom Monera-
Prokaryotes, true bacteria and blue-green algae
2. Kingdom Protoctista-
Eukaryotic algae, protozoa and fungi
3. Kingdom Plantae-
All green plants
4. Kingdom Animalia-
All animals derived from zygote.
Five kingdom classification
Robert H. Whittaker proposed a five kingdom classification.
It is the most accepted classification.
He made a new kingdom for fungi, which acquire nutrition solely by absorption, sufficiently different from plants and animals.
He retained three kingdom that are Monera, plantae and Animalia of the four kingdom classification and divided the kingdom Protista into two kingdoms — kingdom Protista and kingdom fungi.
The major advantage in the five kingdom classification is that it shows clarity of the placement of every organism in the different kingdoms.
It explains the phylogeny evolutionary relationship between these kingdoms that the Monera give rise to protists, the protists give rise to fungi and so on animals are evolved.
Comments
Post a Comment