Discuss how classification systems have undergone several changes over a period of time

NCERT Solutions For Class 11 Biology Biological Classification Topics and Subtopics in NCERT Solutions for Class 11 Biology Chapter 2 Biological Classification : Section Name Topic Name 2 Biological Classification 2.1 Kingdom Monera 2.2 Kingdom Protista 2.3 Kingdom Fungi 2.4 Kingdom Plantae 2.5 Kingdom Animalia 2.6 Viruses, Viroids and Lichens 2.7 Summary NCRT TEXT BOOK QUESTIONS SOLVED 1.Discuss how classification systems have undergone several changes over a period of time? Soln.Biological classification is the scientific procedure of arranging organisms in a hierarchical series of groups and sub-groups on the basis of their similarities and dissimilarities. Scientists have proposed different systems of classification which have undergone several changes from time to time. Earlier Aristotle proposed artificial system of classification, which divided animals and plants on basis of habitat. E.g., Aquatic (fish, whale), terrestrial (e.g., reptiles, cattle) and aerial (e.g., bat, birds). Then, natural system of classification was based on morphology^ anatomy, physiology, reproduction, ontogeny, cytochemistry, etc. After natural system, organisms were classified on basis of evolutionary relationships called phyloge¬netic system. It is based on cytotaxonomy, chemotaxOnomy, numerical taxonomy and cladistic taxonomy. 2.State two economically important uses of: (a) heterotrophic bacteria (b) archaebacteria Soln. (a) Heterotrophic bacteria: They include saprotrophic, symbiotic and...

Gujarat Board Gujarat Board Textbook Solutions Class 11 Biology Chapter 2 Biological Classification GSEB Class 11 Biology Biological Classification Text Book Questions and Answers Question 1. Discuss how classification systems have undergone several changes over a period of time. Answer: Two kingdom systems were unable to describe photosynthetic, non-photosynthetic, uni, and multicellular organisms. Anatomical, environ-mental aspects become a great need for further description. Development in technology has provided many tools for scientists. On the basis of cell-structure, mode of nutrition, reproduction, and phylogenetic relationship R.H. Whittaker has given five-kingdom classifications named Monera, Protista, Fungi, Plantae, and Animalia. But Whittaker has not described viruses, lichens like a cellular organism. These cause many infectious diseases. Stanley described vims, Viroids, smaller than viruses was discovered by T.O. Dienes. Thus classification systems have undergone several changes over a period of time and still changing. Question 2. State two economically important uses of: (1) heterotrophic bacteria (2) archaebacteria Answer: (1) Heterotrophic bacteria : • Nitrogen fixation in roots of leguminous plants • Being decomposers, used in the production of antibiotics (2) Archaebacteria: • Production of biogas from cow-dung. • Lives in the guts of ruminant animals & help them in the digestion of starch. Question 3. What is the nature of cell-wall in diatoms? Answer...

Chapter 2: Biological Classification In Linnaeus’ time, a Two Kingdom system of classification with Plantae and Animalia kingdoms was developed that included all plants and animals respectively. This system did not distinguish between the eukaryotes and prokaryotes, unicellular and multicellular organisms, and photosynthetic (green algae) and non-photosynthetic (fungi) organisms. Classification of organisms into plants and animals was easily done and was easy to understand, but, a large number of organisms did not fall into either category. Hence the two kingdom classification used for a long time was found inadequate. Besides, gross morphology a need was also felt for including other characteristics like cell structure, nature of the wall, mode of nutrition, habitat, methods of reproduction, evolutionary relationships, etc. Classification systems for living organisms have hence, undergone several changes over time. Though plant and animal kingdoms have been a constant under all different systems, the understanding of what groups/organisms be included under these kingdoms has been changing; the number and nature of other kingdoms have also been understood differently by different scientists over time. R.H. Whittaker (1969) proposed a Five Kingdom Classification. The kingdoms defined by him were named Monera, Protista, Fungi, Plantae, and Animalia. The main criteria for classification used by him include cell structure, body organization, mode of nutrition, reproduction, an...

The classification systems have undergone several changes with time. The first attempt of classification was made by Aristotle. He classified plants as herbs, shrubs, and trees. Animals, on the other hand, were classified on the basis of presence or absence of red blood cells. This system of classification failed to classify all the known organisms. Therefore, Linnaeus gave a two-kingdom system of classification. It consists of kingdom Plantae and kingdom Animalia. However, this system did not differentiate between unicellular and multicellular organisms and between eukaryotes and prokaryotes. Therefore, there were large numbers of organisms that could not be classified under the two kingdoms. Views: 5,457 AB positive means that a person has both A and B antigens and also has Rh factor in his blood. 5. It is seen that RBC count is more in the persons living at high altitudes. Indicate the reason behind this. Ans. It is due to the low concentration of O 2 ​ in the air, which enables less O 2 ​ binding capacity of the haemoglobin, this increases RBC count in persons living at high altitude. 6. Why is blood group identification not needed

The classification systems have undergone many changes with time. (i) The Aristotle made the first attempt of classification and classified plants as herbs, shrubs, and trees. Animals, on the other hand, were classified on the basis of presence or absence of red blood cells. This system of classification failed to classify all the known organisms. (ii) Linnaeus developed a two-kingdom system of classification. It consisted of kingdom Plantae and kingdom Animalia. However, this system did not differentiate between unicellular and multicellular organisms or between eukaryotes and prokaryotes. There were large numbers of organisms that could not be placed under the two kingdoms. (iii) A five kingdom system of classification was proposed by R.H Whittaker in 1969. On the basis of characteristics, such as cell structure, mode of nutrition, presence of cell wall, etc., five kingdoms, Monera, Protista, Fungi, Plantae, and Animalia were formed. The economic uses of the following are: (a) Heterotrophic bacteria: (i) Used as bio-fertilizers as they act as decomposers and help in the formation of humus and some of them fix nitrogen. (ii) They help in the production of curd, various antibiotics etc. Many antibiotics are obtained from some species of bacteria (b) Archaebacteria: (i) Used for the production of biogas as they produce methane gas by acting on the excreta of animals. (ii) They are used for the production of commercial products like heat stable enzymes.

Scientific classification of living beings was first done by Aristotle. He used morphological characters as the basis of classification. He classified the living beings into plants and animals. He further classified the plant into trees, shrubs and herbs. He further classified the animals on the basis of presence of absence of red blood. After that, Linnaeus proposed two kingdoms, i.e. Plant Kingdom and Animal Kingdom. But there were certain organisms which could be kept in both of the kingdoms or could not be kept in either of the kingdoms. Hence, a need was felt for a better system of classification. At present, the Five Kingdom Classification is the most accepted one. This was proposed by Robert Whittaker in 1969. Whittaker used phylogenetic relationship to classify the living beings.