Learning Objectives
- Understand the characteristics of living organisms
- Learn about biodiversity and the need for classification
- Understand the concept of taxonomy and systematics
- Know the taxonomic hierarchy and nomenclature rules
- Understand the role of herbaria, botanical gardens, museums, and zoological parks
Key Concepts
What is Living?
Living organisms exhibit certain defining characteristics that distinguish them from non-living matter. These include growth, reproduction, metabolism, cellular organization, consciousness (response to stimuli), and self-replication. Growth in living organisms is from inside (intrinsic growth), unlike non-living things where growth occurs by accumulation of material on the surface.
NEET Important: Metabolism is the defining feature of all living organisms. A non-living object never exhibits metabolism. Consciousness is considered the defining property of living organisms. Even plants respond to external stimuli such as light, water, temperature, and gravity.
Biodiversity
The number and types of organisms present on Earth constitute biodiversity. The term was introduced by Edward Wilson. According to the IUCN (2004), approximately 1.5 million species of plants and animals have been described so far. India contributes about 8.1% of global biodiversity.
Taxonomy and Systematics
Taxonomy: The branch of biology dealing with identification, nomenclature, and classification of organisms. The term was coined by A.P. de Candolle.
Systematics: The study of organisms with regard to their diversity and evolutionary relationships. The term was coined by Carolus Linnaeus.
Characterization: Study of one or more characteristics of an organism. Identification: Determining the correct name and position. Classification: Grouping organisms into categories based on similarities and differences.
Taxonomic Hierarchy
The arrangement of taxonomic categories in descending order: Kingdom → Phylum (Division for plants) → Class → Order → Family → Genus → Species.
Species: A group of organisms that can interbreed and produce fertile offspring. It is the basic unit of classification.
Genus: A group of closely related species. Example: Panthera leo (lion), Panthera tigris (tiger) belong to genus Panthera.
Binomial Nomenclature
Proposed by Carolus Linnaeus. Each organism is given a two-part scientific name: the first part is the genus name (capitalized) and the second is the species epithet (lowercase). Both names are italicized or underlined when handwritten. Example: Homo sapiens, Mangifera indica.
ICBN (International Code of Botanical Nomenclature) governs plant naming. ICZN (International Code of Zoological Nomenclature) governs animal naming.
Taxonomic Aids
Herbarium: A storehouse of collected, dried, pressed, and preserved plant specimens on sheets. Botanical Gardens: Collections of living plants for identification and reference. Famous ones: Kew (London), Indian Botanical Garden (Howrah). Museum: Collections of preserved plant and animal specimens. Zoological Parks: Places where wild animals are kept in protected environments. Key: A taxonomic aid for identification based on contrasting characters (couplet).
Summary
Living organisms are distinguished by metabolism, growth, reproduction, consciousness, and cellular organization. Taxonomy involves identification, nomenclature, and classification. Binomial nomenclature, proposed by Linnaeus, provides a universal naming system. Taxonomic hierarchy arranges organisms from Kingdom to Species. Various taxonomic aids like herbaria, museums, botanical gardens, and zoological parks facilitate the study of biodiversity.
Important Terms
- Metabolism: Sum total of all chemical reactions occurring in the body; the defining feature of life
- Taxonomy: Science of identification, nomenclature, and classification of organisms
- Species: Basic unit of classification; group of organisms capable of interbreeding
- Binomial Nomenclature: Two-part naming system (Genus + species) proposed by Linnaeus
- Herbarium: Collection of dried, pressed, and preserved plant specimens
- Systematics: Study of organisms in relation to their diversity and evolutionary relationships
- ICBN: International Code of Botanical Nomenclature for naming plants
- Taxon: A group of organisms at any level of taxonomic hierarchy
Quick Revision
- Metabolism is the defining property of living organisms
- Linnaeus is the Father of Taxonomy; proposed Binomial Nomenclature
- Taxonomic hierarchy: Kingdom → Phylum → Class → Order → Family → Genus → Species
- ICBN for plants, ICZN for animals
- Species is the basic unit of classification
- Herbarium = dried specimens; Botanical garden = living plants
- Around 1.5 million species described so far