Fern antheridia release sperm that then swim toward archegon

Fern antheridia release sperm that then swim toward archegonia in a watery film. The archegonia release a fluid containing chemicals that attract the sperm. This is an example of chemotaxis, which is the movement of cells or organisms in response to a chemical. a. Assuming sperm availability Is limited, what effect would sperm chemotaxis have on fertilization rates? b. Sperm chemotaxis occurs in a variety of animals, including humans. Do you think sperm chemotaxis is more critical for organisms that perform external fertilization (example: mosses) or organisms that perform internal fertilization (example: humans)? Explain your rationale.

Solution

Answer

1. Chemotaxis will improve the fertilization rate. Sperm chemotaxis increases sperm-egg encounter rates.Chemotaxis play a crucial role in increasing the fertilization rate in ecological conditions where the sperm concentration is low. Due to low sperm concentration their is a risk of eggs remaining unfertilized. In such conditions especially in external fertilizers, sperm chemotaxis is one of several counter-measures to overcome sperm limitation and increase fertilization rate.

2. Sperm chemotaxis is more critical for organisms that perform external fertilization. In internal fertilizers the sperm cells are directly deposited into the female genital tract in high concentration thereby ensuring reliable fertilization of the egg.

On the other hand, for external fertilizers there are several benefits of sperm chemotaxis. For example:

a) Due to sperm chemotaxis, the sperm-egg encounter rates are improved.

b) Sperm chemotaxis increases the effective target size of eggs and help the sperm to orient correctly towards the fertile eggs.

c) Sperm chemotaxis helps to maintain species integrity by facilitating species recognition.