Case Study Questions Class 11 Biology Biological Classification

Case Study Questions Class 11 Biology Chapter 2 Biological Classification

CBSE Class 11 Case Study Questions Biology Biological Classification. Important Case Study Questions for Class 11 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Biological Classification.

At Case Study Questions there will given a Paragraph. In where some Important Questions will made on that respective Case Based Study. There will various types of marks will given 1 marks, 2 marks, 3 marks, 4 marks.

CBSE Case Study Questions Class 11 Biology Biological Classification

CASE 1

 

Bacteria are the sole members of the Kingdom Monera. They are the most abundant micro-organisms. Bacteria occur almost everywhere. They also live in extreme habitats such as hot springs, deserts, snow and deep oceans where very few other life forms can survive. Many of them live in or on other organisms as parasites. Bacteria are grouped under four categories based on their shape –the spherical Coccus (pl.: cocci), the rod-shaped Bacillus (pl.: bacilli), the comma-shaped Vibrium (pl.: vibrio) and the spiral Spirillum (pl.: spirilla).

Though the bacterial structure is very simple, they are very complex in behaviour. Compared to many other organisms, bacteria as a group show the most extensive metabolic diversity. Some of the bacteria are autotrophic, i.e., they synthesise their own food from inorganic substrates. They may be photosynthetic autotrophic or chemosynthetic autotrophic. The vast majority of bacteria are heterotrophs, i.e., they depend on other organisms or on dead organic matter for food.

 

Archaebacteria

These bacteria are special since they live in some of the harshest habitats such as extreme salty areas (halophiles), hot springs (thermoacidophiles) and marshy areas (methanogens). Archaebacteria differ from other bacteria in having a different cell wall structure and this feature is responsible for their survival in extreme conditions. Methanogens are present in the gut of several ruminant animals such as cows and buffaloes and they are responsible for the production of methane (biogas) from the dung of these animals.

 

Eubacteria

There are thousands of different eubacteria or ‘true bacteria’. They are characterised by the presence of a rigid cell wall, and if motile, a flagellum. The cyanobacteria (also referred to as blue-green algae) have chlorophyll a similar to green plants and are photosynthetic autotrophs. The cyanobacteria are unicellular, colonial or filamentous, freshwater/marine or terrestrial algae. The colonies are generally surrounded by gelatinous sheath. They often form blooms in polluted water bodies. Some of these organisms can fix atmospheric nitrogen in specialised cells called heterocysts, e.g., Nostoc and Anabaena. Chemosynthetic autotrophic bacteria oxidise various inorganic substances such as nitrates, nitrites and ammonia and use the released energy for their ATP production. They play a great role in recycling nutrients like nitrogen, phosphorous, iron and sulphur.

Heterotrophic bacteria are most abundant in nature. The majority are important decomposers. Many of them have a significant impact on human affairs. They are helpful in making curd from milk, production of antibiotics, fixing nitrogen in legume roots, etc. Some are pathogens causing damage to human beings, crops, farm animals and pets. Cholera, typhoid, tetanus, citrus canker are well known diseases caused by different bacteria. Bacteria reproduce mainly by fission. Sometimes, under unfavourable conditions, they produce spores. They also reproduce by a sort of sexual reproduction by adopting a primitive type of DNA transfer from one bacterium to the other. The Mycoplasma are organisms that completely lack a cell wall. They are the smallest living cells known and can survive without oxygen. Many mycoplasma are pathogenic in animals and plants.

(1) _____________bacteria is responsible for formation of biogas from cow dung / organic waste

(a) cyanobacteria

(b) Halophiles

(c) Thermoacidophiles

(d) Methanogens

(2) _______________ are the bacteria that can grow and thrive in salty areas.

(a) Methanogens

(b) Halophobic

(c) Halophiles

(d) Thermoacidophiles

(3) true bacteriaare characterised by ______________

(a) Rigid Cell wall

(b) Flagellum present for locomotion

(c) Both a and b

(d) None of the above

(4) Name the eubacteria which is also referred as blue green algae.

(5) What is heterocyst?

(6) What is the thermoacidophiles?

Answer key

(1) d

(2) c

(3) c

(4) The cyanobacteria is also referred to as blue-green algae, they have chlorophyll a similar to green plants and are photosynthetic autotrophs.

(5) Heterocyst is the specialised cells which facilitate the nitrogen fixation. It is found in cyanobacteria e.g., Nostoc and Anabaena.

(6) Thermoacidophiles are the bacteria that can survive, grow and thrive in extreme hot temperature condition and acidic environments

CASE 2

The fungi constitute a unique kingdom of heterotrophic organisms. They show a great diversity in morphology and habitat. Some unicellular fungi, e.g., yeast are used to make bread and beer. Other fungi cause diseases in plants and animals; wheat rust-causing Puccinia is an important example. Some are the source of antibiotics, e.g., Penicillium. Fungi are cosmopolitan and occur in air, water, soil and on animals and plants. With the exception of yeasts which are unicellular, fungi are filamentous. Their bodies consist of long, slender thread-like structures called hyphae. The network of hyphae is known as mycelium. Some hyphae are continuous tubes filled with multinucleated cytoplasm – these are called coenocytic hyphae. Others have septae or cross walls in their hyphae. The cell walls of fungi are composed of chitin and polysaccharides. Most fungi are heterotrophic and absorb soluble organic matter from dead substrates and hence are called saprophytes. Those that depend on living plants and animals are called parasites. They can also live as symbionts – in association with algae as lichens and with roots of higher plants as mycorrhiza.

Reproduction in fungi can take place by vegetative means – fragmentation, fission and budding. Asexual reproduction is by spores called conidia or sporangiospores or zoospores, and sexual reproduction is by oospores, ascospores and basidiospores. The various spores are produced in distinct structures called fruiting bodies. The sexual cycle involves the following three steps:

  • Fusion of protoplasms between two motile or non-motile gametes called plasmogamy.
  • Fusion of two nuclei called karyogamy.
  • Meiosis in zygote resulting in haploid spores.

When a fungus reproduces sexually, two haploid hyphae of compatible mating types come together and fuse. In some fungi the fusion of two haploid cells immediately results in diploid cells (2n). However, in other fungi (ascomycetes and basidiomycetes), an intervening dikaryotic stage (n + n, i.e., two nuclei per cell) occurs; such a condition is called a dikaryon and the phase is called dikaryophase of fungus. Later, the parental nuclei fuse and the cells become diploid. The fungi form fruiting bodies in which reduction division occurs, leading to formation of haploid spores.

(1) ______________ Hyphae are without septa and filled with multinucleated cytoplasm.

(a) Septate

(b) Nucleated

(c) Coenocytic

(d) Both a and c

(2) _____________ is the only single celled fungi organism.

(a) Penicillium

(b) Yeast

(c) Mycorrhiza

(d) Both a and b

(3) What is saprophytic fungi?

(4) Give reason – why fungi are referred as cosmopolitan organism?

(5) Name the fungi which is responsible for rusting disease in wheat plant.

Answer key

(1) c

(2) b

(3) Saprophytic is the mode of obtaining food by absorption of dissolved organic material which is produced by decaying of organic matters. Those fungi obtain their food by this mode are termed as saprophytic fungi.

(4) Fungi shows a great diversity in morphology and habitat. Fungi are widespread. They can be found in air, water, soil, on the body of other living animal, inside the body. They can be found almost every, because of this fungi are referred as cosmopolitan organism.

(5) Puccinia is the fungi, which case rusting disease in wheat plant.

CASE 3

Phycomycetes – Members of phycomycetes are found in aquatic habitats and on decaying wood in moist and damp places or as obligate parasites on plants. The mycelium is aseptate and coenocytic. Asexual reproduction takes place by zoospores (motile) or by aplanospores (non-motile). These spores are endogenously produced in sporangium. A zygospore is formed by fusion of two gametes. These gametes are similar in morphology (isogamous) or dissimilar (anisogamous or oogamous). Some common examples are Mucor, Rhizopus (the bread mould) and Albugo (the parasitic fungi on mustard).

Ascomycetes – Commonly known as sac-fungi, the ascomycetes are mostly multicellular, e.g., Penicillium, or rarely unicellular, e.g., yeast (Saccharomyces). They are saprophytic, decomposers, parasitic or coprophilous (growing on dung). Mycelium is branched and septate. The asexual spores are conidia produced exogenously on the special mycelium called conidiophores. Conidia on germination produce mycelium. Sexual spores are called ascospores which are produced endogenously in sac like asci (singular ascus). These asci are arranged in different types of fruiting bodies called ascocarps. Some examples are Aspergillus, Claviceps and Neurospora. Neurospora is used extensively in biochemical and genetic work. Many members like morels and truffles are edible and are considered delicacies.

Basidiomycetes –Commonly known forms of basidiomycetes are mushrooms, bracket fungi or puffballs. They grow in soil, on logs and tree stumps and in living plant bodies as parasites, e.g., rusts and smuts. The mycelium is branched and septate. The asexual spores are generally not found, but vegetative reproduction by fragmentation is common. The sex organs are absent, but plasmogamy is brought about by fusion of two vegetative or somatic cells of different strains or genotypes. The resultant structure is dikaryotic which ultimately gives rise to basidium. Karyogamy and meiosis take place in the basidium producing four basidiospores. The basidiospores are exogenously produced on the basidium (pl.: basidia). The basidia are arranged in fruiting bodies called basidiocarps. Some common members are Agaricus (mushroom), Ustilago (smut) and Puccinia (rust fungus).

(1) The bread mould fungi belongs to _______________

(a) Basidiomycetes

(b) Phycomycetes

(c) Ascomycetes

(d) Deuteromycetes

(2) Ascomycetes fungi are characterised by presence of ____________.

(a) Presence of asci

(b) Presence of Basidium

(c) Mycelium without septa

(d) Both a and c

(3) What is mean by anisogamousgametes?

(4) Name the fungi which is commonly known as smut fungi?

(5) Give reason – why ascomycetes are termed as sac fungi?

Answer key

(1) b

(2) a

(3) Gametes, which exhibits same morphological feature are termed as anisogamous gametes.

(4) Ustilago is commonly known as smut fungi.

(5) Fungi belongs to phylum ascomycetes, produces sac like structure called asci, which are involved in production of ascospores. This the reason Ascomycetes are commonly called as sac-fungi.

Updated: March 28, 2022 — 10:24 pm

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