If a scientist finds the remains of a plant between a rock layer that
contains 400 million-year-old Phacops fossils and a rock layer that contains
230 million-year-old Tropites fossils, how old could the plant fossil be?

Scientists can infer that the plant existed sometime from 400 million to 230 million years ago

it's the cell cycle, but cytokines is when the cell divides.

theres 3 stages interphase,mitosis,and cytokines.

interphase prepares the cell for division.

mitosis is the process of dividing the cell,it has 4 parts interphase,anaphase,metaphase,and telophase.

lastly there's cytokines,that's when the cell divides into 2 daughter cells

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.