Zoology 3rd Sem #Taxonomy#Ecology.... Biological Species Concept # Succession# Biodiversity

Taxonomy Unit:l

(1) Define Taxonomy .

According to Mayr(1982)

 "Taxonomy is the theory and practice of classifying organisms ".

(2) Define Systematics .

According to Simpson (1961)

"Systematics is the scientific study of the kinds and diversity of organisms and of any and all relationships among them".

(3) Define Zoological classification .

The ordering of animals into groups /sets on the basis of their relationships or of associations by contiguity , similarity or both is called Zoological classification .

(4) Define Phenon .

Different forms or phenotypes  like sexual dimorphism , age stages ,seasonal varities and morphs or individual varients , etc. of a single population are termed as Phenon .

(5) Define Taxon.

According to Simpson 1961 " Taxon is a group of real organisms recognised as a formal unit at any level of a hierarchic classification .

(6) Define Category .

The term used to designate rank or level in a hierarchic classification is a Category.

(Species,genus,family,order,class,phylum)

Biological Species Concept, Unit :l

(7) Write a note on Biological Species  Concept

According to Mayr,1969 , Biological species can be defined as a group of actually or potentially interbreeding natural population which are reproductively isolated from similar other natural population .

 A species is a Mendelian population or a potential gene pool which protects itself against harmful gene flow from other gene pools by the isolating mechanism .If genes from two different gene pool or from two different species mixed , it will lead to high frequency of disharmonious gene combination , whereas if these genes are from a same gene pool , the result will be the formation of harmonious combination . Hence, isolating mechanism is favoured by selection .

For example, Sturnella neglecta and S. magna share same breeding ranges and phenotypic similarities but reproductively isolated because the courtship songs of males are different and females respond to the songs of males  of their  own species only .

Merits:

(i) This concet combines the discreteness of the local species at a given time with an evolutionary potential for continuing change .

(ii) It is widely applied in ecology, physiology , behaviour biology , etc.

This concept is also known as Newer Species Concept  , because it was accepted after the publication of Darwin's "Origin of Species ", ,,1859.

Demerits:

(i) The doubts created by sexual dimorphism, age differences,polymorphism etc.  can not be solved by Biological Species Concept .

(ii) This concept can not be applied on "an asexual biological population  because self fertilization , parthenogenesis , pseudogamy, vegetative reproduction , etc do not fulfill the criteria of interbreeding .

(iii) There are many intermediates like biotypes, races, subspecies, ecotypes ,semispecies , allospecies within a species which are contradictory of the Biological Species Concept . 

e.g. (a)Though the Sibling species are rerouctively isolated but morphologically non-seperated .

(b) Sometimes, isolating mechanism between two species broken down though the members have strong morphological differences .

(iv) Sometimes , before the discovery of hybrid nature hybrid indiviuals are described as Species .

Ecology,Unit:ll

(8)Define ecological nitche .

According to Joseh Grinnel (1971) "the ultimate distributional unit , within which each species is held by its structural and instinctive limitations is termed as nitche ". 

A same ecological nitche can not be occupied by two species from the same general territory for long time .

(9) Define habitat .

The totality of abiotic factors to which a species is exposed in a particular area is the habitat of that species .

(10) Define ecological succession with causes .

A series of complex  natural process by which a locality becomes successively colonised by different groups or communities of plants is called ecological  succession .

Causes of succession : There are three primary causes of succession :

(i) Initial causes : A group of climatic factors like erosion & deposits ,wind ,fire etc.due to lightening or volcanic activities and biotic causes like different activities of organisms turned a bare area into a new colony or desroy an existing population.

(ii)Continuing causes: The edaphic /soil features of an area is changed due to migration, ecesis, aggregation, competition,reaction etc.

(iii) Stabilising causes: The climate of an area may results into stabilisation of the community in that area.

(11) What do you mean by Biodiversity ?

The variability among living organisms from all sources , including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part is termed as biodiversity.

This definition was given in 1992 ,in United Nations Earth Summit,Rio de Janeiro.

According to IUCN,UNEP,1992 ,"The totality of the genes ,species and ecosystems in a region is defined as biodiversity".

 

(12) State the major causes of depletion of biodiversity .

The major causes of depletion of the biodiversity are as follows : 

(i) Habitat destruction :

Increase of human population & its consequences resulted in the destruction of habitat of several species (especially in the tropical forests ) which lead to their extinction .e.g. endangered butterfly of Weastern Ghat are going to be extinct due to habitat destruction .

(ii) Overexploitation :

Overhunting ( e.g. whale hunting ), poaching(e.g.killing of rhino for  horn ) , over use for medcine (e.g. Atropa belladona root for atropine) and  unmethodical collection of rare & vulnerable plants for  academic purposes i.e. consumption of resources at an unsustainable rate is one of the major cause of biodiversity loss .

(iii) Introduced & invasive species :

Introduction  of exotic /alien species deliberately or accidentally may be a serious cause of the destruction of native species ,e.g. Lates niloticus (an exotic species) has driven out half of 400 native cichlid fish populations of Lake Victoria .

Invasive species outcompete native species for food, water,light & space .

(iv) Unsustainable Agricultural Activities:

Use of high yielding varities ignorig indigenous gene pool resulted into loss of genetic diversity as well as biodiversity too .

(v) Global warming:

According to IUCN , 70% of world's known species are at the door of extinction if global temperature rise by more than 3.5°C.

(vi) Natural calamities like earth-quake , volcanic eruption , epidemics , flood , drouht , forest fire etc. may decline Biodiversity .

(13) Write a note on Conservation of Biodiversity.

According to IUCN(1980), Conservation is positive , embracing preservation, maintanance, sustainable utilization ,restoration & enhancement of the natural environment .

Aims of biodiversity conservation:

(i) To conserve rare and endangered species.

(ii) To maintain genetic diversity within the populations.

(iii) To protect ecosystem process like primary & secondary productivity , flow of energy , flow of nutrients, water balance, soil conservation , etc .

Species to be conserved & their types:

(i) IUCN Red List species have got first priority (i.e. critically endangered species, endangered species & vulnerable species).

(ii) Directly harvested plants for medcine, food ,dye,spice, ornaments,etc.got 2nd priority .

(iii) Keystone species , Umbrella species, Flagship species , etc got 3rd priority for conseration .

Keystone species: A species which holds the ecosystem together and its absence results in subside of the ecosystem is considered as a keystone species .e.g. Pisaster ochraceus control the number of mussels by eating. If P.ochraceus are removed from the sea , other species will decline due to over population of mussels.

 

Umbrella species:   A species whose protection results in the indirect protection of other species is termed as Umbrella species .

e.g. Tiger in India is a Umbrella species .

Flagship species: It is the symbol  and leading element of an entire conservation campaign .e.g. polar bear abovethe ice berg is a Flagship species to campaign awareness about global warming .

Types :

Conservation are of three types :

(i) In-situ or On-site conservation : In this type habitat , species and ecosystems are conserved in their natural habitats. .e.g.Biosphere reserves, National parks , Wild Life sanctuary,etc.

(ii) Ex-situ or Off-site Conservation: In this type elements of biodiversity are withdrawn from their natural habitat and conserved in Botanical gardens , Zoological gardens, seed banks, etc.

(iii) In-vitro Conservation involves micropropagation to conserve seeds , embryo ,buds etc.