Characteristics of Living Organisms Lecture Notes

Introduction

• The world is comprised of living and non-living entities.
• Living organisms can be identified by certain characteristics, which may be definitive or non-definitive.

Characteristics of Living Organisms

Growth

• Multicellular Organisms: Growth through cell division leads to an increase in mass.
• Unicellular Organisms: Growth results in forming new organisms (e.g., amoeba).
• Plants: Grow via cell division throughout their lifetime.
• Animals: Grow until a certain age; after which, cell division replaces lost cells.
• Non-Living Growth: Rocks can grow externally, e.g., when sand deposits over them.
• Conclusion: Growth is a non-definitive characteristic of living organisms.

Reproduction

• Unicellular Organisms: Reproduction equals growth (increase in cell number).
• Multicellular Organisms: Reproduction leads to offspring creation.
  • Sexual Reproduction: Seen in higher organisms (e.g., humans, animals).
  • Asexual Reproduction: Seen in lower organisms (e.g., budding in yeast, fragmentation in flatworms).
• Exception: Sterile worker bees do not reproduce but are still living.
• Conclusion: Reproduction is not a definitive characteristic of living.

Metabolism

• Living organisms consist of chemicals that convert into biomolecules.
• Metabolic reactions constitute the organism's metabolism.
• Definitive Feature: Metabolism is a definitive characteristic of living organisms.

Cellular Organization

• Present in all living forms but absent in non-living entities.
• Definitive Feature: Cellular organization is a definitive characteristic.

Consciousness

• Living beings respond to environmental stimuli (e.g., light, temperature).
  • Example: Sunflowers face the sun; humans wear warm clothes in winters.
• Non-living objects do not respond to stimuli.
• Definitive Feature: Consciousness is a definitive characteristic.

Biodiversity and Classification

Biodiversity

• Earth hosts millions of fungi, plants, microorganisms, and animals.
• Increase in diversity with geographical exploration.
• Species: Group of similar individuals sharing a common gene pool.

Nomenclature

• Standardizes names to avoid confusion across the world.
• Identification: Correct description and attachment of a name.
• Scientific Names: Based on international codes (ICBN for plants, ICZN for animals).
• Binomial Nomenclature: Two-components naming system (e.g., Ficus religiosa).
  • Generic name (e.g., Ficus) and specific epithet (e.g., religiosa).
  • Author's name may follow (e.g., Linnaeus abbreviated as Lin.).
  • Written in Latin, underlined (handwritten) or italicized (printed).

Classification and Taxonomy

Importance of Classification

• Taxonomy: Grouping organisms into categories based on observable characteristics.
• Taxa: Recognizable groups or categories.
• Taxonomic Hierarchy: Kingdom, Phylum/Division, Class, Order, Family, Genus, Species.
• Species: Basic taxonomic rank with fundamental similarities.
• Genus: Group of related species.
• Family: Group of related genera.
• Order: Collection of related families.
• Class: Consists of related orders.
• Phylum/Division: Categorizes organisms with common features (e.g., Chordata for animals).
• Kingdom: Highest category (e.g., Animalia and Plantae).

Taxonomical Studies

• Taxonomical Aids: Tools for studying organisms (e.g., herbariums, botanical gardens, museums).
  • Herbariums: Storehouses of dried plants for scientific study.
  • Botanical Gardens: Cultivate a wide variety of plants for various purposes.
  • Biological Museums: Preserve plants and animals for reference.
  • Zoological Parks (Zoos): Study animal behavior in controlled environments.
  • Biological Keys: Help identify organisms through contrasting questions.
• Documentation: Flora, manuals, and monographs provide detailed information for study and reference.

Conclusion

• Taxonomy aids in identifying, classifying, and understanding biodiversity.
• It plays a crucial role in various disciplines and conserves essential information about living organisms.