Diversity in Living Organisms 

Looking around, we will see many living organisms, potted plants, insects, birds, pets or other animals and plants. You cannot see several organisms with your naked eye, but they are all around you. If we were to increase the area where we make observations, the range and variety of organisms seen would increase. If we visit a dense forest, we would likely see a much greater number and kinds of living organisms in it. Each different type of plant, animal or organism that we see represents a species. The number of known and described species ranges between 1.7 and 1.8 million. 

1.0Taxonomy

(Taxis = arrangement, nomos = law) 

• A.P. de proposed this word. Candolle in his book "Theories elementaire de la botanique" (Theory of elementary botany). 
• The branch of biology dealing with identification, nomenclature and classification of organisms is called taxonomy.

2.0Nomenclature 

• The naming of organisms according to international scientific rules is called nomenclature. 
• Both vegetative & reproductive and external & internal characteristics are used during nomenclature.

Classification

• A process by which any organism is grouped into convenient categories based on easily observable characteristics. 
• To study all these points, the characters of organisms must be used, so using characters to describe organisms is called characterization. 

Systematics

• The term systematics was introduced by Linnaeus, and it originates from the Latin word "Systema", meaning the systematic arrangement of organisms. 
• Linnaeus used this concept as the foundation of his famous work titled "Systema Naturae". 
• Systematics is the branch of biology that focuses on studying the diversity of living organisms and understanding their evolutionary relationships.

3.0Taxonomic Categories

• There are seven main taxonomic categories. 
• They are obligate or broad categories, i.e., essentially used at any plant classification time. 
• However, taxonomists have also developed subcategories or extra categories to facilitate more sound placement of various taxa, like subdivision, suborder etc.

4.0Five System of Classification

• R.H. Whittaker (1969) proposed a five-kingdom classification. The kingdoms he defined were Monera, Protista, Fungi, Plantae and Animalia. The main criteria used by him for making classification are: 
• (i) Cell structure (Complexity of cell) 
• (ii) Thallus organization (complexity of organism)/Body organization 
• (iii) Mode of nutrition 
• (iv) Reproduction/Lifestyle 
• (v) Phylogenetic relationship.

Kingdom Plantae

• Kingdom Plantae includes all multicellular, eukaryotic, autotrophic organisms that perform photosynthesis to make their food using sunlight. 
• These organisms are commonly known as plants, and they play a vital role in sustaining life on Earth by producing oxygen, maintaining the carbon cycle, and serving as the primary producers in ecosystems.

Kingdom Animalia

• Kingdom Animalia includes all multicellular, eukaryotic, heterotrophic organisms that do not perform photosynthesis. 
• These organisms are known as animals and are found in almost every habitat on Earth — land, water, and air.