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ClassNotes UNDERSTANDING THE CONCEPTS Q#1 Relate the importance of biodiversity with natural ecosystem through examples? Ans: Biodiversity: Biodiversity is a measure of the variety of organisms present in different ecosystems. The term “biodiversity” has been derived from 'bio' and ‘diversity’. Formerly it was called “natural diversity”. “Diversity” means variety within a species and among species. Importance of biodiversity and natural ecosystem: Plants and animals (flora and fauna) diversity depends on climate, altitude, soils and the presence of other species. Biodiversity is not distributed evenly on Earth. It is richer in the tropics while there are fewer species in the polar regions. In the year 2006 large number of the Earth's species were classified as endangered or threatened species. Examples: i. Most of the hotspots are located in the tropics and most of them established species, are forests. For example, Brazil's Atlantic Forest contains' roughly 20,000 plant species, 1350 vertebrate species, and millions of insect species about half of which occur nowhere else in the world. ii. Biodiversity found on Earth today is the result of 4 billion years of evolution. The origin of life is not well known to science, though limited evidence suggests that until 600 million years ago, all life consisted of bacteria and similar single-celled organisms. www.classnotes.xyz Biology ClassNotes, Inc. © 2020 1
ClassNotes iii. Biodiversity provides food for humans. A significant proportion of drugs are derived, directly or indirectly, from biological sources. iv. A wide range of industrial materials e.g. building materials, fibers, dyes, resins, gums, adhesives, rubber and oil are derived directly from biological resources. v. Biodiversity plays important role in making and maintaining ecosystems. vi. It plays a part in regulating the chemistry of our atmosphere and water supply. vii. Biodiversity is directly involved in recycling nutrients and providing fertile soils. Q#2 Explain the aims and principles of classification, keeping in view its historical background? Ans: Classification: Biological classification is a method by which biologists’ group and categorize species of organisms. Aims of Classification: Taxonomy: The branch of biology which deals with classification is called taxonomy. Systematic: The branch which deals with classification and also traces the evolutionary history of organisms is known as systematics. The main aims of both these branches are: i. To determine similarities and differences among organisms so that they can be studied easily. ii. To find the evolutionary relationships among organisms. Principles of Classification/Basis of Classification: www.classnotes.xyz Biology ClassNotes, Inc. © 2020 2
ClassNotes i. Classification is based on relationship amongst organisms and such relationship is got through similarity in form or structure. ii. These similarities suggest that all organisms are related to one another some point in their evolutionary histories. However, some organisms are more closely related than others. For example, sparrows are more closely related to pigeons than to the insects. It means that the former two have common evolutionary histories. iii. Biologists have classified all the known organisms into groups and subgroups on the basis of similarities. These similarities are seen in structures, biochemistry, cytology and genetics. iv. Modern genetics has provided another type of information to taxonomists. The genetic differences between two studied organisms can be determined and can be used forgetting idea about similarities and differences in their structures and functions. Q#3 Explain the base for establishing five kingdoms of living organisms? Ans: In 1967, Robert Whittaker introduced the five-kingdom classification system. This system is based on: i. The levels of cellular organization i.e. prokaryotic, unicellular eukaryotic and multicellular eukaryotic. ii. The principal modes of nutrition i.e. photosynthesis, absorption, and ingestion. On this basis, organisms are classified into five Kingdoms: Monera, Protista, fungi, plantae and Animalia. Q#3(A). Describe the general characteristics of the five kingdoms. www.classnotes.xyz Biology ClassNotes, Inc. © 2020 3
ClassNotes Ans: The five kingdoms: In 1937, E-Chatton suggested the terms of "Procariotique" to describe bacteria and "Eukariotique" to describe animal and plant cells. In 1967, Robert Whittaker introduced the five-kingdom classification system. This system is based on: i. The levels of cellular organization i.e. prokaryotic, unicellular eukaryotic and multicellular eukaryotic. ii. The principal modes of nutrition i.e. photosynthesis, absorption, and ingestion. On this basis, organisms are classified into five Kingdoms: monera, protista, fungi, plantae, and animalia. Modification in the five kingdoms classification: In 1988, Lynn Margulis and Karlene Schwartz modified the five-kingdom classification of Whittaker by considering cellular organization, mode of nutrition, cytology, genetics and organelles of symbiotic origin (mitochondria and chloroplast) They classified the organisms into the same five kingdoms as proposed by Whittaker. Q#4 Justify why virus are excluded from the Five-Kingdom classification system. Ans: Status of Viruses: Viruses are acellular i.e. they do not possess cellular organization yet show some characters of livings. Viruses are infectious entities which contain either RNA or DNA, normally encased in protein coat and reproduce only in living cells, where they cause a number of diseases. They are not considered as organisms and thus are not included in the five-kingdom classification system. Prions and viroids are also acellular particles and are not included in the five-kingdom classification system. www.classnotes.xyz Biology ClassNotes, Inc. © 2020 4