Question

A group of biology students were studying about algae. They prepared a sample slide using a water sample drawn from a puddle. While observing the sample under a microscope, they noted that those living in the colony and the colony were coated with jelly-like substances. Using these hints identify the organism
A. Ulva
B. Sargassum
C. Volvox
D. Diatom

Answer 1

Algae are photosynthetic species with photosynthetic pigments such as chlorophyll in their possession. They lack true roots, stems and leaves that are typical of vascular plants, however. Some of them are single-celled, while others are multi-cell. They can form colonies as well. The bulk of algae are marine.

Complete Answer:
- Aquatic and photoautotrophic eukaryotes are the essential characteristics of algae. Both species are photosynthetic and, compared to other phototrophic eukaryotes, they have a relatively basic anatomy.
- Their body plan, however, could vary from single-celled to colonial, to multicellular. The algal species are mainly single-celled. Some of them are non-motile (flagellated), while others are motile. Some of them, while others form colonies or filaments, live individually.
- Green algae refers to one of the pigment-containing photosynthetic algae, chlorophyll a and chlorophyll b. They store food inside the plastids as starch. They have different forms: unicellular, multicellular, or colonial (e.g. Micrasterias sp.). Those that appear to be filamentous or forming leaf-like thallus (e.g. Ulva sp.) are multicellular forms.
- Some of them, such as Volvox sp, form colonies. Charophytes (mostly in freshwater habitats) and chlorophytes (mostly marine) are composed of green algae.
- Green algae that live in terrestrial environments (such as soil, rocks, and trees) are also present. In order to form symbiosis on soil, some green algal species have been found.
- Volvox forms spherical or oval hollow colonies containing, often visible to the naked eye, between 500 and 60,000 cells embedded in a gelatin wall.
- Volvox can be found all over the world in rivers, puddles, and bodies of still fresh water. They contribute to oxygen production as autotrophs and serve as food for a number of aquatic organisms, in particular for microscopic invertebrates called rotifers.

The correct Answer is option(C) Volvox.

Note: The first Volvox colonies were identified by the Dutch microscopist Antonie van Leeuwenhoek in 1700 and are widely studied as a genetic model of how organisms grow specialised cells and tissues. Volvox also demonstrates a distinction between somatic (non-sex cells) and reproductive cells, a phenomenon that some biologists consider to be significant in tracing the evolution of higher animals from microorganisms.