Information

Differences on biological classification?


Why we use the term phylum for kingdom animali but for kingdom planti ,fungi and prokaryota we use them division? What difference between phylum and division ?


Phylum and division are both listed under the same taxonomic ranks. The wikipedia page for phylum states that

Traditionally, in botany the term division was used instead of "phylum", although from 1993 the International Code of Nomenclature for algae, fungi, and plants accepted the designation "phylum".

What you have to keep in mind is that the scientists categorizing plants and animals worked in isolation for a long time and only recently have they come together to build a tree of life for all organisms (rather than just working separately on plants / animals / bacteria)


Biological Classification Definition with Basis and Units of Classification in Biology

“The arrangement of organisms into groups and sub-groups on the basis of similarities is called biological classification.” Over 1.5 million species of animals and over half a million species of plants are known. There should be some system or the classification of these organisms. Many types of classifications are possible.

For example classification of the flowering plants on the basis of their color, height, or any other character. It does not give information about the similarities and differences among different individuals. So this type of classification is not accepted.


Welcome to the Living World

- The cell contains a well-defined nucleus and other membrane-bound organelles. Some have flagella or cilia.

- Protists are primarily aquatic.

- It is a link with plants, animals and fungi.

- They reproduce asexually and sexually (cell fusion and zygote formation).

- Protista includes Chrysophytes, Dianoflagellates, Euglenoids, Slime moulds and Protozoans.

- Found in fresh water and marine environments.

- Microscopic and float passively in water currents (plankton).

- Most of them are photosynthetic.

- It includes diatoms & golden algae (desmids).

- Diatoms: They have siliceous cell walls forming two thin overlapping shells, which fit together as in a soap box. The cell wall deposit of diatoms over billions of years in their habitat is known as ‘diatomaceous earth’. This is used in polishing, filtration of oils and syrups.

- Diatoms are the chief ‘producers’ in the oceans.

- Mostly marine and photosynthetic.

- They appear yellow, green, brown, blue or red based on the main pigments present in their cells.

- The cell wall has stiff cellulose plates on the outer surface.

- Most of them have 2 flagella one lies longitudinally and the other transversely in a furrow between the wall plates.

- Red dinoflagellates (E.g. Gonyaulax) undergo rapid multiplication so that the sea appears red (red tides). They release toxins that kill marine animals like fishes.

- Mainly fresh water organisms found in stagnant water.

- Instead of a cell wall, they have a protein rich layer called pellicle. It makes their body flexible.

- They have two flagella, a short and a long one.

- They are photosynthetic in the presence of sunlight. In the absence of sunlight, they behave like heterotrophs by predating on smaller organisms.

- The pigments are identical to those in higher plants.

- They are saprophytic protists.

- The body moves along decaying twigs and leaves engulfing organic material.

- Under suitable conditions, they form an aggregation called plasmodium. It may spread over several feet.

- Under unfavourable conditions, plasmodium differentiates and forms fruiting bodies bearing spores at their tips. Spores have true walls. They are highly resistant and survive for many years. Spores are dispersed by air.


What is Binomial Nomenclature?

Binomial nomenclature (binary nomenclature or two-term naming system) is the scientific naming system of living organisms. It is a two-term naming system developed to name organisms scientifically. Carl Linnaeus formalized the binomial nomenclature as the modern system of naming organisms. Taxonomists use binomial nomenclature, especially when studying and identifying organisms.

Figure 02: Carl Linnaeus

A binomial name, also known as scientific name, consists of two parts. The first name implies the generic name (genus name) while the second name implies the species name. Therefore, a particular species gets a unique name according to the binomial nomenclature. For example, the extant human species scientific name is Homo sapiens. Pyrus malus is the scientific name of apple. Generic name begins with a capital letter while species name begins with a small letter. Moreover, binomial names are usually typeset in italics. When handwritten, a binomial name should be underlined.


Classification

In 1753, a Swedish biologist named Carl Linnaeus (also known as Carl von Linné) proposed a universal system for classifying and naming animals and plants. Scientists still use this Linnean system to classify living things. A hierarchical system, it works like a series of nesting boxes (Fig. 1.9). The largest box is the domain, and all the other levels of classification fit within the domains.

There are three domains that include all the living things on Earth. The domains are Bacteria, Archaea, and Eukarya. Bacteria and Archaea are all single-celled microorganisms that do not have DNA contained within a nucleus. Most of the Archaea live in extreme environments. The Bacteria and Archaea were once grouped together as a single kingdom (called Monera), but scientists later discovered that the Archaea were distinctly different. Archaea are more similar to Eukarya than to Bacteria.

The domain Eukarya includes all organisms that have DNA contained within a nucleus. Within the domain Eukarya, there are four kingdoms: Protista, Fungi, Plantae, and Animalia. Organisms with similar characteristics are grouped within these broad kingdoms.

Organisms are usually grouped together based on their unique characteristics. The classification of an organism often provides useful information about its evolutionary history and which other organisms are related to it. For example, the Hawaiian goose or nēnē (Branta sandvicensis Fig. 1.10) is classified as shown in Table 1.9.

At each level of hierarchy listed in Table 1.9, more information about the nēnē is revealed. If the classification of the nēnē is imagined as a series of nested boxes (Fig. 1.9), the first box is the domain Eukarya box. All organisms in Eukarya (often referred to as eukaryotes) have DNA contained in a nucleus rather than in the cytoplasm like the domains Prokarya and Archaea.

Next is the kingdom Animalia box. Everything in this box must consume other organisms to survive. Other kingdoms within Eukarya, like the kingdom Plantae, have organisms that can make their own food.

Within the kingdom Animalia box, there are several other boxes, each labeled as a different phylum. One is the phylum Chordata box. This box contains everything that has a notochord, gill slits, and a dorsal nerve cord.

The phylum Chordata box contains many classes, one of which is the class Aves. Aves are the birds, with feathers and hollow bones.

The class Aves box includes the box labeled order Anseriformes, the waterfowl that are grouped together due to their webbed front toes.

The order Anseriformes box contains two family boxes. One of these is the family Anatidae—the swans, ducks, and geese that have a broad bill, a keeled sternum, and other unique features.

The family Anatida box contains the genus Branta. Geese in the genus Branta are noted for bold plumage and legs and bills that are black in color.

The genus box Branta holds the species sandvicensis. By examining each level of classification, it becomes clear that Branta sandvicensis is a Hawaiian goose with a black broad bill, legs, webbed toes, feathers, hollow bones, and a notochord. It must also eat other things. Note that several other species found in Hawai‘i are given the species name sandvicensis because Sandwich Islands is an older European name for the Hawaiian Islands. However, no other organism on earth is given the genus Branta and the species sandvicensis. Branta sandvicensis is reserved only for the nēnē.

The classification system tells something about the evolutionary relationships among species. Moving down through each level of classification, the number of species in the group decreases (Table 1.10). Two species within the same genus likely share a recent common ancestor in their evolutionary history. These two species would be more closely related to each other than two species classified into different families.

Table 1.10. The number species decreases in each group moving down the levels of classification.
Kingdom Animalia: Over 1.6 million species
Phylum Chordata (chordates): Approximately 51,500 species
Class Sarcopterygii (includes lobe-finned fishes): Approximately 32,000 species including 2 coelacanths, 6 lungfishes, and all four-limbed vertebrates
Order Coelacanthiformes (coelacanths): 2 species
Family Latimeriidae: 2 species
Genus Latimeria: 2 species
Species chalumnae and menadoensis

The levels of classification might also provide information on the evolutionary history of a species or other taxonomic group. Such is the case with the coelocanths Latimera spp.) whose classification is detailed in Table 1.10. West Indian ocean coelacanth (Latimeria chalumnae Fig. 1.10.1) and its sister species the Indonesia coelacanth (Latimera menadoensis) are the only living members of their genus (Latimera). They are also the only living members of their family (Latimeriidae) and of their order (Coelacanthiformes). All other species belonging to these levels of classification are now extinct.

Coelacanths are also some of the very few surviving fish species within the class Sarcopterygii, a group known as the lobe-finned fishes. All four-limbed vertebrate animals—amphibians, reptiles, birds, and mammals—also belong to class Sarcopterygii. The coelacanths, and the six species of lung fish, are more closely related to each other and to the four-limed vertebrates than to other fishes. For this reason, the coelacanth offers a rare glimpse into the evolutionary history of vertebrate animals and their limb-development.

Classification systems are used in many ways. Compare the classifications shown in Fig. 1.11 and Fig. 1.12. Most people know something about water vehicles, so it is not necessary to say that a speedboat has a motor. In the same way, there is general knowledge that a tuna is classified as a fish. So, a tuna can be described without needing to say that it is a fish because. Thus, if we make the statement that a skipjack tuna is caught while fishing in a speedboat, many details can be left out of the description because there is general, underlying knowledge of the classification of boats and tuna.


Biological Classification Quiz

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Assertion Reason Questions for Biology Chapter 2 Biological Classification

Directions: In the following questions, a statement of assertion is followed by a statement of reason.
Mark the correct choice as:
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.

Q.1. Assertion : Bacteria are prokaryotic.
Reason : Bacteria do not possess true nucleus and membrane bound cell organelles.

Answer Answer: (a) Bacterial cell is prokaryotic. It lacks true nucleus and membrane bound organelles.

Q.2. Assertion : Bacterial photosynthesis occurs by utilizing wavelength longer than 700 nm.
Reason : Here reaction centre is P-890.

Answer Answer: (b) Bacteria utilize the wavelengths longer than 700 nm for photosynthesis and the reaction centre is P-890 the reductant is NADH + H+. In bacteria, donor may be H2S or malate or succinate.

Q.3. Assertion : Sand fly transmits Kala-azar.
Reason : In Kala-azar, the parasite damages the brain.

Answer Answer: (c) Leishmania donovani causes kala-azar. The parasite is transmitted by sandfly. The parasite lives inside the cells of liver, spleen, lymph glands, white blood corpuscles and inner wall cells of blood capillaries. In sleeping sickness disease, the parasite damages the brain.

Q.4. Assertion : Escherichia coli, Shigella sp. and Salmonella sp. are all responsible for diarrhoeal diseases.
Reason : Dehydration is common to all types of diarrhoeal diseases and adequate supply of
fluids and electrolytes should be ensured.

Answer Answer: (b) E. coli, Shigella sp. and Salmonella sp. causes diarrhoea. It is due to intake of contaminated water.

Q.5. Assertion : Gram-negative bacteria do not retain the stain when washed with alcohol.
Reason : The outer face of the outer membrane of gram-negative bacteria contains lipopolysaccharides, a part of which is integrated into the membrane lipids.

Answer Answer: (a) Gram negative bacteria contain lipopolysaccharide in its membrane.

Q.6. Assertion: Two kingdom classification was insufficient.
Reason: Majority of organisms failed to fall into either of the categories in two kingdom classification.

Answer Answer: (a) Two kingdom classification (founded by Linnaeus) worked well for a long time. However, this system failed to distinguish between the eukaryotes and prokaryotes, unicellular and multicellular organisms, photosynthetic and non-photosynthetic organisms. Although, classification of organisms (into plants and animals) was easily done and was easy to understand, but a large number of organisms did not fall into either category. Hence, the two kingdom classification used for a long time was found inadequate.

Q.7. Assertion: Archaebacteria are able to survive in harsh habitats.
Reason: Archaebacteria survive in extreme conditions due to the presence of peptidoglycan in their cell wall.

Answer Answer: (c) Archaebacteria are special since they live in some of the most harsh 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. Archaebacteria are characterised by absence of peptidoglycan in their cell wall. Instead cell wall contains protein and non cellulosic polysaccharide.

Q.8. Assertion: Several ruminant animals contain methanogens within their gut.
Reason: Methanogens help in the production of methane from dung of ruminants.

Answer Answer: (b) Methanogens occur in marshy areas where they convert formic acid and carbon dioxide into methane with the help of hydrogen. Some of the methanogen archaebacteria live as symbionts (e.g., Methanobacterium) inside rumen or first chamber in the stomach of herbivorous animals that chew their cud (ruminants, e.g., cow, buffalo) and thus, helps in production of methane from dung of these animals. These archaebacteria are helpful to the ruminants in fermentation of cellulose.

Q.9. Assertion: The nitrogen-fixing bacteria in leguminous plant nodules live as symbionts.
Reason: Leg-haemoglobin synthesized by leguminous plants protect bacteria.

Answer Answer: (a) Rhizobium form a symbiotic association with roots of leguminous plants producing root nodules. These bacteria reside inside the nodules and reduce atmospheric nitrogen (N2) to ammonia. The fixed nitrogen is taken up by plant. In return, the plant provides both nutrients and protection to bacteria.

Q.10. Assertion: Bacteria are classified among plants.
Reason: They have cell walls.

Answer Answer: (a) Plant cells are characterized by the presence of a rigid cell wall on the basis of which they can be differentiated from animal cells. Hence, in two kingdom classification, bacteria were classified among plants. However, according to the five-kingdom classification, bacteria are grouped under kingdom Monera.

Q.11. Assertion: Bacteria do not always move with the help of flagella.
Reason: Rotary motion of flagellum is employed by flagellated bacteria for movement.

Answer Answer: (b) Myxobacteria do not have flagella and move by gliding movement.

Q.12. Assertion: Some bacteria have the capacity to retain Gram stain after treatment with acid alcohol.
Reason: They are known as gram positive as they are attracted towards positive pole under influence of electric current.

Answer Answer: (c) The cell wall of Gram-negative bacteria contains alcohol-soluble lipid, while the cell wall of Gram-positive bacteria lacks the lipids and therefore resist decolourisation and retain the primary stain, appearing violet. Gram-negative bacteria are decolorized by organic solvents and therefore, take the counter stain, appearing red. Gram + ve bacteria are not attracted towards positive pole under influence of electric current.

Q.13. Assertion: Chemosynthesis is not carried out by autotrophic bacteria.
Reason: Chemosynthetic bacteria trap the small amount of energy released from inorganic compound’s oxidation to use in the reactions that synthesize carbohydrates.

Answer Answer: Chemosynthetic bacteria are without photosynthetic pigments. For the synthesis of their own organic food (carbohydrates), they obtain carbon from Solutions CO2 of the atmosphere and necessary energy from oxidation of inorganic or organic compounds, such as hydrogen sulphide (H2S), ferrous compounds (Fe2+), molecular hydrogen (H2), ammonia (NH3) and nitrites (NO2 –).

Q.14. Assertion : Exotoxins are released by Gram +ve bacteria causing diseases to animals.
Reason: Exotoxins are proteins that react with WBC of animals.

Answer Answer: (a) Mostly pathogenic gram +ve bacteria releases exotoxins outside the cell thus, killing the W.B.C. and causing disease

Q.15. Assertion: All food chains will come to stand still if bacteria disappear from earth.
Reason: Bacteria are only associated with the soil fertility and hardly any role for food chains.

Answer Answer: (c) Bacteria play an important and dual role by disposing off the dead bodies and wastes of organism and by increasing the fertility of soil.

Q.16. Assertion: Broad spectrum antibiotics are produced by Streptomyces.
Reason: Antibiotics can destroy microorganisms by inhibiting DNA replication or protein synthesis.

Answer Answer: (a) Streptomyces is used for production of broad spectrum antibiotics where living microorganism is capable of inhibiting or destroying other many types of microbes.

Q.17. Assertion: Bacterial cell wall is characterised by having mucopolysaccharides.
Reason: Acetyl muramic acid is an example of mucopolysaccharide.

Answer Answer: (d) Chemically bacteria consists of acetylglycosamine, acetyl muramic acid and a peptide chain of four or five amino acids. All these chemicals together form a polymer called peptidoglycan (= murein or mucopeptide). Some other chemical substances deposited on the cell wall are – teichoic acid, protein, polysaccharides, lipoproteins and lipopolysaccharides.

Q.18. Assertion: Anabaena inhabits root nodules of leguminous plants.
Reason: Leguminous plants are an example of symbiotic nitrogen fixation.

Answer Answer: (a) Anabaena found symbiotically in the root nodules of many leguminous plants helps in N2 fixation.

Q.19. Assertion: Bacillus butschli is true bacterium.
Reason: Its cell wall is composed of acetyl muramic acid.

Answer Answer: (a) Bacillus butschli is the Gram positive bacterium and its cell wall consist of acetyl muramic acid.

Q.20. Assertion: Pili are motile appendages found in some bacteria.
Reason: These participate in conjugation.

Answer Answer: (a) In some bacteria, nonmotile appendages called pili or fimbriae are also present. They take part in sexual reproduction, i.e., conjugation.

Q.21. Assertion: Cell secretion does not occur in bacteria.
Reason: Golgi complex is absent in bacteria.

Answer Answer: (a) Cell secretion occurs even in the prokaryotic cells (bacteria) in relation to the production of a variety of enzyme in the medium. While, golgi complex and other membrane bound organelles are absent in prokaryotes.

Q.22. Assertion: Methanogens are obligate anaerobes.
Reason: Halophiles are salt loving bacteria.

Answer Answer: (b) Methanogens are obligate anaerobes and used in biogas fermenters to produce methane. e.g. Methanobacterium, Methanococcus, etc. Halophiles are salt loving bacteria as they are found in to live in environments with a very high salt concentration.

Q.23. Assertion: Cyanobacteria are unicellular and colonial.
Reason: Blue green algae are chemosynthetic.

Answer Answer: (c) Cyanobacteria or Blue green algae are photosynthetic prokaryotes with chlorophyll a, carotenoids and phycobillins. They may be unicellular, colonial or filamentous and marine or terrestrial.

Q.24. Assertion: Cyanobacteria are photosynthetic autotrophs.
Reason: Cyanobacteria have chlorophyll a and b similar to green plants.

Answer Answer: (c) Cyanobacteria (also referred to as bluegreen algae) are photosynthetic autotrophs. They have chlorophyll a similar to green plants.

Q.25. Assertion : Plasmids are double-stranded extra chromosomal DNA.
Reason: Plasmids are possessed by eukaryotic cells.

Answer Answer: (c) In addition of bacterial chromosomes, many bacteria have accessory rings of DNA called plasmids. Plasmids are absent in eukaryotic chromosome.

Q.26. Assertion : Euglena is studied as an animal as well as a plant.
Reason :Euglena is more an animal than a plant.

Answer Answer: (b) Euglena is a typical example of mastigophora. It is phytoflagellate as it possesses both chloroplast and flagella. It is autotrophic in sunlight, but becomes heterotrophic in dark. Because of its two fold nutritional abilities, it is usually studied as a plant as well as an animal. But it is more an animal than plant because of
(a) The absence of cellulose cell wall overlying the plasma membrane.
(b) Presence of centriole.
(c) Reserve food is paramylon which is not a true starch.
(d) Response to various stimuli like an animal.

Q.27. Assertion : Amoeba contains a contractile vacuole.
Reason : It helps in both digestion and osmoregulation.

Answer Answer: (c) Contractile vacuole in Amoeba is a single, clear, rounded, pulsating structure which is filled with a watery fluid and enclosed by a unit membrane. It helps in the osmoregulation and excretory activities. Digestion in Amoeba occurs in the food vacuoles. These are spherical species small and large, contain water and food in various phases of digestion. As soon as the egestion of non digestible food occurs through body, these disappear.

Q.28. Assertion : Chemosynthesis is an autotrophic nutrition.
Reason : Chemoautotrophs contain chlorophyll pigments.

Answer Answer: (b) Chemoautotrophs developed the ability to synthesize organic molecules from inorganic raw materials. Chlorophyll pigments are present in photoautotrophs. The photo-autotrophs utilize the solar energy absorbed by them in synthesizing organic compounds. Certain chemoautotrophs include green sulphur bacteria.

Q.29. Assertion: Cell wall of chrysophytes are indestructible.
Reason: Cell walls of chrysophytes have layer of magnesium pectate embedded in it.

Answer Answer: (c) Chrysophytes include diatoms and golden algae (desmids). They are found in fresh water as well as in marine environments. The cell walls are embedded with silica and thus, the walls are indestructible.

Q.30. Assertion: The protoplasm of plasmodial slime mould is considered purest in the world.
Reason: Protoplasm of plasmodium is differentiated into an outer enucleated and central nucleated portions.

Answer Answer: (a) Vegetative part of slime moulds does not possess cell wall they either occur as free living amoeboid mass of protoplasm (plasmodium) or aggregation of amoebae (pseudoplasmodium). The protoplasm of plasmodial slime mould is considered as purest in the living world. It is differentiated into outer enucleated (hyaloplasm) and central nucleated portions. At maturity, it may contain several hundred to many thousand nuclei. The protoplasm is vacuolated.

Q.31. Assertion: Sporozoans may have silica shells on their surface.
Reason: Shells of sporozoans render protection from acidic environment of the host.

Answer Answer: (d) Sporozoans are endoparasites. Their body is covered with an elastic pellicle or cuticle. Thus, these do not have silica shells on their surface.

Q.32. Assertion: Euglena is called as plant animal.
Reason: Pellicle of Euglena is made up of cellulose and not protein.

Answer Answer: (c) Euglena is studied as plant as well as animal. It is called plant animal. Plant characters of Euglena are presence of chloroplasts with chlorophyll and holophytic (photosynthetic) nutrition in presence of light while, animal characters of Euglena are presence of pellicle which is made up of proteins and not of cellulose, presence of stigma and paraflagellar body (photosensitive structures), presence of contractile vacuole (not found in plants) and presence of longitudinal binary fission.

Q.33. Assertion: Chemosynthetic autotrophic bacteria oxidise various inorganic substances.
Reason: Energy released during oxidation is used in ATP production.

Answer Answer: (b) Chemoautotrophic bacteria are able to manufacture their organic food from inorganic raw materials with the help of energy derived from exergonic chemical reactions involving oxidation of an inorganic substance present in the external medium. The chemical energy obtained from oxidation reaction is trapped in ATP molecules.

Q.34. Assertion: Slime moulds show alternation of generation.
Reason: The sporangia bearing slime moulds represent haplophase.

Answer Answer: (a) Slime moulds exhibit alternation of generation. The diploid plasmodium is a sporophyte. Under certain conditions, it bears sporangia. These sporangia bearing plasmodium and spore producing sporangia constitute the sporophyte generation. It is a diplophase reduction division which takes place at the time of differentiation of resting spore. The resting spores germinate to produce the haploid, uninucleate swarm cells or myxamoebae. The latter meet and fuse in pairs to form a zygote. The haploid resting spores and the swarm cells or myxamoebae represent the haploid or gametophyte generation.

Q.35. Assertion: Trichomonas vaginalis causes infection only in women.
Reason: Trichomonas buccalis lives in the buccal cavity.

Answer Answer: (b) Trichomonas vaginalis infects vagina of women and causes the disease known as leucorrhoea. In males, the parasite produces irritation in urethra. Trichomonas buccalis resides in the buccal cavity, which is nearly harmless

Q.36. Assertion: Erythrocytic merozoites form gametocytes.
Reason: Gametocytes are of two types – male and female.

Answer Answer: (b) Some erythrocytic merozoites enter fresh RBCs and form rounded gametocytes (gamonts). The gametocytes are of two types – (i) Smaller male gametocytes or microgamete and (ii) Larger female gametocytes or macrogamete.

Q.37. Assertion: Plasmodium causes disease in female Anopheles mosquitoes.
Reason: Female Anopheles mosquitoes feed on plasmodial blood.

Answer Answer: (d) The sexual phase of the malarial parasite occurs in the Anopheles mosquito. As the female Anopheles mosquitoes feed on blood, only they can serve as vector hosts of malarial parasites. The parasite does not harm the mosquito.

Q.38. Assertion: Malarial fever appear at merozoite stage of Plasmodium.
Reason: The infective stage of Plasmodium is sporozoite.

Answer Answer: (b) When the mosquito bites man, sporozoites present in the salivary gland of female Anopheles mosquito are injected into the blood of the man. The erythrocytic schizont gives rise to merozoites. Malaria fever occurs when schizonts in red blood corpuscles burst and set free their contained merozoites and malarial pigment (haemozoin) in the blood plasma.

Q.39. Assertion: Schizogony is an asexual reproduction of female Anopheles mosquito.
Reason: It takes place only in human liver cells.

Answer Answer: (c) Schizogony is an asexual reproduction in which schizont is formed. From the human blood, sporozoites enter the liver cells. The sporozoite grows in size to become a rounded schizont called cryptozoite. The latter divides to form cryptomerozoites. The cryptomerozoites formed during preerythrocytic schizogony may enter the human RBCs to start the erythrocytic schizogony, while some of them enter new liver cells to repeat hepatic (liver) schizogony.

Q.40. Assertion: Kingdom-Protista forms a link between monerans and and the other organism like plants, animal and fungi.
Reason: Protist reproduce sexually and asexually by a process involving cell fusion and zygote formation.

Answer Answer: (b) Phylogenetically the Kingdom-Protista acts as a connecting link between the prokaryotic Kingdom- Monera and the complex multicellular kingdom- Fungi, Plantae and Animalia. They reproduce asexually and sexually.

Q.41. Assertion: Euglena cannot be classified on the basis of two kingdom system.
Reason: Euglena is a plant due to presence of chlorophyll.

Answer Answer: (c) Euglena is a green coloured, single celled organism, which moves like animals. Some taxonomists considered it as a plant and included it in the plant kingdom on the basis of chlorophyll, while other included it in the animal kingdom along with the flagellated protozoans because of the locomotion by flagella.

Q.42. Assertion: The protist feeds on red blood corpuscles.
Reason: Amoebiasis is caused by Amoeba

Answer Answer: (c) Person suffering from amoebic dysentery has repeated blood mixed with slimy and foul smelling motions. The protist feeds on red blood corpuscles by damaging the wall of large intestine and reaching the blood capillaries.

Q.43. Assertion : Aflatoxins are produced by Aspergillus flavus.
Reason : These toxins are useful to mankind.

Answer Answer: (c) Aflatoxins, are produced by Aspergillus flavus. Contaminated food is the main source of infection. This toxin causes aflatoxicosis which may lead to haemorrhage and diseases of liver.

Q.44. Assertion : Saccharomyces ellipsoidens is Wine yeast and Saccharomyces cerevisiae is Baker’s yeast.
Reason :Yeast is used to make dry ice.

Answer Answer: (b) The two common yeasts used by brewing industry are Saccharomyces cerevisiae (Beer or Baker’s yeast) and S. ellipsoidens (Wine yeast). In the baking or brewing industry, CO2 is the useful product. It is collected, solidified and sold as “dry ice”.

Q.45. Assertion : Neurospora is commonly called water mould.
Reason : It belongs to basidomycetes fungi.

Answer Answer: (d) Neurospora belongs to class ascomycetes in which ascospores are produced in sac like asci . Neurospora is commonly called as pink or red bread mould. It can be grown easily in laboratory conditions so, used in genetics experiments.

Q.46. Assertion: Phycomycetes are commonly known as sac fungi.
Reason: In phycomycetes, ascospore (sexual spores) are produced endogenously in sac like asci.

Answer Answer: (d) Ascomycetes is commonly known as sacfungi. Sexual spores of Ascomycetes are produced endogenously in sac like asci. Members of Phycomycetes are found in aquatic habitats and on decaying wood in moist and damp places or as obligate parasites on plants

Q.47. Assertion: Deuteromycetes is known as fungi imperfecti.
Reason: In Deuteromycetes, only the asexual phase is known.

Answer Answer: (a) Deuteromycetes are commonly known as imperfect fungi because only the asexual or vegetative phases of these fungi are known and perfect or sexual stage is either absent or not known.

Q.48. Assertion: “Fungi imperfecti” does not show alternation of generation.
Reason: The diploid phase is present in only zygote.

Answer Answer: (c) Fungi imperfecti is that group of fungi where only the imperfect stage (asexual stages) is present. The only known method of reproduction is by conidia (asexual reproduction). As sexual reproduction is absent in this group therefore, diplophase is also absent.

Q.49. Assertion: Rhizopus and Mucor are used in liquor industry.
Reason: These cause fermentation.

Answer Answer: (a) Both Rhizopus and Mucor species are used in alcoholic fermentation. Both of these produce a number of organic acids like citric acid, lactic acid and fumaric acid.

Q.50. Assertion: Morels and Truffles are edible fungi.
Reason: Ascocarps are edible.

Answer Answer: (a) The frutifications of some ascomycetes, i.e., ascocarps are edible, e.g., morels, truffles.

Q.51. Assertion: Yeast are the best source of vitamin B complex.
Reason: Ashbya gossypii is a filamentous yeast.

Answer Answer: (b) Yeasts are the best sources of vitamin B complex. Riboflavin (B6) is obtained from a filamentaous yeast, Ashbya gossypii.

Q.52. Assertion: Claviceps produces lysergic acid.
Reason: It is carcinogenic.

Answer Answer: (c) A derivative of ergot known by name of lysergic acid (LSD) is used in experimental psychiatry, as it is a hallucinogen.

Q.53. Assertion: Mushrooms are called fairy rings.
Reason: Mushroom consists of two parts-stipe and pileus.

Answer Answer: (b) The basidiocarps or mushrooms often lie in rings. Therefore, these are also known as fairy rings. Each basidiocarp consists of two parts-stipe and pileus. The stipe or stalk is fleshy while, pileus is umbrella-like cap of the mushroom.

Q.54. Assertion: Actinomycetes are mycelial bacteria.
Reason: They are called ray fungi.

Answer Answer: (a) Actinomycetes are mycelial (aseptate, branched filamentous) bacteria which form radiating colonies in culture hence, formerly called ray fungi. e.g. Streptomyces.

Q.55. Assertion : Symbiosis is furnished by mycorrhiza.
Reason : In mycorrhiza, symbiosis is established between fungus and alga.

Answer Answer: (c) Mycorrhiza represents mutualistic symbiosis between fungus and roots of higher plants. Fungus helps in absorption of minerals and water more efficiently and protect plant roots from infection. Fungus also gets food from plant.

Q.56. Assertion: Viruses are nucleoproteins and lack cell organelle, etc.
Reason: Viruses are not considered organism.

Answer Answer: (a) Virus is a small infectious agent that can only replicate inside the cells of another organism. Viruses are not considered as organisms as they have no independent machinery.

Q.57. Assertion : TMV is a virus which causes mosaic disease.
Reason : TMV has RNA as genetic material.

Answer Answer: (b) In TMV, the chromosome consists of single stranded, linear RNA molecule coiled into a regular spiral. TMV causes mosaic disease in tobacco and some other plants.

Q.58. Assertion: Mycoplasmas are pathogenic in animals and plants.
Reason: Mycoplasmas lack cell wall and can survive without oxygen.

Answer Answer: (b) Mycoplasmas or mollicutes are the simplest and the smallest of free living prokaryotes, they can survive without oxygen. Mycoplasmas are heterotrophic in their nutrition. Some of them live as saprophytes but majority parasitise plants and animals. The parasitic habit is due to the inability of the most mycoplasmas to synthesise the required growth factors.

Q.59. Assertion: “Contagium Vivum Pasteur Fluidum” was coined by Pasteur.
Reason: Pasteur found that virus infected plant of tobacco can cause infection in healthy plant.

Answer Answer: (d) M.W. Beijerinek (1898) demonstrated that the extract of the infected plants of tobacco could cause infection in healthy plants and called the fluid as Contagium Vivum Fluidum (infectious living fluid).

Q.60. Assertion: Virus is an obligate parasite.
Reason: Virus is host specific.

Answer Answer: (b) Virus is an obligate parasite. It is inert outside the host cell. A virus does not grow, divide or reproduce like typical organisms. Instead it multiplies by independent formation of its parts using host cell’s machinery and then assembly of parts to produce virus particles. Viruses are host specific.

Q.61. Assertion: In lichens, mycobiont and phycobiont are symbiotically associated in algae which is predominant and fungi is a subordinate partner.
Reason: In this symbiotic association, the fungus provides food while the alga protects fungus from unfavourable conditions.

Answer Answer: (d) Lichens are symbiotic associations i.e., mutually useful associations between algae and fungi. The algal component is known as phycobiont and fungal component as mycobiont, which are autotrophic and heterotrophic, respectively. Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for its partner. Fungi dominate the relationship.

Q.62. Assertion: These lichens are upright and have pendulous organisation and are attached to substratum by a discoid structure.
Reason: Fruticose are well branched leafy lichens.

Answer Answer: (c) Fruticose are well branched shruby lichens with upright and pendulous organization. These are attached to substratum by a discoid structure. Plant body can be divided into prostrate, leafy and lobed thallus.

Directions: In the following questions, a statement of assertion is followed by a statement of reason.
Mark the correct choice as:
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.

Q.1. Assertion : Bacteria are prokaryotic.
Reason : Bacteria do not possess true nucleus and membrane bound cell organelles.

Answer Answer: (a) Bacterial cell is prokaryotic. It lacks true nucleus and membrane bound organelles.

Q.2. Assertion : Bacterial photosynthesis occurs by utilizing wavelength longer than 700 nm.
Reason : Here reaction centre is P-890.

Answer Answer: (b) Bacteria utilize the wavelengths longer than 700 nm for photosynthesis and the reaction centre is P-890 the reductant is NADH + H+. In bacteria, donor may be H2S or malate or succinate.

Q.3. Assertion : Sand fly transmits Kala-azar.
Reason : In Kala-azar, the parasite damages the brain.

Answer Answer: (c) Leishmania donovani causes kala-azar. The parasite is transmitted by sandfly. The parasite lives inside the cells of liver, spleen, lymph glands, white blood corpuscles and inner wall cells of blood capillaries. In sleeping sickness disease, the parasite damages the brain.

Q.4. Assertion : Escherichia coli, Shigella sp. and Salmonella sp. are all responsible for diarrhoeal diseases.
Reason : Dehydration is common to all types of diarrhoeal diseases and adequate supply of
fluids and electrolytes should be ensured.

Answer Answer: (b) E. coli, Shigella sp. and Salmonella sp. causes diarrhoea. It is due to intake of contaminated water.

Q.5. Assertion : Gram-negative bacteria do not retain the stain when washed with alcohol.
Reason : The outer face of the outer membrane of gram-negative bacteria contains lipopolysaccharides, a part of which is integrated into the membrane lipids.

Answer Answer: (a) Gram negative bacteria contain lipopolysaccharide in its membrane.

Q.6. Assertion: Two kingdom classification was insufficient.
Reason: Majority of organisms failed to fall into either of the categories in two kingdom classification.

Answer Answer: (a) Two kingdom classification (founded by Linnaeus) worked well for a long time. However, this system failed to distinguish between the eukaryotes and prokaryotes, unicellular and multicellular organisms, photosynthetic and non-photosynthetic organisms. Although, classification of organisms (into plants and animals) was easily done and was easy to understand, but a large number of organisms did not fall into either category. Hence, the two kingdom classification used for a long time was found inadequate.

Q.7. Assertion: Archaebacteria are able to survive in harsh habitats.
Reason: Archaebacteria survive in extreme conditions due to the presence of peptidoglycan in their cell wall.

Answer Answer: (c) Archaebacteria are special since they live in some of the most harsh 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. Archaebacteria are characterised by absence of peptidoglycan in their cell wall. Instead cell wall contains protein and non cellulosic polysaccharide.

Q.8. Assertion: Several ruminant animals contain methanogens within their gut.
Reason: Methanogens help in the production of methane from dung of ruminants.

Answer Answer: (b) Methanogens occur in marshy areas where they convert formic acid and carbon dioxide into methane with the help of hydrogen. Some of the methanogen archaebacteria live as symbionts (e.g., Methanobacterium) inside rumen or first chamber in the stomach of herbivorous animals that chew their cud (ruminants, e.g., cow, buffalo) and thus, helps in production of methane from dung of these animals. These archaebacteria are helpful to the ruminants in fermentation of cellulose.

Q.9. Assertion: The nitrogen-fixing bacteria in leguminous plant nodules live as symbionts.
Reason: Leg-haemoglobin synthesized by leguminous plants protect bacteria.

Answer Answer: (a) Rhizobium form a symbiotic association with roots of leguminous plants producing root nodules. These bacteria reside inside the nodules and reduce atmospheric nitrogen (N2) to ammonia. The fixed nitrogen is taken up by plant. In return, the plant provides both nutrients and protection to bacteria.

Q.10. Assertion: Bacteria are classified among plants.
Reason: They have cell walls.

Answer Answer: (a) Plant cells are characterized by the presence of a rigid cell wall on the basis of which they can be differentiated from animal cells. Hence, in two kingdom classification, bacteria were classified among plants. However, according to the five-kingdom classification, bacteria are grouped under kingdom Monera.

Q.11. Assertion: Bacteria do not always move with the help of flagella.
Reason: Rotary motion of flagellum is employed by flagellated bacteria for movement.

Answer Answer: (b) Myxobacteria do not have flagella and move by gliding movement.

Q.12. Assertion: Some bacteria have the capacity to retain Gram stain after treatment with acid alcohol.
Reason: They are known as gram positive as they are attracted towards positive pole under influence of electric current.

Answer Answer: (c) The cell wall of Gram-negative bacteria contains alcohol-soluble lipid, while the cell wall of Gram-positive bacteria lacks the lipids and therefore resist decolourisation and retain the primary stain, appearing violet. Gram-negative bacteria are decolorized by organic solvents and therefore, take the counter stain, appearing red. Gram + ve bacteria are not attracted towards positive pole under influence of electric current.

Q.13. Assertion: Chemosynthesis is not carried out by autotrophic bacteria.
Reason: Chemosynthetic bacteria trap the small amount of energy released from inorganic compound’s oxidation to use in the reactions that synthesize carbohydrates.

Answer Answer: Chemosynthetic bacteria are without photosynthetic pigments. For the synthesis of their own organic food (carbohydrates), they obtain carbon from Solutions CO2 of the atmosphere and necessary energy from oxidation of inorganic or organic compounds, such as hydrogen sulphide (H2S), ferrous compounds (Fe2+), molecular hydrogen (H2), ammonia (NH3) and nitrites (NO2 –).

Q.14. Assertion : Exotoxins are released by Gram +ve bacteria causing diseases to animals.
Reason: Exotoxins are proteins that react with WBC of animals.

Answer Answer: (a) Mostly pathogenic gram +ve bacteria releases exotoxins outside the cell thus, killing the W.B.C. and causing disease

Q.15. Assertion: All food chains will come to stand still if bacteria disappear from earth.
Reason: Bacteria are only associated with the soil fertility and hardly any role for food chains.

Answer Answer: (c) Bacteria play an important and dual role by disposing off the dead bodies and wastes of organism and by increasing the fertility of soil.

Q.16. Assertion: Broad spectrum antibiotics are produced by Streptomyces.
Reason: Antibiotics can destroy microorganisms by inhibiting DNA replication or protein synthesis.

Answer Answer: (a) Streptomyces is used for production of broad spectrum antibiotics where living microorganism is capable of inhibiting or destroying other many types of microbes.

Q.17. Assertion: Bacterial cell wall is characterised by having mucopolysaccharides.
Reason: Acetyl muramic acid is an example of mucopolysaccharide.

Answer Answer: (d) Chemically bacteria consists of acetylglycosamine, acetyl muramic acid and a peptide chain of four or five amino acids. All these chemicals together form a polymer called peptidoglycan (= murein or mucopeptide). Some other chemical substances deposited on the cell wall are – teichoic acid, protein, polysaccharides, lipoproteins and lipopolysaccharides.

Q.18. Assertion: Anabaena inhabits root nodules of leguminous plants.
Reason: Leguminous plants are an example of symbiotic nitrogen fixation.

Answer Answer: (a) Anabaena found symbiotically in the root nodules of many leguminous plants helps in N2 fixation.

Q.19. Assertion: Bacillus butschli is true bacterium.
Reason: Its cell wall is composed of acetyl muramic acid.

Answer Answer: (a) Bacillus butschli is the Gram positive bacterium and its cell wall consist of acetyl muramic acid.

Q.20. Assertion: Pili are motile appendages found in some bacteria.
Reason: These participate in conjugation.

Answer Answer: (a) In some bacteria, nonmotile appendages called pili or fimbriae are also present. They take part in sexual reproduction, i.e., conjugation.

Q.21. Assertion: Cell secretion does not occur in bacteria.
Reason: Golgi complex is absent in bacteria.

Answer Answer: (a) Cell secretion occurs even in the prokaryotic cells (bacteria) in relation to the production of a variety of enzyme in the medium. While, golgi complex and other membrane bound organelles are absent in prokaryotes.

Q.22. Assertion: Methanogens are obligate anaerobes.
Reason: Halophiles are salt loving bacteria.

Answer Answer: (b) Methanogens are obligate anaerobes and used in biogas fermenters to produce methane. e.g. Methanobacterium, Methanococcus, etc. Halophiles are salt loving bacteria as they are found in to live in environments with a very high salt concentration.

Q.23. Assertion: Cyanobacteria are unicellular and colonial.
Reason: Blue green algae are chemosynthetic.

Answer Answer: (c) Cyanobacteria or Blue green algae are photosynthetic prokaryotes with chlorophyll a, carotenoids and phycobillins. They may be unicellular, colonial or filamentous and marine or terrestrial.

Q.24. Assertion: Cyanobacteria are photosynthetic autotrophs.
Reason: Cyanobacteria have chlorophyll a and b similar to green plants.

Answer Answer: (c) Cyanobacteria (also referred to as bluegreen algae) are photosynthetic autotrophs. They have chlorophyll a similar to green plants.

Q.25. Assertion : Plasmids are double-stranded extra chromosomal DNA.
Reason: Plasmids are possessed by eukaryotic cells.

Answer Answer: (c) In addition of bacterial chromosomes, many bacteria have accessory rings of DNA called plasmids. Plasmids are absent in eukaryotic chromosome.

Q.26. Assertion : Euglena is studied as an animal as well as a plant.
Reason :Euglena is more an animal than a plant.

Answer Answer: (b) Euglena is a typical example of mastigophora. It is phytoflagellate as it possesses both chloroplast and flagella. It is autotrophic in sunlight, but becomes heterotrophic in dark. Because of its two fold nutritional abilities, it is usually studied as a plant as well as an animal. But it is more an animal than plant because of
(a) The absence of cellulose cell wall overlying the plasma membrane.
(b) Presence of centriole.
(c) Reserve food is paramylon which is not a true starch.
(d) Response to various stimuli like an animal.

Q.27. Assertion : Amoeba contains a contractile vacuole.
Reason : It helps in both digestion and osmoregulation.

Answer Answer: (c) Contractile vacuole in Amoeba is a single, clear, rounded, pulsating structure which is filled with a watery fluid and enclosed by a unit membrane. It helps in the osmoregulation and excretory activities. Digestion in Amoeba occurs in the food vacuoles. These are spherical species small and large, contain water and food in various phases of digestion. As soon as the egestion of non digestible food occurs through body, these disappear.

Q.28. Assertion : Chemosynthesis is an autotrophic nutrition.
Reason : Chemoautotrophs contain chlorophyll pigments.

Answer Answer: (b) Chemoautotrophs developed the ability to synthesize organic molecules from inorganic raw materials. Chlorophyll pigments are present in photoautotrophs. The photo-autotrophs utilize the solar energy absorbed by them in synthesizing organic compounds. Certain chemoautotrophs include green sulphur bacteria.

Q.29. Assertion: Cell wall of chrysophytes are indestructible.
Reason: Cell walls of chrysophytes have layer of magnesium pectate embedded in it.

Answer Answer: (c) Chrysophytes include diatoms and golden algae (desmids). They are found in fresh water as well as in marine environments. The cell walls are embedded with silica and thus, the walls are indestructible.

Q.30. Assertion: The protoplasm of plasmodial slime mould is considered purest in the world.
Reason: Protoplasm of plasmodium is differentiated into an outer enucleated and central nucleated portions.

Answer Answer: (a) Vegetative part of slime moulds does not possess cell wall they either occur as free living amoeboid mass of protoplasm (plasmodium) or aggregation of amoebae (pseudoplasmodium). The protoplasm of plasmodial slime mould is considered as purest in the living world. It is differentiated into outer enucleated (hyaloplasm) and central nucleated portions. At maturity, it may contain several hundred to many thousand nuclei. The protoplasm is vacuolated.

Q.31. Assertion: Sporozoans may have silica shells on their surface.
Reason: Shells of sporozoans render protection from acidic environment of the host.

Answer Answer: (d) Sporozoans are endoparasites. Their body is covered with an elastic pellicle or cuticle. Thus, these do not have silica shells on their surface.

Q.32. Assertion: Euglena is called as plant animal.
Reason: Pellicle of Euglena is made up of cellulose and not protein.

Answer Answer: (c) Euglena is studied as plant as well as animal. It is called plant animal. Plant characters of Euglena are presence of chloroplasts with chlorophyll and holophytic (photosynthetic) nutrition in presence of light while, animal characters of Euglena are presence of pellicle which is made up of proteins and not of cellulose, presence of stigma and paraflagellar body (photosensitive structures), presence of contractile vacuole (not found in plants) and presence of longitudinal binary fission.

Q.33. Assertion: Chemosynthetic autotrophic bacteria oxidise various inorganic substances.
Reason: Energy released during oxidation is used in ATP production.

Answer Answer: (b) Chemoautotrophic bacteria are able to manufacture their organic food from inorganic raw materials with the help of energy derived from exergonic chemical reactions involving oxidation of an inorganic substance present in the external medium. The chemical energy obtained from oxidation reaction is trapped in ATP molecules.

Q.34. Assertion: Slime moulds show alternation of generation.
Reason: The sporangia bearing slime moulds represent haplophase.

Answer Answer: (a) Slime moulds exhibit alternation of generation. The diploid plasmodium is a sporophyte. Under certain conditions, it bears sporangia. These sporangia bearing plasmodium and spore producing sporangia constitute the sporophyte generation. It is a diplophase reduction division which takes place at the time of differentiation of resting spore. The resting spores germinate to produce the haploid, uninucleate swarm cells or myxamoebae. The latter meet and fuse in pairs to form a zygote. The haploid resting spores and the swarm cells or myxamoebae represent the haploid or gametophyte generation.

Q.35. Assertion: Trichomonas vaginalis causes infection only in women.
Reason: Trichomonas buccalis lives in the buccal cavity.

Answer Answer: (b) Trichomonas vaginalis infects vagina of women and causes the disease known as leucorrhoea. In males, the parasite produces irritation in urethra. Trichomonas buccalis resides in the buccal cavity, which is nearly harmless

Q.36. Assertion: Erythrocytic merozoites form gametocytes.
Reason: Gametocytes are of two types – male and female.

Answer Answer: (b) Some erythrocytic merozoites enter fresh RBCs and form rounded gametocytes (gamonts). The gametocytes are of two types – (i) Smaller male gametocytes or microgamete and (ii) Larger female gametocytes or macrogamete.

Q.37. Assertion: Plasmodium causes disease in female Anopheles mosquitoes.
Reason: Female Anopheles mosquitoes feed on plasmodial blood.

Answer Answer: (d) The sexual phase of the malarial parasite occurs in the Anopheles mosquito. As the female Anopheles mosquitoes feed on blood, only they can serve as vector hosts of malarial parasites. The parasite does not harm the mosquito.

Q.38. Assertion: Malarial fever appear at merozoite stage of Plasmodium.
Reason: The infective stage of Plasmodium is sporozoite.

Answer Answer: (b) When the mosquito bites man, sporozoites present in the salivary gland of female Anopheles mosquito are injected into the blood of the man. The erythrocytic schizont gives rise to merozoites. Malaria fever occurs when schizonts in red blood corpuscles burst and set free their contained merozoites and malarial pigment (haemozoin) in the blood plasma.

Q.39. Assertion: Schizogony is an asexual reproduction of female Anopheles mosquito.
Reason: It takes place only in human liver cells.

Answer Answer: (c) Schizogony is an asexual reproduction in which schizont is formed. From the human blood, sporozoites enter the liver cells. The sporozoite grows in size to become a rounded schizont called cryptozoite. The latter divides to form cryptomerozoites. The cryptomerozoites formed during preerythrocytic schizogony may enter the human RBCs to start the erythrocytic schizogony, while some of them enter new liver cells to repeat hepatic (liver) schizogony.

Q.40. Assertion: Kingdom-Protista forms a link between monerans and and the other organism like plants, animal and fungi.
Reason: Protist reproduce sexually and asexually by a process involving cell fusion and zygote formation.

Answer Answer: (b) Phylogenetically the Kingdom-Protista acts as a connecting link between the prokaryotic Kingdom- Monera and the complex multicellular kingdom- Fungi, Plantae and Animalia. They reproduce asexually and sexually.

Q.41. Assertion: Euglena cannot be classified on the basis of two kingdom system.
Reason: Euglena is a plant due to presence of chlorophyll.

Answer Answer: (c) Euglena is a green coloured, single celled organism, which moves like animals. Some taxonomists considered it as a plant and included it in the plant kingdom on the basis of chlorophyll, while other included it in the animal kingdom along with the flagellated protozoans because of the locomotion by flagella.

Q.42. Assertion: The protist feeds on red blood corpuscles.
Reason: Amoebiasis is caused by Amoeba

Answer Answer: (c) Person suffering from amoebic dysentery has repeated blood mixed with slimy and foul smelling motions. The protist feeds on red blood corpuscles by damaging the wall of large intestine and reaching the blood capillaries.

Q.43. Assertion : Aflatoxins are produced by Aspergillus flavus.
Reason : These toxins are useful to mankind.

Answer Answer: (c) Aflatoxins, are produced by Aspergillus flavus. Contaminated food is the main source of infection. This toxin causes aflatoxicosis which may lead to haemorrhage and diseases of liver.

Q.44. Assertion : Saccharomyces ellipsoidens is Wine yeast and Saccharomyces cerevisiae is Baker’s yeast.
Reason :Yeast is used to make dry ice.

Answer Answer: (b) The two common yeasts used by brewing industry are Saccharomyces cerevisiae (Beer or Baker’s yeast) and S. ellipsoidens (Wine yeast). In the baking or brewing industry, CO2 is the useful product. It is collected, solidified and sold as “dry ice”.

Q.45. Assertion : Neurospora is commonly called water mould.
Reason : It belongs to basidomycetes fungi.

Answer Answer: (d) Neurospora belongs to class ascomycetes in which ascospores are produced in sac like asci . Neurospora is commonly called as pink or red bread mould. It can be grown easily in laboratory conditions so, used in genetics experiments.

Q.46. Assertion: Phycomycetes are commonly known as sac fungi.
Reason: In phycomycetes, ascospore (sexual spores) are produced endogenously in sac like asci.

Answer Answer: (d) Ascomycetes is commonly known as sacfungi. Sexual spores of Ascomycetes are produced endogenously in sac like asci. Members of Phycomycetes are found in aquatic habitats and on decaying wood in moist and damp places or as obligate parasites on plants

Q.47. Assertion: Deuteromycetes is known as fungi imperfecti.
Reason: In Deuteromycetes, only the asexual phase is known.

Answer Answer: (a) Deuteromycetes are commonly known as imperfect fungi because only the asexual or vegetative phases of these fungi are known and perfect or sexual stage is either absent or not known.

Q.48. Assertion: “Fungi imperfecti” does not show alternation of generation.
Reason: The diploid phase is present in only zygote.

Answer Answer: (c) Fungi imperfecti is that group of fungi where only the imperfect stage (asexual stages) is present. The only known method of reproduction is by conidia (asexual reproduction). As sexual reproduction is absent in this group therefore, diplophase is also absent.

Q.49. Assertion: Rhizopus and Mucor are used in liquor industry.
Reason: These cause fermentation.

Answer Answer: (a) Both Rhizopus and Mucor species are used in alcoholic fermentation. Both of these produce a number of organic acids like citric acid, lactic acid and fumaric acid.

Q.50. Assertion: Morels and Truffles are edible fungi.
Reason: Ascocarps are edible.

Answer Answer: (a) The frutifications of some ascomycetes, i.e., ascocarps are edible, e.g., morels, truffles.

Q.51. Assertion: Yeast are the best source of vitamin B complex.
Reason: Ashbya gossypii is a filamentous yeast.

Answer Answer: (b) Yeasts are the best sources of vitamin B complex. Riboflavin (B6) is obtained from a filamentaous yeast, Ashbya gossypii.

Q.52. Assertion: Claviceps produces lysergic acid.
Reason: It is carcinogenic.

Answer Answer: (c) A derivative of ergot known by name of lysergic acid (LSD) is used in experimental psychiatry, as it is a hallucinogen.

Q.53. Assertion: Mushrooms are called fairy rings.
Reason: Mushroom consists of two parts-stipe and pileus.

Answer Answer: (b) The basidiocarps or mushrooms often lie in rings. Therefore, these are also known as fairy rings. Each basidiocarp consists of two parts-stipe and pileus. The stipe or stalk is fleshy while, pileus is umbrella-like cap of the mushroom.

Q.54. Assertion: Actinomycetes are mycelial bacteria.
Reason: They are called ray fungi.

Answer Answer: (a) Actinomycetes are mycelial (aseptate, branched filamentous) bacteria which form radiating colonies in culture hence, formerly called ray fungi. e.g. Streptomyces.

Q.55. Assertion : Symbiosis is furnished by mycorrhiza.
Reason : In mycorrhiza, symbiosis is established between fungus and alga.

Answer Answer: (c) Mycorrhiza represents mutualistic symbiosis between fungus and roots of higher plants. Fungus helps in absorption of minerals and water more efficiently and protect plant roots from infection. Fungus also gets food from plant.

Q.56. Assertion: Viruses are nucleoproteins and lack cell organelle, etc.
Reason: Viruses are not considered organism.

Answer Answer: (a) Virus is a small infectious agent that can only replicate inside the cells of another organism. Viruses are not considered as organisms as they have no independent machinery.

Q.57. Assertion : TMV is a virus which causes mosaic disease.
Reason : TMV has RNA as genetic material.

Answer Answer: (b) In TMV, the chromosome consists of single stranded, linear RNA molecule coiled into a regular spiral. TMV causes mosaic disease in tobacco and some other plants.

Q.58. Assertion: Mycoplasmas are pathogenic in animals and plants.
Reason: Mycoplasmas lack cell wall and can survive without oxygen.

Answer Answer: (b) Mycoplasmas or mollicutes are the simplest and the smallest of free living prokaryotes, they can survive without oxygen. Mycoplasmas are heterotrophic in their nutrition. Some of them live as saprophytes but majority parasitise plants and animals. The parasitic habit is due to the inability of the most mycoplasmas to synthesise the required growth factors.

Q.59. Assertion: “Contagium Vivum Pasteur Fluidum” was coined by Pasteur.
Reason: Pasteur found that virus infected plant of tobacco can cause infection in healthy plant.

Answer Answer: (d) M.W. Beijerinek (1898) demonstrated that the extract of the infected plants of tobacco could cause infection in healthy plants and called the fluid as Contagium Vivum Fluidum (infectious living fluid).

Q.60. Assertion: Virus is an obligate parasite.
Reason: Virus is host specific.

Answer Answer: (b) Virus is an obligate parasite. It is inert outside the host cell. A virus does not grow, divide or reproduce like typical organisms. Instead it multiplies by independent formation of its parts using host cell’s machinery and then assembly of parts to produce virus particles. Viruses are host specific.

Q.61. Assertion: In lichens, mycobiont and phycobiont are symbiotically associated in algae which is predominant and fungi is a subordinate partner.
Reason: In this symbiotic association, the fungus provides food while the alga protects fungus from unfavourable conditions.

Answer Answer: (d) Lichens are symbiotic associations i.e., mutually useful associations between algae and fungi. The algal component is known as phycobiont and fungal component as mycobiont, which are autotrophic and heterotrophic, respectively. Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for its partner. Fungi dominate the relationship.

Q.62. Assertion: These lichens are upright and have pendulous organisation and are attached to substratum by a discoid structure.
Reason: Fruticose are well branched leafy lichens.

Answer Answer: (c) Fruticose are well branched shruby lichens with upright and pendulous organization. These are attached to substratum by a discoid structure. Plant body can be divided into prostrate, leafy and lobed thallus.


Biological classification

Biological classification is defined as the ordering or ranking of organisms into groups on the basis of similarities or closeness or relationship. As there are large numbers of plants and animals in the world, so it is easier to study them after they are arranged in some small or large groups.

Forms of biological classification: –

Two distinct forms of classification are as follow –
i) Classification of overlapping sequences or Keys.
ii) Classification following taxonomical hierarchy.

Basis of Biological classification: –

i) Biological classification initially was based on superficiality morphological characteristics.
ii) With the development of natural system of classification, the morphological characteristics were considered in every minute detail, along with that, there was also consideration of the reproductive features.
iii) The phylogenetic system of biological classification considered is the gradual evolution of organisms and their phylogenetic relationships.
iv) The modern system considers all the relevant data from other branches of biology and it is developed by adequate computation.

Purposes of biological classification: –

i) Biological classification helps in the arrangement of living plants and animals.
ii) It provides explanation for the diversity of organisms.
iii) It keeps proper knowledge of evolution of organisms.
iv) It gives the scope for the discovery of new spaces.
v) It helps in the storage of data about living organisms in the form of key and utilise them whenever necessary.
vi) It is a tool for identifying organisms.

Types of biological classification: –

There are mainly three types of classification system those are artificial system, natural system and phylogenetic system of classification.

Artificial system: –

This system is based on one or two superficial characteristic without considering any morphological details or phylogenetic relationships.

Merit of artificial system:
It was the first novel attempts of classification of living organisms and therefore it have some importance of the history of biological classification.

Demerit of artificial system:
In this system closely related species may be placed distinctly apart and distant species might be placed together. The evolutionary relationships were not understood by this type of classification.

Natural system: –

This is the system of biological classification which is based on several natural characteristics. These simplest organisms are placed early while the complex ones are placed latter in this system. This system relied on the constancy of spaces. George Bentham and J. D. Hooker proposed system in 1862 and 1883 respectively. Several morphological characters were taken into consideration in these system and for this reason it is widely accepted and glands are arranged according to this system in many organised botanical Gardens

Merits of natural system:
This system of biological classification gives an easy means of identification of plants which are unknown. Morphological characters of plants have been studied before placing them in their respective positions. It has been widely accepted due to an original novel attempt describing 97,205 spaces.

Demerits of natural system:
Gymnosperms were wrongly placed between dicotyledonous and monocotyledonous plants. There was no phylogenetic consideration in this system and some of the closely related species are placed distantly while distant places are placed close to each other.

Phylogenetic system: –

This system of biological classification is based on evolutionary sequence and genetic relationships taken in consideration. After the publication of Darwin’s theory in 1859 the system was actually developed and along with the natural morphological characteristics which are inputs from fossils records the genetic constitutions were also considered. Due to this it is largely accepted by modern biologist.

Merits of phylogenetic system:
This system gives the phylogenetic relationship and has resulted in the development of experimental taxonomy. It has the estimated hollowness and is widely accepted by the biologist.


Biological Classification

In our daily life, we come across several animals, plants, and microbes, which have been named in order to understand their importance and to communicate with them. However, this communication about organisms becomes difficult in an area or a region where they do not occur or if they occur but are recognized by some other name. Further, organic evolution has caused a great number of biodiversity adding another problem to biologists to remember, and to identify new ones. All these factors contribute to a need for developing a system, called taxonomy.Taxonomy is the branch of science dealing with naming,
Taxonomy is the branch of science dealing with naming, the grouping of organisms on the basis of the degree of similarity and arranging them in an order on the basis of their evolutionary relationship. Therefore, in other words, taxonomy is related to nomenclature, classification and phylogeny of organisms. Taxonomy unlike natural sciences such as Botany, Zoology, Physics, Chemistry, etc. is considered as a synthetic (man-made) and multidisciplinary science. It owes its progress on the advancement made in other branches of sciences like morphology, histology, physiology, cell biology, biochemistry, genetics, molecular biology, computational biology etc.
Nomenclature and Taxonomic Hierarchy
Carolus Linnaeus (1707-78) a Swedish botanist known as the father of taxonomy is credited for the establishment of taxonomy as a separate science. He was instrumental in framing the rules for naming the organisms, which he applied uniformly while giving his classification. It was he who popularized the binomial nomenclature that is the modern scientific way of naming organisms.

  • In binomial nomenclature name of every organism is composed of two parts: first is called generic name representing the taxon – Genus to which it belongs and second is called specific epithet- Species.
  • The generic name always starts with the capital letter and specific name always with the small letter.
  • These scientific names are used uniformly regardless of regions/countries or
    languages and two different organisms cannot possess the same scientific name.
  • The names of different organisms used in binomial nomenclature system must be derived from Latin or if names to be used are from different languages they must be treated as Latin.

The nomenclature of organisms is governed by a set of rules framed by International Codes of Nomenclature. There are different codes of nomenclature for different groups of organisms for example, naming of bacteria, animals and plants are governed by International Code for Nomenclature for Bacteria (ICNB), International Code of Zoological Nomenclature (ICZN) and International Code of Botanical Nomenclature (ICBN) respectively. The scientific name of an organism, when cited in any text, is always mentioned as in italics or underlined font style. The name of the author who first gave the correct name as per rules is written in abbreviated form after the specific name and is written in Roman.

Another aspect of taxonomy is classification, which is the grouping of different organisms on the basis of shared features into different categories called taxa. Different taxa are then arranged in a hierarchical manner starting from lower to higher ranks that is:

This ordered arrangement of various taxa is called taxonomic hierarchy.

An organism is placed in different groups (ranks) on basis degree of similarity. All related groups are arranged in a hierarchical fashion starting from lowest, Species to highest. Dissimilarity among different related groups increases of hierarchical order. Example- as shown in the figure classification of rolling alga- Volvox aureus.

In this taxonomic hierarchy, each organism is assigned a species name and species of very similar organisms are grouped into a genus. The genera having very similar characteristics are grouped together into a family and similarly, several families form an order, several orders into a class and ultimately on the top, all similar classes are grouped into a kingdom
In recently proposed classifications, a new higher rank- domain/empire has been added on the top of rank, kingdom.Classification is done in order to make the process of identification of known organisms
Classification is done in order to make the process of identification of known organisms simpler. While classifying the organisms it is presumed that all the organisms have diverged through organic evolution from one common ancestor. This is called the concept of unity amongst diversity. Another important point to remember about classification is that members of higher level of ranks share fewer characteristics than those in lower level ranks. One of the objectives of taxonomy is to classify organisms according to their evolutionary (ancestral) relationship (phylogeny), which is not an easy task especially in absence of connecting fossils links. Creating a universally accepted system of classification has always remained a problem in the field of taxonomy. This is because being synthetic branch, taxonomy is very subjective, and there is no consensus among biologists over the uniformity of importance given to different characters in relation to evolution. Moreover, our knowledge about living organisms is still incomplete therefore any change or addition in this knowledge-database always reflects in the field of taxonomy.
Earlier taxonomists divided the living organisms on the basis of morphological characters, as there was no any sophisticated tool available to study living world. So, whatever information was available it was about visible macro-organisms. Therefore organisms were arranged into two groups- plants and animals based on easily observable (phenotypic) characteristics.

CharacterKingdom
PlantaeAnimalia
Body organizationSimple, Organ systems like excretory, sensory, nervous etc. absentWell developed and organ systems like excretory, sensory, nervous etc. present
MobilityAbsent as organs of locomotion are not presentPresent due to occurrence of organs of locomotion
Growth and developmentIndefiniteDefinite as body grows to certain size and then stop.
NutritionAutotrophic through either photosynthesis or absorptionHeterotrophic through ingestion

This system of classification was called two-kingdom classification and it was followed for a very long period in history of biological sciences. However, invention of microscope in 16th century made it possible to explore the living world, which was not earlier possible to explore through human-naked-eyes. This exploration revealed an altogether new world of microorganisms sharing features of both plants and animals. For example, Euglena, a green, autotrophic, motile organism having definite shape and size, and obtains food by ingestion process in absence of light. Similarly Chlamydomonas, a photoautotrohic organism but also has animal-like feature such as motility and definite shape and growth. Further, fungi although have plant-like features such as immobility, irregular shape, and indefinite growth but also possess heterotrophic mode of nutrition, a characteristic feature of animals. Therefore such microorganisms could not have appropriate placement in two kingdom classification. In order to classify these microorganisms, Ernst H. Haeckel in 1866 proposed a three-kingdom classification in which he added a new kingdom – Protista.

Tree of life based on three-kingdomnm classification.

In this new kingdom he included all simple microscopic living organisms such as bacteria, microalgae, protozoa, fungi and sponges. Further advancement in the techniques of microscopy and their application to biology generated new information that added to the scientific knowledge. Studies of various organisms at cellular and subcellular level in 19th and 20th centuries proved that all organisms are made up of a basic unit called cell, which could be structurally simple (prokaryotic cell) or complex (eukaryotic cell). All the known organisms possess either prokaryotic or eukaryotic cell organization and therefore they can be accordingly called as either prokaryotes or eukaryotes, respectively. Several taxonomists insisted on inclusion of this fact (cell type) in classification of organisms. In 1956, Lynn Margulis and H. F. Copeland adapted this criterion in their classification and proposed a four-kingdom classification system in which kingdom- Protista was divided into two new kingdoms, Monera containing all prokaryotes and Protoctista containing all simple, microscopic eukaryotic organisms like algae, protozoa and fungi. In 1969, R. H. Whittaker proposed a five-kingdom classification in which kingdom –
In 1969, R. H. Whittaker proposed a five-kingdom classification in which kingdom – Protoctista was split into kingdoms- Protista and Fungi. Carl Woese (1990) suggested further rectification in system of classification. Relying on the information gathered with the help of various techniques of molecular biology about different prokaryotes he proposed revision of kingdom- Monera. In this classification kingdom- Monera was abolished and a new category- domain on the top of category, Kingdom was introduced. This taxonomic system is known as a three-domain classification that includes domains – Bacteria, Archaea and Eukarya.
Thus, in conclusion, taxonomy is still a growing discipline, and system of classification and status of evolutionary relationship amongst various groups will remain unsettled until we have complete information about all the organisms present on this earth. Till then we have to revisit our taxonomic system again and again in light of new information and knowledge as we have been doing so since past.

Progress has taken place in classification system as a result of incorporation of new information.

Five Kingdom Classification
This is one of the most widely accepted systems of classification proposed by an American taxonomist, R. H. Whittaker in 1969. After Whittaker, this system is also called Whittaker’s system of classification. In this classification, cellular organisms have been divided into five kingdoms namely, Monera, Protista, Fungi, Plantae and Animalia. This classification is an improvement of earlier proposed four-kingdom classification as in this system a new kingdom- Fungi has been erected.

Whittaker’s five-kingdom classification based on complexity of cell, cellular organization, mode of nutrition and ecological role played

Whittaker delimited the five kingdoms on the basis of three main criteria viz. cell structure type, the degree of cellular organization and mode of nutrition. Besides these major characteristics, he has also given importance to characters of ecological role-played and mode of reproduction.
Major criteria on which five-kingdom classification is based

He also attempted to establish phylogentic relationship amongst various groups of different
kingdoms.

Phylogenetic relationship among different groups in five-kingdom classification

According to him the earliest living forms (progenote) produced prokaryotic organisms or monerans. Monera gave rise to protists probably through association of several types of primitive and advanced monerans. Protists in tern gave rise to fungi, plants and animals.
The characteristic features and members of each of five kingdoms are briefly discussed:
Kingdom – Monera

  1. It is the kingdom of all the prokaryotes and includes eubacteria, cyanobacteria (bluegreen algae) and archebacteria.
  2. The organisms are unicellular, colonial, mycelial and filamentous in form.
  3. They lack true nuclei and other membrane bound organelles such as mitochondrion, chloroplast, Golgi bodies, lysosomes etc. and DNA, which is the genetic material and is called nucleoid, is not found associated with histone proteins cell wall is often present but chemically made up material other than cellulose.
  4. Mode of nutrition varies from autotrophy to heterotrophy.
  5. Sexual reproduction is absent and asexual reproduction may take place through fission, fragmentation, budding and sporulation.

Kingdom – Protista

  1. It is a group of organisms differing widely with one another except that they all are simple and minute eukaryotes. It includes microalgae, protozoa and slime moulds.
  2. Majority of them are unicellular but some may be colonial in form.
  3. They contain true nuclei and membrane bound organelles cell wall may or may not be present.
  4. Nutrition is very diversified and may be autotrophic (via photosynthesis) or heterotrophic (ingestion/absorption).
  5. Asexual means of reproduction is common but when organisms reproduce sexually, embryo is not formed.

Kingdom – Fungi

  1. It is the group of mostly multicellular or multinucleate achlorophyllous and sporeproducing eukaryotic organisms and includes mildews, moulds, yeasts, morals, truffles, mushrooms, rusts etc.
  2. The body of organisms is mycelial in form cell wall is present and made up of chitin or cellulose.
  3. Nutrition is absorptive heterotrophy where organism secretes digestive enzymes into the substrate and then absorbs the digested food.4. Asexual reproduction is primary mode of reduction and sexual reproduction causes
  4. Asexual reproduction is primary mode of reduction and sexual reproduction causes formation of specialized spores.
  5. They play the ecological role of decomposer.

Kingdom – Plantae

  1. It includes all coloured multicellular photosynthetic eukaryotic organisms commonly called as plants. The important constituents are macroalgae, bryophytes,
    pteridophytes, gymnosperms and angiosperms.
  2. Plant body is either thalloid (algae and some of bryophytes) or differentiated into
    root, stem and leaves nonmotile Cell wall is present and it is chemically made up of cellulose.
  3. Nutrition by: autotrophy (photosynthetic)
  4. Both asexual and sexual reproductions occur. An embryo stage is present except in algal group.
  5. They play the ecological role of producers.

Kingdom – Animalia

  1. It is a group of all macroscopic animals derived from zygote and includes sponges, coelentrates, worms, annelids, arthopodes, mollusces, star fishes, fishes, amphibians, reptiles, birds and mammals.
  2. Organisms are multicellular with higher degree of body organization where tissue differentiation usually leads to specialized organ formation. Eukaryotic cell is without cell wall and chlorophyll pigments.
  3. They exhibit mobility, sensitivity to different stimuli and definite growth.
  4. They reproduce primarily by sexual reproduction and embryo stage is usually present.
  5. They play ecological role of consumer.

Demerits of five- kingdom Classification
Although this system is considered to be an advanced system but still objections have been raised against this, which are following.

  1. It fails to distinguish between archaebacteria and eubacteria.
  2. The kingdom- Protista is highly heterogeneous group of organisms, which seems to be having polyphylatic evolution.
  3. Placement of algae on the basis of degree of cellular organization into different kingdoms appears to be unrealistic.
  4. Red and brown algae placed in kingdom – Plantae are not related to other members.
  5. Viruses an important form of life has not been considered in this system of classification.

Three Domain Classification
Progress done in molecular biology especially in biochemistry and molecular genetics in later decades of 20th century provided new techniques to study and compare organisms. The study of chemical structure and sequence of macromolecules such as proteins and nucleic acid can give insights in understanding the functions and evolutionary relationship of different organisms. For example, cytochrome c protein, a component of electron transport chain occurring in mitochondria rbcl gene, encoding rubisco enzyme present in chloroplast and small subunit ribosomal RNAs (SSUrRNAs) are very useful in such studies. Among various probable contender macromolecules that can help in determining the relationship amongst entire living world, rRNA fits the requirement the most as this form of ribonucleic acid is (a) found uniformly distributed in all the self-replicating cells as one of the basic components of ribosomes (b) easy to isolate (c) structurally stable due to its very low mutation rate therefore making it an ideal molecule for detecting the relatedness amongst distant species. Carl Woese and George Fox (1977) compared 16s/18s rRNA present in different species and concluded that rather than two different basic cell types (prokaryotic and eukaryotic cells) as suggested by cytological data, molecularly, there are, in actual, three basic types of cells –

  • one, present in eubacteria
  • second, present in archaebacteria and
  • third, present in eukaryotes.

If organisms are grouped on the basis of three basic cells, the molecular dissimilarity among different cell type based groups appears so prominent that these groups cannot be Biological Classification Institute of Lifelong Learning, University of Delhi 15
considered equivalent to the taxon, kingdom. Therefore, Carl Woese et al. introduced a new taxon – domain above the level of kingdom in their new system of classification, which they proposed in 1990. Under this system, life has been divided into three domains, the Bacteria, the Archaea and the Eukarya.

Three domains of life showing phylogenetic relationship among groups on the basis of rRNA data.

Just beneath domain is the rank of kingdom. The question of exact number of kingdoms in each domain has been left unaddressed for future settlement, as new emerging molecular data will soon throw more light on such natural groupings. However, in domain- Bacteria the elevation of different phyla, proposed in earlier contemporary systems, to the ranks of kingdoms has been suggested. Similarly, in domain- Eukarya three kingdoms: Plantae, Animalia and Fungi and division of protists (kingdom-Protista) into various kingdoms on the basis of molecular characterization have been suggested. Domain, Archaea contains two kingdoms- Euryarchaeota (group of methanogens) and Crenarchaeota (group of extreme thermophiles).
Characteristic features of three domains.

CharacterBacteriaArchaeaEukarya
Cell typeProkaryoticProkaryoticEukaryotic
Cell wallPresent contain peptidoglycanPresent peptidoglycan absentPresent/absent peptidoglycan absent
Membrane lipidsDiacyl glycerol diestersisoprenoid glycerol diethers or diglycerol tetraethersGlycerol fattyacyl diesters
Genetic materialSmall circular DNA not associated with histonesSmall circular DNA associated with histones like proteinsLarge linear DNA associated with histones
Translation (first amino acid)FormylmethionineMethionineMethionine
RNA polymeraseOne simpleOne complexOne complex
tRNA (TψC arm)Thymine presentThymine absentThymine present
IntronAbsentPresent rarelyPresent
Antibiotic sensitivityYesNoNo
Diphtheria toxin sensitivityNoYesYes
ReproductionSpore formation presentSpore formation absentSpore formation present or absent
HabitVariableExtremophileVariable

The distinguishing features of these domains :Domain – Bacteria
Domain – Bacteria


Welcome to the Living World

Aristotle’s classification: Plants to trees, shrubs & herbs. Animals to those with red blood & without red blood.

Linnaeus: 2-Kingdom classification (Plantae & Animalia).

  • Prokaryotes & eukaryotes under Plants.
  • Unicellular and multicellular organisms in same group.
  • No differentiation between fungi and plants.

Polysaccharide + amino acid

Multicellular, loose tissue

Most abundant microorganisms.

  • Halophiles: Live in salty areas.
  • Thermoacidophiles: In hot springs.
  • Methanogens: In marshy areas and guts of ruminant animals. Produce methane (biogas).

Rigid cell wall and a flagellum.

  • Have chlorophyll a.
  • Cyanobacteria (blue-green algae) colonies have gelatinous sheath. Some fix nitrogen in heterocysts. E.g. Nostoc & Anabaena.

b. Chemosynthetic autotrophs: Oxidize inorganic substances and release energy.

c. Heterotrophic bacteria: Most abundant. Decomposers.

Some have flagella or cilia.

Reproduction: Asexual & sexual (cell fusion → zygote).

  • Diatoms & golden algae (desmids).
  • Diatoms have siliceous cell walls. Their cell wall deposit is called diatomaceous earth.
  • Mostly marine and photosynthetic.
  • Cell wall: stiff cellulose plates.
  • Most have 2 flagella.
  • Red dinoflagellates (E.g. Gonyaulax)- sea appears red (red tides).
  • Have a protein rich layer (pellicle) & 2 flagella.
  • Photosynthetic in sunlight. Heterotrophs in darkness.
  • E.g. Euglena.
  • Saprophytic protists.
  • Suitable condition → form an aggregation (plasmodium).
  • Unfavourable conditions → plasmodium differentiates → fruiting bodies bearing spores.
  • Amoeboid protozoans: Move & capture prey by pseudopodia (false feet). E.g. Amoeba, Entamoeba (parasite).
  • Flagellated protozoans: Have flagella. Parasites cause diseases like sleeping sickness. E.g. Trypanosoma.
  • Ciliated protozoans: Move by cilia. E.g. Paramoecium.
  • Sporozoans: Have infectious spore-like stage. E.g. Plasmodium (malarial parasite).

Except yeasts, fungi are filamentous.

Hyphae: Thread-like structures of the body.

Mycelium: Network of hyphae.

  • Coenocytic hyphae: Continuous tubes with multinucleated cytoplasm.
  • Septate hyphae: Have septae or cross walls.
  • Vegetative propagation: Fragmentation, fission & budding.
  • Asexual: Spores (conidia, sporangiospores & zoospores).
  • Sexual: By oospores, ascospores & basidiospores. They are produced in fruiting bodies.
  1. Plasmogamy: Fusion of protoplasm between two motile or non-motile gametes.
  2. Karyogamy: Fusion of two nuclei.
  3. Meiosis in zygote to give haploid spores.

In some fungi, 2 haploid cells fuse → diploid cells (2n).

In ascomycetes & basidiomycetes, a dikaryotic stage or dikaryophase (2 nuclei) occurs. Such condition is called a dikaryon. Later, parental nuclei fuse → diploid.


NEET Coaching Biology: Biological Classification

NEET Coaching Biology: Biological Classification Sample Questions (Plus One Topic)

    1. Select the correct statement
      1. The three-domain system has also been proposed divides the Kingdom Monera into one domains, leaving the remaining eukaryotic kingdoms with second and third domain and thereby a six kingdom classification.
      2) Marine forms of amoeboids have silica shells on their surface.
      3) Slime moulds are saprophytic protists. The body moves along decaying twigs and leaves engulfing organic material. Under suitable conditions, they form an aggregation called plasmodium which may grow and spread over only few cm.
      4) The below diagram represent saprophytic protozoans.
    2. Select the correct options regarding prions
      1) In modern medicine certain infections neurological diseases were found to be transmitted by an agent consisted of normally folded protein.
      2) The agent was large in size compared to viruses. These agents were called prions.
      3) The most notable diseases caused by prions are bovine spongiform encephalopathy (BSE) commonly called mad cow disease in cattle
      4) Its homologous variant Cr–Jacob disease (CJD) in humans.
    3. In lichens mycobionts do …………..A……… .and phycobionts do……….B…….
      1) A= provide shelter and absorb mineral nutrients and water B= prepare food
      2) A= prepare food B= provide shelter and absorb mineral nutrients and water
      3) A= provide shelter B= prepare food and absorb mineral nutrients and water
      4) A= absorb mineral nutrients and water B= prepare food and provide shelter
    4. Viroids are
      1) Main cause of bovine spongiform encephalopathy
      2) High molecular weight RNA cause potato spindle
      3) Free RNA that lack protein coat discovered by T O Diener in 1981
      4) A new infectious agent that was smaller than viruses and caused potato spindle tuber disease
    5. The name virus that means venom or poisonous fluid was given by
      1) Pasteur
      2) D.J. Ivanowsky
      3) M.W. Beijerinek
      4) W.M. Stanley
    6. …………………. (1892) recognised certain microbes as causal organism of the mosaic disease of tobacco .These were found to be …………………….because they passed through bacteria-proof filters.
      1) D.J. Ivanowsky 1893, smaller than bacteria
      2) Pasteur 1892, larger than bacteria
      3) D.J. Ivanowsky 1892, smaller than bacteria
      4) M.W. Beijerinek 1898, smaller than bacteria
    7. Find the mismatch
      1) M.W. Beijerinek (1898) -demonstrated that the extract of the infected plants of tobacco Contagium vivum fluidum
      2) W.M. Stanley (1935) -viruses could be crystallised and crystals consist largely of proteins.
      3) D.J. Ivanowsky 1893-demonstrated that the extract of the infected plants of tobacco Contagium vivum fluidum
      4) All are correct
    8. Bacteriophages are
      1) Usually single stranded DNA viruses that infect the bacteria
      2) Usually double stranded RNA viruses that infect the bacteria
      3) Usually double stranded DNA viruses that infect the bacteria
      4) Usually double stranded RNA viruses that infect the plants
    9. Select the correct option regarding the diagram

      A B C D
      1) Head collar sheath Tail fibres
      2) Head sheath collar Tail fibres
      3) DNA Collar Sheath Tail fibres
      4) Head collar Sheath basal plate
      1. The viruses are
        1) Acellular organisms that are characterised by having an inert crystalline structure inside the living cell.
        2) Non-cellular organisms that are characterised by having an inert crystalline structure inside the living cell.
        3) Non-cellular organisms that are characterised by having an inert crystalline structure outside the living cell.
        4) Non-cellular organisms that are characterised by having an inert crystalline structure inside and outside the living cell.
      2. Find out the mismatched pair
        1) Bladderwort -insectivorous plants
        2) Cuscuta –parasite
        3) Venus fly trap -insectivorous plants
        4) Sundew- parasite
      3. Select the correct statements regarding dueteromycetes
        A. Once perfect (sexual) stages of members of dueteromycetes were discovered they were often moved to ascomycetes and basidiomycetes.
        B. The deuteromycetes reproduce only by sexual spores known as conidia
        C. The mycelium is Aseptate and branched.
        D. Some members are saprophytes or parasites while a large number of them are decomposers of litter and help in mineral cycling.
        E. Some examples are Alternaria, Colletotrichum andTrichoderma.
        1) A,B,C
        2) A,D,E
        3) B,C,D,E
        4) A,C,D,E
        1. Basidiospores are
          1) Exogenous spores found in fruiting bodies of Agaricus Ustilago and neurospora.4 in one basidium
          2) Endogenous spores found in fruiting bodies of Agaricus Ustilago and Puccinia 8 in one basidium
          3) Exogenous spores found outside fruiting bodies of Agaricus Ustilago and Puccinia .8 in one basidium
          4) Exogenous spores found in fruiting bodies of Agaricus Ustilago and Puccinia . 4 in one basidium
        2. Asexual spores are absent in
          1) Neurospora Ustilago and Puccinia
          2) Agaricus Ustilago and Puccinia
          3) Agaricus Ustilago Neurospora and Puccinia
          4) Agaricus Ustilago claviceps and Puccinia
        3. Neurospora is used
          1) Extensively in biochemical and genetic work. They posses endogenous spores called ascospores
          2) Very less in biochemical and genetic work. They posses endogenous spores called ascospores
          3) Extensively in biochemical and genetic work. they posses exogenous spores called basidiospores
          4) Extensively in biochemical and genetic work.the posses exogenous spores called ascospores
        4. Find the correct sequence of life cycle in Ascomycytes
          1) Plamogamy -dikaryon–fruiting body-karyogamy-meiosis-ascospores-haploid hyphae
          2) Fruiting body – Plamogamy –dikaryon-karyogamy-meiosis-ascospores-diploid hyphae
          3) Plamogamy- dikaryon –fruiting body-karyogamy-meiosis-ascospores-diploid hyphae
          4) Fruiting body- Plamogamy –dikaryon-karyogamy-meiosis-ascospores-haploid hyphae
        5. Coprophilous fungi include
          1) Peziza and pilobolus dueteromycetes
          2) Peziza and pilobolus basidiomycetes
          3) Peziza and pilobolus ascomycetes
          4) Agaricus and colletotrichum-basidiomycete
        6. Fungi causing ring worm infections are
          1) Trichoderma.-Dueteromycetes
          2) Aspergillus – Ascomycytes
          3) Alternaria, Colletotrichum-phycomycetes
          4) None of the above
          1. Non motile endogenous asexual spores are
            1) Zoospore
            2) Aplanospore
            3) Ascospores
            4) Conidiospores
          2. Dikaryon phase is found in
            A. Rhizopus
            B. Albugo
            C. Ustilago
            D. Aspergillus
            E. Mucor
            F. Puccinia
            G. Colletotrichum
            H. Penicillium
            I. Claviceps
            J. Neurospora
            K. Yeast
            1) C,D,F,H,I,J
            2) A,C,D,J
            3) B,D,E,F,G,H,I
            4) A,C,D,J,K
          3. Many members like morels and truffles are.
            1) Edible and are considered delicacies in basidiomycetes
            2) Not edible and are considered delicacies in ascomycetes
            3) edible and are not considered delicacies in ascomycetes
            4) Edible and are considered delicacies in dueteromycetes
          4. Select the incorrect statements
            1) White spots seen on mustard leaves are due to a parasitic algal fungi- albugo
            2) Some unicellular fungi, e.g., yeast are used to make bread and beer.
            3) Wheat rust-causing Puccinia belongs to ascomycetes
            4) Some are the source of antibiotics, e.g., Penicillium.
            1. Symbiotic forms of fungi seen in association with lichens are
              1) Usnea
              2) Cladonia
              3) Rocella
              4) All the above
            2. Storage form of food in fungi is
              1) Oil
              2) Oil and glycogen
              3) Oil,glycogen and starch
              4) Laminarin and mannitol
            3. Fusion of gametangia is seen in
              1) Rhizopus,mucor,albugo
              2) Puccinia ,aspergillus
              3) Trichoderma,Colletotricum
              4) All the above
            4. Find the correct pair
              A. Primary mycelium-monokaryotic and haploid
              B. Secondary mycelium-monokaryotic and diploid(2n)
              C. Tertiary mycelium- dikaryotic and diploid(2n)
              1) 1 only
              2) 1 and 2 only
              3) 1,2 and 3
              4) None are correct
            5. Cell wall of fungi is made of
              1) Chitin – a heteropolysaccharide
              2) Chitin and pectin- homopolysaccharides
              3) Chitin –a homopolysaccharide
              4) Chitin,pectin and hemicellulose
            6. Select the parasitic fungi from the following
              1. Puccinia
              2. Penicillium
              3. Albugo
              4. Peziza
              5. Pilobolus
              6. Ustilago
              1) 1,4,5,6
              2) 1,3,6
              3) 1 and 6 only
              4) All the above
            7. The three-domain system has also been proposed that divides the Kingdom …..A………into two domains, leaving the remaining ….B……….kingdoms in the third domain and thereby a six kingdom classification.
              A B
              1) Protista Eukaryotes
              2) Monera Prokaryotes
              3) Fungi Eukaryotes
              4) Monera Eukaryotes
              1. Select the correct statements regarding earlier classification systems
                I. Included bacteria, blue green algae, fungi, mosses, ferns, gymnosperms and the angiosperms under ‘Plants’.
                II. The character that unified this whole kingdom was that all the organisms included had a cell wall in their cells.
                III. It brought together the prokaryotic bacteria and eukaryotic blue green algae with other groups which were eukaryotic.
                IV. It also grouped together the unicellular organisms and the multicellular like Chlamydomonas and Spirogyra were placed together under algae.
                V. The classification did not differentiate between the heterotrophic group – fungi, and the autotrophic green plants
                1) I,ii,iii,iv
                2) I,ii,iv,v
                3) I,ii,v
                4) All are correct
              2. Kingdom Protista has brought together
                1. Chlamydomonas,
                2. Chlorella
                3. Paramoecium
                4. Amoeba
                1) 1 and 2
                2) 3 and 4
                3) All the above
                4) None of these
              3. Classification system is usuallybased on
                A. Morphological
                B. Physiological
                C. Reproductive similarities
                D. Phylogenetic,
                1) A and B
                2) A and C
                3) A, B and D
                4) All the above
              4. Structure shown below is a microscopical view of

                1) Spores of Coccus
                2) Bacillus with some spores
                3) Coccus
                4) Spirilla
              5. Most extensive metabolic diversity is seen in
                1) Monera
                2) Protista
                3) Fungi
                4) Plantae and Animalia
              6. The vast majority of bacteria are
                1) Photosynthetic autotrophic
                2) Chemosynthetic autotrophic.
                3) Heterotrophs and decomposers
                4) 2 and 3
              7. Bacterial structure is …….A…., they are very ……..B……….in behaviour
                A B
                1) Simple simple
                2) Simple complex
                3) Complex simple
                4) Complex complex
              8. Motile eubacteria should posses
                1) Pili and fimbria
                2) flagellum
                3) Cilia and flagellum
                4) 1 and 2
              9. Main difference between archaebacteria and eubacteria is
                1) Cell membrane structure
                2) Cell wall structure
                3) Mesosomes
                4) All the above
              10. Select the odd one
                1) Salty areas -Halophiles,
                2) Hot springs –Thermoacidophiles
                3) Marshy areas- Methanogens
                4) Heterocyst – nostoc
                1. Select the incorrect statements about cyanobacteria
                  1) Have chlorophyll a, b,d and carotenoids similar to green plants and are photosynthetic autotrophs
                  2) The cyanobacteria are unicellular, colonial or filamentous, freshwater marine or terrestrial algae.
                  3) The colonies are generally surrounded by gelatinous sheath
                  4) They often form blooms in polluted water bodies.
                2. These organisms can fix atmospheric nitrogen in specialised cells called heterocysts,found in
                  1) Nostoc found in association with alnus
                  2) Anabaena found in coralloid roots of cycas
                  3) Spirulina
                  4) Chlorella
                3. Some members ofcyanobacteria oxidise various inorganic substances such as …………………………….and use the released energy for their ATP production.
                  1) Nitrates,
                  2) Nitrites
                  3) Ammonia
                  4) all the above
                4. Cyanobacteria somemembers play a great role in recycling nutrients like
                  A. Nitrogen
                  B. Phosphorous
                  C. Carbon
                  D. Chlorine
                  E. calcium
                  F. Iron
                  G. Sulphur.
                  1) A,B,G
                  2) A,B,D,E,G
                  3) A,B,F,G
                  4) All the above
                5. Bacteria mainly reproduce by
                  1) Spore formation
                  2) Budding
                  3) Fission
                  4) Conjugation
                6. Mycoplasma
                  a. Is the smallest cell without a cell wall
                  b. Belongs to kingdom monera
                  c. Anaerobic and pathogenic
                  d. Pathogenic to animals and plants
                  e. Pathogenic to animals only
                  1) a,b,c,e
                  2) a,b,c,d
                  3) b,c,d
                  4) b,c,e
                7. Diatoms and golden algae (desmids). They are found
                  1) In fresh water environments only. They are microscopic and does not float in water currents
                  2) In marine environments only. They are microscopic and float passively in water currents
                  3) In fresh water as well as in marine environments. They are large massive and float passively in water currents
                  4) In fresh water as well as in marine environments. They are microscopic and float passively in water currents
                8. Chief producers in oceans are
                  1) Gonyaulax
                  2) Euglena
                  3) Planktons
                  4) All the above
                9. Diatoms cell wall deposits are used in
                  1) Polishing, filtration of oils and syrups
                  2) Making sound proof walls
                  3) Heat resistant bricks
                  4) All the above
                10. Cell wall of the organism given below is

                  1) Made of cellulose and double layered
                  2) Made of silica and has two valves
                  3) Made of pectin and cellulose and highly sculptured
                  4) Made of outer pectin and inner cellulosic layer
                11. Select the correct statement regarding the organism given below
                  a. fresh water organisms found in stagnant water
                  b. Marine water organisms found in stagnant water
                  c. Have cell wall
                  d. Have protein coat
                  e. Have unequal flagella
                  f. Have similar pigments like higher plants
                  g. Heterotroph
                  h. always autototroph
                  i. Myxotroph
                  j. Connecting link between plantae and animalia
                  1) a,c,e,i
                  2) b,d,ef,i
                  3) a,d,e,f
                  4) a,d,e,f,i,j


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