Question

True nucleus is absent in
A. Vaucheria
B. Volvox
C. Anabaena
D. Mucor

Answer 1

Hint:These multicellular organisms are also called blue-green algae and are prokaryotic. True nucleus is absent in prokaryotes. They are known for nitrogen-fixing abilities.

Complete answer:
All organisms are made up of cells or cell aggregates. Cells vary in shape, size and activity or function. On the basis of the presence or absence of a nuclear membrane and other organelles, the cells and therefore organisms may be called eukaryotic or prokaryotic.

Prokaryotes are the organisms that lack a nucleus and other cell organelles. They have a region called nucleoid which contains the genetic material. All unicellular organisms are prokaryotic. Eukaryotic cells are cells that contain a nucleus and organelles, and are covered by a plasma membrane.

Vaucheria is a genus of a eukaryotic green-yellow alga. Vaucheria species are characterized by multinucleate tubular branches that lack cross walls except when associated with reproductive organs or when injured. Volvox is a eukaryotic green algae. Algae of the genus Volvox are an example of the link between colonial organisms and multicellular organisms. Mucor is the genus of mould and is a eukaryotic fungus found in soil, plants, decaying fruits and vegetables.

Anabaena, also known as blue green algae, is a prokaryotic organism. Despite their name, these algae are actually a colony of bacteria capable of photosynthesis. They belong to cyanobacteria. Anabaena Like other prokaryotes, lack a true nucleus and other cell organelles.

Thus, the correct answer is option C i.e., Anabaena.

Note:Prokaryotes are the species that lack nucleus in their cells. They have an irregularly formed region inside the cell called nucleoid where genetic material is present. Unlike the nucleus of the eukaryotic cell, it is not enclosed by a nuclear membrane.