Explanation
A.The distinct characteristic of Volvox is to show individuality.Each cell contributes for the good of the colony more or less acting as a multicellular organism. Hence, Volvox is the most developed in the series of genera that form spherical colonies. The vegetative cells of volvox comprise of a flagella facing outward and the cells are motile. They swim in a coordinated way towards light.B.The option is incorrect because it is not the name of any species of algae but a characteristic feature of a few protozoans. C.Ulothrix is fresh water and marine, green filamentous algae but it is definitely not the most avanced and motile unicellular organisms.D.This option is not a name of an algal plant body.It is only a significant characteristic of a few protozoans.
Riboflavin is abundant in Porphyra. It is a coldwater seaweed that grows in cold, shallow seawater. More specifically, it belongs to foliose red algal genus. Porphyra is rich in riboflavin, which is vitamin B$$_2$$. Riboflavin is important for many enzymatic reactions in the body. Riboflavin is found in many other marine weeds, but it is in abundance in Porphyra. Thus, the correct answer is option A.
Algae have great economic importance to man as it is a rich source of protein and some algae may be used as future food apart from this, it is also true that algae enriches the soil and can be a good source to make the soil fertile. Algae are being commercially used by man in many ways. Red algae is used to produce edible gelatin. Thus, the correct answer is option D.
The sea lettuces comprise the genus Ulva, a group of edible green algae, that is widely distributed along the coasts of many oceans of the world. The lettuce type species within the genus Ulva is Ulva lactuca, lactuca is the Latin name for "lettuce". Few members of this genus are known under the common name, green nori. Individual blades of Ulva can grow more than 400m but this only occurs when the plants are growing in sheltered areas. Thus, the correct answer is option A.
Acetabularia is the largest unicellular organism. Acetabularia is a genus of green algae, specifically of the Polyphysaceae family. It is typically found in subtropical waters. Acetabularia is a single-celled organism, but gigantic in size and complex in form, making it an excellent model organism for studying cell biology. Thus, the correct answer is option E.
The algae that forms motile colonies is Volvox. Volvox is the most developed in a series of genera, that form spherical colonies.
Each mature Volvox colony is composed of numerous flagellate cells similar to Chlamydomonas, up to 50,000 in total, and embedded in the surface of a hollow sphere or coenobium containing an extracellular matrix made of a gelatinous glycoprotein. Except, during the formation of daughter colonies, vegetative cells comprise a single layer with the flagella facing outward. The cells swim in a coordinated fashion, with distinct anterior and posterior poles. Hence, form a motile colonies. Thus, the correct answer is option A.
Heterocysts are specialized, pale-yellow, thick-walled cells with the function of nitrogen-fixing formed during nitrogen starvation by some filamentous cyanobacteria, such as Nostoc punctiforme, Cylindrospermum stagnale, and Anabaena sphaerica. They fix nitrogen from di-nitrogen (N$$_2$$) in the air using the enzyme nitrogenase, in order to provide the cells in the filament with nitrogen for biosynthesis. Nitrogenase is inactivated by oxygen, so the heterocyst must create a micro anaerobic environment. Hence, their main function is nitrogen fixation. Thus, the correct answer is option B.
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