Characteristics of Living Organisms

Segregating Living and Non-Living

• Certain characteristics distinguish living organisms from non-living matter
• Characteristics can be definitive or non-definitive

Growth

• Living organisms (cellular or unicellular) grow via cell division
  • Multicellular organism: cell division increases mass
  • Unicellular organism (e.g., amoeba): cell division results in two new organisms
  • Plants: grow via cell division throughout life
  • Animals: grow up to a certain age; cell division occurs mainly to replace lost cells
• Non-living objects (e.g., rocks) can grow externally (e.g., sand deposition)
• Internal vs External Growth: Internal growth is a characteristic of living organisms

Reproduction

• Unicellular organisms: growth and reproduction lead to an increase in cell number
• Multicellular organisms: reproduction creates offspring; can be sexual or asexual
  • Sexual: seen in higher organisms (humans, animals)
  • Asexual: seen in lower organisms (e.g., yeast - budding, flatworm - fragmentation)
• Some organisms (e.g., sterile worker bees) do not reproduce but are still considered living
• Conclusion: Reproduction is not a definitive characteristic

Metabolism

• Organisms produce and convert chemicals into biomolecules through metabolic reactions
• Metabolism occurs in all living organisms
• In vitro reactions: isolated metabolic reactions are not considered living
• Conclusion: Metabolism is a definitive feature of living organisms

Cellular Organization

• Living organisms are made up of cells
• Not observed in non-living matter
• Conclusion: Cellular organization is a definitive feature

Consciousness

• Living organisms sense and respond to environmental stimuli
  • Examples: sunflower facing the Sun, humans wearing woolens in winter
• Conclusion: Consciousness is a definitive feature

Summary

• Definitive characteristics of living organisms: Metabolism, Cellular Organization, Consciousness

Biodiversity and Classification

Biodiversity

• Earth's diversity: millions of species of fungi, plants, animals
• Every species: group of similar individuals sharing a common gene pool, interbreeding freely
• Approximately 1.7 to 1.8 million known species

Nomenclature

• Standardized naming to avoid confusion
• Identification: knowing the correct description
• Scientific Naming: Based on principles from ICBN (plants) and ICZN (animals)
  • Example: Ficus religiosa (sacred fig)
  • Binomial nomenclature: Generic name + Specific epithet
  • Devised by Carolus Linnaeus
  • Formatting: Italics in print, underlined when handwritten
  • Capitalization: Genus starts with a capital letter, specific epithet with a lowercase letter

Taxonomy and Classification

• Classification: grouping based on observable characters
• Taxa: Groups with specific characteristics (e.g., mango trees, dogs)
• Systematics: Study of organisms' relationships, including identification, classification, nomenclature, and evolutionary relationships

Taxonomic Categories

• Classification hierarchy: Kingdom, Phylum/Division, Class, Order, Family, Genus, Species
• Species: Basic unit, group with fundamental similarities
• Genus: Group of related species
• Family: Group of related genera
• Order: Collection of related families
• Class: Group of related orders
• Phylum/Division: Group with common features
• Kingdom: Largest category; all animals (Animalia), all plants (Plantae)
• Characteristics decrease in commonality from Species to Kingdom

Importance of Taxonomy

• Simplifies the study of organisms
• Tools: Herbariums, Botanical Gardens, Museums, Zoos, Keys
  • Herbarium: Collection of dried plant specimens
  • Botanical Gardens: Cultivated plant collections
  • Museums: Collections of preserved plants and animals
  • Zoos: Wild animals in protected environments
  • Keys: List of questions for identification and classification

Other Taxonomical Aids

• Flora: Information about plants in a region or period
• Manuals: Help identify plant and animal species in an area
• Monographs: Detailed description of a single taxon

Conclusion

• Taxonomical aids are crucial for studying and conserving biodiversity