Our planet is gifted with numerous living organisms, which vary in their size, shape, habitat, nutrition, reproduction and a lot more. Based on their physical features and their habitat, these animals of Kingdom Animale are classified into different order and class.
Animals living in different environments, including the water, land, deserts, forests, grasslands, ice land and water and ice to deserts and forests and grasslands. All these organisms consist of something called cells.
Cells are the building blocks of life and one of the most important characteristics of living organisms. They are structural units of life carrying out specifically assigned functions. A group of such cells form a tissue.
Diversity in living organisms can be experienced everywhere on earth. The warm and humid regions of the earth are highly diverse and are called the region of mega biodiversity. 12 countries in the world have more than half of the biodiversity in the world. India is one of them.
Each individual has a unique DNA set up. We differ amongst human beings in the way we look and different attributes contributing to it such as our height, complexion etc. If we compare ourselves with a different species like a horse or a fish, we would definitely vary greatly in almost all aspects but if a horse is compared to a zebra, we would be able to draw a few differences only.
The arrangement of the organisms in groups on the basis of their similarities and differences is known as classification.
Basis Of Classification
Over millions of years, we have seen diversity in living beings. We have evolved from ape-like beings to homo sapiens. We look for similarities between organisms so that we can classify them into classes and hence study them as a whole, for this, fundamental characteristics need to be decided which would form the foundation for classifying.
Classification can be carried out based on many factors such as:
Presence of nucleus
Body design – make up of cells(Single-celled or Multicellular organisms)
Production of food
Level of the organization in bodies of organisms carrying out photosynthesis
In animals – an organization of one’s body parts, development of body, specialized organs for different functions
These features can differ in both plants and animals as they differ in their body design. Hence, these prominent designs and characteristic features can be used to make subgroups and not aa broad classification.
The classification system is of two types:
Two-Kingdom Classification- This system was proposed by Carolus Linnaeus who classified organisms into two types- plants and animals.
Five-Kingdom Classification- This kingdom was proposed by H.Whittaker who divided the organisms into five different classes:
Hierarchy of Classification
Carolus Linnaeus arranged the organisms into different taxonomic groups at different levels. The groups from top to bottom are:
Characteristics of Five Kingdoms
These are unicellular prokaryotes.
They lack a true nucleus.
They may or may not contain a cell wall.
They may be heterotrophic or autotrophic.
For eg., Bacteria, Cyanobacteria
These contain unicellular, eukaryotic organisms.
They exhibit an autotrophic or heterotrophic mode of nutrition.
They possess pseudopodia, cilia, flagella for locomotion.
For eg., amoeba, paramaecium
These are multicellular, eukaryotic organisms.
They exhibit a saprophytic mode of nutrition.
The cell wall is made up of chitin.
They live in a symbiotic relationship with blue-green algae.
For eg., Yeast, Aspergillus
These are multicellular, eukaryotic organisms.
The cell wall is made up of cellulose.
They prepare their own food by means of photosynthesis.
Kingdom Plantae is sub-divided into- Thallophyta, Bryophyta, Pteridophyta, Gymnosperms, Angiosperms.
For eg., Pines, ferns, Mango tree
These are multicellular, eukaryotic organisms without a cell wall.
They are heterotrophs.
The organisms in kingdom Animalia can be simple or complex.
They are genetically diverse.
They exhibit an organ-system level of organization.
It is sub-divided into different phyla such as Porifera, Coelenterata, Echinodermata, Chordata, etc.
For eg., Earthworms, Hydra, etc.
Also read: The Living World
Classification And Evolution
Classification of organisms is closely related to evolution. Evolution is the changes that have accumulated over the years in the body design of organisms for better survival. In 1859, Charles Darwin first described the idea of evolution in his book ‘The Origin Of Species’.
Listed below are inferences drawn when evolution is connected to classification:
‘Lower’ or ‘primitive’ organisms are the organisms having the ancient body type and seem to have not changed over the years.
‘Higher’ or ‘advanced’ organisms are those who are relatively recent and have acquired their particular body designs.
But these terms cannot used be used in classifying organisms, hence we use terms like ‘younger’ and ‘older’ organisms as there is a possibility of witnessing changes with passing time due to increase in the complexity of body designs. Hence, we can simply say, older organisms are simpler compared to younger organisms.
Also read: Cells
Diversity in Living Organisms is a fundamental topic introduced in the higher primary classes. We have reintroduced content revamped for better understanding and comprehension, leading to the creation of Diversity in Living Organisms Class 9.
Learn more in detail about Diversity in Living Organisms and other related topics at CoolGyan’S Biology.