Todays topic for class 7 biology chapters icsc is Kingdom Classification
Classification is the process to arrange and set things in groups on the basis of some similar properties. Biological classification is to group organisms together on the basis of their similarities and separate them into different groups on the basis of their differences. Taxonomy is the branch of science that deals with the classification and naming of organisms.
What is the need of classification?
It is difficult to remember the characteristics of 3 lakh types of plants and 12 lakh types of animals individually. So biologists have grouped them into different groups on the basis of their similarities and differences that makes it easier to study about them.
Characteristics of other organisms can be understood by studying the properties of one member of the group.
What are the advantages of classification?
It helps in the study of different types of organisms easily as it makes the study simple and systematic. It helps to identify and classify such as insects, birds, pathogens etc. The study of a few representatives of a group provides knowledge about the characteristics of the other organisms present in that group. It gives the idea of evolution i.e development of organisms from simpler to complex forms.
System of classification
(A) Artificial System of Classification -
Animals and plants were characterized first on the basis of their size, body parts and life span.
Aristotle was the first man who classified animals. He classified them on the basis of these characteristics such as -
1.presence or absence of red blood corpuscles/cells.
2.Ability to give birth to young ones or lay eggs.
3.Hard or soft covering of the body.
The major disadvantage of this classification was that different organisms were kept in the same group.For example - Birds and insects were put under the same group on the basis of the idea of presence or absence of wings.
(B) Natural System of Classification - It is also known as Modern System of Classification or Two System of Classification. Two System of Classification was suggested by Carolus Linnaeus. He was known as the father of taxonomy.He classified living organisms into two major kingdoms on the basis of their structural and physical similarities. These were -
1. Kingdom Plantae - can't move but can prepare their own food.
2. Kingdom Animalia - can move but cannot prepare their own food.
He further classified these two kingdoms into smaller groups on the basis of similar characteristics.
Kingdom Kingdom
Division Phylum
Class Class
Order Order
Family Family
Genus Genus
Species Species
* Species - It is the basic and smallest unit of classification and is the lowermost category . Each organism belongs to a particular species. When members of a species interbreed, they produce new offsprings. Apart from a few variations, members of species almost resemble each other in anatomy, physiology and behaviour. Different members of species look very similar to each other but not exactly the same. For example - species of humans is sapiens while that of tigers is tigris.
* Genus - Closely related species are grouped into a higher level known as genus. Genus is a group of species having common external features. For example - tiger (Panthera tigris), panther (Panthera pardus ) and lion ( Panthera leo ) belong to different species but one similar genus 'Panthera'.
* Family - Family consists of a group of similar genera that have same characteristics. For example - tiger (Panthera tigris) and cat ( Felis domestica) constitute the same family 'Felidae'.
* Order - Order constitutes similar families. For example - apes and humans are categorised under the same order 'Primates'.
* Class - Similar orders are grouped together into similar classes. For example - apes and humans constitute the same class 'Mammalia'.
* Phylum - Classes that are related closely are grouped together under phylum. For example - the phylum of tiger, cat and man 'Chordata'.
* Kingdom - It is the largest unit of classification. Similar phyla ( for plants) or similar division ( for animals) constitutes kingdom. For example - cat, lion and tiger constitute same kingdom.
What were the drawbacks of Two Kingdom Classification?
These were the drawbacks of Two Kingdom Classification -
1. Prokaryotes such as bacteria ( lack true nucleus ) and eukaryotes such as plant (possess true nucleus) were grouped together.
2. Bacteria were placed under plant kingdom as they possess cell wall.
3. Fungi lack chlorophyll and can't make their own food but they were placed under plant kingdom.
4. Unicellular and multicellular organisms were kept under the same group.
5. Some animals were not kept under any group as they show characteristics similar to both animals and plants. For example - Euglena and slime moulds.
6. He didn't consider viruses as nobody knew viruses properly at that time.
Note -This chapter has three parts.This was the part 1 of this chapter.Please check part 2 and part 3 of this chapter also.
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