4. In a food chain,
A the number of organisms increases at each
higher level.
® each level contains only about 10 percent
of the energy present in the previous
level.
© only the heterotrophs are included.
0 consumers serve as the base.

b

Explanation:

a is wrong bc the number organisms actually decrease significantly at each level. and c is wrong also. however b is right bc there must be more foood available for the lower levels so that the required energy is available.

So say that you cut your finger, this causes tissue damage, which is registered by microscopic pain receptors in your skin, and each one of those pain receptors creates one end of a nerve cell. The nerve cell is connected to the other end of the spinal cord with a long nerve axon.

A neuron is a nerve cell that is the basic building block of the nervous system.

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