Question
Ciliates differ from all other protozoans in [NEET 2018]
(a) using pseudopodia for capturing prey
(b) having a contractile vacuole for removing excess water
(c) using flagella for locomotion
(d) having two types of nuclei
Answer/Explanation
Ans. (d)
Cillates differ from all other protozoans in having two types of nuclei.
These two nuclei are usually of different size, i.e. one is meganucleus and the other is micronucleus. The former controls metabolism whereas the latter is concerned with reproductions, e.g. paramecium.
In other protozoans, like Amoeba, single nucleus is present which is involved in metabolism and reproduction. Other options are incorrect because Ciliates use filtre feeding mechanism for obtaining food.
Like other protozoans, they also possess contractile vacuoles. Ciliates use cilia for locomotion.
Question
Chrysophytes, euglenoids, dinoflagellates and slime moulds are included in the kingdom [NEET 2016, Phase I]
(a) Protista
(b) Fungi
(c) Animalia
(d) Monera
Answer/Explanation
Ans. (a)
All single celled eukaryotic organisms like chrysophytes [diatoms and desmids], euglenoids [Euglena] dinoflagellates and slime moulds are included in kingdom-Protista.
Question
Select the wrong statement. [NEET 2016, Phase II]
(a) The walls of diatoms are easily destructible
(b) ‘Diatomaceous earth’ is formed by the cell walls of diatoms
(c) Diatoms are chief producers in the oceans
(d) Diatoms are microscopic and float passively in water
Answer/Explanation
Ans. (a)
Diatoms are single celled plant like protists that produce intricately structured cell walls made of nand(-) silica (SiO $)$. Thus, the walls are indestructible. Hence, only option (a) is wrong and rest of the options are correct.
Question
Pick up the wrong statement. [CBSE AIPMT 2015]
(a) Cell wall is absent in Animalia
(b) Protista have photosynthetic and heterotrophic modes of nutrition
(c) Some fungi are edible
(d) Nuclear membrane is present in Monera
Answer/Explanation
Ans. (d)
In Protista kingdom members exhibit. both autotrophic as well as heterotrophic nutrition. Animal cells lack cell wall and there are a few fungi that are edible. Monera is the kingdom that contains unicellular organisms with a prokaryotic cell organisation, i.e. which lacks nuclear membrane and other membrane bound organelles.
Question
51 In which group of organisms the cell walls form two thin overlapping shells which fit together? [CBSE AIPMT 2015]
(a) Chrysophytes
(b) Euglenoids
(c) Dinoflagellates
(d) Slime moulds
Answer/Explanation
Ans. (a)
Chrysophytes are placed under the kingdom-Protista. This group includes diatoms and golden algae (desmids). Most of them are photosynthetic. In diatoms, the cell walls form two thin overlapping cells, which fit together as in a soap box.
Question
What is common about Trypanosoma, Noctiluca, Monocystis and Giardia? [CBSE AIPMT 2006]
(a) These are all unicellular protists
(b) They have flagella
(c) They produce spores
(d) These are all parasites
Answer/Explanation
Ans. (a)
Trypanosoma, Noctiluca, Monocystis and Giardia are all unicellular protists.
Trypanosoma gambiense is the single celled, parasitic zooflagellate causing trypanosomiasis or sleeping sickness. Giardia or the ‘Grand old man of the intestine’ is a parasitic flagellate occurring in the intestine of man and other animals and causes giardiasis or diarrhoea (i.e. very loose and frequent stool containing large quantity of fat).
Noctiluca is a marine, colourless dinoflagellate. It is a voracious predator and has a long, motile tentacle, near the base of which, its single short flagellum emerges.
Monocystis is a microscopic, unicellular endoparasitic protozoan found in the coelom and seminal vesicles of earthworm. As it is an endoparasite, it does not possess any special structure for locomotion.
Question
53 Auxospores and hormocysts are formed respectively by [CBSE AIPMT 2005]
(a) several diatoms and a few cyanobacteria
(b) several cyanobacteria and several diatoms
(c) some diatoms and several cyanobacteria
(d) some cyanobacteria and many diatoms
Answer/Explanation
Ans. (a)
Auxospores and hormocysts are formed by several diatoms and a few cyanobacteria respectively.
Bacillariophyceae members (diatoms) are microscopic, eukaryotic, unicellular or colonial coccoid algae. These algae are sexually reproduced by the formation of auxospores in most cases. Bozi (1914)and Fermi (1930) reported that short sections of living cells at the tips of the trichomes of Wertiella lanosa become invested by a thick, lamellated, pigmented sheath. Such mullicellular spore like structures function as perennating bodies. They are specially modified hormogones and are called hormospores or hormocysts.
Question
$\overline{54}$ Which of the following unicellular organism has a macro-nucleus for trophic function and one or more micro-nuclei for reproduction? [CBSE AIPMT 2005]
(a) Eugleno
(b) Amoeba
(c) Paramecium
(d)Trypanosoma
Answer/Explanation
Ans. (c)
Paramecium is a heterokaryotic organism, i.e. it has two nuclei near the cytostome (oral-shaped opening called mouth). The macronucleus, which is a conspicuous larger ellipsoidal vegetative nucleus, divides amitotically and controls the vegetative characters and micronucleus is a small compact reproductive nucleus which divides mitotically and controls the reproduction.
Question
When a freshwater protozoan possessing a contractile vacuole is placed in a glass containing marine water, the vacuole will [CBSE AIPMT 2004]
(a) increase in number
(b) disappear
(c) increase in size
(d) decrease in size
Answer/Explanation
Ans. (b)
Fresh water protozoans live in hypotonic environment so, for regulation of excess of water which comes in the protoplasm through the process of endosmosis, contractile vacuoles have developed. When these protozoans are placed in marine water, i.e. hypertonic water, the contractile vacuoles become disappear because the process of endosmosis does not. occur and thus, water does not come in the protoplasm.
Question
The chief advantage of encystment to an Amoeba is [CBSE AIPMT 2003]
(a) the chance to get rid of accumulated waste products
(b) the ability to survive during adverse physical conditions
(c) the ability to live for some time without ingesting food
(d) protection from parasites and predators
Answer/Explanation
Ans. (b)
Encystment of Amoeba is occurred regularly to tide over unfavourable conditions like drought and extreme temperature, etc. During these conditions, the Amoebo forms a covering or cyst wall around itself.
Thus, it is an adaptation to sunrise during adverse conditions
(extranuclear inheritance adverse condition).
Question
In which animal, dimorphic nucleus is found? [CBSE AIPMT 2002]
(a) Amoeba
(b) Trypanosoma gambiense
(c) Plasmodium vivax
(d) Paramecium caudatum
Answer/Explanation
Ans. (d)
Poramecium is heterokaryotic, it possesses a dimorphic nuclear apparatus (a single large macronucleus which controls metabolism and one or more small micronuclei concerned with reproduction).
Question
Extranuclear inheritance occurs in [CBSE AIPMT 2001]
(a) killer strain in Paramecium
(b) colour blindness
(c) phenylketonuria
(d) Tay Sachs disease
Answer/Explanation
Ans. (a)
Paramecium exhibits cytoplasmic inheritance due to the presence of Kappa particles(self replicating bodies that produce toxin called paramecin). Besides binary fission and conjugation other reproductive processes that occurs in Paramecium are autogamy. endomixis and cytogamy.
Tay Sachs disease it is a rare autosomal recessive genetic disorder.
Colour blindness it is X-chromosome related disease. So, it is a sex-linked disease.
PKU autosomal recessive genetic disorder characterised by homozygous or compound heterozygous mutation in the gene.
Question
$\overline{59}$ Which of the following organisms possesses characteristics of both a plant and an animal? [CBSE AIPMT 1995]
(a) Bacteria
(b) Mycoplasma
(c) Euglena
(d) Paramecium
Answer/Explanation
Ans. (c)
Euglena is a connecting link between animals and plants. Euglena contains chlorophyll, yet it resembles animals, because it feeds like animals in the absence of sunlight. It resembles the ancestral form from which the plants and animals evolved.
Question
Macro and micronucleus are the characteristic feature of [CBSE AIPMT 1995, 2002, 05]
(a) Paramecium and Vorticella
(b) Opelina and Nictothirus
(c) Hydra and Ballantidium
(d) Vorticella and Nictothirus
Answer/Explanation
Ans. (a)
Paramecium and Vorticella have dimorphic nuclei(heterokaryotic).
Micronucleus that is inactive except during cell division and houses the master copy of the genome.
Macronucleus controls daily synthetic activities or on going metabolic functions of the cell and asexual reproduction. Macronucleus contains multiple copies of DNA.
Question
When a freshwater protozoan possessing a contractile vacuole, is placed in a glass containing marine water, the vacuole will [CBSE AIPMT 2004]
(a) increase in number
(b) disappear
(c) increase in size
(d) decrease in size
Answer/Explanation
Ans. (b)
Freshwater protozoans live in hypotonic solution so, for regulation of excess of water which comes in the protoplasm through the process of endosmosis, contractile vacuoles have developed. When these protozoans are placed in marine water, i.e. hypertonic water, the contractile vacuoles disappear because the process of endosmosis does not happen and thus, water does not come in the protoplasm.
Question
In Protozoa like Amoeba and Paramecium, an organelle is found for osmoregulation which is [CBSE AIPMT 2002]
(a) contractile vacuole
(b) mitochondria
(c) nucleus
(d) food vacuole
Answer/Explanation
Ans. (a)
Unicellular organisms such as Amoeba, Poramecium have some organelles called contractile vacuole for excretion. These are freshwater animals, i.e. they live in hypotonic solution. Therefore, water flows from outside to inside of the body of the organism.
The contractile vacuoles in these organisms collect this excess water and gradually increase in size. When the vacuoles reach a critical size they contract, squeezing out their contents through the process of simple diffusion.
Question
Excretion in Amoeba occurs through [CBSE AIPMT 1995]
(a) lobopodia
(b) uroid portion
(c) plasma membrane
(d) contractile vacuole
Answer/Explanation
Ans. (d)
Endoplasm of Amoeba in the posterior part contains a single clear rounded and pulsating contractile vacuole.
Contractile vacuole is analogous to uriniferous tubules of frog, it functions in excretion and osmoregulation.
Question
Protistan genome has [CBSE AIPMT 1994]
(a) membrane bound nucleoproteins embedded in cytoplasm
(b) free nucleic acid aggregates
(c) gene containing nucleoproteins condensed together in loose mass
(d) nucleoprotein in direct contact with cell substance
Answer/Explanation
Ans. (a)
Eukaryotic(e.g. protistan) genome is organised in the form of nucleus. It is differentiated into nuclear envelope, chromatin, one or more nucleoli and nucleoplasm. Nuclear DNA is linear, associated with histone proteins. A small quantity of DNA is also found in the plastids and mitochondria. In contrast, prokaryotic (bacterial) DNA is circular and lies freely in the cytoplasm.
Question
Entamoeba coli causes [CBSE AIPMT 1994]
(a) pyorrhoea
(b) diarrhoea
(c) dysentery
(d) None of these
Answer/Explanation
Ans. (d)
Entamoeba coll is the common parasitic genera of phylum-Protozoa. It harbours the upper part of large intestine (colon) and very often in the liver, brain and testes and causes constipation.
Question
Protists obtain food as [CBSE AIPMT 1994]
(a) photosynthesisers, symbionts and holotrophs
(b) photosynthesisers
(c) chemosynthesisers
(d) holotrophs
Answer/Explanation
Ans. (a)
Protistans have variable modes of nutrition. They are photosynthetic heterotrophic, i.e. saprophytic, parasitic and ingestive.
Question
African sleeping sickness is due to [CBSE AIPMT 1991]
(a) Plasmodium vivax transmitted by tse-tse fly
(b) Trypanosoma lewsii transmitted by bed bug
(c) Trypanosoma gambiense transmitted by Glossina palpalis
(d) Entamoeba gingivalis spread by house fly
Answer/Explanation
Ans. (c)
The disease African sleeping sickness is caused by Trypanosoma gambiense and this is transmitted by tse-tse fly (Glossina palpalis).
Question
In Amoeba and Paramecium osmoregulation occurs through [CBSE AIPMT 1991, 95, 2002]
(a) pseudopodia
(b) nucleus
(c) contractile vacuole
(d) general surface
Answer/Explanation
Ans. (c)
Amoeba and Paromecium contains two contractile vacuoles (anterior and posterior, the latter being faster)for osmoregulation, i.e. maintaining water balance in the body.
Question
Genetic information in Paramecium is contained in [CBSE AIPMT 1990]
(a) micronucleus
(b) macronucleus
(c) Both (a) and (b)
(d) mitochondria
Answer/Explanation
Ans. (a)
Ciliates (Parameclum) show nuclear dimorphism, large macronucleus controls metabolic activities and growth. It is called vegetative nucleus. Micronucleus contains genetic informatioin and thus, takes part in reproduction.
Question
Plasmodium, the malarial parasite, belongs to class [CBSE AIPMT 1990]
(a) Sarcodina
(b) Ciliata
(c) Sporozoa
(d) Dinophyceae
Answer/Explanation
Ans. (c)
Plasmodium, the malarial parasite belongs to class-Sporozoa.
Sporozoans are intracellular parasites, reproduce by multiple fission and life cycle may include the two different hosts.
Question
What is true about Trypanosoma? [CBSE AIPMT 1990]
(a) Polymorphic
(b) Monogenetic
(c) Facultative parasite
(d) Non-pathogenic
Answer/Explanation
Ans. (a)
Trypanosoma is an obligate parasite, it. is digenetic polymorphic (Trypanosoma is adult form in human, whereas, crithidal and leptomonal are developmental forms in tse-tse fly).
Question
Trypanosoma belongs to class [CBSE AIPMT 1989]
(a) Sarcodina
(b) Zooflagellata
(c) Ciliata
(d) Sporozoa
Answer/Explanation
Ans. (b)
Zooflagellates are protozoan parasites which possess one to several flagella for locomotion. They are generally uninucleate (occasionally multinucleate), body is covered by a firm pellicle, e.g. Trypanosoma, Leishmania, Trichomonas, etc.