CLASSIFICATION OF LIVING ORGANISMS
If we just revolve our eyes in our surroundings, we see many organisms around us. Some very small like bacteria while some big even as an elephant. Some transparent while some colorful. Some that which live only a few days while some lives for thousands of years. Some plants are small as Algae and while some tall as Redwood trees of California.
And it is not easy to study all of them in detail. So all of them are classified on the basis of their similarities between them.
What is classification?
Grouping of organisms on the basis that how they are closely related.
What is the basis of classification?
Classification is done on the basis of three things.
Autotrophic type of organisms makes their own food by the process of photosynthesis in the presence of sunlight. These mainly include plants.
Heterotroph organisms are dependent on the autotrophs of their foods. These are mainly animals.
The complexity of cell– some are prokaryotic organisms and some eukaryotic organisms.
Prokaryotic organisms are the organisms which do not have well-defined membrane-bound organelles.
Eukaryotic organisms are the organisms which have well-defined membrane-bound organelles
Unicellular or Multicellular
some organisms have a single cell which performs all the functions while some organisms have many cells and specified cells are to do specified functions. The organisms which have a single cell is called unicellular organism and the organisms which have multiple cells are known as multicellular organisms.
And it is not easy to study all of them in detail. So all of them are classified on the basis of their similarities between them.
What is classification?
Grouping of organisms on the basis that how they are closely related.
What is the basis of classification?
Classification is done on the basis of three things.
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Mode of nutrition
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Complexity of cells
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Unicellular or multicellular
Autotrophic type of organisms makes their own food by the process of photosynthesis in the presence of sunlight. These mainly include plants.
Heterotroph organisms are dependent on the autotrophs of their foods. These are mainly animals.
The complexity of cell– some are prokaryotic organisms and some eukaryotic organisms.
Prokaryotic organisms are the organisms which do not have well-defined membrane-bound organelles.
Eukaryotic organisms are the organisms which have well-defined membrane-bound organelles
Unicellular or Multicellular
some organisms have a single cell which performs all the functions while some organisms have many cells and specified cells are to do specified functions. The organisms which have a single cell is called unicellular organism and the organisms which have multiple cells are known as multicellular organisms.
Importance of classification
There are quite a few importance of classification they are1 They make the study of organism easier
2 It summarizes all life forms.
3 It helps us to learn the relationship between different kinds of organisms.
4 It is basic for all other biological sciences like ecology, zoology etc.
The hierarchy of classification - groups
Many biologists have tried to classify organisms into the category of kingdoms. Some of them are Ernst Haeckel, Robert Whittaker, and Carl Woese
The classification proposed by Whittaker have five kingdoms they are:
Monera,
Protista,
Fungi,
Plantae,
Animalia.
The further classification is done by naming of organisms into different subgroups. The classification scheme is
- Kingdom
- phylum [for animals ] / division [for plant]
- class
- order
- family
- genus
- species
Genus - similar kinds of species are classified into the genus.
Family- similar genera are grouped into family
Order – similar families are grouped into order
Class – similar orders are grouped into classes
Phylum – similar classes are grouped into phylum
Kingdom– similar phyla are grouped into a kingdom
The 5 kingdom classification proposed by Whittaker are -
Kingdom Monera
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They are prokaryotic organisms and do not have defined nucleus or organelles.
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They are mostly unicellular organisms, some have cell wall while some don't.
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Their mode of nutrition may be autotrophic or heterotrophic.
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They are usually non – motile animals.
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Example – blue-green algae, bacteria, mycoplasma
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They are eukaryotic organisms and have well-defined nucleus and organelles.
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They are unicellular organisms.
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Their mode of nutrition may be autotrophic or heterotrophic.
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They have flagella for moving around.
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Example – amoeba , paramecium , euglena etc.
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They are eukaryotic, multicellular organisms.
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They are mostly non-motile.
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They are saprophytes i.e, they depend on dead and decaying organisms for their food.
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They have a cell wall made of chitin.
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Examples – yeast, mushroom etc.
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They are eukaryotic, multicellular organisms.
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They have a cell wall made of cellulose.
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They are auto-trophic organisms.
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They store carbohydrates in the form of starch.
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Example – all plants
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They are eukaryotic, multicellular organisms.
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Their cells do not have cell wall instead they have a cell membrane.
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They are heterotrophic.
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They are motile i.e., they have legs for locomotion.
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