20. Which of the following statements are accurate?

A. Repolarization of a neuron results from potassium diffusing out of the cell.
B. At rest, excitable cells (e. g. neurons) have a negative charge.
C. Once a depolarization reaches threshold, an action potential will occur and can not be prevented.
D. To reach threshold, cells at rest must depolarize.
E. Sodium diffusing into a neuron will cause depolarization.

Statements A,C,D and E are correct

Statement B is wrong.

Explanation:

A. An efflux of extra potassium ion out of the cell leads to the cell being repolarized.

C. Once the threshold of depolarization reaches there much be an occurrence of action potential.

D. Depolarization of a cell at rest makes it reach it's threshold

E. Depolarization leads to the opening of the voltage-gated Na+ channels for Na+ influx.

phylogenetic tree is the tree of life or evolution tree. it shows the different branches of evolution. the sequence goes like tissues - coelom - backbone - endoskeleton - segmentation