 Ulva is a flat sheet of Cells |
 Ventricularia is Spherical |
A sphere has the lowest surface to volume ratio. This means that for a particular volume a sphere has the lowest surface area. Since evaporation takes place where a wet surface meets an atmosphere, less evaporation will occur from a spherical object compared to a flat one. A completely flat surface would have the maximal surface area and therefore would have the largest area available for the evaporation of any liquid. A cylinder would have an intermediate surface to volume ratio.
The sea lettuce (Ulva) is only two cells thick. It has a sheet-like thallus which would have a greater surface area compared to a spherical organism of the same volume, like Ventricularia which is sphrical.
Ulva is a flat sheet of Cells |
Ventricularia is Spherical |
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| The lamina of a filmy fern may be one cell layer thick in places. | Some ferns produce leaves with a thick lamina. |
| Which of the two ferns would best survive water stress? | |
