Examlex
Which of the following is explained by von Thünen's model?
Amnion
A membranous sac that surrounds and protects an embryo or fetus in the amniotic cavity of vertebrates.
Yolk Sac
An extra-embryonic membrane in many vertebrates that provides food for the embryo via absorbed nutrients.
Gas Exchange
The biological process through which organisms exchange oxygen and carbon dioxide with their environment, typically occurring in the lungs or gills.
Fetus
A developing mammal or human from the end of the embryonic stage, recognizably human in form, until birth.
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