In response to being startled, an animal involuntarily contracts a skeletal muscle, causing it to shorten. what process is described by an animal's ability to involuntarily contract a skeletal muscle without receiving a direct signal from the brain, and which type of muscle contraction occurred as a result?

The answer is reflex action. Impulse that triggers a reflex action does not pass through the brain so as to shorten the time for response. It passes through a reflex arch and this is why the muscles are contracted even without time to think of what happened. The sensory and motor neurons only arch at the spinal cord.

nucleic acid molecules are incredibly complex, containing the code that guarantees the four different nucleotide units comprise dna, the nucleic acid of interest to the genealogist. and one of four nitrogen-containing molecules called nucleotides