ascending signals in the spinal cord travel via gray matter, while descending signals travel via white matter.

Why is earth's outer core hotter than earth’s oceanic crust? earth’s oceanic crust is denser than earth’s outer core is. earth’s oceanic crust has lava flowing from the mantle. earth’s outer core has a composition of solid iron and nickel. earth’s outer core is deeper within earth than oceanic crust is.

There are only about 250,000 known fossil species. true or false

Explain why it’s important for scientists to study the sun. list at least two challenges researchers face when examining earth’s nearest star.