1. Difference Between Living and Non‑Living
| Characteristic | Living | Non‑Living |
|---|---|---|
| Cellular organisation | Present (made of cells) | Absent |
| Growth | Internal (intrinsic) – by cell division | External (accumulation of material) – e.g. crystals, mountains |
| Reproduction | Ability to reproduce (asexual/sexual) | No reproduction |
| Metabolism | Yes – constant catabolic & anabolic reactions | No metabolic activity |
| Consciousness | Unique to living – awareness of surroundings | None |
| Response to stimuli | Respond to external factors (light, touch, etc.) | No response |
| Life span | Definite (birth to death) | Indefinite (no fixed span) |
| Evolution | Populations evolve over time | No evolution |
| Examples | Plants, animals, microorganisms | Rocks, water, soil |
NEET key pointConsciousness is the defining property of living organisms – it is present even in the smallest of organisms.
2. Important Definitions (Term & Definition)
| Term | Definition |
|---|---|
| Nomenclature | Standardised naming of living organisms so that a particular organism is known by the same name globally. |
| Binomial Nomenclature | Two‑component naming system (generic name + specific epithet); given by Carolus Linnaeus. |
| Identification | Correctly describing and recognising the organism to which a name is attached. |
| Classification | Grouping organisms into convenient categories based on easily observable characters. |
| Taxonomy | Study of principles and procedures of classification; includes characterisation, identification, classification, and nomenclature. |
| Taxonomic Category | A rank or level in the taxonomic hierarchy (e.g., species, genus, family, etc.). |
| Taxonomic Hierarchy | Arrangement of taxonomic categories in a descending (or ascending) order: Kingdom → Phylum/Division → Class → Order → Family → Genus → Species. |
| Taxon (pl. Taxa) | A category of organisms at any level in the hierarchy (e.g., plants, animals, mammals). |
| Generic Name | The first word in a binomial name; denotes the genus (e.g., Mangifera). |
| Specific Epithet | The second word; denotes the species (e.g., indica). |
Mnemonic: “G‑S‑I‑C”For binomial nomenclature: Genus first, Specific epithet second; Italics in print; genus Capitalised.
3. Difference Between Taxonomy and Systematics
| Aspect | Taxonomy | Systematics |
|---|---|---|
| Meaning | Study of principles and procedures of classification. | Study of diversity of organisms and their evolutionary relationships. |
| Scope | Characterisation, identification, classification and nomenclature. | Includes taxonomy plus evolutionary relationships and phylogeny. |
| Objective | To classify organisms into taxa based on similarities and differences. | To arrange organisms systematically reflecting their evolutionary history. |
| Focus | Classification and naming of organisms. | Understanding relationships among organisms and their diversity. |
| Evolutionary relationship | May or may not consider evolutionary relationships. | Explicitly considers evolutionary (phylogenetic) relationships. |
| Modern usage | Often considered a part of systematics. | Broader field that includes taxonomy and evolutionary biology. |
Origin of term“Systematics” is derived from the Latin systema – Linnaeus used it in his book Systema Naturae.
4. Comparison of Taxonomic Categories
| Rank | Definition | Characteristics | Example (Plants) | Example (Animals) |
|---|---|---|---|---|
| Species | Group of individuals with fundamental similarities; lowest category. | Morphologically distinct from other species; interbreeding (in many cases). | Mangifera indica (mango) | Homo sapiens (human) |
| Genus | Group of closely related species; share more common characters. | Aggregate of species with comparable morphological features. | Solanum (potato, brinjal) | Panthera (lion, tiger, leopard) |
| Family | Group of related genera; fewer similarities than genus. | Based on vegetative and reproductive features (plants); animals – similar anatomical traits. | Solanaceae (Solanum, Petunia) | Felidae (Panthera, Felis) |
| Order | Assemblage of related families; few similar characters. | Characters are more general; often based on floral (plants) or morphological (animals) features. | Polymoniales (Convolvulaceae, Solanaceae) | Carnivora (Felidae, Canidae) |
| Class | Group of related orders. | Aggregate of orders sharing a few common features. | Dicotyledonae (orders including Polymoniales) | Mammalia (Primata, Carnivora) |
| Phylum / Division | Group of related classes; in animals – phylum, in plants – division. | Major grouping based on fundamental body plan / structural organisation. | Angiospermae (division) | Chordata (all vertebrates) |
Species
→
Genus
→
Family
→
Order
→
Class
→
Phylum / Division
→
Kingdom
NEET Quick FactAs we move from species to kingdom, common characteristics decrease. Lower taxa share more characters; higher categories are broader and more inclusive.