Question

Spirogyra is commonly called as pond silk because
(a) Silk is manufactured from it
(b) It looks like a thread
(c) It is slimy to touch
(d) All of the above

Answer 1

Hint: They are one of the long filamentous, unbranched, special types of algae.

Complete answer:
Algae also known as thallophytes are unicellular or multicellular structures bearing chlorophyll. They are autotrophic and largely aquatic (both freshwater and marine water). They are also seen in moist stones, soils and woods.

1. Algae are classified as Chlorophyta, Phaeophyta, and Rhodophyta.
2. Chlorophyta are the class of algae which contains chlorophyll a and b, they are freshwater habitat may be unicellular or multicellular.
3. Spirogyra belongs to a class of algae called Chlorophytes.
4. They are unbranched, filamentous, free floating green alga of stagnant fresh water.
5. It shows a presence of mucilage sheath on the outer side.
6. The cell wall is made up of two layers outer of pectin and inner of cellulose.
7. The outer part (pectin) dissolves in the water to form a mucilaginous sheath.
8. It gives a slimy touch to the spirogyra.

Hence, spirogyra is also called pond silk.

So, the answer is option (c) It is slimy to touch.

Additional information:
1) Spirogyra is also known as mermaid’s tresses or water silk.
2) Spirogyra reproduce through vegetative, asexual and sexual reproduction.
3) Other examples of Chlorophyta are Chlorella, Ulothrix, Volvox, Chlamydomonas.

Note:
1. Pectin is a naturally occurring heteropolysaccharide.
2. Phaeophyta shows presence of chlorophyll a, c, fucoxanthin and are known as brown algae.
3. Rhodophyta (red algae) shows presence of red pigment called phycoerythrin.