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1800-102-2727Chapter number 2 "Biological Classification" of class 11 Biology subject throws light on the features of Kingdom Monera, Fungi, and Protista as given by the Whittaker System of Classification. The plant and animal kingdoms, which are technically known as Kingdoms Plantae and Animalia, respectively are introduced briefly in this chapter. Apart from the five Kingdoms mentioned above, Biological Classification also talks about the Kingdoms Viroids, Lichens, and Viruses. Following are the sub-topics that are a part of this chapter.
The minute differences in the morphological characteristics that originally led to animal and plant species classification were minute. The criteria based on which the five-kingdom classification was designed were cell structure, body organization, reproduction, mode of nutrition, and phylogenetic relationships. The entities classified in the five-kingdoms displays tremendous metabolic diversity.
Kingdom Monera includes bacteria as well, even though bacterias are cosmopolitan in distribution.
Organisms classified under Kingdom Protista are single-celled eukaryotes
The species included under Kingdom Fungi reveal substantial diversity in their structure and habitat.
Entities that consist of eukaryotic chlorophyll property come under the Kingdom Plantae.
All the multicellular, and heterotrophic eukaryotic entities, in which there is a dearth of a cell wall are a part of the Kingdom Animalia.
Viruses are infectious agents who either have a single-stranded RNA or double-stranded RNA surrounded with a protein coat. Whereas, viroids are also infectious agents, but short ones have a single-stranded RNA with no protein coat.
Q1. Discuss how classification systems have undergone several changes over a period of time?
Answer:
The classification systems keep on changing as new species are found and classified. Till now, the classification system has undergone several changes. The first-ever classification was given by Aristotle who divided plants into herbs, shrubs, and trees based on their habit and animals based on the presence or absence of red blood.
Later on, this classification system was rejected because it was misleading. Linnaeus then classified all organisms into two large kingdoms i.e. plants and animals. Since, this system could not distinguish between eukaryotes or prokaryotes, unicellular or multicellular organisms, it was also rejected. Further, three-kingdom and four-kingdom classification were proposed by Ernst Haeckel and Copeland respectively. These were soon replaced by the five-kingdom classification by R.H Whittaker. In this system, organisms were divided into five kingdoms on the basis of cell structure, body organization, mode of nutrition and reproduction, and phylogenetic relationships,namely monera, protista, fungi, plantae, and animalia. Even this classification system was not up to the mark, so corrections are being made in this. Thus, we can conclude that classification systems have undergone several changes over a period of time.
Q2. State two economically important uses of (a) heterotrophic bacteria (b) archaebacteria
Answer:
(a). Economically important uses of heterotrophic bacteria
1. Some heterotrophic bacteria are decomposers and they help in humus formation.
2. Heterotrophic bacteria like Rhizobium also aid in fixing nitrogen for plants.
3. Heterotrophic bacteria like Lactobacillus help in the formation of curd
(b). Economically important uses of archaebacteria
1. Archaebacteria such as Methanobacterium and some others are used in the production of gobar gas which is used as fuel as it contains methane.
2. Certain archaebacteria are used in bioleaching of minerals.
3. Archaebacteria such as Thermus aquaticus are used to obtain Taq polymerase enzyme which is used in recombinant DNA technology.
Q3. What is the nature of cell walls in diatoms?
Answer:
The cell wall of diatoms is composed of two layers, thin overlapping shells which fit together in such a way that they look like a soap case. The cell wall is impregnated with silica in characteristic patterns. Diatom cell walls are almost indestructible and on accumulation, they form diatomaceous earth which is used for purification and filtration of petroleum and other crude products.
Q4. Find out what do the terms mean; algal bloom and red-tides; signify.
Answer:
Algal bloom- An algal bloom is a term used for excessive growth of algae over a water body causing discoloration of the water body. This abnormal growth is due to availability of high amounts of mineral and nutrient content in water bodies spilled off from fields and industries which contain chemicals utilized by algae for growth. Algal blooms result in the death of fishes and other aquatic organisms as it consumes the oxygen available for its own growth and metabolic processes.
Red tides- Red tide is the red coloration of seawater due to the presence of dinoflagellate Gonyaulax. This dinoflagellate produces toxins that lead to the death of fish.
Q5. How are viroids different from viruses?
Answer:
Viroids are different from viruses in the following aspects :
Q6. Describe briefly the four major groups of Protozoa.
Answer:
All protozoans are single-celled, cell-wall-lacking, heterotrophic organisms that live as predators or parasites. Protozoans are considered to be primitive relatives of animals. Protozoa are divided into four groups based on their organ of motility.
Q7. Plants are autotrophic. Can you think of some partially heterotrophic plant?
Answer:
Q8. What do the terms phycobiont and mycobiont signify?
Answer:
Q9. Give a comparative account of the classes of Kingdom Fungi under the following:
ii. mode of reproduction
Answer:
A comparative account of the classes of Kingdom Fungi is as follows:
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Q10. What are the characteristic features of Euglenoids?
Answer:
Characteristic features of Euglenoids:
Q11. Give a brief account of viruses with respect to their structure and nature of genetic material. Also, name four common viral diseases.
Answer:
Q12. Organize a discussion in your class on the topic; Are viruses living or nonliving?
Answer:
Viruses are considered to be intermediates between living and non-living entities. They resemble living beings in the following aspects:
Viruses are made up of organic macromolecules which is a characteristic of only living beings.
Thus, based on these features, viruses must be categorized as living. However, viruses also resemble non-living characters in the following aspects:
Thus, based on these features viruses can be classified as non-living. The status of the virus as living or non-living is controversial.
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