The living world - Biology

what is a biology?

biology is the branch of science that deal with the study of life and living organisms. Life is a characteristic quality that differentiates an inanimate from the animate.

characteristics of Living Beings

The attributes or characteristics of living from can be discussed as follows: 

1.Cellular organisation     

It refers to the composition and arrangement of cells in body.

Based on the number of cells, the organisms are: 

• Unicellular organisation 

The organisms which have single -cell ,called unicellular organisms ,e.g Amoeba,Paramecium etc. 

• Multicellular organisms 

  the organisms which have multiple cells of various types are called multicellular organisms,e.g. human,etc.

2. Homeostasis  

 It is the process of regarding body temperature and maintenance of internal environment in order in continue metabolic processes ,e.g. thermoregulation Its failure leads to 

• Heat stroke  

It indicates the increase in body temperature above normal level.

• Hypothermia 

It means decrease in body temperature below normal level.

3. Reproduction

It is the process of producing young ones by living beings. On the basic of involvement of gametes , It is two types:

•  Asexual reproduction

 the process which do not involve the fusion of gametes or sex cells ,e.g. Amoeba.

• Sexual reproduction

the process which involves the fusion of gametes ,e.g. humans.

4.Consciousness and irritability

It is the ability of an organism to sense  the environment and respond to external stimuli .

5. Adaptation 

It refers to the genetic mechanism of an organism to survive, thrive and reproduce by constantly enhancing itself . It is following types: 

• short-term adaptation   

theses are temporary changes in response to changing environment,e.g.hibernation and aestivation.

• Long-term adaptation 

these are permanent changes in response to changing environment,e.g.mimicry. 

6.Growth

All living organisms grow by increase in mass and increase in number individuals cells .A multicellular organism grows by cell division.

7.Metabolism 

A series of chemical processes catalysed by enzymes ,occurring within the body of living beings.it is of two type:

• Catabolism

 

the process of breakdown of complex substances into simpler ones or catabolic reactions, which release energy,e.g.pespiration.

 

• Anabolism

The process of formation of complex substances from simpler ones is by anabolic reactions which store energy ,e.g.photosynthesis.

8.Death   

It is the termination of functional  life of living being. It occur in two ways :

• clinical

 

The stoppage or vital function like pulse, heartbeat,etc.

• Biological  

 The death is which is cell of the body parts degenerate and die. clinical death is followed by biological death.

what is the Diversity in the world ?

The planet earth is full of animals and plants. This refers to biodiversity.Each different kind of Plant and animal represents a species.The number of species that are known and described ,range between 1.7-1.8 million The number of known species are increasing day-by-day because of Projects like global biodiversity information facility and species 2000.the estimated number of living organisms on earth now is between 5-30 million ,most occurring in dense tropical rain forests and under water reefs.

Systematics

It is the study of diversity of living organisms and evolutionary relationship between them. lt is the systematic arrangement of organisms on the  basis of following four fields viz, identification, classification,nomenclature and taxonomy.

Identification

lt aims to identify the correct name and position of an organism in the already established classification system.lt is done with the help of keys.key is a list of alternating characters found in organisms.

classification 

It involves the scientific grouping of identified organisms into convenient categories or taxa based on some easily observable and fundamental characters. the various categories are kingdom, phylum, class , order ,family,genus and species. 

Nomenclature

It is the science of providing distinct and proper names to organism so that they can be easily recognised and differentiated from others.

Scientific or technical Names                                        

These are the names given to the organisms by biologists based on agreed principles and criteria for their acceptability all over the world.these are as follows: 

• Binomial system of nomenclature  

this system was proposed by carolus Linnaeus in 1753 in his book  species Plantarum.though the idea of binomial nomenclature wes first introduced by Gaspard Bauhin.                                           
As per this system name of any organism consists of two parts or ,i.e.generic epithet and specific epithet,e.g. the botanical name of mango is Mangifera indica L, in which Mangifera is generic  epithet  representing the genus and indica is specific epithet representing its species  .L represents the name of the scientist (Linnaeus), who gave the scientific name to mango.

• Trinomial system of nomenclature

Sometimes binomial nomenclature can also be extended to trinomial system of nomenclature where the name of sub-species or varieties  can be incorporated,e.g. Brassica oleracea botrytis.Here botrytis is a variety.

• Polynomial  system of nomenclature 

Prior to 1750, biologists used descriptive names for organisms with  each name  being made  up of several Latin words e.g. Caryophyllum saxatilis, Folis   gramineus , Umbellatus corymbia (caryophyllum growing on rocks having grass-like leaves and umbellate corymb flower). 

Rules for Nomenclature

Rules were initially framed by Linnaeus and have been revised by various codes since then. these are as below:

• Biological names are printed in italics to indicates their latin origin.

• When handwritten,  both words are underlined separately.

• The genus starts with the capital letter while , specific epithet is always with small letter.

• Name of the author is pointed in roman bold letter.

• The name of categories higher then the rank of genus are not printed in italics. Bold letters can however be used.

• Sometimes generic and common names can be same e.g. Gorilla  gorilla, Rattus rattus. these are called Tautonyms  and are valid in zoological names only.

        

   Codes of Biological Nomenclature  

there  are five codes of nomenclature which help to avoid errors, duplication and ambiguity in scientific names .

Codes of biological nomenclature are as below: 

ICBN    International Code of Botanical Nomenclature 

ICZN    International Code of Zoological Nomenclature 

ICVN    International Code of viral Nomenclature 

ICBN    International  Code of Bacteriological   Nomenclature 

ICNCP  International  Code of Nomenclature for Cultivated Plants 

Types of Annotations Used in nomenclature 

On the basis of their origin and uses, it can be categorised into following types:

• Holotype    lt is a prototype spcimen, from which description of a new species iis established 

• Syntype       lt refers to any of two or more  specimens cited by an author when there is no holotype.

• Lectotype     The specimen selected from original material, when there is no holotype available for it.

• Paratype     It  Indicates the specimens described along with the holotype. 

• Neotype       It is new nomenclatural  type, when the holotype is not available.

• Isotype        It works as duplicate of holotype  

  What is Taxonomy?

Taxonomy 

lt deals with the principles and procedures of identification, nomenclature and classification of organisms . lt reflects the natural and phylogenetic among organisms.

It also provides the details of external and internal structures,cellular structure and ecological information of organisms. the term taxonomy was coined by AP de Candolle.

Branches of Taxonomy

The Various branches of taxonomy are:

 Classical taxonomy  alpha- taxonomy or old systematics is based on the morphological traits.

Artificial taxonomy  makes use of habit and habitat of organisms, Pling used this system frist time.

Practical taxonomy  is based  on the utility of organisms,

Natural taxonomy is based on the natural similarities amongst organism.

Phylogenetic taxonomy is based on phylogeny or evolutionary history of a species.

Experimental taxonomy is based on experimental determination of genetic inter-relationships.

Chemotaxonomy is based on the presence or absence of chemical in cells or tissies, e.g. amino acids, protein, etc. 

Numerical taxonomy is based on the number of shared characters of various organisms. It is also called phenetic or Adamsonian classification. 

cytotaxonomy is based on cytological studies.

Karyotaxonomy is based on nuclear and chromosomal studies.

Morphotaxonomy is based on morphological studies of organisms.

Type of Taxonomy 

Alpha  taxonomy considers only morphology, Beta taxonomy considers genetic,anatomy ,physiology ,etc. and the omega taxonomy is based on phylogenetic relationships.

Modern taxonomy/New Systematics 

The concept of modern taxonomy  was given by Julian Huxley.1940 ( father of neotaxonomy) According  to it,the species are dynamic and ever -changing entity. Studies of organisms are done on a huge number of variations .It includes cytotaxonomy ,numerical taxonomy, chemotaxonomy etc.

Taxonomy categories 

classification is not single step process. It involves hierarchy of steps in which each step represents a rank of category. Since, the category is a part of overall taxonomic arrangement .It is called the taxonomic category and all categories together consitutes the taxonomic hierarchy. It was frist introduced by Linnaeus (1751) and hence, is also know as Linnaean Hierarchy. It was given in his book systems Naturae.

• Taxon represents the rank, each category and referred to as a unit of classification, The term 'texon' was first introduced by ICBN during 1956. According to Mayr (1964), taxon is a group of any rank that is sufficiently distinct to be  worthy of being assigned a definite category, In simple words, taxon refers to a group of similar, genetically related individuals having certain characters distinct from those of other groups.
• The taxonomic categories ,Which are always used in hierarchical classification of organisms are called obligate categories.
• The sub- categories like sub-species ,sub-class, sub- family, etc. Which facilitate more sound and scientific placement of various taxa are called intermediate categories.      
•  The taxonomic categories for both plants and animals can be demonstrated as follwos -( in descending hierarchy)

For Plants 

  Kingdom ------- Division ------ Class ------- Order------ Family ------ Genus

------- Species.

For Animals

  Kingdom------- Phylum ------ Class ------ Order ------ Family ------- Genus 

------- species. 

Each taxa can be explained under the following levels:

•  KIngdom

  It is the highest category is taxonomy. A kingdom includes all the organisms ,which share a set of distinguished characters.

• Phylum or Division

 ( Cuvier ,Eichler ) is a taxonomic categories higher than class and lower  in rank to kingdom, The term phylum is used for animals, while division is commonly employed for plants . It consists of more than one class having some similar correlated characters.

• Class

 (Linnaeus) is a major category , which includes related orders.

• Order

 An order (Linnaeus) is a group of one or more related families that posses some  similar/corelated characters, which are lesser in number as compared to a family or genera.

• Family

 Family (John ray ) is a group of related genera with less number of similarities as compared to genus and species. All the genera of a family have some common features. They are separable from genera of a related family by important differences in both vegetative and reproductive features.

• Genus

 (john ray) comprises of a group of related species ,which have more characters common in comparison to species of other genera. In other words genera are the aggregates of closely related species. 

• Species

 (John ray)  is group of individuals which resemble one another in all morphological and reproductive characters and interbreed freely to produce fertile offsprings (as defined by Ernst Mayr). It is the lowest or basic taxonomic categories.