The Living World Class 11 Notes Biology Chapter 1 - CBSE

Chapter : 1

What Are The Living World ?

Unique Characteristics Of Living Organisms

Growth

Living organisms grow in mass and number (Internal growth).
Plants show continuous growth.
Non-living organism show external growth.

Reproduction

Production of progeny possessing features more or less similar to those of parents.

Sexual

Involves two parents

Asexual

Involves single parents, e.g. Fission, Regeneration, Fragmentation, Budding etc.

Growth

Sum total of chemical reactions occurring in the body.
Defining feature of all living organisms.

Cellular Organisms

Consciences

Diversity In The Living World

Occurrence of variety of life form differing in morphology, size, colour, anatomy, habitat and habits. 1.07-1.8 million living organisms are known today.

Systematics

Branch of Biology that deals with cataloging plants, animals and other organism into categories that can be named, compared and studied.

Need For Classification

To organize the vast number of microorganisms, Plants and animals into categories that can be named, remembered, studied and understood.

Nomenclature

Process of standardize naming of living organism.

Binomial Nomenclature

Given by Carolus Linnaeus. Each name has two components: Generic Name and Specific epithet.

Taxonomic Categories

Classification involves hierarchy of step where each step represents a taxonomic category (rank).
All category together constitutes a taxonomic hierarchy.
Each category represents a unit classification.

Kingdom ⇒ Phylum ⇒ Class ⇒ Order ⇒ Family⇒ Genus ⇒ Genus⇒ Species

Three Domains Of Life

The three-domain system is a biological classification introduced by Carl Woese, Otto Kandler, and Mark Wheelis in 1990.
This system divides cellular life forms into three domains, namely Archaea, Bacteria, and Eukaryota.
The key difference from earlier classifications such as the two-empire system and the five-kingdom classification is the splitting of Archaea from bacteria as completely different organisms. It has been challenged by the two-domain system that divides organisms into Bacteria and Archaea only, as Eukaryotes are considered as one group of Archaea.