What are melanocytes and what do they do to the skin

The unique structure of the neuron is dedicated to the efficient and rapid transmission of neural signals. the relationship between neurons, the spinal cord, and the brain constitutes an elaborate communication system throughout the human body. all but one of the functions listed below are a result of this interaction.

Diffusion and osmosis are forms of passive transport

In general, characteristics that an organism survive and reproduce become more common over time. what mechanism of evolution causes this?