CBSE Questions for Class 11 Medical Biology Plant Kingdom Quiz 4 - MCQExams.com

Algae are a very large and diverse group of eukaryotic organisms, ranging from unicellular genera, such as Chlorella and the diatoms to multicellular forms such as, the giant kelp, a large brown alga that may grow up to 50 meters in length. Most are autotrophic and lack many of the distinct cell and tissue types found in land plants, such as stomata, xylem and phloem. Algae have photosynthetic machinery ultimately derived from Cyanobacteria, that produce oxygen as a by-product of photosynthesis. The photosynthetic yield of the protist autotrophic algae is 80%.

In Vaucheria, the multiflagellate compound zoospores also known as synzoospores or coenozoospores are developed in these genus usually in aquatic forms. A single compound zoospore develops in a single zoosporangium. Any distal branch of the thallus may convert into a zoosporangium. Much of the food reserves, chloroplasts and nuclei accumulate in the distal end of the branch of the thallus. It is multi flagellate. From each peripheral nucleus, a pair of flagella is given out. The zoospore swims for about 15 to 20 minutes and then settles down to some substratum, withdraws its flagella and secretes a wall around it. Very soon, it germinates giving rise to 2 or 3 tubular outgrowths and a new branched thallus develops. Thus, the correct answer is option C.

Macrocystis is the largest algal form. Macrocystis is a genus of kelp or large brown algae. This genus contains the largest of all the phaeophyceae or brown algae. Macrocystis has pneumatocysts at the base of its blades. Sporophytes are perennial, and individual stipes may persist for many years. It is common along the coast of the eastern Pacific Ocean.

Red tides are caused by dinoflagellates. Red tide is a common name for a phenomenon known as an algal bloom (large concentrations of aquatic microorganisms) when it is caused by a few species of dinoflagellates and the bloom takes on a red or brown color. Red tides are events in which estuarine, marine, or fresh water algae accumulate rapidly in the water column, resulting in coloration of the surface water. It is usually found in coastal areas.

Option A and C are correct as In Chlorophyceae, the stored food material is starch and the major pigments are chlorophyll a and b while, Floridian starch is the characteristic photosynthetic reserve substance of red algae, occurring abundantly in certain basin shaped grain cells. Most Rhodophyceae store starch outside the chloroplast, often as a cap over a bulging pyrenoid. The major carbohydrate storage product of red algae is a type of starch molecule (Floridian starch) that is more highly branched than amylopectin. Floridian starch is stored as grains outside the chloroplast. Thus, the correct answer is option C.

Red algae represent triphasic lifecycle. They display alternation of generations; in addition to gametophyte generation, many have two sporophyte generations, the carposporophyte-producing carpospores, which germinate into a tetrasporophyte this produces spore tetrads, which dissociate and germinate into gametophytes. The gametophyte is typically (but not always) identical to the tetrasporophyte. Carpospores may also germinate directly into thalloid gametophytes, or the carposporophytes may produce a tetraspore without going through a (free-living) tetrasporophyte phase. Tetrasporangia may be arranged in a row (zonate), in a cross (cruciate), or in a tetrad. In its diploid phase, a carpospore can germinate to form a filamentous "conchocelis stage", which can also self-replicate using monospores. The conchocelis stage eventually produces conchosporangia. The resulting conchospore germinates to form a tiny prothallus with rhizoids, which develops to a cm-scale leafy thallus. This too can reproduce via monospores, which are produced inside the thallus itself. They can also reproduce via spermatia, produced internally, which are released to meet a prospective carpogonium in its conceptacle. Hence, it undergoes a complex triphasic lifecycle.

Cephaleuros is a genus of parasitic thalloid algae and its common name is red rust. Dichotomous branches are formed in these algae. The alga is parasitic on some important economic plants of the tropics and subtropics such as tea, coffee, mango and guava causing damage limited to the area of algal growth on leaves or killing new shoots, or may be disfiguring fruit. Members of the genera may also grow with a fungus to form lichen, that does not damage the plants. Thus, the correct answer is option 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 Janosa become invested by a thick, lamellated, pigmented sheath. Such multicellular spore-like structures function as perennating bodies. They are specially modified hormones and are called homosporous or hormocysts.
  
• Hence Auxospores and hormocysts are formed respectively by Several diatoms and a few Cyanobacteria.
• So, the correct answer is 'Several diatoms and a few Cyanobacteria'.

A lichen is a composite organism, that emerges from algae or cyanobacteria (or both) living among filaments of a fungus in a mutually beneficial (symbiotic) relationship. The whole combined life form has properties, that are very different from properties of its component organisms.

There are many different groups of phytoplankton species found many different groups of phytoplankton species found in world’s ocean, but among the most common are diatoms, dinoflagellates. These algae have primary chloroplasts, i.e., the chloroplasts are surrounded by two membranes and probably developed through a single endosymbiotic event. Euglena is a unicellular protist which has chloroplast.The chloroplasts of red algae often have chlorophyll a and c, and phycobilins, while those of green algae have chloroplasts with chlorophyll a and b without phycobilins. thusthe correct answer is option D.

Floridian starch is the characteristic photosynthetic reserve substance of red algae, occurring abundantly in certain basin-shaped grain cells. Most Rhodophyceae store starch outside the chloroplast, often as a cap over a bulging pyrenoid. The major carbohydrate storage product of red algae is a type of starch molecule (Floridean starch), that is more highly branched than amylopectin. Floridian starch is stored as grains outside the chloroplast. Thus, the correct answer is option B.

In the world of filamentous freshwater algae of division Chlorophyta, the genus Zygnema, with its two stellate (star shaped) chloroplasts per cell, is a standout. Found often alongside Spirogyra, another still-water green algal genus, Zygnema species are classified as conjugate algae of phylum Gamophyta because of their means of sexual reproduction by conjugation. Forming green or yellow-brown mats of macroscopic threads or filaments, Zygnema can reproduce asexually, sexually, or vegetatively. Thus, the correct answer is option D.

Batrachospermum is one of the fresh water forms of Rhodophyceae. This alga is found in slow running shallow streams and on the banks of lakes and ponds. It is more commonly found in well aerated waters. The plants are blue-green, olive-green, violet and reddish in colour. The variation in colour is as a result, of the differences in light intensity. The species which grow in deep water are reddish or violet in colour whereas the species growing in shallow water are olive-green in colour. The alga is also known as the frog spawn or the eggs of frog, because the plants are mucilaginous, moniliform or beaded in appearance to the naked eye. The thallus is filamentous, profusely branched and with a mucilaginous feel. Hence, looks like frog eggs. The plants may reach a length of twenty centimetres and may easily be collected from well aerated water bodies. Thus, the correct answer is option A.

Solution:

Correct answer is option A.
Explanation for correct option:

• Pteridophytes are vascular plants, i.e., they have tissues specialized in the conduction of water and nutrients. 
• Bryophytes are nonvascular plants. 
• In pteridophytes, transportation is done through vessels, and in bryophytes, that transportation occurs by diffusion. 

Anthoceros species are host to species of Nostoc, a symbiotic relationship in which Nostoc provides nitrogen to its host through cells known as heterocysts, and which are able to carry out photosynthesis. Anthoceros is a genus of hornworts in the family Anthocerotaceae. The genus is global in its distribution. Its name means 'flower horn'.

• Bryophytes are small, non-vascular plants, such as Mosses, Liverworts, and Hornworts. 
• They have an independent gametophyte phase in their life cycle, but the sporophytic phase depends on gametophyte for water and nutrient.
• The male reproductive structure is the antheridium while the female reproductive structure is the archegonium responsible for producing male and female gamete, respectively.
• Lack of vascular tissue and independent sporophyte are the characteristics features of division Bryophyta.
• Marchantia is an example of a Bryophyte. 

• The diploxylic vascular bundle is a condition found in some plants where there are two types of xylem i.e centripetal xylem (present towards the centre) and centrifugal xylem (present towards the outside). 
• It is the characteristic of Cycas. 
• Hence, diploxylic vascular bundles are found in Cycas.
• So, the correct answer is 'Cycas'.

Solution

Correct answer is option A.

Explanation for correct option:

In addition to normal roots, Cycas develop specialized organs called coralloid roots. These roots help them form a mutualistic and symbiotic relationship with cyanobacteria.
In fact, these coralloid roots are produced in clusters at the base of the stem which because of its apogeotropic growth protrudes out over the ground. It is dichotomously branched and is in symbiosis with Anabaena allowing nitrogen fixation.
The coralloid roots contain symbiotic cyanobacteria (blue-green algae), which fix nitrogen and, in association with root tissues, produce such beneficial amino acids as asparagine and citrulline.