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Question
what is the advantage of having the blastodisc on the top of the egg?
It's pretty complicated, but basically the cytoplasm is shoved into one part of the egg because the rest of the space is taken up by yolk to provide energy. The blastodisc is on the outer side of the yolk near the shell, but I wouldn't describe it quite as being on top of the egg - the narrow or wide ends. See http://www.swarthmore.edu/NatSci/sgilber1/DB_lab/Chick/Chick_dev.html
for details.
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Answers by Expert:
Roger Lederer
Expertise
Any and all about WILD birds - the science of ornithology. Information about birdwatching, ecology, conservation, migration, behavior, banding, rehabilitation, feeding, songs, binoculars, identification, and careers in ornithology. No questions about pet or caged birds, please.
Experience
Have a PhD and over forty years as a professional ornithologist - research, teaching, author, speaker, webmaster of Ornithology.com . Have written thirty scientific papers, three bird field guides, a textbook in ecology and two recent books entitled "Amazing Birds" and "Birds of New England". Have traveled to over 90 countries watching birds.
Education/Credentials
PhD in Zoology/Ornithology; Emeritus Professor of Biological Sciences; former Dean of the College of Natural Sciences at California State University, Chico
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