Notes " The Living World"

 Notes " The Living World"

By Nagraj Sir

The objects exhibiting growth, development, reproduction, respiration, responsiveness and other characteristics of life are designated as living beings.

1. Growth- Living organisms grow in mass and number. A multicellular organism increases its mass by cell division. In plants growth continuous throughout life in their meristematic area but in animals, growth occurs to a certain age. Unicellular organisms also grow by cell division.
2. Reproduction- It is the formation of new individuals of the similar kind. In sexual reproduction two parents are involved and In asexual reproduction single parent is involved and individual is copy of the parent. 
3. Metabolism- The sum total of all types of chemical reactions occurring in an individual due to specific interactions amongst different types of molecules in the interior of cells is called metabolism. 
4. Consciousness- It is the awareness of the surroundings and responding to external stimuli. Consciousness therefore, becomes the defining property of living organisms.

Biodiversity is the occurrence of variety of life forms differing in morphology, size, colour, anatomy, habitats and habits. Each different kind of plant, animal or microorganisms represents a species.

• Identification
• Nomenclature
• Classification
• Systematics is branch of biology that deals with cataloguing plants, animals and other organism into categories that can be named, compared and studied.
• Identification is the finding of correct name and place and place of an organism in a system of classification. 
• Nomenclature is the process of standardize naming of living organism such that a particular organism is known by the same name all over the world. For plants scientific names are based on international code of botanical nomenclature (ICBN) and animals names on international code of zoological nomenclature (ICZN). 
• Classification- It is the process by which anything is grouped into convenient categories based on some easily observable characteristics. Classification makes the study of organisms convenient.

Biological (Binomial nomenclature)– It is the universally accepted principles to provide scientific name to known organisms. Each name has two components- generic name (genus) and specific epithet (species). This system of nomenclature was provided by Carolus Linnaeus.

Mango- Mangifera indica.

Human beings- Home sapience.

Universal rules of nomenclature:-

1. Biological names are generally in Latina and written in italics.
2. The first word in a biological name represents the genus while the second component denotes the specific epithet.
3. Both the words in biological name, when handwritten, are separately underlined, or printed in italics.
4. The first word denoting the genus starts with a capital letter while the specific epithet starts with small letter.

Taxonomy- The process of classification on the basis of external and internal structure along with internal structure of cell, development process and ecological information is known as taxonomy.

Taxonomic categories

A taxonomic category is a rank or level in the hierarchical classification of organism. There are seven obligate categories and some intermediate categories. Since the category is a part of overall taxonomic arrangement, it is called taxonomic category and all categories together constitute the taxonomic hierarchy.

Taxonomic hierarchy is shown below:-

KINGDOM

DIVISION/PHYLLUM

CLASS

ORDER

FAMILY

GENUS

SPECIES

• Species- Species are the natural population of individuals or a group of population which resemble one another in all essential morphological and reproductive characters so that they are able to interbreed freely and produce fertile offspring. For Mango tree indica is species of genus Mangifera(Mangifera indica).
• Genus- it is a group of related species which resemble one another in certain correlated characters. All species of genus presumed to have evolved from a common ancestor. Lion, Tiger, Leopard are closely related species and placed in same genus Panther.
• Family- It is a taxonomic category which contains one or more related genera. All genera of a family have some common features or correlated characters. Family Solanacaeae contains a number of genera like Solanum, Withania, Datura etc.
• Order- This category includes one or more related families. Families felidae and canidae are included in same order carnivore.
• Class- A class is made of one or more related orders. The class dicotyledoneae of flowering plants contains all dicots which are grouped into several orders like roales, polemoniales, renales etc.
• Division/Phylum- The term phylum is used for animals while division is used for plants. They are formed of one or more class. The phylum chordate of animals contains not only the mammals but also aves, reptiles, amphibians, etc.
• Kingdom- It is the highest taxonomic category. All plants are included in the kingdom Plantae while all animals belong to kingdom Animalia.