Protista (Unicellular eukaryotes) Questions in English

(A) The vegetative phase of acellular slime moulds $(Myxomycetes)$ consists of a multinucleated,amoeboid,and naked mass of protoplasm called a $Plasmodium$.
This $Plasmodium$ can grow to several feet in size and moves by amoeboid movement,engulfing organic matter.
Under unfavorable conditions,the $Plasmodium$ differentiates and forms fruiting bodies bearing spores.

(B) Trypanosoma is a parasitic protozoan that belongs to the class Flagellated (Mastigophora) protozoans.
These organisms are either free-living or parasitic and possess flagella for locomotion.
Trypanosoma is the causative agent of sleeping sickness.

(A) $Trypanosoma$ is a genus of kinetoplastids,a monophyletic group of unicellular parasitic flagellate protozoa.
It is known to be polymorphic,meaning it exhibits different morphological forms during its life cycle (e.g.,trypomastigote,epimastigote,amastigote).
It is digenetic,requiring two hosts (an insect vector and a vertebrate host) to complete its life cycle.
It is an obligate parasite,meaning it cannot complete its life cycle without a host.
It is highly pathogenic,causing diseases such as African sleeping sickness and Chagas disease.
Therefore,the most distinct characteristic among the given options is that it is polymorphic.

(C) The malaria parasite,$Plasmodium$,is a member of the kingdom $Protista$.
Within the group of protozoan protists,$Plasmodium$ is classified under the class $Sporozoa$ (also known as $Apicomplexa$).
These organisms are characterized by having an infectious spore-like stage in their life cycle.
Therefore,the correct option is $C$.

(A) $Paramecium$ exhibits nuclear dimorphism,meaning it possesses two types of nuclei: the micronucleus and the macronucleus.
The micronucleus is diploid and contains the germline genetic information,which is responsible for reproduction and genetic recombination during conjugation.
The macronucleus is polyploid and controls the metabolic activities and vegetative functions of the cell.
Therefore,the primary genetic information for inheritance is stored in the micronucleus.

(C) Osmoregulation is the process of maintaining the water and salt balance within an organism. In freshwater protozoans like $Amoeba$ and $Paramecium$,the contractile vacuole is the specialized organelle responsible for osmoregulation. It collects excess water from the cytoplasm and expels it out of the cell to prevent the organism from bursting due to the influx of water by osmosis.

(C) African sleeping sickness is a parasitic disease caused by the protozoan $Trypanosoma$ $gambiense$ (or $Trypanosoma$ $brucei$ $gambiense$).
It is transmitted to humans through the bite of the tsetse fly,which belongs to the genus $Glossina$ (specifically $Glossina$ $palpalis$ or $Glossina$ $morsitans$).
Therefore,the correct option is $C$.

(A) Protists are a diverse group of eukaryotic organisms. Their mode of nutrition is highly varied:
$1$. Photosynthetic: Many protists like diatoms and dinoflagellates perform photosynthesis.
$2$. Symbiotic: Some live in symbiotic relationships with other organisms.
$3$. Holotrophic (Holozoic): Many protists like Amoeba ingest food particles through phagocytosis.
Therefore,protists exhibit a combination of these nutritional strategies.

(C) Protozoans are eukaryotic organisms. In eukaryotes,the genetic material $(DNA)$ is associated with histone proteins to form nucleoproteins,which are organized into chromatin within the nucleus. The genome of a protozoan consists of genes associated with nucleoproteins,which are organized within the nuclear structure. Among the given options,option $C$ is the most appropriate description of this organization.

(A) The presence of two types of nuclei,a large macronucleus and a small micronucleus,is a characteristic feature of the phylum $Ciliophora$ (ciliates).
$Paramecium$,$Vorticella$,$Nyctotherus$,and $Balantidium$ are all examples of ciliates.
However,among the given options,$Paramecium$ and $Vorticella$ are the most classic examples of organisms exhibiting nuclear dimorphism (macronucleus and micronucleus).
Therefore,the correct option is $A$.

(C) The organism $Euglena$ is a unique member of the kingdom $Protista$.
It possesses characteristics of both plants and animals.
Like plants,$Euglena$ contains chlorophyll and performs photosynthesis in the presence of sunlight (autotrophic nutrition).
In the absence of sunlight,it behaves like a heterotroph by feeding on other organic matter (holozoic or saprophytic nutrition).
Additionally,it lacks a rigid cell wall,which is a characteristic feature of animal cells.

(B) Freshwater protozoans like $Amoeba$ possess a contractile vacuole to perform osmoregulation,which involves expelling excess water that enters the cell due to the hypotonic environment.
When placed in seawater,which is a hypertonic solution,the external environment has a higher solute concentration than the cytoplasm of the protozoan.
Due to exosmosis,water moves out of the cell into the surrounding seawater.
As a result,there is no excess water to be expelled,and the contractile vacuole,which functions to remove water,becomes inactive and eventually disappears.

(C) Auxospores are specialized cells produced by certain diatoms to restore their normal size after repeated asexual divisions lead to a reduction in cell size.
Hormocysts are thick-walled, resting structures produced by many cyanobacteria (such as $Westiellopsis$ and $Hapalosiphon$) under unfavorable conditions to survive and propagate.
Therefore, auxospores are produced by certain diatoms and hormocysts are produced by many cyanobacteria.

(A) All the organisms mentioned ($Trypanosoma$,$Noctiluca$,$Monocystis$,and $Giardia$) belong to the Kingdom $Protista$.
$Trypanosoma$ is a flagellated protozoan.
$Noctiluca$ is a dinoflagellate.
$Monocystis$ is a sporozoan.
$Giardia$ is a flagellated protozoan.
While they have different modes of locomotion or life cycles,the common characteristic among all these organisms is that they are all unicellular eukaryotic organisms classified under the Kingdom $Protista$.

(A) Chrysophytes,which include diatoms and golden algae,are characterized by cell walls that form two thin overlapping shells,which fit together like a soap box.
These walls are embedded with silica,making them indestructible.

(A) The cell walls of diatoms are embedded with silica and thus are indestructible. They form large deposits of 'diatomaceous earth' over billions of years. Diatoms are the chief producers in the oceans and are microscopic organisms that float passively in water currents (plankton). Therefore,the statement that their cell walls are easily destructible is incorrect.

(A) According to the $5$-kingdom classification system proposed by $R.H. Whittaker$,the kingdom $Protista$ includes all unicellular eukaryotic organisms.
Chrysophytes,euglenoids,dinoflagellates,and slime molds are all examples of unicellular eukaryotes.
Therefore,they are classified under the kingdom $Protista$.

(A) Slime molds are saprophytic protists. Under suitable conditions,they form an aggregation called $Plasmodium$ which may grow and spread over several feet. This $Plasmodium$ is the vegetative,thalloid body of the slime mold. During unfavorable conditions,the $Plasmodium$ differentiates and forms fruiting bodies bearing spores at their tips.

(B) 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 several feet. During unfavourable conditions,the plasmodium differentiates and forms fruiting bodies bearing spores at their tips. $Physarum$ is a well-known example of a slime mould. $Rhizopus$ is a fungus,$Thiobacillus$ is a bacterium,and $Anabaena$ is a cyanobacterium.

(A) The cell walls of most fungi are composed of chitin. However,$Pythium$ is a member of the Oomycetes (water molds),which are fungus-like protists.
Unlike true fungi,the cell walls of Oomycetes are primarily composed of cellulose and glucans,not chitin.
$Xanthomonas$ and $Pseudomonas$ are bacteria,whose cell walls are made of peptidoglycan.
$Saccharomyces$ (yeast) is a true fungus,and its cell wall is composed of chitin and glucans.
Therefore,$Pythium$ is the correct answer.

(D) Dimorphic nucleus refers to the presence of two types of nuclei within a single cell, specifically a large macronucleus and a small micronucleus.
This condition is a characteristic feature of the phylum Ciliophora.
Among the given options, $Paramecium \text{ } caudatum$ belongs to the class Ciliata (Ciliophora) and exhibits nuclear dimorphism.
The macronucleus controls vegetative functions, while the micronucleus is involved in reproductive processes.

(C) The organism $Paramecium$ exhibits nuclear dimorphism,meaning it possesses two types of nuclei:
$1$. $A$ large $macronucleus$ (vegetative nucleus) which controls metabolic and nutritional activities.
$2$. $A$ small $micronucleus$ (generative nucleus) which is involved in reproduction and genetic exchange during conjugation.
Therefore,the correct option is $C$.

(B) Freshwater protozoans like $Amoeba$ possess contractile vacuoles to perform osmoregulation by expelling excess water that enters the cell via osmosis.
Seawater is a hypertonic environment compared to the cytoplasm of freshwater protozoans.
When placed in seawater,the external environment has a higher solute concentration,causing water to move out of the protozoan cell into the surrounding medium due to exosmosis.
Since there is no excess water entering the cell,the contractile vacuole is no longer required for osmoregulation and eventually disappears.

(B) Ciliates,such as $Paramecium$,are unique among protozoans because they possess two types of nuclei: a large macronucleus and a small micronucleus.
The macronucleus controls vegetative functions,while the micronucleus is involved in reproduction and genetic exchange.
Other protozoans like amoeboids,flagellates,and sporozoans do not exhibit this specific nuclear dimorphism.

(C) Diatoms are microscopic,photosynthetic organisms belonging to the kingdom $Protista$ (class $Bacillariophyceae$).
They are found in both fresh water and marine environments.
In the oceans,they are the primary source of food for many aquatic organisms and are responsible for a significant portion of global photosynthesis.
Due to their massive abundance and photosynthetic activity,they are famously known as the 'chief producers' in the oceans.

(D) The correct answer is $D$.
$A$: Mitochondria are absent in prokaryotes (Monera) and present in all eukaryotes. This statement is correct.
$B$: Fungi have cell walls made of chitin,and plants have cell walls made of cellulose. This statement is correct.
$C$: Mushrooms (Agaricus) are well-known examples of Basidiomycetes. This statement is correct.
$D$: Sporozoans (like Plasmodium) lack locomotory structures like pseudopodia,flagella,or cilia. Pseudopodia are characteristic of Sarcodines (Amoeboid protozoans). Therefore,this statement is incorrect.

(B) Myxomycetes,commonly known as acellular slime molds,consist of a slimy mass of multinucleate protoplasm called a plasmodium. They exhibit amoeboid movement using pseudopodia to engulf food particles. Their reproduction occurs through the formation of spores or by fragmentation of the plasmodium.

(A) Slime moulds are saprophytic protists.
$(i)$ The body moves along decaying twigs and leaves engulfing organic material,which is correct.
$(ii)$ Under suitable conditions,they form an aggregation called Plasmodium which may grow and spread over several feet. When conditions become unfavourable,the Plasmodium differentiates and forms fruiting bodies bearing spores at their tips,which is correct.
$(iii)$ The spores possess true walls (cellulosic),so statement $(iii)$ is incorrect.
$(iv)$ The spores are dispersed by air currents,which is correct.
$(v)$ The spores are extremely resistant and survive for many years,even under adverse conditions,which is correct.
$(vi)$ Plasmodium can grow up to several feet,which is correct.
Therefore,statements $(i), (ii), (iv), (v)$ and $(vi)$ are correct.

(D) Cilia are hair-like structures on a $Paramecium$ used for locomotion and capturing food.
An oral groove acts as a mouth, and food vacuoles are involved in the digestion of ingested food particles.
The absence of chloroplasts confirms that the organism cannot perform photosynthesis.
These features collectively indicate that the organism relies on preformed organic matter for energy, which is defined as $heterotrophic \text{ nutrition}$.

(B) The cell walls of diatoms are composed of silica,which makes them indestructible.
Their cell wall structure is known as a $frustule$.
It consists of two thin overlapping shells that fit into each other like a soap box.
When diatoms die,the silica in their cell walls accumulates over billions of years to form $diatomaceous$ $earth$.
This $diatomaceous$ $earth$ is gritty,soft,and chemically inert,making it useful for the filtration of oils,syrups,and various industrial applications.

(A-D) Protozoa are microscopic unicellular protists with a heterotrophic mode of nutrition. They may be holozoic,saprobic,or parasitic. They are divided into four major groups:
$(1)$ Amoeboid protozoa: These are unicellular,jelly-like organisms found in fresh water,sea water,or moist soil. They lack a periplast and may be naked or covered by a calcareous shell. They use temporary protoplasmic outgrowths called pseudopodia for movement and capturing prey. Examples include $Amoeba$ (free-living) and $Entamoeba$ (parasitic).
$(2)$ Flagellated protozoa: These are free-living or parasitic,non-photosynthetic organisms that possess flagella for locomotion and capturing prey. An example is $Trypanosoma$,which causes sleeping sickness in humans.
$(3)$ Ciliated protozoa: These are aquatic organisms characterized by the presence of numerous cilia on their entire body surface and two types of nuclei. Cilia beat in a coordinated manner to move food-laden water into a cavity called the gullet. Examples include $Paramoecium$ and $Vorticella$.
$(4)$ Sporozoans: These include diverse organisms,most of which are disease-causing endoparasites. They are uninucleate,covered by a pellicle,and lack locomotory organelles like cilia or flagella. $A$ well-known example is $Plasmodium$,which causes malaria.

(N/A) Some characteristic features of Euglenoids are as follows:
$1$. Euglenoids (such as $Euglena$) are unicellular protists commonly found in stagnant fresh water.
$2$. Instead of a cell wall,they have a protein-rich layer called a $pellicle$ which makes their body flexible.
$3$. They possess two flagella,a short one and a long one,at the anterior end of the body.
$4$. They contain a light-sensitive eyespot $(stigma)$ that helps in detecting light.
$5$. They are photosynthetic in the presence of sunlight due to the presence of chlorophyll pigments identical to those in higher plants. However,in the absence of sunlight,they behave like heterotrophs by predating on other smaller organisms.
$6$. Due to the presence of both plant-like (photosynthesis) and animal-like (heterotrophy/flexibility) features,they are considered a connecting link between plants and animals.

(N/A) $\rightarrow$ All single-celled eukaryotes are placed under Protista,but the boundaries of this kingdom are not well-defined.
$\rightarrow$ Habitat: Members of Protista are primarily aquatic.
$\rightarrow$ This kingdom forms a link with others dealing with plants,animals,and fungi.
$\rightarrow$ Structure: Being eukaryotes,the protistan cell body contains a well-defined nucleus and other membrane-bound organelles.
$\rightarrow$ Some have flagella or cilia for locomotion.
$\rightarrow$ Reproduction: Protists reproduce asexually and sexually by a process involving cell fusion and zygote formation.
$\rightarrow$ Groups of Protista: The kingdom includes Chrysophytes,Dinoflagellates,Euglenoids,Slime moulds,and Protozoans.

(A-D) Protozoans are heterotrophic organisms that live as predators or parasites and are believed to be primitive relatives of animals.
They are classified into four major groups based on their locomotory organelles:
$1$. Amoeboid protozoans: These organisms live in fresh water,sea water,or moist soil. They move and capture their prey by putting out pseudopodia (false feet),e.g.,$Amoeba$.
$2$. Flagellated protozoans: These members are either free-living or parasitic. They possess flagella for locomotion. Parasitic forms cause diseases such as sleeping sickness,e.g.,$Trypanosoma$.
$3$. Ciliated protozoans: These are aquatic,actively moving organisms because of the presence of thousands of cilia. They have a cavity (gullet) that opens to the outside of the cell surface,e.g.,$Paramecium$.
$4$. Sporozoans: This group includes organisms that have an infectious spore-like stage in their life cycle. The most notorious is $Plasmodium$ (malarial parasite) which causes malaria in humans.

(A) Chrysophytes include diatoms and golden algae (desmids).
$1$. Habitat: They are found in both fresh water and marine environments.
$2$. Nature: They are mostly photosynthetic and microscopic,floating passively in water currents (plankton).
$3$. Cell Wall: Their cell walls form two thin overlapping shells,which fit together like a soap box. These walls are embedded with silica,making them indestructible.
$4$. Diatomaceous Earth: Due to the accumulation of these cell walls over billions of years,they form 'diatomaceous earth'.
$5$. Examples: $Diatoms$ and $Desmids$ (golden algae).

(N/A) Slime moulds are saprophytic protists. Their characteristics are as follows:
$1$. The body moves along decaying twigs and leaves engulfing organic material.
$2$. Under suitable conditions,they form an aggregation called $Plasmodium$ which may grow and spread over several feet.
$3$. During unfavorable conditions,the $Plasmodium$ differentiates and forms fruiting bodies bearing spores at their tips.
$4$. The spores possess true walls,which are extremely resistant and survive for many years,even under adverse conditions.
$5$. The spores are dispersed by air currents.

(D) Flagellate protozoans are a group of protists characterized by the following features:
$1$. Locomotion: They possess one or more flagella,which are whip-like structures used for movement.
$2$. Lifestyle: They can be free-living in aquatic environments or parasitic,living inside other organisms.
$3$. Pathogenicity: Many parasitic forms are known to cause serious diseases in humans and animals. For example,$Trypanosoma$ is a flagellate protozoan that causes sleeping sickness.
$4$. Nutrition: They can be autotrophic,heterotrophic,or saprophytic depending on the species.
Therefore,all the given statements are correct.

(N/A) Ciliated protozoans are aquatic,actively moving organisms because of the presence of thousands of cilia.
$1$. They possess a cavity (gullet) that opens to the outside of the cell surface.
$2$. The coordinated movement of rows of cilia causes the water laden with food to be steered into the gullet.
$3$. An example of a ciliated protozoan is $Paramoecium$.

(N/A) Euglenoids are a group of freshwater organisms found in stagnant water. Their key characteristics are as follows:
$1$. Pellicle: Instead of a cell wall,they have a protein-rich layer called a $Pellicle$ which makes their body flexible.
$2$. Photosynthetic and Heterotrophic: They possess chlorophyll $a$ and $b$ identical to higher plants,allowing them to perform photosynthesis in the presence of sunlight. However,in the absence of sunlight,they behave like heterotrophs by predating on other smaller organisms.
$3$. Flagella: They typically possess two flagella,one short and one long.
$4$. Mixotrophic Nutrition: Due to their dual mode of nutrition (autotrophic and heterotrophic),they are described as mixotrophic.
Example: $Euglena$.

(C) Euglena is considered a connecting link between plants and animals because it exhibits dual characteristics.
$1$. Algal characteristics: It contains chlorophyll pigments and performs photosynthesis in the presence of sunlight,making it autotrophic.
$2$. Protozoan characteristics: In the absence of sunlight,it behaves like a heterotroph by feeding on organic matter. It also lacks a rigid cell wall,possessing instead a flexible protein-rich layer called a pellicle,which allows for amoeboid movement.

(A) Diatoms are the chief producers in the oceans and are very important photosynthesizers.
Their cell walls are embedded with silica,forming large deposits known as 'diatomaceous earth' or 'diatomite'.
Diatomite deposits are often accompanied by petroleum fields.
Due to their gritty nature,they are used in polishing,filtration of oils and syrups,and as an abrasive in toothpastes.
Mycorrhiza is a symbiotic association between fungi and the roots of higher plants.
It helps the plant in the absorption of phosphorus from the soil and provides resistance to root-borne pathogens.

(N/A) Diatoms are called 'Pearls of Ocean' because they are the primary producers in the ocean,forming the base of the aquatic food chain,and their cell walls are impregnated with silica,which gives them a glass-like,shimmering appearance under light.
Diatomaceous earth is the accumulation of the cell walls of diatoms over billions of years. Since these cell walls are made of silica and are indestructible,they form large deposits on the ocean floor. This soil is gritty,chemically inert,and used in polishing,filtration of oils and syrups,and as an insulating material.

(N/A) The observable features in Trypanosoma that justify its classification under Kingdom Protista are:
$(i)$ It is a unicellular eukaryotic organism.
$(ii)$ It possesses a well-defined nucleus enclosed by a nuclear membrane.
$(iii)$ It contains membrane-bound organelles.
$(iv)$ It exhibits locomotion through a flagellum,which is a characteristic feature of many protists.
$(v)$ It stores food material in the form of granules within the cytoplasm.

(B) $(i)$ Red dinoflagellates (e.g.,$Gonyaulax$) undergo rapid multiplication,making the sea appear red. This phenomenon is known as red tides.
$(ii)$ $Slime$ $molds$ are saprophytic protists. They feed on decaying twigs and leaves by engulfing organic material. $Euglena$ is a mixotrophic protist (photosynthetic in the presence of light and heterotrophic in the absence of light).

(A) $(i)$ All protozoans are heterotrophs and live as predators or parasites. This statement is correct.
$(ii)$ $Trypanosoma$ is a flagellated protozoan that causes sleeping sickness. This statement is correct.
Therefore,both statements are true.

(N/A) $\rightarrow$ This group includes diatoms and golden algae (desmids).
$\rightarrow$ Habitat: They are microscopic and float passively in water currents (plankton).
$\rightarrow$ Mode of nutrition: Most of them are photosynthetic.
$\rightarrow$ Body organization: In diatoms, the cell wall forms two thin overlapping shells, which fit together like a soap box.
$\rightarrow$ The walls are embedded with silica, making them indestructible.
$\rightarrow$ Diatoms have left behind large amounts of cell wall deposits in their habitat; this accumulation over billions of years is referred to as "diatomaceous earth".
$\rightarrow$ Function: Being gritty, this soil is used in polishing and the filtration of oils and syrups.
$\rightarrow$ Diatoms are the chief 'producers' in the oceans.