The Living World : A Comprehensive Study Notes for Class - 11, Chapter - 1, Study notes of Biology

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Life is a unique, complex organization of molecules, expressing through chemical

reactions which lead to growth, development, responsiveness, adaptation &

reproduction.

It is the increase in number, mass and size of cells. In plants, growth by cell division occurs continuously throughout their life span. In animals, growth is only up to a certain age. However, cell division occurs in certain tissues to replace lost cells. Non-living objects grow by accumulation of material on the surface. In living organisms, growth is from inside.

It is the production of progeny having features similar to those of parents. Organisms reproduce asexually and sexually. Growth is the increase in cell number or mass. Hence in unicellular organisms, growth & reproduction are same. Many organisms do not reproduce (e.g. mules, worker bees, infertile human couples, etc). Hence, reproduction is not a perfect defining characteristic of living organisms.

The system of naming with two components (Binomial nomenclature) is proposed by Carolus Linnaeus. Botanical names are based on the rules provided in International Code for Botanical Nomenclature (ICBN). Zoological names are based on International Code for Zoological Nomenclature (ICZN).

Classification involves hierarchy of steps in which each step

represents a rank (taxonomic category or taxon).

All categories together constitute the taxonomic hierarchy.

Eachtaxon represents a unit of classification.

It is a group of individual organisms with fundamental similarities. It is the lowest category. E.g.

Generic name Specific epithet Common name

Mangifera indica Mango

Solanum tuberosum Potato

Solanum nigrum Nightshade

Panthera leo Lion

Panthera tigris Tiger

Homo sapiens Modern man

It is the assemblage of related orders.

Class Dicotyledonae

Class Mammalia Order Sapindales

Order Primata

Order Urticales Order Carnivora

It is the assemblage of related classes. In cases of plants the related classes form division.

Phylum Chordata Division Angiospermae Class Amphibia Class Class Reptilia Dicotyledonae Class Aves Class Class Mammalia Monocotyledonae

The assemblage of various Phyla/Division. It is the highest category.

Kingdom Plantae Kingdom Animalia

Division Angiospermae

Phylum Chordata

Division Gymnospermae

Phylum Arthropoda

These are specialized gardens having collections of living plants for reference and identification purposes. Each plant is labeled with its botanical name and family.

Famous botanical gardens

Royal Botanical Garden at Kew (England). Indian Botanical Garden, Howrah (West Bengal, India). National Botanical Research Institute, Lucknow (India).

It is the device used to identify each species in a group of organisms based on similarities and dissimilarities. Keys are based on the contrasting characters generally in a pair called couplet. It represents the choice made between two opposite options. This results in acceptance of only one and rejection of the other. Each statement in the key is called a lead.

These are the places wherelive wild

animals are kept in protected

environments under human care.

It enables to learn about their food habits and behaviour.

These are the means of recording descriptions.

Flora:

It contains the actual account of habitat and distribution of plant species of a given area.

Manuals:

It helps in providing information for identification of names of species found in an area.

Monographs:

It contains information on any one taxon.