What level of organization is Spirogyra?

Analyzing the question The question asks about the level of organization of Spirogyra. Think about what kind of organism it is and how its body is built.

The concept Biological organization runs from small to large: Cell → Tissue → Organ → System → Organism

Spirogyra is a filamentous green alga. Its body is a thread made of many cells joined end to end. Each cell carries out all the life functions on its own: photosynthesis (using its spiral chloroplast), respiration, and so on. The cells are not specialized into tissues, organs, or systems.

Working through the options

• A. System: Systems (such as the digestive system) need several organs working together. Spirogyra has none, so this is wrong.
• B. Organ: An organ is made of different tissues, and Spirogyra has no tissues. Wrong.
• C. Cell: Spirogyra is a simple, thread-like organism whose cells are essentially alike and each function independently. It is classed at the cellular level of organization, so this is the best fit.
• D. Tissue: A tissue is a group of specialized cells doing a particular job. Spirogyra's cells are not differentiated into such groups. Wrong.

Note on the answer Strictly speaking, a filament is a colony or multicellular chain, but since the cells are undifferentiated, WASSCE treats Spirogyra as the cellular level of organization.

Answer: C. Cell

Exam tip: Algae like Spirogyra, Chlamydomonas, and Volvox are usually linked with the "cellular" or "cell-colony" level. If you see "tissue," "organ," or "system" in the options, ask yourself whether the organism has specialized cells. If not, choose cell.