Multiple Choice Questions (MCQs): Algae - NEET MCQ

The gelling agent in agar is an unbranched polysaccharide obtained from the cell walls of some species of red algae, primarily from tengusa (Gelidiaceae) and ogonori (Gracilaria). ... In chemical terms, agar is a polymer made up of subunits of the sugar galactose.

Topic in NCERT: Algae and their commercial uses

Line in NCERT: "agar, one of the commercial products obtained from gelidium and gracilaria are used to grow microbes and in preparations of ice-creams and jellies."

Blue green algae reproduce by simple division/fragmentation or nonmotile spores and do not exhibit any motile phase during the life cycle. Red algae (Rhodophyceae) are characterized by the absence of any motile phase. Brown algae (Pheophyceae) are characterized by the presence of motile reproductive phase with two lateral flagella. Green algae are characterized by unicellular flagellated cells or microscopic colonies of flagellated or non-flagellated cells and reproduce by zoospores. Thus, the correct answer is option C.

Topic in NCERT: Sexual reproduction in algae

Line in NCERT: "sexual reproduction may be isogamous, anisogamous or oogamous."

Thallophyta (algae) reproduce sexually when male gametes and female gametes fuse to form zygote. Zygote immediately undergoes meiosis and it gives haploid gametes. Thus, embryo is not formed.
So, the correct option is 'Zygotic meiosis'.

Topic in NCERT: Zygote development in plants

Line in NCERT: "zygotes do not undergo reduction division immediately."

Topic in NCERT: Bryophytes

Line in NCERT: "the female sex organ called archegonium is flask-shaped and produces a single egg."

Chlamydomonas is best example for the evolution of sexual reproduction as the evolution of sex in algae has not taken place in any one phylogenetic line. This has taken place along several independent lines. For example, in Volvocales, where Gonium is isogamous, Pandorina slightly anisogalnous, Eudorina and Pleodorina marked by anisogamy and Volvox oogamous. It is correlated with the evolution from isogamy to oogamy through anisogamy. Whereas on the other hand, in another genus of Volvocales, i.e., Chlamydomonas, where species within the genus show all gradations from isogamy to oogamy, e.g., Chlamydomonas snowiae is isogamous, C. braunii is anisogamous and C. coccifera is oogamous.  
Thus, the correct answer is option A.

Topic in NCERT: Sexual reproduction in algae

Line in NCERT: "sexual reproduction shows considerable variation in the type and formation of sex cells and it may be isogamous, anisogamous or oogamous."

• Multiple fission is a process through which many individuals are produced by repeated nuclear division.
• Multiple fission takes place under unfavourable conditions.
• During multiple fission, an outer layer called cyst is formed.
• Nucleus divides repeatedly and new individuals are formed inside the cyst after which cyst breaks to release new individuals.

• Most of the algae reproduce using spore formation.
• Asexual spores are called as zoo-spores and the reproductive part in algae is called zoosporangium.
• Under favourable conditions, these organisms germinate to form new organism.
• Zoo-spores are motile and flagellated.

Topic in NCERT: Algae

Line in NCERT: "they are flagellated (motile) and on germination gives rise to new plants."

Bga typically has a thick, gelatinous cell wall. They lack flagella, but hormogonia of some species can move about by gliding along surfaces. ... So correct option is B.

Topic in NCERT: Sexual reproduction in algae

Line in NCERT: "the sexual reproduction shows considerable variation in the type and formation of sex cells and it may be isogamous, anisogamous or oogamous."

Red algae (Rhodophyceae) contain Chl a and d and main pigment is Phycoerythrin . Red algae are red due to Phycoerythrin.it helps in photosynthesis in great depth in ocean and also on surface of water.

Topic in NCERT: Rhodophyceae

Line in NCERT: "the members of rhodophyceae are commonly called red algae because of the predominance of the red pigment, r-phycoerythrin in their body."

Cyanobacteria resemble the eukaryotic algae in many ways, including morphological characteristics and ecological niches, and were at one time treated as algae, hence the common name of blue-green algae. Cyanobacteria may be unicellular or filamentous. Many have sheaths to bind other cells or filaments into colonies.

Topic in NCERT: Algae

Line in NCERT: "the algae are divided into three main classes: chlorophyceae, phaeophyceae and rhodophyceae."

The term thallus is a botanical term that refers to the body of a plant that does not have leaves, stems and roots. In botany, historically, this term has been applied to algae, fungi and the various divisions of bryophytes.

Topic in NCERT: Vegetative reproduction in algae

Line in NCERT: "vegetative reproduction usually takes place by fragmentation. each fragment develops into a thallus."

Solution Bryophytes and algae are both autotrophic, plant body is thallus-like and devoid of vascular tissues. Instead of roots, rhizoids are present for attachment and absorption purpose. Both algae and bryophytes have motile sperms and need water for fertilization. But bryophytes can be separated from algae (Thallophyta) because archegonium originated for the first time in bryophytes in the plant kingdom. It is a flask-shaped structure with swollen base called venter and upper elongated neck. The venter contains a venter canal cell and an egg cell. It is surrounded by one-celled thick sterile jacket layer. In algae, sex organs are non-jacketed and unicellular.

Topic in NCERT: Gymnosperms

Line in NCERT: "the gymnosperms are the plants in which ovules are not enclosed by any ovary wall."

Classification of algae is mainly based upon the nature of their pigments.
Red Algae (Rhodophyceae) are characterized by the pigments - Phycoerythrin and Phycocyanin.
Brown Algae (Phaeophyceae) are brown due to the pigment Fucoxanthin.
Green Algae (Chlorophyceae) are characterized by pigments Chlorophyll-a, b, Carotenes, Xanthophyll. Hence option C is correct.

Topic in NCERT: Algae classification

Line in NCERT: "pigment possesed and the type of stored food, algae are classfied into three classes, namely chlorophyceae, phaeophyceae and rhodophyceae."

It Is cycas besides paddy fields it also found in vegetative part of cycas ..And being a cyanobacteria it acts as a symbiont and readily perform activity of nitrogen fixation so cycad is more correct answer.

Topic in NCERT: Gymnosperms

Line in NCERT: "small specialised roots called coralloid roots are associated with n2- fixing cyanobacteria."

A species of yellow-green alga called Vaucheria sessilis is an example of a sexually reproducing alga. The reproductive structures consist of an antheridium, which contains male gametes, and two oogonia, which contain female gametes.

Topic in NCERT: Bryophytes

Line in NCERT: "the female sex organ called archegonium is flask-shaped and produces a single egg."

Correct option is D. Fucus
 Fucus are brown algae which is found in the intertidal zones of rocky seashores. These algae belong to the class Phaeophyceae and order Fucales, which stored food in the form of laminarin, mannitol, and oil. Mannitol is stored as a food reserve in Fucus. They are common littoral seaweed growing in the hard-rocky areas of the sea.

Topic in NCERT: Phaeophyceae brown algae

Line in NCERT: "the food is stored as complex carbohydrates, which may be in the form of laminarin or mannitol."

Pyrrophyta refers to dinoflagellates. And gonyaulax and noctiluca are the dinoflagellates which show bioluminiscense.

Topic in NCERT: Reproduction in algae

Line in NCERT: "algae usually reproduce vegetatively by fragmentation, asexually by formation of different types of spores and sexually by formation of gametes which may show isogamy, anisogamy or oogamy."

The green algae are a large, informal grouping of algae consisting of the Chlorophyta and Charophyta/Streptophyta, which are now placed in separate divisions, as well as the potentially more basal Mesostigmatophyceae, Chlorokybophyceae and Spirotaenia.

Topic in NCERT: Sexual reproduction in algae

Line in NCERT: "sexual reproduction may be isogamous, anisogamous or oogamous."

There is no motile stage found in life cycle of red algae and BGA i.e. cilia & flagella are absent. But in some algae, calcium carbonate is also present in the cell wall, due to which their thallus become stony.

Topic in NCERT: Sexual reproduction in algae

Line in NCERT: "sexual reproduction may be isogamous, anisogamous or oogamous."

Clamydomonas and Ulothrix in green algae best explains the evolution of sexual reproduction. 
The first sexuality was seen in the Clamydomonas and Ulothrix in the from of isogamy that the gamates formed were of plus and minus strains. Next evolution is seen is the ansiogamy that the gametes are of different size. Hence, the correct option is Option A. 
The further more advanced evolution in the sex repdroduction is seen in the red algae and brown algae. so the Options B and C are not correct.

Topic in NCERT: Sexual reproduction in algae

Line in NCERT: "sexual reproduction may be isogamous, anisogamous or oogamous."

• The vegetative cells in Phaecophyceae are made up of two layers with the inner one being made of cellulose and the other being made of gelatinous coating of algin.
• A leaf like photosynthetic organ in Phaecophyceae is called as frond.
• They also have a stalk called stipe and a substratum called as holdfast.

Topic in NCERT: Pteridophytes

Line in NCERT: "the plant body is usually attached to the substratum by a holdfast, and has a stalk, the stipe and leaf like photosynthetic organ - the frond."

Oedogonium filaments are typically unbranched and only one cell thick.  Asexual reproduction is by motile and nonmotile spores, formed only in cells with an apical cap. The motile reproductive bodies are characterized by a ring of cilia at the anterior end.

Topic in NCERT: Sexual reproduction in algae

Line in NCERT: "sexual reproduction may be isogamous, anisogamous or oogamous."

Topic in NCERT: Phaeophyceae

Line in NCERT: "the members of phaeophyceae or brown algae are found primarily in marine habitats."

The brown algae contains xanthophyll pigment fucoxanthin, chlorophyll 'a' and 'c' (no chlorophyll b), beta-carotene. 
Red algae contain chlorophyll  'a'  and 'd' as well as phycobilins, red and blue pigments involved in photosynthesis. 
Yellow green algae contains chlorophyll 'a' but lack chlorophyll 'b'. They possess chlorophylls 'e' or 'c'. Besides these they also possess xanthophylls and beta carotene.
Therefore, the correct answer is option B.

Topic in NCERT: Phaeophyceae

Line in NCERT: "the members of phaeophyceae or brown algae are found primarily in marine habitats. they possess chlorophyll a, c, carotenoids and xanthophylls."

• The male gamete in sexual reproduction of algae is called antherozoid and the female gamete is called egg.
• These two gametes fuse to form a zygote which will further develop to form spores.

Topic in NCERT: Bryophytes

Line in NCERT: "antheridia and female sex organs called archegonia. the male and female gametes produced fuse to form zygote which produces a multicellular body called a sporophyte."

Starch is stored in plants as food reserve. Starch is present in two forms- Amylose- which is linear chain of glucose and Amylopectin is a branched chain polymer of glucose Algae are chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic (both. fresh water and marine) organisms. They occur in a variety of other habitats: moist stones, soils and wood. Some of them also occur in association with fungi (lichen) and animals.

Topic in NCERT: Rhodophyceae

Line in NCERT: "the food is stored as floridean starch which is very similar to amylopectin and glycogen in structure."

The fact that the land surface is covered in plants, not algae, indicates that plants are the most effective photoautotroph in most terrestrial habitats. In the open ocean, however, you will find mostly microalgae and some cyanobacteria, such as Prochlorococcusare particularly numerous. If you are wondering why these algae, which have a higher photosynthetic efficiency (measured as carbon fixed per quantity of photons), lose out to plants on land, then the short answer is that efficiency very rarely confers a reproductive or competitive advantage in biology.
As for why cyanobacteria and microalgae are more efficient at photosynthesis, it is mostly because they are small, (usually) single-celled, and have a enzymes to actively pump carbon dioxide into their cells (plants rely on passive diffusion). Being small gives them a very high surface-to-volume ratio. Being single-celled means that all cells are doing photosynthesis as opposed to a plant which needs to feed non-photosynthetic tissues. The carbon dioxide pumping enzymes lets cyanobacteria and microalgae avoid some of the harmful byproducts of photosynthesis that accumulate when there isn’t enough carbon dioxide in the cell to match the supply of energy from the light reactions.

Topic in NCERT: Algae

Line in NCERT: "at least a half of the total carbon dioxide fixation on earth is carried out by algae through photosynthesis."

Option B because Blue green algae can fix nitrogen in their specialised cell known as heterocyst .

Topic in NCERT: Algae and their commercial uses

Line in NCERT: "certain marine brown and red algae produce large amounts of hydrocolloids (water holding substances), e.g., algin (brown algae) and carrageen (red algae) which are used commercially."

A seaweed may belong to one of several groups of multicellular algae: the red algae, green algae, and brown algae.

Topic in NCERT: Phaeophyceae

Line in NCERT: "the members of phaeophyceae or brown algae are found primarily in marine habitats."

Kingdom Plantae includes green, brown and red algae, liverworts, mosses, ferns and seed plants with or without flowers. ... Algae lack embryo stage. Life cycle consists of alternating haploid gametophyte and diploid sporophyte generation. This phenomenon is called alternation of generation.

Topic in NCERT: Gametophyte

Line in NCERT: "the main plant body of the bryophyte is haploid. it produces gametes, hence is called a gametophyte."