Chapter 1: The Living World 

1.1 What is ‘Living’?

Life is defined by a set of characteristics that distinguish living organisms from non-living things. These characteristics include:

Key Characteristics of Living Beings:

  1. Growth
    • Increase in mass and number of individuals.
    • Unicellular organisms: Growth is by cell division (e.g., Amoeba).
    • Multicellular organisms: Growth occurs through cell division and differentiation.
    • Non-living things can also grow (e.g., crystals) but their growth is external by accumulation, not from within.
  2. Reproduction
    • Production of progeny similar to the parents.
    • Modes: Asexual (binary fission in Amoeba) and Sexual (in higher organisms).
    • Exceptions: Mules, sterile worker bees, and infertile human couples do not reproduce but are still living.
  3. Metabolism
    • Sum total of all chemical reactions in the body.
    • Occurs in cells and involves catabolism (breakdown) and anabolism (synthesis).
    • Unique feature of life: No non-living object exhibits metabolism.
  4. Cellular Organization
    • All living organisms are made up of one or more cells.
    • Cell is the basic structural and functional unit of life.
  5. Consciousness
    • Ability to sense the environment and respond.
    • Plants respond to light, gravity, touch (e.g., Mimosa pudica).
    • Human beings have the highest level of consciousness.
  6. Self-replication and Self-regulation
    • Living beings can reproduce, repair, and regulate their internal environment.

Conclusion: No single definition is comprehensive, but metabolism, cellular organization, and consciousness are universally accepted as signs of life.

1.2 Diversity in the Living World

Biodiversity

  • Variety of living organisms on Earth.
  • Over 1.7–1.8 million species have been identified.
  • Includes plants, animals, fungi, microorganisms, etc.

Need for Classification

  • To identify, study, and understand organisms.
  • Easier communication and data handling.

1.3 Taxonomy and Systematics

Taxonomy

  • Study of principles and procedures of classification.
  • Includes: Identification, Nomenclature, and Classification.

Systematics

  • Coined by Carl Linnaeus.
  • Deals with classification + evolutionary relationships (phylogeny).
  • Focuses on taxonomic hierarchy and interrelations.

1.4 Concept of Species

  • A species is a group of organisms that can interbreed and produce fertile offspring.
  • Basic unit of classification.

1.5 Taxonomic Hierarchy

Organisms are classified into categories called taxa, arranged in a hierarchy from broad to specific.

Hierarchical Levels (Descending Order):

  1. Kingdom
  2. Phylum (for animals) / Division (for plants)
  3. Class
  4. Order
  5. Family
  6. Genus
  7. Species

Mnemonic: King Philip Came Over For Good Soup.

Example: Mango (Mangifera indica)

  • Kingdom: Plantae
  • Division: Angiospermae
  • Class: Dicotyledonae
  • Order: Sapindales
  • Family: Anacardiaceae
  • Genus: Mangifera
  • Species: indica

1.6 Binomial Nomenclature

Introduced by: Carl Linnaeus

Rules (ICBN – International Code of Botanical Nomenclature):

  1. Scientific name has two words: Genus + species.
  2. Printed in italics, handwritten underlined.
  3. Genus name starts with capital, species name in lowercase.
    • e.g., Homo sapiens, Panthera leo

1.7 Tools for Study of Taxonomy

1. Herbarium

  • Storehouse of dried, pressed, and preserved plant specimens.
  • Used for reference and classification.

2. Botanical Gardens

  • Institutions maintaining living plant collections.
  • e.g., Indian Botanical Garden (Howrah), National Botanical Research Institute (Lucknow)

3. Museum

  • Preserves animal specimens in jars or dry containers.
  • Also includes skeletons, models, and fossils.

4. Zoological Parks

  • Enclosures where animals are kept in natural habitats for study and public view.

5. Key

  • Helps in identification of organisms using contrasting characteristics (couplets).
  • Separate keys for plants and animals.

6. Flora

  • Book providing information on plant species of a particular area.

7. Manuals

  • Provide information for identification of names and species.

8. Monographs

  • Detailed account of one taxon.

Important Scientists to Remember:

  • Aristotle: Father of Biology
  • Carolus Linnaeus: Father of Taxonomy, introduced Binomial Nomenclature
  • Ernst Mayr: Defined modern concept of species

Important Terms to Revise:

  • Taxon: Each category in taxonomic hierarchy
  • Classification: Grouping based on similarities and differences
  • Nomenclature: Naming of organisms
  • Identification: Recognition of an organism based on characteristics

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