Plant Kingdom Test - 24

Diatomaceous earth or Kieselguhr is the deposits of fossil diatoms, which is mined for many industrial uses, as a mild abrasive in metal polishes, as filtering medium, for insulation of boilers and blast furnaces.

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.

Diatoms have been placed in the division Bacilliariophyta, which is distinguished by the presence of an inorganic cell wall composed of hydrated silica. Diatoms use the pigments chlorophyll 'a' and 'c' to collect energy from the sun through photosynthesis. They also contain the accessory pigments fucoxanthin and (beta) carotene, which give them a characteristic golden color.

• Chlamydomonas is a genus of green algae consisting of unicellular flagellates, found in stagnant water and on damp soil, in freshwater, seawater but not known as the gulf weed.
  
• Volvox is a genus of chlorophytes, a type of green algae. It forms spherical colonies. They live in a variety of freshwater habitats, but definitely not known as gulf weed.
  
• Chara is a genus of green algae in the family Characeae. They are multicellular and superficially resemble land plants. But the option is incorrect as it is not known as the gulf weed.
  
• Sargassum is commonly called as gulfweed; in fact, a whole marine area is named after it, as 'Sargasso sea'. 

Laminaria is a genus of brown algae (Phaeophyceae) commonly called "kelp". Some species are also referred to as tangle. This economically important genus is characterized by long, leathery laminae and relatively large size. The greater proportion of commercial cultivation of Laminaria is for algin, iodine and mannitol.

The chloroplasts of the algal cell have sub cellular microcompartments known as pyrenoids. These play an important role in carbon dioxide (CO₂) fixation. These are the centers which are involved in generating and maintaining a CO₂ rich environment around the photosynthetic enzymes.  While these are also found in Bryophytes such as hornworts, these are absent in the liverworts (Riccia and Marchantia)

Porphyra is a nutritionally and culturally important species of red algae. This species, along with Porphyra torta and possibly others, is still harvested from wild populations. It is dried and processed and served in a variety of ways: toasted as a snack, cooked with clams, salmon eggs, or fish in soup, or sprinkled on other foods as a condiment.

Silica, alginates and agar-agar, all the three are obtained from algae and are also of commercial importance to man. 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.

Kelps are large seaweeds belonging to the brown algae (Phaeophyceae). Kelp grows in underwater "forests" (kelp forests) in shallow oceans, and is thought to have appeared in the Miocene period, 23 to 5 million years ago. The organisms require nutrient-rich water with temperatures between 6$$^o$$ and 14$$^o$$ C. They are known for their high growth rate. Thus, the correct answer is option C.