Short & Long Question Answers with Solution: Biological Classification | Biology Class 11 - NEET PDF Download

Short Answer Type Questions

Q1. Why is Neurospora an important genetic tool?
Ans:  Neurospora can thrive readily in laboratory settings when supplied with organic salts, carbohydrates, and vitamins. By subjecting Neurospora cells to X-ray treatments, mutations can be effortlessly induced, and the process of meiotic division becomes readily observable. 

Q2. What is diatomaceous earth? Why are diatoms referred to as ‘pearls of the ocean’?
Ans: For billions of years, there has been a continuous buildup of substantial diatom deposits, creating a silica layer spanning hundreds of meters. Diatoms serve as the primary oceanic producers, generating nourishment not only for themselves but also for various other marine organisms. Their physical structure consists of a siliceous shell referred to as a frustule.

Q3. What is the role of fungi our daily lives?
Ans: Fungi play various important roles in our everyday lives, including:

• Some fungi, such as Agaricus compestris, are abundant sources of nutrients and serve as food.
• Saprophytic fungi break down and transform complex organic matter into simpler compounds, which plants can then absorb as nutrients.
• Certain fungi, like Mucor and Absidia, have the ability to bind soil particles together, improving soil quality for cultivation.
• Fungi can provide natural resistance against pests in certain contexts.
• Fungi are employed in the production of alcohol and yeast thanks to their fermentation capabilities, exemplified by Saccharomyces.

 
Q4. State important uses of (a) heterotrophic bacteria and (b) archaebacteria.
Ans: Key applications of Heterotrophic bacteria include their role as decomposers, contributing to the creation of organic manure known as humus. Additionally, they encompass bacteria like Rhizobium, which aids in the nitrogen fixation process in plants, and Lactobacillus, which plays a crucial role in curd formation.

As for Archaebacteria, they find significant utility in mineral bleaching and serve as polymerase enzymes in recombinant DNA technology. A notable example of Archaebacteria is Methanobacterium, which contributes to methane production, a valuable fuel source.

Q5. Please give a brief account of viruses concerning their structure and nature of genetic material. Also, name four common viral diseases.
Ans: A virus is a contagious entity that becomes active within the host organism. Its genetic material is not fixed; it can be either RNA or DNA but never both simultaneously. These viral particles are enveloped by a protein coat and exhibit a crystalline structure. Plant-infecting viruses typically carry single-stranded RNA as their genetic material, while those infecting animals may contain double-stranded RNA or DNA as their genetic makeup. Common viral diseases include AIDS, Herpes, Rabies, and Influenza. 

Q6. What do you understand by ‘phycobiont’ and ‘mycobiont’?
Ans: The algal part of lichens is referred to as the phycobiont, and the fungal part is known as the mycobiont. These two organisms engage in a mutually beneficial symbiotic relationship. The algae produce nourishment for the fungi, while the fungi, in exchange, offer protection and absorb nutrients from the soil.

Q7. Find out what the terms ‘algal bloom’ and ‘red tides’ signify.
Ans: An algal bloom refers to the proliferation of algae and other phytoplankton at the surface of water bodies. These blooms hinder the penetration of sunlight into the deeper layers of the water, leading to reduced light availability. The surface algae compete for dissolved oxygen, which can result in the mortality of aquatic organisms. The primary cause of algal blooms is often an increase in the nitrate levels within water bodies.

Red tides, on the other hand, occur when there is a sudden elevation in the levels of photosynthetic accessory pigments. This spike in accessory pigments triggers a rapid expansion of phytoplankton populations, which produce toxins that can be detrimental to the aquatic flora and fauna within the water bodies.

Q8. What are the Insectivorous plants?
Ans: Plants that obtain their nutrients by capturing and consuming insects, arthropods, or protozoans are commonly referred to as insectivorous plants or carnivorous plants. Acidic bogs provide some of the most notable examples of these insectivorous plants.

Q9. Plants are autotrophic. Can you think of some heterotrophic plants?
Ans: Plants can be categorized into two primary types based on their nutritional mode: autotrophic and heterotrophic. Autotrophic plants are capable of producing their own food and energy, while heterotrophic plants rely on insects and other plants as a source of nourishment and energy. Examples like Drosera and Nepenthes fall into the category of heterotrophic plants because they consume insects to obtain nitrogen, which is subsequently utilized in the process of photosynthesis.

Q10. Name a few plants that are partially heterotrophic.
Ans: Below are some examples of partial heterotrophs:

• Loranthus and Viscum are partial stem parasites characterized by their leathery leaves. They obtain sap from the xylem tissue of various fruit and forest trees through the use of haustoria.
• Insectivorous plants capture insects and break them down with proteolytic enzymes produced by the leaf epidermis.

Long Answer Type Questions

Q1. Discuss how the classification system has undergone several changes over a period of  time. 
Ans:  Aristotle initially categorized plants into herbs, shrubs, and trees, while he also attempted to classify animals into two groups based on the presence or absence of red blood cells. However, this classification proved inadequate.

Subsequently, Carolus Linnaeus introduced a two-kingdom classification system, comprising Plantae for plants and Animalia for animals. This system, however, lacked differentiation between eukaryotes, prokaryotes, single-celled, and multicellular organisms, rendering it insufficient.

R.H. Whittaker later developed a more comprehensive classification system of five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia. These kingdoms were categorized based on criteria such as reproductive methods, nutritional modes, cell structure, and overall body organization.

Q2. What are the different groups of fungi?
Ans: Fungi are categorized into four primary types of classification, which can be broadly described as follows:

• Artificial classification: A prime example of this classification is "Imperfect fungi." In this system, once divided, they exhibit no relationship to their sexual stage, evolutionary history, or origin. This classification was proposed by Linnaeus.
• Natural classification: Proposed by George Bentham and Joseph Dalton Hooker, this classification is based on the inherent affinities, including external and internal characteristics of organisms.
• Phylogenetic classification: This higher-level classification of fungi encompasses 195 taxa and involves diverse categories based on phylogenetic analysis.
• Phenotypic classification: This classification, primarily used for research and study purposes, involves the separation and examination of cultivated fungi strains.

Q3. Give an account of the asexual reproduction by spores in algae.
Ans: Asexual reproduction in algae encompasses various types of spore formation:

• Zoospores: These are mobile, unencased spores equipped with two, four, or multiple flagella. For example, Chlamydomonas produces biflagellate zoospores, Ulothrix produces quadriflagellate zoospores, and Oedogonium generates multiflagellate zoospores.
• Aplanospores: Non-motile spores that can form individually or through protoplast division to yield several aplanospores. They typically develop within sporangia during unfavorable conditions. For instance, Microspora is an example.
• Tetraspores: Produced by diploid algae, these are a specialized type of haploid aplanospore formed within tetrasporangia.
• Akinetes: These are robust, spore-like structures containing ample food reserves, enabling them to endure adverse conditions.
• Exospores: These spores are separated from the parent cell through septum formation, usually near the mother cell's end. Chamaesiphon is an example of an organism that produces exospores.
• Endospores: Formed as a result of the mother protoplast dividing and generating these spores, they are also referred to as conidia or gonidia. Endospores are produced as a survival strategy during unfavorable conditions. Dermocarpa is an example of an organism that forms endospores.

Q4. What is Taxonomy?
Ans: The field of science concerned with naming, identifying, describing, and categorizing all living organisms, encompassing animals, birds, insects, microbes, and plants, is known as Taxonomy. Within taxonomy, classification primarily relies on various factors such as characterization, behavior, identification, variations, genetics, and more.
Living organisms are systematically organized into various hierarchical levels, which include Kingdom, Phylum, Class, Order, Family, Genus, and Species.

Q5. Give a detailed account of the classes of Kingdom Fungi under the following:
(i) Mode of nutrition
(ii) Mode of reproduction
Ans: 
(i) Nutritional Method – This pertains to the manner in which organisms obtain their sustenance and is primarily categorized into autotrophic and heterotrophic modes. In the fungal kingdom, four main classes exist. Phycomycetes are obligatory parasites that thrive on decaying organic matter. Ascomycetes are sporophytic and also play a role in decomposition. Basidiomycetes grow on logs or tree stumps and are responsible for diseases like plant rust. Deuteromycetes encompass a group of fungi that include sporophytic species and parasites.
(ii) Reproductive Mechanisms – Reproduction involves the processes by which organisms propagate and proliferate. In the case of Phycomycetes fungi, reproduction occurs via zoospores produced within sporangia. Ascomycetes utilize ascospores located within sac-like structures known as ascocarps for reproduction. Basidiomycetes employ fragmentation as their reproductive method, while Deuteromycetes rely on asexual spores referred to as conidia for reproduction.

Q6.

• What are heterocysts?
• Write a note on dikaryophase.
• Differentiate the Protista and Fungi in terms of their nutrition. 

Ans: Heterocysts are colorless cells that belong to the cyanobacteria group. These specialized cells are responsible for nitrogen fixation and house the enzyme nitrogenase. For example, Nostoc and Anabaena are known for this feature.

The term "dikaryophase" is also referred to as the "dikaryotic phase." Cells in this phase do not have a diploid configuration but instead contain two nuclei. This phase is observed in fungi groups like Basidiomycetes and Ascomycetes, serving as an intermediate stage in the fungal life cycle.

Protists are unicellular eukaryotic organisms that reproduce sexually through gametes. The primary divisions within the Protista kingdom include algae, molds, and protozoans. Many protists are autotrophic, meaning they can produce their own food, while some are heterotrophic. Conversely, fungi possess chitin cell walls and are heterotrophic, relying on other organisms for their survival.

Q7. Explain sexual reproduction in bacteria. 
Ans: There are three main steps for bacterial reproduction. The steps are as follows – 

• Conjugation was originally discovered by Lederberg and Tatum. In this process, the male cell, also known as the donor cell, transfers its DNA to the recipient cell.
• Transformation, as elucidated by Griffith, involves the death of the donor cell, releasing its DNA content into the surrounding environment. This released DNA is then incorporated into active cells. The new cell that takes up the donor cell's DNA is termed the recipient cell, which inherits all the characteristics of the donor cell. The recipient cell is also referred to as a recombinant cell.
• Transduction, discovered by Zinder and Lederberg, entails the transfer of donor genes into the recipient cell facilitated by a virus.

Q8. How many types of bacteria are there?
Ans:  Bacteria can be found in pairs, chains, clusters, or as single cells. They exhibit various shapes and are categorized according to their morphology, Gram stain characteristics, and oxygen requirements.

In terms of their shapes, bacteria are grouped into five categories:

• Bacilli, which are rod-shaped bacteria.
• Spirilla, characterized by their spiral shape.
• Vibrios, which are comma-shaped bacteria.
• Cocci, displaying a spherical shape.
• Spirochaetes, with a corkscrew-like appearance.

Regarding their cell wall composition, bacteria fall into two main groups:

• Gram-positive bacteria.
• Gram-negative bacteria.

Bacteria can also be classified based on their respiration mode or oxygen demands into two categories:

• Aerobic bacteria or aerobes.
• Anaerobic bacteria or anaerobes.

Lastly, bacteria can be categorized by their nutritional mode into two groups:

• Autotrophic bacteria.
• Heterotrophic bacteria.

Q9. How many types of bacteria are there?
Ans: Bacteria, microscopic single-cell organisms, are ubiquitous in the environment, inhabiting surfaces and the air, although they remain invisible to the naked eye. They are categorized according to their physical characteristics, which include rod-like, spiral-shaped, comma-shaped, and spherical shapes.

The rod-shaped bacteria are referred to as bacilli.

Spiral-shaped bacteria are identified as spirilla.

Comma-shaped bacteria are known as vibrios, and spherical-shaped bacteria are called cocci.

Moreover, they can be classified based on their respiratory requirements into aerobic and anaerobic types. Aerobic bacteria rely on oxygen for their growth and development, whereas anaerobic bacteria can thrive in the absence of oxygen.

Q10. What are the characteristic features of euglenoids?
Ans: The characteristic features of euglenoids are:

• They are unicellular protists, commonly found in freshwater.
• The cell membrane is rich in proteins and is known as a pellicle.
• Two flagella are present on the anterior end of the body.
• They possess a small light-sensitive eyespot.
• They are autotrophic because of the presence of photosynthetic pigment chlorophyll. However, in the absence of light, they behave as heterotrophs.
• They are known as the connecting-link between plants and animals because they possess features common to both plants and animals.