What´s the difference between spindle and microtubules?

a spindle fiber is one single filament which is coming from the poles onto the center. Remember that this spindle fiber isn't part of the chromosome, it just helps with holding everything in place. Microtubules are responsible for pushing the poles of the spindle apart.

I hope this helps!! 

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.

sex cells are usually half's then they find another half and make a fertilize egg