Which of the following statements regarding contraction of a skeletal muscle fiber is true?

a) thick filaments shorten when muscle fibers contract.
b) some contractions occur without activation of myosin heads.
c) contracting muscle fibers do not always shorten.
d) contraction does not always require the occurrence of an action potential.
e) contraction only occurs following summation of action potentials from many motor neurons.

Select all the correct answers. lactobacillus is a bacteria that live inside humans. these bacteria live on the nutrients from our bodies. they to keep our gut clean and healthy. s. typhi is a bacteria that enter our bodies through contaminated food. this bacteria causes infections in the body. based on this information, which two statements about the association between these bacteria and humans are true? a. lactobacillus shares a parasitic relationship with humans. b. s .typhi shares a parasitic relationship with humans. c. both lactobacillus and s. typhi share a parasitic relationship with humans. d. both lactobacillus and s. typhi share a mutualistic relationship with humans. e. lactobacillus shares a mutualistic relationship with humans, and s. typhi shares a parasitic relationship multiply chrse

An easy way to calculate the amount of energy available at each level is to what?

Me . based on the data in your tables, did the light-colored moths have a higher or lower survival rate after the industrial revolution?