Lecture Notes: Characteristics and Classification of Living Organisms

Distinguishing Between Living and Non-Living

• Living and non-living entities are segregated based on characteristics.
• Growth:
  • Living organisms: Growth due to cell division. Multicellular organisms increase in mass, unicellular organisms like amoeba form new organisms.
  • Plants: Grow throughout their lifespan through cell division.
  • Animals: Grow up to a certain age, after which cell division replaces lost cells.
  • Non-living entities: Growth is external, e.g., a rock growing due to sand deposition.

Characteristics of Living Organisms

• Growth: Non-definitive characteristic.
• Reproduction:
  • Unicellular organisms: Growth synonymous with increase in cell number.
  • Multicellular organisms: Reproduction through sexual or asexual means.
  • Exceptions: Sterile organisms (e.g., worker bees) are living but do not reproduce.
• Metabolism: Definitive characteristic.
  • Chemical reactions and conversions in living beings, termed as metabolism.
  • Can be imitated in vitro but not considered living.
• Cellular Organization:
  • Essential and definitive characteristic, not found in non-living systems.
• Consciousness:
  • Living organisms respond to environmental stimuli.
  • Example: Sunflowers face the sun, humans wear woolens in winter.

Biodiversity and Classification

• Species: Group of similar individuals, interbreeding freely.
• Biodiversity: Refers to the diversity of living organisms on Earth.
• Nomenclature: Standardization of names to avoid confusion.
  • Scientific Names: Based on ICN in botany, ICZN in zoology.
  • Binomial Nomenclature: Developed by Carolus Linnaeus.
  • Format: Genus with capital letter, specific epithet with small letter, e.g., Ficus religiosa.

Taxonomy and Systematics

• Classification: Group organisms into categories called taxa.
  • Categories: Kingdom, Phylum, Class, Order, Family, Genus, Species.
  • Hierarchy: From species to kingdom, common characteristics decrease.
• Systematics: Study of relationships among organisms.
• Taxonomic Hierarchy:
  • Species: Basic rank, fundamental similarities.
  • Genus: Related species with similar characteristics.
  • Family: Related genera with fewer similarities.
  • Order: Collection of related families.
  • Class: Related orders.
  • Phylum/Division: Related classes.
  • Kingdom: Highest category, all animals in Animalia, all plants in Plantae.

Taxonomic Aids

• Herbarium: Collection of dried plant specimens for study.
• Botanical Gardens: Cultivated plants for research and education.
• Museums: Collections of preserved plants and animals.
• Zoological Parks: Wild animals in natural-like habitats for study.
• Keys: Lists that help identify organisms based on contrasting characters.
• Flora, Manuals, Monographs: Provide detailed information and descriptions of species.

Importance of Taxonomy

• Helps in the easy identification and study of organisms.
• Facilitates understanding of biodiversity and conservation efforts.