THE LIVING WORLD
NCERT Masterclass & NEET Biology Study Module
1. What is 'Living'? (Characteristics of Life)
To understand what constitutes life, we look for distinctive characteristics exhibited by living organisms. These are classified into two categories: Defining Features (found in ALL living organisms without exception and NOT in non-living things) and Non-Defining Features.
- Growth: Twin characteristics of growth are increase in mass and increase in number of individuals. In plants, growth is continuous (indeterminate); in animals, it is definite (determinate).
- Metabolism: The sum total of all chemical reactions occurring in our body. Isolated metabolic reactions in vitro are not living things but surely living reactions.
- Consciousness: The most obvious and technically complicated feature of all living organisms. Self-consciousness is a property exclusively found in human beings.
2. Diversity in the Living World
The number of species that are known and described ranges between $1.7 - 1.8 \times 10^6$ (1.7 to 1.8 million). This refers to Biodiversity.
To standardize the naming of living organisms, scientific names are assigned.
For Plants: Provided by ICBN (International Code for Botanical Nomenclature).
For Animals: Provided by ICZN (International Code of Zoological Nomenclature).
3. Binomial Nomenclature
Proposed by Carolus Linnaeus. Each scientific name has two components: the Generic name and the Specific epithet.
Universal Rules of Nomenclature:
- Biological names are generally in Latin and written in italics. They are Latinised or derived from Latin irrespective of their origin.
- The first word represents the genus while the second component denotes the specific epithet.
- When handwritten, both words are separately underlined. When printed, they are in italics to indicate their Latin origin.
- The first letter of the genus starts with a Capital letter, while the specific epithet starts with a small letter.
- The author's name appears after the specific epithet in an abbreviated form (e.g., Linn. for Linnaeus).
4. Taxonomic Categories
Classification is not a single step process but involves a hierarchy of steps. Each step represents a rank or category. All categories together constitute the Taxonomic Hierarchy.
Taxon (pl. taxa): Represents a unit of classification at any level (e.g., Mammalia is a taxon, Dogs represent a taxon).
- Species: Lowest category. A group of individual organisms with fundamental similarities, capable of interbreeding.
- Genus: Comprises a group of related species which has more characters in common in comparison to species of other genera (e.g., Panthera leo, Panthera pardus).
- Family: Characterized on the basis of both vegetative and reproductive features of plant species. (e.g., Solanaceae, Felidae).
- Order: Assemblage of families exhibiting a few similar characters. (e.g., Polymoniales, Carnivora).
- Class: Includes related orders. (e.g., Mammalia includes Primata and Carnivora).
- Phylum (Animals) / Division (Plants): Higher category grouping classes.
- Kingdom: Highest category (e.g., Plantae, Animalia).
Organisms with their Taxonomic Categories (NEET Essentials)
- Man: Homo sapiens $\rightarrow$ Homo $\rightarrow$ Hominidae $\rightarrow$ Primata $\rightarrow$ Mammalia $\rightarrow$ Chordata.
- Housefly: Musca domestica $\rightarrow$ Musca $\rightarrow$ Muscidae $\rightarrow$ Diptera $\rightarrow$ Insecta $\rightarrow$ Arthropoda.
- Mango: Mangifera indica $\rightarrow$ Mangifera $\rightarrow$ Anacardiaceae $\rightarrow$ Sapindales $\rightarrow$ Dicotyledonae $\rightarrow$ Angiospermae.
- Wheat: Triticum aestivum $\rightarrow$ Triticum $\rightarrow$ Poaceae $\rightarrow$ Poales $\rightarrow$ Monocotyledonae $\rightarrow$ Angiospermae.
🚀 NEET LIVING WORLD MEGA QUIZ (100 MCQ)
Solve the 5 parts below to master Characteristics of Life, Nomenclature, and Taxonomic Categories.
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