THE KINGDOM PROTISTA (OR PROTOCTISTA)
MULTIPLE CHOICE QUESTIONS
Q.01: Each question has five options. Encircle the correct option.
(i) Amoeba move and obtain food by means of:
(a) Plasmodium
(b) Flagella
(c) Cilia
(d) Pseudopodia
(e) Gametangia
ANSWER: (d) Pseudopodia
EXPLANATION: Amoebae lack flagella and move by forming specialized cytoplasmic projections called pseudopodia (false feet).
(ii) The sexual process exhibited by most ciliates is called:
(a) Oogamy
(b) Binary fission
(c) Conjugation
(d) Fertilization
(e) Zygote
ANSWER: (c) Conjugation
EXPLANATION: Most ciliates are capable of a sexual process called conjugation. During conjugation two individuals come together and exchange genetic material.
(iii) Parasitic protozoans that form spores at some stage in their life belong to which group?
(a) Ciliates
(b) Actinopods
(c) Diatoms
(d) Apicomplexans
(e) Zooflagellates
ANSWER: (d) Apicomplexans
EXPLANATION: Apicomplexans, at some stage in their lives, develop a spore, a small infective agent transmitted to the next host. For example, plasmodium is transmitted as sporozoites from female Anopheles mosquitoes to man.
(iv) Algae which have shells composed of two halves that fit together like petri dish belong to:
(a) Brown algae
(b) Diatoms
(c) Euglenoids
(d) Green algae
(e) Red algae
ANSWER: (b) Diatoms
EXPLANATION: The cell wall of each diatom consists of two shells that overlap where they it together, much like a petri dish. Silica is deposited in the shell, and this glasslike material is laid down in intricate patterns.
(v) Algae in which body is differentiated into blades, stipes and holdfast belong to:
(a) Golden algae
(b) Diatoms
(c) Kelps
(d) Euglenoids
(e) Green algae
ANSWER: (c) Kelps
EXPLANATION: The largest brown algae, called the kelps are tough and leathery in appearance. They possess leaf-like blades, stem-like stipes, and root-like anchoring holdfast.
(vi) Chl. a, Chl. b and carotenoids are found in:
(a) Brown algae, golden algae and diatoms
(b) Green algae, golden algae and euglenoids
(c) Green algae, euglenoids and plants
(d) Red algae, euglenoids and brown algae
(e) Red algae, golden algae and plants
ANSWER: (c) Green algae, euglenoids and plants
EXPLANATION: Green algae are photosynthetic, with chlorophyll a, chlorophyll b & carotenoids present in the chloroplasts.
(vii) The feeding stage of a slime mold is called:
(a) Mycelium
(b) Pseudopodium
(c) Hyphae
(d) Plasmodium
(e) Rhizoids
ANSWER: (d) Plasmodium
EXPLANATION: The feeding stage of a slime mold is a plasmodium, a multinucleate mass of cytoplasm that can grow to 30 cm (1 ft) in diameter. The plasmodium, which is slimy in appearance, streams over damp, decaying logs and leaf litter. It often forms a network of channels that cover a large surface area. As it creeps along, it ingests bacteria, yeasts, spores and decaying organic matter.
(viii) Cell wall in oomycetes is chemically composed of:
(a) Cellulose
(b) Chitin
(c) Proteins
(d) Lignin
(e) Proteins and some carbohydrates
ANSWER: (a) Cellulose
EXPLANATION: The cell walls of oomycetes are made up of cellulose, not chitin.
Q.02: SHORT QUESTIONS
Write two characteristics of each of the following groups: (i) Protozoa (ii) Dinoflagellates (iii) Diatoms (iv) Slime molds (iv) Oomycetes
ANSWER:
Characteristics:
(i) Protozoa:
(1) All protozoans are unicellular.
(2) Most of them ingest their food by endocytosis.
(ii) Dinoflagellates:
(1) The cells of dinoflagellates are often covered with shells of interlocking cellulose plates impregnated with silicates.
(2) Dinoflagellates are known to have occasional population explosions or blooms. These blooms frequently colour the water orange, red or brown and are known as red tides.
(iii) Diatoms:
(1) The cell wall of each diatom consists of two shells that overlap where they it together, much like a petri dish.
(2) Diatoms are the major producers in the aquatic (marine and freshwater) ecosystems because of their extremely large numbers.
(iv) Slime Molds:
(1) The feeding stage of a slime mold is a plasmodium, a multinucleate mass of cytoplasm that can grow to 30 cm (1 ft) in diameter.
(2) During unfavourable condition, slime mold forms resistant haploid spore by meiosis within stalked structures called sporangia. When conditions become favourable again, spores germinate into biflagellated or amoeboid reproductive or swarm cells which unite to form diploid zygote.
(iv) Oomycetes:
(1) The cell walls of Oomycotes contain cellulose, not chitin.
(2) Their hyphae are aseptate (without cross walls).
Q.03: EXTENSIVE QUESTIONS
(i) Discuss important features of protists. Why are protists so difficult to classify?
ANSWER:
Kingdom Protista consists of unicellular, colonial or simple multicellular organisms that possess a eukaryotic cell organization.
It is very difficult to place protists in other eukaryotic kingdoms. This is due to the fact that other eukaryotic kingdoms have their evolutionary origin in kingdom Protista. All other eukaryotic kingdoms Animalia, Plantae, Fungi have evolved from protists in different ways.
(ii) What are the reasons for grouping simple eukaryotic organisms into a separate kingdom Protista?
ANSWER:
The simple eukaryotic organisms are placed in a separate kingdom Protista or Protoctista because:
(1) All protists are eukaryotic and have evolved from prokaryotes.
(1) It is very difficult to place protists in other eukaryotic kingdoms. This is due to the fact that other eukaryotic kingdoms have their evolutionary origin in kingdom Protista. All other eukaryotic kingdoms Animalia, Plantae, Fungi have evolved from protists in different ways.
(iii) How are protists important to humans? What is their ecological importance?
ANSWER:
Protists are important to humans as they serve as a fundamental part of the food chain, provide oxygen through photosynthesis, and have biotechnological applications such as biofuel production.
Protists are ecologically important as they contribute to nutrient cycling, participate in symbiotic relationships, and serve as indicators of environmental health.
(iv) What are three major groups of protists?
ANSWER:
The kingdom Protista contains four major groups of eukaryotic organisms which are:
(1) Single celled protozoans
(2) Unicellular algae
(3) Multicellular algae
(4) Slime molds and oomycotes.
(v) Discuss general characteristics of algae.
ANSWER:
Four General Characters of Algae:
(1) Algae are photosynthetic protists, carrying out about 50 to 60% of the photosynthesis on earth.
(2) The sex organs which are unicellular and the zygote is not protected by the parent body.
(3) Chlorophyll a, yellow and orange carotenoids are the photosynthetic pigments found in all algae. Some other algal phyla possess other pigments such as xanthophylls and phycoerythrin.
(4) All algae, except members of the phylum Rhodophyta (red algae), have forms with flagellated motile cells in at least one stage of their life cycle.
(vi) Green algae are considered ancestral organisms of green land plants. Discuss.
ANSWER:
Green algae have many similar characteristics with plants. For example:
(1) Green algae have pigments, energy reserve products, and cell walls that are identical to those of plants.
(2) They have chlorophyll a, chlorophyll b, and carotenoids present in the chloroplasts.
(3) Their main energy reserving material is starch.
(4) Most green algae possess cell walls with cellulose.
Because of these similarities and some other, it is generally accepted that plants arose from ancestral green algae. Evidence from RNA sequencing also indicates that green algae and the plants form a monophyletic lineage.
(vii) What features distinguish Oomycotes from fungi?
ANSWER:
Fungus-like protists (Oomycotes) are different from fungi for several reasons. For example:
(1) Many of these protists have centrioles, whereas fungi lack centrioles.
(2) Many of them (water molds) produce cellulose as a major component of their cell walls, whereas fungi have cell walls of chitin.
(viii) Describe structure and reproduction of slime molds.
ANSWER:
Consult textbook at page 109 — 110.
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