DDDIVERSITY IN L L LIVINGIVINGIVING O O ORGANISMS

1 Have you ever thought of the multitude oflife-forms that surround us? Each organismis different from the other to a lesser or greaterextent. For instance, consider yourself and afriend. Are you both of the same height? Does your nose look exactly like yourfriend s nose? Is your hand-span the same as yourfriend s?However, if we were to compare ourselvesand our friends with a monkey, what wouldwe say? Obviously, we and our friends havea lot in common when we compare ourselveswith a monkey. But suppose we were to adda cow to the comparison? We would thenthink that the monkey has a lot more incommon with us than with the We have heard of desi cows and Jerseycows. Does a desi cow look like a Jersey cow? Do all desi cows look alike? Will we be able to identify a Jersey cowin a crowd of desi cows that don t looklike each other? What is the basis of our identification?In this activity, we had to decide whichcharacteristics were more important informing the desired category.

2 Hence, we werealso deciding which characteristics could , think of all the different forms inwhich life occurs on earth. On one hand wehave microscopic bacteria of a few micrometrein size. While on the other hand we have bluewhale and red wood trees of Californiaof approximate sizes of 30 metres and100 metres respectively. Some pine trees livefor thousands of years while insects likemosquitoes die within a few days. Life alsoranges from colourless or even transparentworms to brightly coloured birds and bewildering variety of life around ushas evolved on the earth over millions ofyears. However, we do not have more than atiny fraction of this time to try andunderstand all these living ORGANISMS , so wecannot look at them one by one. Instead, welook for similarities among the ORGANISMS ,which will allow us to put them into differentclasses and then study different classes orgroups as a order to make relevant groups to studythe variety of life forms, we need to decidewhich characteristics decide morefundamental differences among would create the main broad groups oforganisms.

3 Within these groups, smaller sub-groups will be decided by less do we classify ORGANISMS ? three examples of the rangeof variations that you see in life-forms around is the Basis ofClassification?Attempts at classifying living things intogroups have been made since timeimmemorial. Greek thinker Aristotle classifiedanimals according to whether they lived onQ7 DDDDDIVERSITYIVERSITYIVERSITYIVERSITYIVE RSITY INININININ L L L L LIVINGIVINGIVINGIVINGIVING O O O O ORGANISMSRGANISMSRGANISMSRGANISMSRGANISM SC hapter2021-22land, in water or in the air. This is a verysimple way of looking at life, but misleadingtoo. For example, animals that live in the seainclude corals, whales, octopuses, starfishand sharks. We can immediately see thatthese are very different from each other innumerous ways. In fact, habitat is the onlypoint they share in common. This is not anappropriate way of making groups oforganisms to study and think therefore need to decide whichcharacteristics to be used as the basis formaking the broadest divisions.

4 Then we willhave to pick the next set of characteristicsfor making sub-groups within these process of classification within eachgroup can then continue using newcharacteristics each we go on, we need to think aboutwhat is meant by characteristics . When weare trying to classify a diverse group oforganisms, we need to find ways in whichsome of them are similar enough to bethought of together. These ways , in fact, aredetails of appearance or behaviour, in otherwords, form and we mean by a characteristic is aparticular feature or a particular function. Thatmost of us have five fingers on each hand isthus a characteristic. That we can run, but thebanyan tree cannot, is also a , to understand how somecharacteristics are decided as being morefundamental than others, let us consider howa stone wall is built. The stones used will havedifferent shapes and sizes.

5 The stones at thetop of the wall would not influence the choiceof stones that come below them. On the otherhand, the shapes and sizes of stones in thelowermost layer will decide the shape and sizeof the next layer and so stones in the lowermost layer are likethe characteristics that decide the broadestdivisions among living ORGANISMS . They areindependent of any other characteristics intheir effects on the form and function of theorganism. The characteristics in the next levelwould be dependent on the previous one andwould decide the variety in the next level. Inthis way, we can build up a whole hierarchyof mutually related characteristics to be usedfor , we look at many inter-relatedcharacteristics starting from the nature of thecell in order to classify all living are some concrete examples of suchcharacteristics used for a hierarchicalclassification? A eukaryotic cell has membrane-boundorganelles, including a nucleus, whichallow cellular processes to be carried outefficiently in isolation from each , ORGANISMS which do not havea clearly demarcated nucleus and otherorganelles would need to have theirbiochemical pathways organised in verydifferent ways.

6 This would have an effecton every aspect of cell design. Further,nucleated cells would have the capacityto participate in making a multicellularorganism because they can take upspecialised functions. Therefore, nucleuscan be a basic characteristic ofclassification. Do the cells occur singly or are theygrouped together and do they live as anindivisible group? Cells that grouptogether to form a single organism usethe principle of division of labour. In sucha body design, all cells would not beidentical. Instead, groups of cells willcarry out specialised functions. Thismakes a very basic distinction in thebody designs of ORGANISMS . As a result,an Amoeba and a worm are very differentin their body design. Do ORGANISMS produce their own foodthrough the process of photosynthesis?Being able to produce one s ownfood versus having to get food fromoutside would make very differentbody designs.

7 Of the ORGANISMS that performphotosynthesis (plants), what is the levelof organisation of their body? Of the animals, how does the individual sbody develop and organise its differentparts, and what are the specialisedorgans found for different functions?DIVERSITY IN living ORGANISMS812021-22 SCIENCE82We can see that, even in these few questionsthat we have asked, a hierarchy is characteristics of body design used forclassification of plants will be very differentfrom those important for classifying is because the basic designs are different,based on the need to make their own food(plants), or acquire it (animals). Therefore,these design features (having a skeleton, forexample) are to be used to make sub-groups,rather than making broad do you think is a more basiccharacteristic for classifyingorganisms?(a)the place where they live.(b)the kind of cells they aremade of. Why?

8 Is the primary characteristicon which the broad division oforganisms is made? what bases are plants andanimals put into differentcategories? and EvolutionAll living things are identified and categorisedon the basis of their body design in form andfunction. Some characteristics are likely tomake more wide-ranging changes in bodydesign than others. There is a role of time inthis as well. So, once a certain body designcomes into existence, it will shape the effectsof all other subsequent design changes,simply because it already exists. In otherwords, characteristics that came intoexistence earlier are likely to be more basicthan characteristics that have come intoexistence means that the classification of lifeforms will be closely related to their is evolution? Most life forms that wesee today have arisen by an accumulation ofchanges in body design that allow theorganism possessing them to survive Darwin first described this idea ofevolution in 1859 in his book, The Origin we connect this idea of evolution toclassification, we will find some groups oforganisms which have ancient body designsthat have not changed very much.

9 We willalso find other groups of ORGANISMS that haveacquired their particular body designsrelatively recently. Those in the first groupare frequently referred to as primitive or lower ORGANISMS , while those in the second groupare called advanced or higher ORGANISMS . Inreality, these terms are not quite correct sincethey do not properly relate to the that we can say is that some are older ORGANISMS , while some are younger ORGANISMS . Since there is a possibility thatcomplexity in design will increase overevolutionary time, it may not be wrong to saythat older ORGANISMS are simpler, whileyounger ORGANISMS are more to knowBiodiversity means the diversity of lifeforms. It is a word commonly used torefer to the variety of life forms foundin a particular region. Diverse life formsshare the environment, and areaffected by each other too. As a result,a stable community of different speciescomes into existence.

10 Humans haveplayed their own part in recent timesin changing the balance of suchcommunities. Of course, the diversityin such communities is affected byparticular characteristics of land,water, climate and so on. Roughestimates state that there are about tenmillion species on the planet, althoughwe actually know only one or twomillions of them. The warm and humidtropical regions of the earth, betweenthe tropic of Cancer and the tropic ofCapricorn, are rich in diversity of plantand animal life. This is called the regionof megadiversity. Of the biodiversityon the planet, more than half isconcentrated in a few countries Brazil, Colombia, Ecuador, Peru,Mexico, Zaire, Madagascar,Australia, China, India, Indonesia IN living ORGANISMS are calledprimitive and how are theydifferent from the so-calledadvanced ORGANISMS ? advanced ORGANISMS be thesame as complex ORGANISMS ?