Which of the following is considered the key innovation that started chordates along the evolutionary path that led to vertebrates?
A. a flexible rod to which muscles are attached, which allowed lateral movement of the back
B. an internal endoskeleton
C. a skin covering the entire body to prevent desiccation
D. a hard shell encasing the body
E. amniotic egg
A. a flexible rod to which muscles are attached, which allowed lateral movement of the back
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Which excitatory neurotransmitter is responsible for muscle contraction in vertebrates?
A. dopamine B. norepinephrine C. nitrous oxide D. glutamate E. acetylcholine
The natural habitat of the bacterium Sphingobacterium is:
a. environment. b. animal oral and respiratory flora. c. environment, cold climates. d. human normal flora.
The origin of the mitochondrion and chloroplast is hypothesized to have involved
A. the absorption of RNA from prokaryotic cells. B. prokaryotic cells that became internal symbionts within an early eukaryotic cell. C. the fusion of two archean cells to form an early eukaryote. D. the uptake of free DNA from the environment. E. prokaryotic cells being engulfed and becoming external symbionts within an early bacteria cell.
Some vertebrates like frogs and humans do not have a conspicuous tail, yet even humans have the remnants of one known as the
A. sacrum. B. coccyx. C. fundus. D. lumbar.