CHAPTER 1-THE LIVING WORLD

Chapter 1

THE LIVING WORLD

Definition of life: This question has two hidden questions within it. The first is a technical one and seeks answer to what living is as opposed to the non-living,and the second is a philosophical one, and seeks answer to what the purpose of life is.Life is a unique, complex organization of molecules, expressing through chemical reactions in order to bring about life activities.‘Living  organisms  can  be  considered  as  self  replicating,  evolving  &  self-regulating interactive systems capable of responding to external stimuli’.

Properties of living organisms
Non-defining properties	Growth	-Increase in mass  or number of cells characterise growth. -plants grow throughout life. -Animals grow to certain age . -Non living objects also grow externally by accumulation of material on surface. -Living objects grow from inside. -Growth cannot be considered as defining property of living beings.
	Reproduction:	-Characteristics of living beings to produce progenies possessing features of their own type. -Reproduction is of sexual& asexual type. -Fungi produce spores for asexual reproduction. -Organism viz. Planaria reproduce by regeneration in which a fragment of body forms whole organism. Fungi,filamentousalgae,protonema of moss reproduce by fragmentation also. -In unicellular organisms growth & reproduction are synonymous.Certain organisms do not reproduce viz. mule ,worker bees, infertile human couple.
Defining property	Metabolism:	-Several chemical reactions occur in living organisms.-Some of these reactions are anabolic others are catabolic. -All the reactions together are called metabolic reactions & process is called metabolism. -It has no exception.
	Cellular organisation:	-living organisms consist of cells & their products with DNA and RNA as genetic materials.
	Consciousness:	Ability to sense environment & respond to environmental factors -Living  beings  sense&  respond  to  environmental  factors  viz.  Light,water,temperature,other  organisms, pollutants etc.

Diversity in Living World:

Ø  The number of species that are known and described range between 1.7-1.8 million.

Ø  This refers to biodiversity or the number and types of organisms present on earth.

Ø  Taxonomy- The branch of science which deals with identification, nomenclature and classification of organisms.

Ø  Systematics- The branch of study dealing about different kinds of organisms and their diversities, the relationships among them.

Ø   Classification – Grouping of organisms in to categories based on observable characters.

Ø  (category –taxa)

Ø  Systematics - Different kinds of organisms and their relationships Linnaeus – Systema Naturae (evaolutionary relationships among organisms).

Ø  Earnest Mayer is regarded as Darwin of twentieth century

 Rules for nomenclature are provided by:

a) ICBN – International Code for Botanical Nomenclature

b) ICZN – International Code for Zoological Nomenclature

Binomial Nomenclature:

Binomial Nomenclature:Carolous Linnaeus – Father of Taxonomy. Name with two parts: - Generic name (Genus) & Specific epithet (Species)

i. It should be in Latin / derived from Latin. ii. If it is written in Italics when types and underlined when handwritten. iii. It contains two parts, first word is Genus ; second word is Species. iv. Genus name starts with Capital while species name starts with small letters. v. Name should be short, precise & easy to pronounce. vi. Name of the author is written is an abbreviated form after the species name.

Ex: Mangifera indica (Mango), Homo sapiens ( Human), Panthera pardus (Leopard), Felis domestica (Cat)

Taxonomical Hierarchy
Each rank or category of classification is termed as taxonomic category.Arrangement of categories in sequence is termed as Taxonomic Hierarchy.Taxonomical Hierarchy – Similarities decreases/ Differences increases
Kingdom	All animals belonging to various phyla are assigned to the highest category called Kingdom Animalia in the classification system of animals. The Kingdom Plantae, on the other hand, is distinct, and comprises all plants from various divisions	Eg.Plantae, Animalia
Phylum /Division	It includes all organisms belongng to different Classes having a few Common Characters.	Eg.Arthropoda,Annelida,Angiospermae Chordata
Class	This category includes related orders.	Dicotyledonae, Monocotyledonae, Mammalia, amphibians
Order	Order being a higher category, is the assemblage of families which exhibit a few similar characters. The similar characters are less in number as compared to different genera included in a family.	Polymoniales, Sapindales, Carnivora, Primata
Family	Family, has a group of related genera with still less number of similarities as compared to genus and species. Families are characterized on the basis of both vegetative and reproductive features of plant species.	Solanaceae, Convolvulaceae, Felidae, Canidae
Genus	Genus comprises a group of related species which has more characters in common in comparison to species of other genera. We can say that genera are aggregates of closely related species.	Solanum, Petunia, Datura, Panthera, Felis
Species	Taxonomic studies consider a group of individual organisms with fundamental similarities as a species. One should be able to distinguish one species from the other closely related species based on the distinct morphological differences.	S. tuberosum,S. nigrum, S.melongena, P. leo, P,pardus, P,tigris

Common Name	Biological Name	Genus	Family	Order	Class	Phylum/ Division
Man	Homo sapiens	Homo	Hominidae	Primata	Mammalia	Chordata
Housefly	Musca domestica	Musca	Muscidae	Diptera	Insecta	Arthropoda
Mango	Mangifera indica	Mangifera	Anacardiaceae	Sapindales	Dicotyledonae	Angiospermae
Wheat	Triticum aestivum	Triticum	Poaceae	Poales	Monocotyledonae	Angiospermae

Taxonomical Aids Tools helpful in correct identification & classification of organisms are called taxonomical aids.
1-Herbarium:	Store house of collected plant specimens that are dried, pressed & preserved on sheets. Sheets are arranged according to universally accepted classification system-used as ready reference in scientific studies.
2. Botanical Gardens :	Collection of various living plant species in form of gardenfor identification purpose Used for identification of plants.Example: Royal Botanical Garden at Kew, England, Indian Botanical Garden Howrah, National Botanical Research Institute Lucknow etc.
3-Museum :	-Collection of preserved plant &animal specimens. -Specimens may be preserved in preservative solutions viz.Formalin (40%). -Specimens may also be preserved as dry specimenseg. Insects and stuffed large animals. -Skeleton of animals may be also as museum specimen. -Used as actual material for study and identification.
4-Zoological Parks:	Place where wild animals are kept in protected environment under human care . eg. Mysore zoo, Kolkata, West BengalNational Zoological Park of New DelhiUsed as aid to learn about food habits and behaviour, Life cycle.
5-Key : .	Keys are used for identification of plants and animals based on similarities and dissimilarities.Taxonomical aid based on contrasting characters called as coupletCouplet has two opposite statements, each called lead.Separate keys for separate taxonomic categories needed.Used to classify organism.It is analytical in nature.
6-Flora :	Actual account of habitat & distribution of plant species in an area.
7-Manual : .	•Have description of species in an area. • Used for getting information foridentification of names.
8-Monograph :	1. Has information of any one taxon. 2. Used for classification purpose.

Three Domains of Life: Proposed by Carl Woese in 1990 who also proposed the six kingdom classification for living organisms. The three Do-mains are Archaea, Eubacteria and Eukarya.

DOMAINS
ARCHAE	EUBACTERIA	EUKARYOTA
·         ARCHAEBACTERIA	·         MONERA	·         PROTISTA ·         MYCOTA ·         PLANTAE ·         ANIMALIA