Get the Class 11 Biology Chapter 2 Biological Classification Solutions (Exercise Questions)
The detailed answers to this chapter are given below. These answers are prepared by subject experts that follows the NCERT guidelines closely. Students can refer to the Class 11 Biology Chapter 2 Biological Classification question answer to gain clarity.
Q1. Discuss how classification systems have undergone several changes over a period of time.
Answer:
How we classify living things has shifted as we understand more. Aristotle initially classified plants according to appearances and animals according to blood, but that wasn't effective either. Linnaeus created a two-kingdom system, but it wasn't effective either. Thus, scientists developed a 5-kingdom system, which is implemented nowadays.
Q2. State two economically important uses of: (a) heterotrophic bacteria, (b) archaebacteria
Answer:
(a) In what way are heterotrophic bacteria beneficial?
They decompose dead matter, which is good for the soil.
They provide plants with nitrogen.
They are employed in producing curd (yogurt).
(b) In what way are archaebacteria useful?
They produce gobar gas (biogas), which is employed as fuel.
They assist in obtaining minerals from rocks.
They produce an enzyme that is used in DNA technology.
Q3. What is the nature of cell walls in diatoms?
Answer:
Diatoms are single-celled algae with unique and intricate cell walls. The cell walls, known as frustules, are made of silica (silicon dioxide), the same material from which glass is made. A frustule is made up of two wrapped-around halves that look like a petri dish or soapbox, which are very similar to one another. This creates a protective layer and support framework for diatoms. The silica in the cell walls is extremely hard and resistant to rot, so the frustules will survive long after the diatom has died. Millions of years later, the frustules accumulate on the ocean floor and form huge diatomaceous earth deposits. Diatomaceous earth is utilized for several purposes, including as a filtering medium, an abrasive in toothpaste, and an insecticide. Their optical properties are also studied in nanotechnology for the intricate patterns on diatom cell walls.
Q4. Find out what the terms algal bloom and red tides signify.
Answer:
Algal Bloom: A rapid growth of algae in a water body, giving color to the water. Algal blooms will reduce the concentration of oxygen in water, causing fish and other aquatic organisms to die.
Red Tide: When a type of dinoflagellate (Gonyaulax) explodes, giving a reddening of seawater. They emit poisons capable of killing fish.
Q5. How are viroids different from viruses?
Answer:
Viroids and viruses are both causative agents, but they have a wide variation in structure and complexity. Viruses are intricate particles with a nucleic acid genome (DNA or RNA) covered by a protein shell referred to as a capsid. Viruses may also contain an outer lipid-protein envelope. Viruses infect a variety of organisms, ranging from bacteria and plants to animals. Viroids, however, are far more basic in composition. They have only a minute, ring-shaped RNA molecule with no protein cover. Due to their basic structure, viroids are much smaller than viruses. Viroids are found to infect mostly plants and cause different diseases that can influence crop production and agricultural output. The absence of a protein coat in viroids increases their resistance to degradation and enables them to replicate directly in the host cell.
Q6. Describe briefly the four major groups of Protozoa.
Answer:
Protozoa are divided into four categories based on the method of movement:
Amoeboid Protozoa – They occur in water and moist soil and move and consume food using pseudopodia (false feet). Example: Amoeba.
Flagellated Protozoa – They have whip-like bodies called flagella to move. Some are parasites, and others exist freely. Example: Trypanosoma (sleeping sickness).
Ciliated Protozoa – They are moving with extremely short hair-like bodies called cilia and have two nuclei. Example: Paramecium.
Sporozoa – They do not have cilia and flagella. They reproduce through spores and are usually parasites. Example: Plasmodium (that causes malaria). Classification of Protozoa is a fundamental chapter of the Biological Classification.
Q7. Plants are autotrophic. Can you think of some plants that are partially heterotrophic?
Answer:
Most plants are autotrophic and nourish themselves by synthesizing food in the process of photosynthesis, but certain plants are partly heterotrophic. The Pitcher Plant (Nepenthes) is green and photosynthetic but survives in nitrogen-free soil. It obtains nitrogen by digesting insects trapped using its pitcher leaves. As it makes its food but also digests insects to obtain nutrients, it is partly heterotrophic. These enchanting plants contribute further information to Plantae in Biological Classification.
Q8. What do the terms phycobiont and mycobiont signify?
Answer:
"Phycobiont" and "mycobiont" are terms used to explain the two components of a lichen. Lichens are an association between fungi and algae.
Phycobiont is the algal partner, which produces food for the lichen by the process of photosynthesis.
Mycobiont is the fungal partner, which gives support and protection, and absorbs water and minerals from the surroundings. These symbiotic associations are an interesting feature of Biological Classification.
Q9. Give a comparative account of the classes of Kingdom Fungi under the following:
(i) Mode of nutrition
(ii) Mode of reproduction
Answer:
A comparative account of the classes of Kingdom Fungi is as follows:
Class | Mode of Nutrition | Mode of Reproduction |
Phycomycetes | Live on decaying matter or as parasites. | Asexual: spores (zoospores or aplanospores). Sexual: gamete fusion (joining of sex cells). |
Ascomycetes | Can be decomposers, parasites, or live on dung. | Asexual: conidia (special spores). Sexual: ascospores (spores formed in a sac-like structure). |
Basidiomycetes | Mostly decomposers with saprotrophic nutrition. | Asexual: rare. Sexual: basidiospores (spores formed on a club-shaped structure). |
Deuteromycetes | Can be saprophytes, decomposers, or parasites. | Asexual: conidia (special spores). Sexual: Not known (this is why they are called "imperfect fungi"). |
Q10. What are the characteristic features of Euglenoids?
Answer:
Euglenoids are unicellular organisms that can behave as both plants and animals (mixotrophic).
They lack a cell wall but possess a soft protein covering known as a pellicle, which provides them with shape and facilitates smooth movement.
They possess chlorophyll and are capable of photosynthesis, but when in the dark, they behave like heterotrophs and obtain food from their environment.
They swim through two flagella (whip-like appendages) at the front of their body.
They possess a light-sensitive "eyespot" to detect sunlight for photosynthesis. All these features qualify them under Protista in Biological Classification.
Q11. Give a brief account of viruses with respect to their structure and the nature of their genetic material. Also, name four common viral diseases.
Answer:
Viruses are small particles that can only multiply within a living cell. They infect animals, plants, and even bacteria.
Nucleic acid: The virus's genetic material, either DNA or RNA. It carries the instructions for producing more viruses.
Capsid: A protein shell that encloses and covers the nucleic acid.
Envelope: Certain viruses have an outer membrane known as an envelope, composed of lipids and proteins.
Enzymes: Certain viruses have special enzymes with them that assist them in their reproduction within the host cell.
Common viral diseases:
Common cold
AIDS
Swine flu
Hepatitis
Q12. Organise a discussion in your class on the topic: Are viruses living or nonliving?
Answer:
Viruses are a mystery since they possess both the properties of living and non-living objects.
They contain genetic material (DNA or RNA).
They are capable of reproduction (but only within a host cell).
They are capable of evolving and mutating over time.
Why viruses may be thought to be non-living:
They are not composed of cells.
They cannot replicate on their own.
They lack their metabolism (they are unable to generate their energy).
They can be crystallized, such as non-living chemicals.
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