MadSci Network: General Biology |
Hi Christl -- Great question! I asked my colleagues next door in a developmental biology lab how a chick knows which way is up, and they agreed that gravity was the answer, somehow. The details were supplied by an article on the National Wildlife Federation website. As the chick grows, the air space remaining at the top of the egg decreases, while the chick occupies the lower portions of the egg. In the days prior to hatching, the chick assumes a position with its head tucked under one shoulder. Head movements oriented towards the diminishing air supply eventually result in contact with the shell, and further pecking movements. See this article for a more detailed answer: http://www.nwf.org/intlwild/eggs.html Cheers, Amanda Kahn amandak@phy.ucsf.edu
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