Within Chapter Questions Class 11 Chapter 2 Biology Maharashtra Board

Systematics of Living Organisms

Can you recall? Page No. 6

What is the Five Kingdom System of Classification?

Answer: The Five Kingdom System of Classification, proposed by R.H. Whittaker in 1969, is a phylogenetic classification that organizes living organisms into five kingdoms based on their characteristics and evolutionary relationships. This system addresses the limitations of the earlier two-kingdom classification (Plantae and Animalia) by including organisms with mixed characteristics, such as bacteria, fungi, and Euglena. The five kingdoms are:

1. Kingdom Monera: Includes unicellular, prokaryotic organisms like bacteria and cyanobacteria, with no well-defined nucleus and cell walls made of peptidoglycan. They reproduce asexually, primarily through binary fission or budding.
2. Kingdom Protista: Comprises unicellular, eukaryotic organisms that can be plant-like (e.g., diatoms), animal-like (e.g., protozoans), or fungi-like (e.g., slime molds), showing diverse nutritional modes.
3. Kingdom Plantae: Consists of multicellular, autotrophic eukaryotes with chlorophyll and cellulosic cell walls, including plants like algae, mosses, and flowering plants. They exhibit alternation of generations.
4. Kingdom Fungi: Includes eukaryotic, heterotrophic organisms with chitinous cell walls, such as mushrooms and yeasts, which perform extracellular digestion and reproduce both sexually and asexually.
5. Kingdom Animalia: Comprises multicellular, heterotrophic eukaryotes with no cell walls, adapted for holozoic nutrition and capable of locomotion, such as insects, fish, and mammals.

This system reflects phylogenetic relationships and helps understand evolutionary connections among organisms.

Can you recall? Page No. 7

Which characters of organisms are visible characters?

Answer: Visible characters of organisms include easily observable traits such as habit (growth form), habitat, color, and morphological features like shape, size, and structure. These are often used in artificial classification systems, such as Linnaeus’ system, which focuses on non-evolutionary traits. Name the recent approaches in taxonomy. Recent approaches in taxonomy include:

• Chemotaxonomy: Classification based on similarities and differences in chemical constituents, such as cell wall composition (e.g., peptidoglycan in bacteria, chitin in fungi).
• Numerical Taxonomy: Uses quantification of characters and algorithms (e.g., cluster analysis) to create objective classifications, proposed by R. Sokal and P. Sneath in 1963.
• DNA Barcoding: A method to identify species using a short DNA sequence from a tissue sample, aiding in species identification and understanding ecological and evolutionary relationships.

What is DNA barcoding?

Answer: DNA barcoding is a method for identifying species using a short, standardized DNA sequence from a tiny tissue sample. It involves two steps: (a) collecting DNA barcode data of known species and (b) matching the barcode sequence of an unknown sample against a barcode library. Applications include protecting endangered species, pest control, identifying disease vectors, authenticating natural products, and identifying medicinal plants.

What is evolution?

Answer: Evolution is the process of constant struggle and progress among living beings, leading to the appearance of more complex and diverse life forms from simpler ancestors. It involves changes in organisms over generations, driven by mechanisms like natural selection, resulting in adaptations and the formation of new species.

Enlist uses of taxonomy.

Answer: Uses of taxonomy include:

• Organizing and classifying organisms into hierarchical categories for easy identification and study.
• Understanding evolutionary and phylogenetic relationships among organisms.
• Facilitating communication through standardized scientific names (binomial nomenclature).
• Aiding in biodiversity conservation by identifying and protecting species.
• Supporting applications in agriculture, medicine, and ecology, such as identifying pests, medicinal plants, or disease vectors.

Can you recall? Page No. 9

1. Why horse and ass are considered to be two different species or animals?

Answer:
1. Species is a group of organisms that can interbreed under natural conditions to produce fertile offsprings.
2. Horse and ass (donkey) are considered to be two different species or animals, because they cannot interbreed under natural condition to produce fertile offspring.

2. Make a flow chart showing taxonomic hierarchy.

Answer:

Can you tell? Page No. 11

1. What are salient features of Monera?

Answer:

• Unicellular, prokaryotic organisms with no defined nucleus (nucleoid instead).
• Cell wall made of peptidoglycan; DNA is circular, with plasmids often present.
• Lack membrane-bound organelles; have 70S ribosomes.
• Reproduce asexually via binary fission or budding; some use conjugation.
• Nutritionally diverse: photoautotrophs, chemoautotrophs, or heterotrophs.

2. What will be the shape of a bacillus and coccus type of bacteria?

Answer:

• Bacillus: Rod-shaped.
• Coccus: Spherical.

3. Write a note on useful and harmful bacteria.

Answer:

• Useful Bacteria: Nitrogen-fixing bacteria (e.g., Azotobacter) enrich soil; Lactobacilli aid in milk curdling; Streptomyces produce antibiotics; some decompose organic matter or degrade oil.
• Harmful Bacteria: Pathogens like those causing typhoid, cholera, tuberculosis, and tetanus harm humans; some affect plants and animals.

Can you tell? Page No. 14

1. Write a note on economic importance of fungi.

Answer: Fungi have significant economic importance. Mushrooms are consumed as food, while yeast (Saccharomyces) is used in baking and brewing. Penicillium produces antibiotics, aiding medicine. However, some fungi, like Puccinia, cause plant diseases, leading to agricultural losses. Lichens, formed by fungi and algae, indicate pollution levels and contribute to soil formation.

2. Why are fungi considered as heterotrophic organisms?

Answer: Fungi are considered heterotrophic because they cannot synthesize their own food using photosynthesis due to the absence of chlorophyll. They rely on external organic material, obtaining nutrients through extracellular digestion and absorption, either as saprophytes, parasites, or symbionts.

3. What are coenocytic hyphae?

Answer: Coenocytic hyphae are non-septate, multinucleate filaments found in some fungi. They lack cross-walls, allowing multiple nuclei and cytoplasm to share a continuous structure, as seen in species like Mucor and Rhizopus.

4. Classify fungi into their types.

Answer: Fungi are classified into:

• Phycomycetes: Aseptate, coenocytic hyphae; e.g., Mucor, Rhizopus, Albugo.
• Ascomycetes: Septate hyphae, sac fungi; e.g., Aspergillus, Penicillium, Neurospora.
• Basidiomycetes: Septate hyphae, club fungi; e.g., Agaricus, Puccinia, Ustilago.
• Deuteromycetes: Imperfect fungi, reproduce asexually; e.g., Alternaria, Colletotrichum.

Can you tell? Page No. 14

1. Differentiate between Plantae and Animalia.

Answer:

• Plantae: Multicellular, autotrophic (with chlorophyll), have cellulosic cell walls, exhibit alternation of generations, and show indeterminate growth.
• Animalia: Multicellular, heterotrophic (holozoic nutrition), lack cell walls and chlorophyll, have determinate growth, and are capable of locomotion.

2. How are fungi different from plants?

Answer: Fungi differ from plants as they are heterotrophic (lacking chlorophyll for photosynthesis), have chitinous cell walls (not cellulosic), perform extracellular digestion, and lack alternation of generations, unlike plants which are autotrophic and have cellulosic walls.

3. Have you seen any diseased plant in your farm?

Answer: I do not have personal observations or access to real-time data about your farm. However, the document mentions fungi like Puccinia causing plant diseases, which you might observe as rusts on leaves or stems. Check your plants for such signs.

Can you tell? Page No. 15

1. Why are viruses called infectious nucleoproteins?

Answer: Viruses are called infectious nucleoproteins because they consist of a nucleic acid (DNA or RNA) core surrounded by a protein coat (capsid), and they can infect host cells, taking over their cellular machinery to replicate and cause disease.

2. Describe genetic material in plant and animal viruses as well as in bacteriophages.

Answer:

• Plant Viruses: Typically have single-stranded RNA (e.g., Tobacco Mosaic Virus), though some may have double-stranded RNA or DNA.
• Animal Viruses: Contain either single-stranded RNA (e.g., influenza virus) or double-stranded DNA (e.g., herpes virus), but never both together.
• Bacteriophages: Usually have double-stranded DNA, though some may have single-stranded DNA or RNA.

3. Differentiate between viruses and viroids.

Answer:

• Viruses: Infectious nucleoproteins with a protein coat (capsid) around DNA or RNA; they require a host to replicate and cause diseases like mosaic formation in plants or flu in animals.
• Viroids: Smaller, infectious single-stranded RNA without a protein coat; they cause diseases like potato spindle tuber disease by interfering with host cell processes.