The level of organization in spirogyra and volvox is

Analyze the question: It asks about the level of organization (cell, tissue, organ, system, organism) shown by Spirogyra and Volvox.

Concept: Biological organization runs from cell → tissue → organ → organ system → organism. Algae are simple thallophytes, so they have no true tissues, organs, or systems.

• Spirogyra is a filamentous green alga. Its cells are joined end to end in an unbranched chain, and each cell carries out all of its own life functions. There is no division of labour and no specialized tissue.
• Volvox is a colonial green alga. It is a hollow sphere of hundreds to thousands of flagellated cells held together in a colony. Apart from a few reproductive cells, the cells are largely similar and independent. This is a colonial level of organization, which is still the cellular level.

Solution:

1. Neither organism has true tissues, because there are no groups of specialized cells with distinct functions.
2. They therefore have no organs or organ systems.
3. Their organization is based on cells, whether they are in filaments (Spirogyra) or colonies (Volvox). This is the cellular level.

Answer: C. cell.

Tip: Remember "Spirogyra = filament, Volvox = colony, both = cell level." Whenever you see algae like Spirogyra, Volvox, Chlamydomonas, or Pandorina, think "cellular or colonial, no true tissues." Tissue-level organization starts with simple multicellular animals like Hydra, and with higher plants.