NCERT Exemplar Class 11 Biology Solutions Chapter 2 Biological Classification

Biological Classification Excercise

Multiple Choice Question:

Question:1

All eukaryotic unicellular organisms belong to
a) Monera
b) Protista
c) Fungi
d) Bacteria

Answer:

The answer is the option (b) Protista.
Explanation: All eukaryotic unicellular organisms belong to Protista. This is because Monera consists of prokaryotic organisms and bacteria falls under the category of Monera, whereas Fungi consists of both unicellular as well as multicellular organisms.

Question:2

The five-kingdom classification was proposed by
a) R.H. Whittaker
b) C. Linnaeus
c) A. Roxberg
d) Virchow

Answer:

The answer is the option
(a) R.H. Whittaker.
Explanation: In 1959, R.H. Whittaker proposed the five-kingdom theory.

Question:3

Organisms living in salty areas are called as
a) Methanogens
b) Halophiles
c) Heliophytes
d) Thermoacidophiles

Answer:

The answer is the option (b) Halophiles.

Explanation: Halophiles are organisms living in salty areas. Halos refer to salt, Where as phile refers to living.

Question:4

Naked cytoplasm multinucleated and saprophytic are the characteristics of
a) Monera
b) Protista
c) Fungi
d) Slime molds

Answer:

The answer is the option (d) Slime molds
Explanation: Slime molds contain the above-mentioned characteristics. They were initially classified as fungi, but since they are multinucleated and have a naked protoplasm, they are now classified under monera.

Question:5

An association between roots of higher plants and fungi is called
a) Lichen
b) Fern
c) Mycorrhiza
d) BGA

Answer:

The answer is the option (c).
Explanation: It is called Mycorrhiza. The association between fungi and algae is lichen; ferns are categorised as Pteridophyta and BGA is the abbreviation of Blue Green Algae.

Question:6

A dikaryon is formed when
a) Meiosis is arrested
b) The two haploid cells do not fuse immediately
c) Cytoplasm does not fuse
d) None of the above

Answer:

The answer is the option (b) The two haploid cells do not fuse immediately

Explanation: A dikaryon is formed when the two haploid cells do not fuse immediately.

Question:7

Contagium vivum fluidum was proposed by

1. D. J Ivanowsky

2. M.W Beijerinek

3. Stanley

4. Robert Hook

Answer:

The answer is the option (b) M.W Beijerinek.
Explanation: M. W Beijerinek proposed the contagium vivum fluidum. This term refers to an infectious living fluid.

Question:8

Association between Mycobiont and Phycobiont are found in
a) Mycorrhiza
b) Root
c) Lichens
d) BGA

Answer:

The answer is option (c) Lichens.
Explanation: The mycobiont, i.e., the fungal element and the Phycobiont i. e, the algae elements are found in lichens.

Question:9

Difference between Virus and Viroid is
a) Absence of protein coat in viroid but present in virus
b) Presence of low molecular weight RNA in virus but absent in viroid
c) Both a and b
d) None of the above

Answer:

The answer is option (a) Absence of protein coat in viroid but present in virus.
Explanation: The difference between the virus and the viroid is the absence of a protein coat in the viroid but present in the virus.

Question:10

With respect to fungal sexual cycle, choose the correct sequence of events
a) Karyogamy, plasmogamy, meiosis
b) Meiosis, plasmogamy, karyogamy
c) Plasmogamy, karyogamy, and Meiosis
d) Meiosis, karyogamy, plasmogamy

Answer:

The answer is the option (a) Karyogamy, plasmogamy, meiosis

Explanation: The correct order is plasmogamy, karyogamy and meiosis

Question:11

Viruses are non-cellular organisms but replicate themselves once they infect the host cell. To which of the following kingdom do viruses belong
a) Monera
b) Protista
c) Fungi
d) None of the above

Answer:

The correct answer is option (d) none of the above.
Explanation: This is because viruses are considered to be living as well as non-living and therefore are not classified under any particular kingdom.

Question:12

Members of Phycomycetes are found in
i) Aquatic habitats
ii) On decaying wood
iii) Moist and damp places
iv) As obligate parasites on plants

Choose from the following options

a) None of the above
b) (i) and (iv)
c) (ii) and (iii)
d) All of the above

Answer:

The answer is option (c) All of the above.
Explanation: Phycomycetes are found to be living in aquatic habitats with Moist and damp places, as obligate parasites and on decaying wood as well.

Very Short Answer Type Questions:

Question:1

What is the principle underlying the use of cyanobacteria in agricultural fields for crop improvement?

Answer:

Several cyanobacteria species are known to carry out nitrogen fixation in soil.Therefore, they are utilised in agricultural fields to improve crops.

Question:2

Suppose you accidentally find an old preserved permanent slide without a label. In your effort to identify it, you place the slide under microscope and observe the following features:

(a) Unicellular
(b) Well defined nucleus
(c) Biflagellate–one flagellum lying longitudinally and the other transversely.

What would you identify it as? Can you name the kingdom it belongs to?

Answer:

All unicellular eukaryotes are classified under the kingdom Protista. Therefore, this organism falls under Protista.

Question:3

How is the five-kingdom classification advantageous over the two-kingdom classification?

Answer:

When there was only two-kingdom classification, several unrelated organisms were categorised as the same kingdom. To remove this five-kingdom classification has proven to be effective. For example, the bacteria were classified as the plant kingdom initially, but many bacteria are heterotrophic. Now bacteria falls under its own kind.

Question:4

Polluted water bodies have usually extremely high abundance of plants like Nostoc and Oscillatoria. Give reasons.

Answer:
Nutrients are available in abundance in polluted water for these organisms.Therefore, they grow in such conditions and are found in large quantities in polluted water.

Question:5

Are chemosynthetic bacteria-autotrophic or heterotrophic?

Answer:

Chemosynthetic bacteria are considered to be autotrophic since they are capable of synthesising their own food. In the process of chemosynthesis, it utilises chemicals as an energy source.

Question:6

The common name of pea is simpler than its botanical (scientific) name Pisum sativum. Why then is the simpler common name not used instead of the complex scientific/ botanical name in biology?

Answer:

The well-known term 'pea' is an English term and is termed differently in different languages. It is much more convenient to keep in mind a standard scientific name in relation to innumerable names. Therefore, it is preferable to use scientific, universally accepted names.

Question:7

A virus is considered as a living organism and an obligate parasite when inside a host cell. But viruses are not classified along with bacteria or fungi. What are the characteristics of viruses that are similar to non-living objects?

Answer:

Attributes of virus that are similar to that of non-living objects are -
(a) They consist of inert crystalline structure around the living cell.
(b) No cell organelles are present.

Question:8

In the five-kingdom system of Whittaker, how many kingdoms are eukaryotes?

Answer:

In the five-kingdom system of Whittaker, the following four kingdoms are eukaryotes namely,
(a) Protista
(b) Fungi
(c) Plantae
(d) Animalia

Short Answer Type Questions:

Question:1

Diatoms are also called 'pearls of the ocean' why? What is diatomaceous earth?

Answer:

Ans. Diatoms are also known as the pearls of the ocean since they are the main producers in the marine world. Their walls are composed of silica and leave behind a considerable amount of cell deposits in their environment. This substance is known as diatomaceous earth. Diatomaceous earth has a gritty texture and is used in polishing and oil and syrup filtration.

Question:2

There is a myth that immediately after heavy rains in forest, mushrooms appear in large numbers and make a very large ring or circle, which may be several metres in diameter. These are called 'Fairy rings' Can you explain this myth of fairy rings in biological terms?

Answer:

The mushrooms mycelium draws in nutrients from the soil. When at the centre there is a lack of nutrients they increase in diameter and develop a circle-like structure. The ring keeps increasing in diameter over the years. They are known as the fruiting bodies of the fungus. This ring is also known as the Fairy Ring.

Question:3

Neurospora - an ascomycetes fungus has been used as a biological tool to understand the mechanism of plant genetics much in the same way as Drosophila has been used to study animal genetics. What makes Neurospora so important as a genetic tool?

Answer:

Neurospora is utilised as a model organism to study the genetics of plants.Many attributes of this organism make it perfect to be used for studies related to genetics. Some of these characteristics are as follows:

• Quick procreation and therefore is easy to culture

• Requires only minimum media

Question:4

Cyanobacteria and heterotrophic bacteria have been clubbed together in Eubacteria of kingdom Monera as per the "Five Kingdom Classification"even though the two are vastly different from each other. Is this grouping of the two types of taxa in the same kingdom justified? If so, why?

Answer:

All the prokaryotes are classified under the kingdom Monera. Cyanobacteria as well as heterotrophic bacteria fall under prokaryotes and therefore are categorised under the same kingdom. The biggest difference between cyanobacteria and heterotrophic bacteria is nutrition. Therefore, this categorisation is justified.

Question:5

At a stage of their cycle, ascomycetes fungi produce the fruiting bodies like apothecium, perithecium or cleistothecium. How are these three types of fruiting bodies different from each other?

Answer:

Ascocarp is the fruiting body of ascomycetes. This can be classified under three categories apothecium, perithecium, and cleistothecium. Apothecium is shaped like a saucer. Perithecium has the shape of a flask with a pore-like outlet, and cleistothecium is a closed structure with no outlet.

Question:6

What observable features in Trypanosoma would make you classify it under kingdom Protista?

Answer:

There are a few attributes of Trypanosoma which can be categorised under kingdom Protista:
- It is Unicellular in nature.
- The nucleus is located at the centre.
- It is asexual.
- Food substances are preserved as granules.

Question:7

Fungi are cosmopolitan, write the role of fungi in your daily life.

Answer:

Role of fungi in our everyday life is as follows :

- Fungi can lead to rotting of food materials; for example, you can see them developing on stale bread, fruits, and vegetables.
- Yeast causes fermentation.
- Some life-threatening plant and animal illnesses are the results of fungi.
- Some fungi are useful in the production of antibiotics.

Long Answer Type Questions:

Question:1

Algae are known to reproduce asexually by a variety of spores under different environmental conditions. Name these spores and the conditions under which they are produced.

Answer:

Algae procreates asexually with the help of various spores in different environmental conditions. These spores and the environmental conditions in which they are produced: -

Type of spore
Zoospore - They have thin walls, have flagellated motile spores as they contain flagella.
They develop in favourable conditions and spread by wind.
Aplanospore - They have thin walls, have non-motile spores, and are equipped with flagella.
They develop in unfavourable conditions.
Hypnospore - The spores are made up of thick cell walls to withstand unfavourable conditions. They develop in unfavourable conditions.Akinetes -
They develop from vegetative cells and are known to serve as resting cells. They develop in unfavourable conditions.
Statospores - They resemble akinetes and are found in diatoms.
They develop in unfavourable conditions.

Question:2

Apart from chlorophyll, algae have several other pigments in their chloroplast. What pigments are found in blue-green, red, and brown algae that are responsible for their characteristic colours?

Answer:

In the chloroplasts of algae, there are other pigments are present too other than chlorophyll.

- Chlorophyceae - They are Green algae. Contain Chlorophyll a, b and are green in colour.
- Phaeophyceae - They are Brown algae. Contain chlorophyll a, c,Fucoxanthin (A xanthophyll pigment) and are brown in colour.
- Rhodophyceae - They are Red algae. Contain Chlorophyll a, d, r-phycoerythrin and are Red in colour.

Question:3

Make a list of algae and fungi that have commercial value as a source of food, chemicals, medicines, and fodder.

Answer:

Following are some algae that have commercial importance: -

- Agar (taken from red algae Gelidium and Gracilaria) - Utilised as a culture
medium in the laboratory.
- Algin (taken from brown algae) carrageen (derived from red algae) -
Utilised as gelling agent in food and in medical dressing.
- Biofuels (derived from various types of algae) - Used in the production of
biofuels.
- Fertiliser (derived from various types of algae) - Utilised as a fertiliser in
several countries.
- Food (Taken from several species of Porphyra, Laminaria, Sargassum) -
These marine algae are consumed as food items. This occurs more in the
East Asian nations.
- Single cell protein (Taken from Chlorella and Spirullina) - Many algae
have high quantities of protein and are utilised as food supplements.

Following are some fungi of commercial importance: -
- Medicine - Penicillium notatum is a fungus used for developing antibiotics of the penicillin group.
- Diseases - Several fungi are known to cause illnesses in both animals and plants.
- Food processing - Yeast for centuries now has been used for fermentation.Alcoholic beverages and bakery items are produced due to the fermentation caused by yeast.
- Food - Different variations of Agaricus are consumed as food in several countries.
- Ripening of cheese - Different variations of fungi are utilised to ripe cheese.
- Spoilage of food - Rhizopus the mould usually found on stale bread is known to ruin many food items. For example, as found in stale bread, fruits and vegetables.

Question:4

'Peat' is an important source of domestic fuel in several countries. How is 'peat' formed in nature?

Answer:

Ans. Partially decayed and degenerated vegetation and organic matter accumulate to form peat. When plant substances present in generally wet areas do not decay completely due to acidic and anaerobic environment conditions, it leads to the formation of peat. This wetland vegetation is the main component of peat. The main producer of peat is Sphagnum. However, several other plants may also be included in the formation of peat. Most of the modern peat was formed in high latitudes when the glaciers retreated in the ice age.

This phenomenon took place around 12,000 years back. Peat accumulates at a terribly slow rate of around 1 millimetre a year.Peat proves to be a major source of domestic fuel in several countries like Europe and America. It is also valuable in improving the fertility of the soil.

Question:5

Biological classification is a dynamic and ever-evolving phenomenon which keeps changing with our understanding of life forms. Justify the statement taking any two examples.

Answer:

Ans. This is true that biological classification is a dynamic and ever-evolving phenomenon which keeps changing our understanding of life forms.

Biological classification is forever changing. Initially, living beings were only categorised as animals and plants. This was on the basis of the morphological attributes. Then scientists figured out certain misleading information in the categorisation method and came up with better classifications. The five-kingdom theory is the most universally accepted theory in today world.

This theory by Whittaker classifies living beings on the basis of structural organisation and phylogenetic relationship; According to this theory; all prokaryotes are classified under one kingdom, i.e. Monera. Eukaryotes are classified into four kingdoms. All the photosynthetic autotrophs are categorised under the plant kingdom, and all the eukaryotic heterotrophs (without a cell wall) are classified as the animal kingdom. However, there are limitations in even this method of categorisation.
For example, the chemosynthetic autotrophs are classified under the kingdom Protista. Lately, some scientists have also claimed that there should be three domains of life, and some have even proposed a Six-Kingdom categorisation.