How it works
This unlabeled diagram of Volvox puts both drawings on one sheet: the colony cut through the middle, and under it three cells from its surface, enlarged. Twelve parts want a name. Eight have a label line and four do not.
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The twelve names, by drawing
On the colony: somatic cells, gonidia, daughter colonies, gelatinous matrix, colony. On the enlarged cells: flagella, chloroplast, nucleus, eyespot, contractile vacuoles, pyrenoid, cytoplasmic strands.
Eight lines, and four parts without one
On the colony the lines end on the bracket (colony), a cell in the ring at its edge (somatic cells) and a large cell with a dot (gonidia). Below, they end on a small circle (contractile vacuoles), the dark oval (eyespot), the thick cup (chloroplast), the round body in its base (pyrenoid) and a thread between cells (cytoplasmic strands). Write the other four beside their parts: daughter colonies by a ball of tiny cells, gelatinous matrix in the plain filling, flagella by the long threads, nucleus by the round body with a dark spot.
- For a number on all twelve parts, with a line or without, switch the sheet to Numbered before you print.
- Nucleus or pyrenoid? Both are round. The nucleus lies in the hollow of the cup, the pyrenoid in its base.
- A class may say coenobium for the colony, stigma for the eyespot and protoplasmic threads for the strands.
Questions and answers
Where is Volvox found?
In fresh water all over the world: in ponds and ditches, and even in shallow puddles.
What does the name Volvox mean?
It comes from the Latin volvere, to roll. The genus was given the name in 1758, and because the colonies are spheres they are sometimes called globe algae.
How does Volvox reproduce?
Both asexually and sexually. The sheet shows an asexual colony, whose gonidia each divide many times over into a new colony. A sexual colony makes eggs or packets of sperm, and those are not drawn.
What does Volvox look like under a microscope?
A hollow green ball of up to 50,000 cells, distinctive and easy to identify. The sheet draws it with the focus on the middle of the ball, so its cells show as a ring at the edge.