Systematics of Living Organisms
Short Questions
1. What is systematics?
Answer: Systematics is the study of kinds, diversity, and evolutionary relationships of organisms.
2. Who coined the term taxonomy?
Answer: A.P. de Candolle, a Swiss botanist, coined the term taxonomy.
3. What is artificial classification?
Answer: Artificial classification is based on easily observable, non-evolutionary features like habit or color.
4. What is a cladogram?
Answer: A cladogram is a branching diagram showing hypothetical relationships among organisms and their ancestors.
5. Name the three domains of life.
Answer: The three domains of life are Archaea, Bacteria, and Eukarya.
6. What is chemotaxonomy?
Answer: Chemotaxonomy is classification based on similarities in chemical constituents of organisms.
7. What is numerical taxonomy?
Answer: Numerical taxonomy uses quantification of characters and algorithms for classification.
8. What is DNA barcoding used for?
Answer: DNA barcoding identifies species using DNA sequences from small tissue samples.
9. What is the lowest taxonomic unit?
Answer: Species is the lowest taxonomic unit in biological classification.
10. What is binomial nomenclature?
Answer: Binomial nomenclature is a system of naming organisms with two Latin/Greek words: genus and species.
11. What is the cell wall composition of fungi?
Answer: Fungi have cell walls made of chitin or fungal cellulose.
12. What are extremophiles?
Answer: Extremophiles are Archaebacteria that survive in extreme conditions like high temperature or salinity.
13. What is the shape of bacillus bacteria?
Answer: Bacillus bacteria are rod-shaped.
14. What causes red tide?
Answer: Red tide is caused by dinoflagellates, such as Gonyaulax.
15. What are viroids?
Answer: Viroids are single-stranded RNA infectious agents lacking a protein coat.
Long Questions
1. Explain the difference between artificial, natural, and phylogenetic classification systems.
Answer: Artificial classification relies on a few observable, non-evolutionary traits like color, ignoring relationships, as seen in Linnaeus’s system. Natural classification uses objectively significant features, considering organism relationships, like Bentham and Hooker’s system. Phylogenetic classification, such as Engler and Prantl’s, is based on common evolutionary descent, emphasizing evolutionary relationships.
2. Describe the salient features of Kingdom Monera.
Answer: Kingdom Monera includes unicellular, prokaryotic organisms with no defined nucleus, having DNA in a nucleoid. They have peptidoglycan cell walls (except Archaebacteria), lack membrane-bound organelles, and reproduce asexually via binary fission. They are omnipresent, with some being autotrophic (photo- or chemoautotrophic) and others heterotrophic, including pathogens and decomposers.
3. What is the significance of binomial nomenclature in taxonomy?
Answer: Binomial nomenclature provides a universal, standardized naming system using two Latin/Greek words (genus and species), ensuring clarity across languages. It overcomes confusion from vernacular names, which vary regionally, as seen with Mangifera indica having multiple Sanskrit names. Governed by ICNAFP, it facilitates international communication and includes the author’s name for historical context.
4. Discuss the role of DNA barcoding in biological classification.
Answer: DNA barcoding identifies species by analyzing DNA sequences from small tissue samples, aiding in species discovery and classification. It involves collecting barcode data of known species and matching unknown samples against a library, supporting ecological and evolutionary studies. Applications include protecting endangered species, pest control, and authenticating medicinal plants.
5. How does the three-domain system classify life forms?
Answer: Proposed by Carl Woese, the three-domain system classifies life into Archaea, Bacteria, and Eukarya based on ribosomal RNA differences. Archaea and Bacteria are prokaryotic, with Archaea lacking peptidoglycan and surviving extreme conditions, while Bacteria have peptidoglycan cell walls. Eukarya includes eukaryotic organisms like plants (cellulosic walls) and fungi (chitinous walls), all sharing a common ancestor.
6. Explain the structure and reproduction of fungi.
Answer: Fungi are eukaryotic, heterotrophic organisms with a body of unicellular or mycelial hyphae, which may be septate or coenocytic, with chitinous cell walls. They reproduce asexually via fragmentation, fission, or budding, and sexually in some groups, forming spores. They exhibit saprophytic, parasitic, or symbiotic (e.g., lichens, mycorrhiza) lifestyles, thriving in warm, humid environments.
7. What are the characteristics of plant-like protists?
Answer: Plant-like protists, or chrysophytes, are unicellular, eukaryotic, and mostly photosynthetic, serving as major ocean producers. Diatoms have silica cell walls forming diatomaceous earth, while dinoflagellates, like Gonyaulax, have cellulosic plates and cause red tides. Euglenoids, such as Euglena, lack cell walls but have a proteinaceous pellicle and can switch between photosynthesis and heterotrophy.
8. Describe the economic importance of fungi.
Answer: Fungi are economically vital as food sources (e.g., mushrooms, morels), industrial agents (Saccharomyces for baking/brewing), and medicinal producers (Penicillium for antibiotics). They contribute to nutrient recycling as decomposers and form symbiotic relationships like lichens (pollution indicators) and mycorrhiza (enhancing plant nutrient uptake). However, some fungi, like Puccinia, cause plant diseases, impacting agriculture.
9. Differentiate between viruses and viroids.
Answer: Viruses are infectious nucleoproteins with a protein capsid surrounding either DNA or RNA (never both), requiring a host to replicate, causing diseases like AIDS or plant mosaics. Viroids are smaller, consisting only of single-stranded RNA without a protein coat, infecting plants (e.g., potato spindle tuber disease). Unlike viruses, viroids lack a capsid and are simpler infectious agents.
10.What are lichens, and why are they considered pollution indicators?
Answer: Lichens are symbiotic associations between algae (phycobiont) and fungi (mycobiont), where algae provide food and fungi offer shelter and minerals. They thrive in extreme environments but are highly sensitive to pollution, absent in polluted areas due to their inability to tolerate toxins. This sensitivity makes them effective indicators of environmental pollution levels.
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