In which of the following multicellular organisms is-interdependence of cells maintained?

Analyze the question: The question asks which organism is multicellular and shows interdependence (division of labour) among its cells. This is a colonial organization concept.

Concept:

• Colonial algae such as Volvox, Eudorina and Pandorina are made of many cells grouped together in a colony.
• In simple colonies like Pandorina (16 cells) and Eudorina (32 cells), the cells are mostly alike and each can often live independently if separated. They show little or no specialization.
• In Volvox (up to thousands of cells in a hollow sphere), there is a real division of labour. Most cells are somatic (vegetative), handling photosynthesis and movement via flagella. A few cells at one end are reproductive (germ) cells, forming gametes and daughter colonies. Somatic cells cannot reproduce, so they depend on the reproductive cells, and the reproductive cells depend on the somatic cells for food and movement. This is interdependence of cells.
• Spirogyra is a filamentous alga. Its cells are all similar and each can carry out all life functions. If the filament breaks, each fragment can continue to grow, so there is no real interdependence.

Solution:

1. Spirogyra: cells are identical and independent, so it is not the answer.
2. Eudorina: a colony with minimal specialization, and cells are nearly independent, so it is not the best answer.
3. Pandorina: a colony of identical cells, so it is not the answer.
4. Volvox: cells are differentiated into somatic and reproductive cells that depend on one another, so this is the answer.

Answer: B. Volvox

Tip: Think "Volvox = Very advanced colony." Whenever WAEC asks about division of labour or interdependence among algal colony cells, choose Volvox.