How it works
This labeled diagram of Volvox has two views. The colony shows the whole ball cut through the middle. One cell shows three of its cells enlarged.
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The colony
A Volvox colony is a hollow ball of jelly, the gelatinous matrix, with its somatic cells in one layer at the surface. The gonidia are the few large cells without flagella. Each one divides to make a daughter colony, which grows inside the parent.
One cell
Each somatic cell carries two flagella, an eyespot, a cup-shaped chloroplast with a pyrenoid in its base, a nucleus and two contractile vacuoles. In some kinds of Volvox, cytoplasmic strands join each cell to its neighbors.
- For a simple labeled volvox diagram, start with five names: somatic cells, gonidia, daughter colonies, flagella and eyespot.
- Gonidia have no flagella; every somatic cell has two.
Questions and answers
What are the parts of a Volvox colony?
The colony is a hollow ball of jelly with somatic cells in a single layer at its surface. A few large gonidia lie in the rear half, and daughter colonies grow inside until the parent breaks open.
What is the difference between somatic cells and gonidia?
Somatic cells are small, have two flagella and move the colony; they do not form new colonies. Gonidia are large, have no flagella and divide again and again to form daughter colonies.
Is Volvox unicellular or multicellular?
Volvox is made of many cells: hundreds to thousands in one colony, of two types that do different jobs. Biologists use it to study how many-celled life arose from single cells.
How does Volvox move?
Each somatic cell beats its two flagella, and together they roll the colony through the water. The eyespots sense light, so the colony can swim toward it.