CBSE Class 11 Biology Biological Classification Assignments

MCQ Questions Class 11 Biology Biological Classification :->

SYSTEMS OF CLASSIFICATION:
- Earliest Classification was given by Aristotle. Divided plants into herbs, shrubs and trees.
- Animals into those with RBCs and those who do not have it.
- Two kingdom classification: Given by Carolous Linnaeus - Plant kingdom and Animal kingdom.
- Five kingdom classification: By R. H. Whittaker. Monera, Protista, Fungi, Plantae and Animalia are the five kingdoms.

Kingdom Monera:
- Has bacteria as sole members.
- Bacteria can have shapes like: Coccus (spherical), Bacillus (rod-shaped), Vibrio (comma shaped) and Spirillum (spiral shaped).
- Bacteria found almost everywhere and can be Photosynthetic autotrophs, Chemosynthetic autotrophs or Heterotrophs.

Bacteria:
- Archaebacteria:
  - Halophiles (salt-loving)
  - Thermoacidophiles (in hot springs)
  - Methanogens (in marsh and in gut of ruminant animals. Produce methane gas.)
- Eubacteria:
  - Photosynthetic autotrophs like Cyanobacteria. Some like Anabaena have specialised cells called heterocysts for nitrogen fixation.
  - Chemosynthetic autotrophs: Oxidise various inorganic substances like nitrates/nitrites, ammonia and use released energy for their ATP production.
  - Heterotrophic bacteria: Most abundant. Helpful in making curd, production of antibiotics, nitrogen fixation, cause diseases like cholera, typhoid.

Mycoplasma: Completely lack cell wall. Smallest living cells. Can survive without oxygen. Pathogenic in animals and plants.

Kingdom Protista (Comprises of all single-celled eukaryotes):
- Forms a link between plants, animals and fungi.
(i) Chrysophytes (Has diatoms and golden algae):
- Cell walls have silica and cell walls overlap to fit together like a soap box.
- Their accumulation forms 'Diatomaceous Earth'.
- Used in polishing, filtration of oils and syrups.
(ii) Dinoflagellates: - Marine, photosynthetic, cell wall has cellulose.
- Two flagella - one longitudinal and other transversely in a furrow between wall plates.
- Example: Gonyaulax multiplies rapidly, make sea appear red (red tides) and produce toxins to kill marine animals.
(iii) Euglenoids: - Have protein rich layer 'pellicle' which makes body flexible.
- Photosynthetic in presence of sunlight but become heterotrophs if they do not get sunlight.
- Example: Euglena
(iv) Slime Moulds: - Saprophytic protists
- Form aggregates to form plasmodium, grows on decaying twigs and leaves.
- Spores have true walls which are extremely resistant and survive for many years.
(v) Protozoans:
  - Amoeboid: Catch prey using pseudopodia, e.g., Amoeba.
  - Flagellated: Have one or more flagella. Cause disease like sickness e.g., Trypanosoma.
  - Ciliated: Have cilia to move food into gullet and help in locomotion. e.g., Paramecium.
  - Sporozoans: Have infective spore like stage in life cycle, e.g., Plasmodium which causes Malaria.

KINGDOM FUNGI:
- Hyphae which have multinucleate cytoplasm are called coenocytic hyphae
- Cell wall of chitin and polysaccharides
- Grow in warm and humid places
- Saprophytic, parasitic, symbiotic (Lichen)
- e.g., Puccinia (rust causing), Penicillium, Yeast is a unicellular fungus.

CLASSES OF FUNGI:
(i) Phycomycetes:
- grow on decaying wood
- Mycelium aseptate
- Spores produced endogenously
- Asexual reproduction by Zoospores or Aplanospores
- Zygospores are formed by the fusion of gametes.
- e.g., Rhizopus, Albugo.
(ii) Ascomycetes:
- Also known as 'sac fungi'
- Mycelium branched and septate
- Spores: Asexual spores are called conidia produced exogenously on the conidiophores. Sexual spores are called ascospores produced endogenously in ascus, produced inside fruiting body called Ascocarp.
- e.g., Aspergillus, Neurospora.
(iii) Basidiomycetes:
- Mycelium septate.
- Generally asexual spores are not found.
- Vegetative reproduction by fragmentation.
- Sexual reproduction by fusion of vegetative or somatic cells to form basidium produced in basidiocarp.
- Basidium produces four basidiospores after meiosis.
- e.g., Agaricus, Ustilago.
(iv) Deuteromycetes:
- Called as 'Fungi Imperfecti' as sexual form (perfect stage) is not known for them.
- Once sexual form is discovered the member is moved to Ascomycetes or Basidiomycetes.
- Are saprophytic, parasitic or decomposers.
- e.g., Alternaria, Colletotrichum.

Viruses:
- They did not find a place in classification. Take over the machinery of host cell on entering it and become living but as such they have inert crystalline structure appear non-living. So, difficult to call them living or non-living.
- Pasteur gave the term 'Virus' i.e., poisonous fluid.
- D. J. Ivanowsky found out that certain microbes caused Tobacco Mosaic Disease in tobacco plant.
- M. W. Beijerinck called fluid as 'Contagium vivum fluidum' as extracts of infected plants of tobacco could cause infection in healthy plants.
- W. M. Stanely showed viruses could be crystallised to form crystals of protein which are inert outside their specific host.

Structure of Virus:
- It is a nucleoprotein made up of protein coat called Capsid. Capsid is made up of capsomeres arranged in helical or polygeometric forms. Have either DNA or RNA as genetic material which may be single or double stranded.
- Usually plant viruses have single stranded RNA; bacteriophages have double stranded DNA and animal viruses have single or double stranded RNA or double stranded DNA.
- Diseases caused: Mumps, Small pox, AIDS etc.

Viroids:
- Infectious agent, free RNA (lack protein coat)
- RNA has low molecular weight.
- Causes potato spindle tuber disease.
- Discovered by T. O. Diener.

Lichens:
- Symbiotic association between algal component (phycobiont) and fungal component (mycobiont). Algae provides food. Fungi provides shelter and absorb nutrients for alga.
- Good pollution indicators as they do not grow in polluted areas.

QUESTIONS

Very Short Answer Questions (1 mark each)

Question 1. Nostoc and Anabaena have specialised cells called heterocysts. What is the function of these cells?
Answer: Heterocysts are specialised cells in cyanobacteria such as Nostoc and Anabaena that function primarily in nitrogen fixation by providing an anaerobic environment and the necessary enzymes (such as nitrogenase) to convert atmospheric nitrogen into ammonia.
In simple words: Heterocysts help fix atmospheric nitrogen into usable forms for plants.

Exam Tip: Always mention 'nitrogen fixation' and 'anaerobic environment' to secure full marks.

Question 2. Which group comprises of single celled eukaryotes only?
Answer: Kingdom Protista.
In simple words: All single-celled eukaryotes are grouped under Protista.

Exam Tip: Specify the exact Kingdom name clearly.

Question 3. Which organisms are the chief producers in oceans?
Answer: Diatoms (Chrysophytes) are the chief producers in the oceans.
In simple words: Diatoms produce most of the food in marine ecosystems.

Exam Tip: Remember that diatoms belong to Chrysophytes.

Question 4. Name the fungus which causes disease in wheat (i) rust (ii) Smut.
Answer: (i) Rust in wheat is caused by Puccinia.
(ii) Smut in wheat is caused by Ustilago.
In simple words: Puccinia causes rust and Ustilago causes smut in wheat plants.

Exam Tip: Underline scientific names or write them in italics.

Question 5. Which Ascomycetes has been used extensively in biochemical and genetic work?
Answer: Neurospora (a member of Ascomycetes) has been used extensively in biochemical and genetic work (often referred to as the Drosophila of the plant kingdom).
In simple words: Neurospora is widely used in genetics and biochemistry experiments.

Question 6. How are bacteria classified on the basis of their shapes?
Answer: Based on their shapes, bacteria are classified into four major categories:
1. Bacillus (Rod-shaped)
2. Coccus (Spherical)
3. Vibrio (Comma-shaped)
4. Spirillum (Spiral-shaped)
In simple words: Bacteria are grouped into rod, spherical, comma, and spiral shapes.

Exam Tip: List all four shapes with their correct biological terms for full credit.

Question 7. What is the mode of reproduction in bacteria?
Answer: Bacteria primarily reproduce asexually, mainly by binary fission. Under unfavorable conditions, they produce spores. They also reproduce through a sort of sexual reproduction by adopting a primitive type of DNA transfer from one bacterium to another.
In simple words: Bacteria reproduce mainly by splitting (fission), forming spores in bad conditions, or by transferring DNA.

Exam Tip: Mention fission, spore formation, and primitive DNA transfer.

Question 8. Why are red tides caused and why are they harmful?
Answer: Red tides are caused by the rapid multiplication of red dinoflagellates, particularly Gonyaulax, which makes the sea appear red. They are harmful because these organisms release large amounts of toxins that can kill marine animals such as fishes.
In simple words: Rapid growth of certain dinoflagellates turns the water red and releases deadly toxins that kill sea life.

Exam Tip: Cite Gonyaulax as the classic example of dinoflagellates causing red tides.

Question 9. Viruses and viroids differ in structure and the diseases they cause. How?
Answer: Viruses possess genetic material (DNA or RNA) enclosed in a protein coat called a capsid, and they cause diseases like AIDS, smallpox, and mumps. Viroids consist only of a free, low molecular weight single-stranded RNA molecule without a protein coat, and they cause plant diseases such as potato spindle tuber disease.
In simple words: Viruses have a protein coat protecting their genetic material, whereas viroids are just naked RNA strands.

Exam Tip: Highlight the presence of the protein coat in viruses and its absence in viroids.

Question 10. Which class of kingdom fungi has both unicellular as well as multicellular members? When is a fungus called coprophilous?
Answer: Ascomycetes includes both unicellular members (e.g., Yeast) and multicellular members (e.g., Penicillium). A fungus is called coprophilous when it grows on dung (animal excreta).
In simple words: Ascomycetes has single-celled and multi-celled fungi, and dung-loving fungi are termed coprophilous.

Exam Tip: Give Yeast as the unicellular example in Ascomycetes.

Short Answer Questions-I (3 marks each)

Question 11. Who gave five kingdom classification? What was the criteria used for such classification?
Answer: The five-kingdom classification was proposed by R. H. Whittaker in 1969. The main criteria used for this classification include:
1. Cell structure (prokaryotic or eukaryotic)
2. Thallus organization (unicellular or multicellular body design)
3. Mode of nutrition (autotrophic or heterotrophic)
4. Reproduction
5. Phylogenetic relationships (evolutionary history)
In simple words: Whittaker classified organisms into five kingdoms based on cell type, body structure, nutrition, reproduction, and evolution.

Exam Tip: List all five criteria clearly for full marks.

Question 12. What are the steps in the sexual cycle in kingdom fungi?
Answer: The sexual cycle in fungi generally involves the following three steps:
1. Plasmogamy: Fusion of protoplasm between two motile or non-motile gametes.
2. Karyogamy: Fusion of two nuclei.
3. Meiosis: Zygotic meiosis resulting in the formation of haploid spores.
Additionally, in many fungi (like Ascomycetes and Basidiomycetes), an intervening dikaryotic stage (dikaryophase) occurs where two nuclei per cell (\(n + n\)) exist before karyogamy takes place.
In simple words: Fungal sexual reproduction involves protoplasm fusion, nuclear fusion, and meiosis to form spores, often with an intermediate two-nuclei stage.

Exam Tip: Clearly state the terms Plasmogamy, Karyogamy, and Meiosis in sequential order.

Question 13. Some symbiotic organisms are very good pollution indicators and composed of a chlorophyllous and a non-chlorophyllous member. Describe them.
Answer: These organisms are Lichens. They represent a symbiotic association between an algal component (phycobiont) and a fungal component (mycobiont). The algal component is chlorophyllous (prepares food by photosynthesis), and the fungal component is non-chlorophyllous (provides shelter and absorbs mineral nutrients and water for the algae). They are sensitive to sulfur dioxide and thus act as excellent pollution indicators, refusing to grow in polluted areas.
In simple words: Lichens are mutually beneficial partnerships between algae and fungi that die in polluted air.

Exam Tip: Mention the terms phycobiont and mycobiont to score maximum marks.

Long Answer Questions (5 marks each)

Question 14. Some primitive relatives of animals live as predators or parasites and are divided into four major groups. Elaborate.
Answer: These organisms are Protozoans, which are considered primitive relatives of animals. They are heterotrophs and live as predators or parasites. They are divided into four major groups:
1. Amoeboid Protozoans: Live in fresh water, sea water or moist soil. They move and capture their prey by putting out pseudopodia (false feet), e.g., Amoeba. Marine forms have silica shells on their surface.
2. Flagellated Protozoans: Either free-living or parasitic. They have flagella. Parasitic forms cause diseases such as sleeping sickness, e.g., Trypanosoma.
3. Ciliated Protozoans: Aquatic, actively moving organisms using thousands of cilia. They have a cavity (gullet) that opens to the outside of the cell surface, e.g., Paramecium.
4. Sporozoans: Include organisms that have an infectious spore-like stage in their life cycle. The most notorious is Plasmodium (malarial parasite), which causes malaria.
In simple words: Animal-like protists are divided into amoeba-like, flagella-bearing, cilia-bearing, and spore-forming groups.

Exam Tip: Provide clear examples for each of the four groups of protozoans.

Question 15. Differentiate between various classes of kingdom Fungi on the basis of their (i) Mycelium, (ii) Types of spores and (iii) Type of fruiting body. Also give two examples for each class.
Answer:

In simple words: Fungi classes are distinguished by their cell structure, how they make spores, their fruiting bodies, and example species.

Exam Tip: Presenting this comparison in a tabular format is the best way to score full marks in long answer questions.