For humans and most vertebrates the body is supported primarily by
a. an exoskeleton.
b. only nonskeletal structures.
c. a hydrostatic skeleton.
d. an endoskeleton.
e. joined exo- and endoskeletons.
D
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The __________ __________ model assumes that evolution occurs in spurts, between which there are long periods of stasis with little evolutionary change.
Fill in the blank(s) with the appropriate word(s).
During which stage of development does implantation occur, followed by initial development of the nervous system, limb buds and all other systems?
a. critical period b. sensitive period c. embryonic period d. fetal period
Which of the following is considered the key innovation that started chordates along the evolutionary path that led to vertebrates?
A. A skin covering the entire body to prevent desiccation B. An internal endoskeleton C. A flexible rod to which muscles are attached, which allowed lateral movement of the back D. Amniotic egg E. A hard shell encasing the body
Pigs rich in omega-3 fatty acids:
A) have never been produced using biotechnology. B) were produced using the PCR technique. C) are examples of transgenic animals. D) would not be healthier to eat than regular pigs.