Some breeds of dogs that are specialized to retrieve objects from bodies of water have webbing between their toes. A change in what cellular response to positional information during digit formation could account for this morphological feature?
A. Signals that cause differentiation to toes are not received by cells that become webbing.
B. Signals to cause apoptosis are not received by cells that become webbing.
C. Cells between the future digits migrate, but do not divide once they are in the region that will become toes.
D. Cells between the future digits divide, but do not migrate to the region that will become toes.
E. Cells between the future digits do not divide before migrating to the region that will become toes.
B. Signals to cause apoptosis are not received by cells that become webbing.
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In humans, spermatogenesis differs from oogenesis in that spermatogenesis ____
a. involves meiosis while oogenesis involves mitosis b. begins at birth while oogenesis begins at puberty c. has unequal cytoplasmic divisions, while oogenesis does not d. produces somatic cells while oogenesis produces gametes e. produces four functional gametes while oogenesis produces one functional gamete
__________ stimulate cell division, release lateral buds from apical dominance, and inhibit
senescence. Fill in the blank(s) with the appropriate word(s).
Primates first appear in the fossil record in the:
A) Cenozoic era. B) Cambrian period. C) Paleozoic era. D) Mesozoic era.
In photosynthesis, the oxygen atoms present in CO2 end up _____.
a. as molecular oxygen and water b. in sugar molecules and carbon dioxide c. in water and carbon dioxide d. as molecular oxygen and in sugar molecules e. in sugar molecules and in water