D, the black squirrels have survived because black has provided them with an advantage in this environment.
If you cut a flatworm in half, both halves can grow into a new individual by fission.
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A point mutation can indeed be a frameshift mutation
Triggering of the muscle action potential occurs after Ach binds to chemically gated channels in the motor end plate membrane. Acetylcholine (Ach) is a neurotransmitter produced by nerve cells.
An action potential is an electrical signal that travels along the cell membrane as a wave.
This action potential (muscle action potential) drives the contraction of muscle fibers.
When the action potential reaches the neuromuscular junction (i.e., the motor end-plate), acetylcholine (Ach) is released into the synaptic cleft.
Subsequently, Ach can bind and open specific channels localized on the surface of the muscle cells, thereby depolarizing them and triggering muscle contraction.
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