Q1. State two economically important uses of heterotrophic bacteria.

A1: Heterotrophic bacteria have many economic uses:

  1. Dairy Industry: They are used for making curd from milk (e.g., Lactobacillus).
  2. Antibiotic Production: Many important antibiotics (like Streptomycin) are produced from bacteria.
  3. (Additional) Nitrogen Fixation: Some bacteria (like Rhizobium) live in the roots of legumes and fix atmospheric nitrogen, enhancing soil fertility.

Q2. State two economically important uses of archaebacteria.

A2:

  1. Biogas Production: Methanogens (a type of archaebacteria) are found in the guts of ruminants and in sewage treatment. They are essential for the production of methane (biogas) from organic waste.
  2. Biotechnology: Enzymes from thermoacidophiles (which can withstand high temperatures) are used in biotechnological processes like the Polymerase Chain Reaction (PCR).

Q3. What are the characteristics of prokaryotic cells?

A3: The key characteristics of prokaryotic cells (which make up Kingdom Monera) are:

  1. No well-defined nucleus: The genetic material (a single circular chromosome) is concentrated in a region called the nucleoid, not enclosed by a nuclear membrane.
  2. No membrane-bound organelles: They lack organelles like mitochondria, chloroplasts, endoplasmic reticulum, and Golgi bodies.
  3. Cell Wall: Most prokaryotes have a cell wall (e.g., made of peptidoglycan in eubacteria), though some (like Mycoplasma) do not.
  4. Ribosomes: They have 70S ribosomes for protein synthesis.

Q4. What is the nature of cell walls in diatoms?

A4: In diatoms, the cell walls form two thin, overlapping shells that fit together like a soap box. These walls are embedded with silica, which makes them indestructible and resistant to decay.

Q5. Find out what do the terms 'algal bloom' and 'red-tides' signify.

A5:

  • 'Algal bloom' refers to the rapid increase in the population of algae (often cyanobacteria) in aquatic ecosystems, usually due to nutrient enrichment (eutrophication). These blooms can deplete oxygen and be toxic.
  • 'Red-tides' specifically refer to the rapid multiplication of certain red dinoflagellates (like Gonyaulax). These blooms make the sea appear red and can release toxins that are fatal to fish and other marine life.

Q6. What are the characteristic features of Euglenoids?

A6: The key characteristics of Euglenoids are:

  1. They are freshwater organisms found in stagnant water.
  2. They lack a cell wall but have a flexible, protein-rich layer called a pellicle.
  3. They possess two flagella (one long, one short).
  4. They exhibit a mixotrophic mode of nutrition: they are photosynthetic in light but become heterotrophic in the dark.
  5. Their photosynthetic pigments are identical to those in higher plants.

Q7. Describe briefly the four major groups of Protozoa.

A7:

  1. Amoeboid Protozoans: Move and capture prey using pseudopodia (false feet). Example: Amoeba, Entamoeba (parasite).
  2. Flagellated Protozoans: Have flagella for movement. Example: Trypanosoma (causes sleeping sickness).
  3. Ciliated Protozoans: Have thousands of cilia for locomotion and to move food into their gullet. Example: Paramoecium.
  4. Sporozoans: Are non-motile parasites that have an infectious, spore-like stage in their life cycle. Example: Plasmodium (causes malaria).

Q8. Discuss how classification systems have undergone several changes over a period of time.

A8: Classification systems have evolved from being based on simple morphological characters (Aristotle) to the two-kingdom system (Linnaeus: Plantae and Animalia). This was found to be inadequate because it didn't account for prokaryotes vs. eukaryotes, unicellular vs. multicellular organisms, or photosynthetic vs. non-photosynthetic organisms (like fungi). R.H. Whittaker's (1969) Five Kingdom classification, based on cell structure, body organisation, mode of nutrition, reproduction, and phylogenetic relationships, became widely accepted. Modern systems often use genetic data to refine these relationships further.

Q9. How are viroids different from viruses?

A9: Viroids differ from viruses in two main ways:

  1. Structure: Viroids consist only of a free, low-molecular-weight RNA molecule. Viruses are nucleoproteins, with genetic material (DNA or RNA) enclosed in a protein coat (capsid).
  2. Protein Coat: Viroids lack a protein coat, whereas viruses always have one.

Q10. Plants are autotrophic. Can you think of some plants that are heterotrophic?

A10: Yes, while the vast majority of plants are autotrophic, some are heterotrophic. These are generally of two types:

  1. Parasitic Plants: These plants derive their nutrition from other living plants (the host). A common example is Cuscuta (dodder), a non-photosynthetic plant that twines around a host plant.
  2. Insectivorous Plants: These plants are partially heterotrophic. They grow in nutrient-poor soil (especially nitrogen-deficient) and supplement their nutrition by trapping and digesting insects. Examples include the Pitcher plant, Venus fly trap, and Bladderwort.

Q11. What do the terms 'phycobiont' and 'mycobiont' signify?

A11: These terms refer to the two components of a lichen:

  • Phycobiont: This is the algal partner. It is autotrophic and provides food for the fungus.
  • Mycobiont: This is the fungal partner. It is heterotrophic and provides shelter, water, and mineral absorption.

Q12. Give a comparative account of the classes of Kingdom Fungi based on mycelium type and mode of nutrition.

A12:

  • Phycomycetes: Mycelium is aseptate and coenocytic. Nutrition is saprophytic or parasitic.
  • Ascomycetes: Mycelium is branched and septate. Nutrition is saprophytic, parasitic, or coprophilous (dung-growing).
  • Basidiomycetes: Mycelium is branched and septate. Nutrition is saprophytic or parasitic.
  • Deuteromycetes: Mycelium is branched and septate. Nutrition is primarily saprophytic/decomposers, or parasitic.

Q13. What are the characteristic features of Euglenoids?

A13: The key characteristics are:

  1. They are freshwater organisms found in stagnant water.
  2. They lack a cell wall, having a flexible, protein-rich layer called a pellicle instead.
  3. They possess two flagella (one long, one short).
  4. They exhibit a mixotrophic mode of nutrition (photosynthetic in light, heterotrophic in dark).

Q14. Give a brief account of viruses with respect to their structure and nature of genetic material.

A14:

  • Structure: A virus is a non-cellular nucleoprotein. It consists of a protein coat, called a capsid, which is made of small subunits called capsomeres. This capsid encloses the genetic material.
  • Genetic Material: The genetic material is either DNA or RNA, but never both. It can be single-stranded or double-stranded. For example, plant-infecting viruses often have single-stranded RNA, while bacteriophages (viruses that infect bacteria) usually have double-stranded DNA.

Q15. Are viruses living or non-living?

A15: Viruses exist at the boundary of living and non-living.

  • Non-living characteristics: They are acellular, have an inert crystalline structure outside a host, and cannot perform metabolic functions or reproduce on their own.
  • Living characteristics: Once they infect a host cell, they take over the host's machinery to replicate their genetic material and synthesize proteins, effectively 'reproducing'. Because of this dual nature, they are not placed in any of the five kingdoms and are best described as infectious nucleoprotein particles.

Q16. What is a 'dikaryon'? In which fungal classes is this stage observed?

A16: A dikaryon is a condition in a fungal mycelium where a single cell contains two haploid nuclei (n + n). This intervening stage occurs after plasmogamy but before karyogamy. This dikaryotic phase is characteristic of the fungal classes Ascomycetes and Basidiomycetes.

Q17. What are the main differences between the five kingdoms?

A17:

  • Monera: Prokaryotic, unicellular.
  • Protista: Eukaryotic, unicellular.
  • Fungi: Eukaryotic, multicellular (mostly), heterotrophic (absorptive), cell wall of chitin.
  • Plantae: Eukaryotic, multicellular, autotrophic (photosynthetic), cell wall of cellulose.
  • Animalia: Eukaryotic, multicellular, heterotrophic (ingestive), no cell wall.

Q18. What are prions and how do they differ from all other infectious agents?

A18: Prions are infectious agents that consist only of abnormally folded proteins. They are unique because they lack any genetic material (DNA or RNA). They cause fatal neurological diseases like Mad Cow Disease (BSE) in cattle and Creutzfeldt-Jakob Disease (CJD) in humans.

Q19. What are heterocysts and what is their function?

A19: Heterocysts are specialized, thick-walled, non-photosynthetic cells found in certain filamentous cyanobacteria (like Nostoc and Anabaena). Their primary function is to perform atmospheric nitrogen fixation by protecting the nitrogenase enzyme from oxygen.

Q20. What are Mycoplasma? How are they unique?

A20: Mycoplasma are the smallest known living cells and belong to Kingdom Monera. They are unique for two main reasons:

  1. They completely lack a cell wall, which makes them resistant to antibiotics like penicillin that target cell wall synthesis.
  2. They can survive without oxygen.

Q21. What is diatomaceous earth and why is it useful?

A21: Diatomaceous earth is a gritty, soil-like substance formed from the accumulation of the indestructible silica cell walls of diatoms over billions of years. Due to its porous and abrasive nature, it is used commercially in polishing, filtration of oils and syrups, and as an absorbent.

Q22. What is the sexual reproduction sequence in Ascomycetes and Basidiomycetes, and what is a dikaryon?

A22: In both classes, sexual reproduction involves plasmogamy (fusion of cytoplasm) followed by a delay, then karyogamy (fusion of nuclei), and finally meiosis. The delay between plasmogamy and karyogamy results in an intervening dikaryotic stage (n+n), where a single cell contains two haploid nuclei. This is a key feature of these two fungal classes.

Q23. Why are Deuteromycetes known as 'imperfect fungi'?

A23: They are called 'imperfect fungi' because only their asexual or vegetative reproductive phases are known. The sexual (or 'perfect') stage has not been observed. If and when the sexual stage of a species in this class is discovered, it is reclassified and moved into either Ascomycetes or Basidiomycetes, depending on its characteristics.

Q24. What is the main difference between the cell wall of plants and fungi?

A24: The primary chemical component is different. The cell wall of organisms in Kingdom Plantae is made mainly of cellulose. The cell wall of organisms in Kingdom Fungi is made of chitin and polysaccharides.

Q25. How is the mode of nutrition in Kingdom Animalia different from Kingdom Fungi?

A25: Both kingdoms are heterotrophic, but their mode of nutrition differs.

  • Animalia: Have a holozoic mode of nutrition, which involves the ingestion of food into an internal cavity for digestion.
  • Fungi: Have a saprophytic or parasitic mode of nutrition, which involves absorption. They secrete digestive enzymes onto their food source and absorb the resulting soluble organic molecules.

Q26. What is meant by 'alternation of generations' in plants?

A26: Alternation of generations refers to the life cycle of plants that includes two distinct multicellular phases.

  1. The diploid (2n) sporophyte generation, which produces haploid (n) spores through meiosis.
  2. The haploid (n) gametophyte generation, which produces haploid (n) gametes through mitosis. These two generations alternate with each other (spores grow into gametophytes, and the zygote from gamete fusion grows into a sporophyte).

Q27 What are the key food reserve materials in Kingdom Plantae and Kingdom Animalia?

A27:

  • Kingdom Plantae: The primary food reserve is starch.
  • Kingdom Animalia: The primary food reserves are glycogen and fat.

Q28. Name four common viral diseases.

A4: Four common viral diseases in humans are:

  1. Influenza (Flu)
  2. AIDS (Acquired Immuno Deficiency Syndrome)
  3. Herpes
  4. Smallpox (Others include mumps, measles, and the common cold).

Q29. What is biological classification and why is it necessary?

A29. Biological classification is the scientific arrangement of organisms into groups based on similarities and differences. It is necessary for studying the vast diversity of organisms, understanding evolutionary relationships, and identifying new species.

Q30. Distinguish between prokaryotes and eukaryotes.

A30. Prokaryotes lack a true nucleus and membrane-bound organelles (e.g., Bacteria), whereas eukaryotes have a well-defined nucleus and organelles (e.g., Protists).