Diversity of Living Organisms

Introduction

• Life on Earth is diverse, with millions of organisms varying in size, shape, habitat, and behavior.
• This chapter explains the need to classify organisms, the systems of classification, and the tools used to study biodiversity.

1. What is Biodiversity?

• Definition: The variety of life forms, including microorganisms, plants, animals, and ecosystems.
• Types of Biodiversity:
  1. Genetic Diversity: Variations within a species (e.g., different breeds of dogs).
  2. Species Diversity: Number and variety of species in a habitat (e.g., coral reefs).
  3. Ecosystem Diversity: Different types of ecosystems (e.g., forests, grasslands).

2. Why is Classification Needed?

• Organizes the vast diversity of organisms into categories.
• Helps in identifying and naming species systematically.
• Makes studying relationships among organisms easier.

3. Classification Systems

A. Early Systems

• Aristotle: Divided animals based on their habitat (land, water, air).
• Linnaeus: Introduced binomial nomenclature and a hierarchical classification.

B. Modern Systems

• Two-Kingdom System: Classified organisms into Plantae and Animalia.
• Five-Kingdom System (by Whittaker):
  1. Monera: Prokaryotes like bacteria.
  2. Protista: Eukaryotic unicellular organisms (e.g., Amoeba).
  3. Fungi: Decomposers (e.g., mushrooms).
  4. Plantae: Autotrophic, photosynthetic organisms.
  5. Animalia: Heterotrophic and motile organisms.

4. Taxonomy and Systematics

• Taxonomy: Science of naming, describing, and classifying organisms.
• Systematics: Study of evolutionary relationships among species.

Taxonomic Hierarchy

• Kingdom > Phylum > Class > Order > Family > Genus > Species
  Example: Human (Homo sapiens):
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Mammalia
  • Order: Primates
  • Family: Hominidae
  • Genus: Homo

5. Nomenclature Rules

• Scientific names are in Latin and consist of two parts:
  • Genus: Always capitalized.
  • Species: Always in lowercase.
• Example: Mangifera indica (Mango).
• Rules are standardized by the International Code of Nomenclature (ICN).

6. Tools to Study Biodiversity

1. Herbarium: Preserved plant specimens.
2. Museums: Preserved specimens of animals and plants.
3. Botanical Gardens: Living plants for study.
4. Zoological Parks: Protected habitats for animals.
5. Taxonomic Keys: Guides for identifying species based on features.

7. Biological Classification

A. Kingdom Monera

• Includes bacteria and cyanobacteria.
• Characteristics: Prokaryotic, unicellular, lack a nucleus.

B. Kingdom Protista

• Unicellular eukaryotes.
• Examples: Algae, Protozoa.

C. Kingdom Fungi

• Heterotrophic, often decomposers.
• Examples: Yeast, Penicillium.

D. Kingdom Plantae

• Multicellular autotrophs that perform photosynthesis.
• Examples: Trees, algae, flowers.

E. Kingdom Animalia

• Multicellular, heterotrophic, motile organisms.
• Examples: Insects, mammals.

8. Evolutionary Relationships

• Classification reflects evolutionary history.
• Phylogeny: Study of evolutionary relationships based on molecular evidence like DNA.

Summary

• Biodiversity highlights the variety of life forms and ecosystems.
• Classification simplifies the study of living organisms and their evolutionary links.

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