Quick Revision Notes

Class 11 Biology - Chapter 1: The Living World

MP Board Education

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1. What is Living? (सजीव क्या है?)

Biology is the science of life forms and living processes. To define a "living" organism, certain distinctive characteristics are used:

• Growth (वृद्धि):
  • Increase in mass and number of individuals.
  • Defining feature? No. Non-living objects also grow by accumulation of material on the surface (accretion, e.g., mountains, boulders).
  • Plants: Grow continuously throughout their life span.
  • Animals: Grow up to a certain age. In multicellular organisms, growth and reproduction are mutually exclusive events.
• Reproduction (जनन):
  • Formation of progeny possessing features similar to those of parents.
  • Defining feature? No. Many organisms do not reproduce (e.g., mules, sterile worker bees, infertile human couples).
  • Types: Asexual (spores, budding, fragmentation, binary fission) and Sexual.
• Metabolism (चapचपचय / उपापचय):
  • The sum total of all chemical reactions occurring in a living body.
  • Defining feature? Yes. Non-living objects do not exhibit metabolism. Metabolic reactions can be demonstrated outside the body in cell-free systems.
• Consciousness / Response to Stimuli (चेतना):
  • Ability to sense surroundings and respond to environmental stimuli (physical, chemical, or biological).
  • Defining feature? Yes. All organisms, from prokaryotes to the most complex eukaryotes, handle chemical substances entering their bodies and respond to external stimuli. Humans possess self-consciousness.

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2. Diversity in the Living World (जीव जगत में विविधता)

• Biodiversity (जैव विविधता): The number and types of organisms present on earth. It ranges from 1.7 to 1.8 million species identified and described to date.
• Taxonomy (वर्गिकी): The branch of science dealing with identification, nomenclature, and classification of organisms.
• Systematics (सिस्टमैटिक्स / क्रमबद्धता): Derived from the Latin word systema, which means systematic arrangement of organisms. It deals with evolutionary relationships between organisms.

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3. Taxonomic Categories (वर्गिकी संवर्ग)

Classification is not a single step process but involves a hierarchy of steps in which each step represents a rank or category.

• Taxon (टैक्सॉन): A unit of classification representing a rank at any level (e.g., Species, Genus, Family).
• Hierarchy of Categories (Ascending Order): Species $\rightarrow$ Genus $\rightarrow$ Family $\rightarrow$ Order $\rightarrow$ Class $\rightarrow$ Phylum (for animals) / Division (for plants) $\rightarrow$ Kingdom

Category (संवर्ग)	Definition / Description
Species (जाति)	Group of individual organisms with fundamental similarities capable of breeding among themselves. (Lowest basic unit of classification).
Genus (वंश)	Comprises a group of related species which has more characters in common in comparison to species of other genera.
Family (कुल)	Group of related genera with still less number of similarities as compared to genus and species.
Order (गण / आर्डर)	Assemblage of families which exhibit a few similar characters.
Class (वर्ग)	Includes related orders. For example, order Primata and Carnivora are placed in class Mammalia.
Phylum / Division (संघ / प्रभाग)	Classes with a few similar characters are assigned to higher category called Phylum (for animals) or Division (for plants).
Kingdom (जगत)	Highest taxonomic category containing all plants/animals sharing a set of common distinguishing features. (e.g., Kingdom Plantae, Kingdom Animalia).

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4. Binomial Nomenclature (द्विनाम नामपद्धति)

Proposed by Carolus Linnaeus (कारोलस लिनियस). It provides a standardized name to every organism consisting of two words.

Universal Rules of Binomial Nomenclature:

1. Biological names are generally in Latin and written in italics.
2. The first word in a biological name represents the Genus (starts with a capital letter), while the second component denotes the Specific epithet (starts with a small letter).
3. Both the words, when handwritten, are underlined separately, or printed in italics to indicate their Latin origin.
4. Name of the author appears at the end of the biological name (in an abbreviated form), e.g., Mangifera indica Linn.

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5. Taxonomic Aids (वर्गिकी सहायता साधन)

Techniques and procedures used to store and preserve information as well as specimens of organisms.

• Herbarium (हरबेरियम):
  • A store house of collected plant specimens that are dried, pressed, and preserved on sheets.
  • Sheets are arranged according to a universally accepted classification system.
  • Contains labels stating date, place of collection, English/local/botanical names, family, and collector's name.
• Botanical Gardens (वनस्पति उद्यान):
  • Collections of living plants for reference and identification.
  • Famous Examples: Royal Botanical Garden (Kew, England), Indian Botanical Garden (Howrah, India), National Botanical Research Institute (Lucknow, India).
• Museum (संग्रहालय):
  • Set up in educational institutes (schools/colleges) for preserving plant and animal specimens.
  • Specimens are preserved in containers/jars in preservative solutions or as dry specimens (insects, stuffed birds/mammals, skeletons).
• Zoological Parks (प्राणी उद्यान / चिड़ियाघर):
  • Places where wild animals are kept in protected environments under human care, enabling study of their food habits and behavior.
• Key (कुंजी):
  • Taxonomic aid used for identification of plants and animals based on similarities and dissimilarities.
  • Based on contrasting characters generally in a pair called couplet.
  • Each statement in the key is called a lead.
• Flora, Manuals, Monographs, and Catalogues:
  • Flora: Index to the plant species found in a particular area.
  • Manuals: Useful in providing information for identification of names of species found in an area.
  • Monographs: Contain information on any one taxon.