Considering both Model 1 and Model 2, which checkpoint in the cell cycle is regulated by the concentration of MPF?

Epinephrine is a hormone released from the adrenal gland of the body, most often in a stressful situation. it is known as the "fight-or-flight" hormone. one way that it causes a response in the body is to activate receptors on muscle cells. where are these cellular receptors located? a. on the cell membrane b. in the nucleus c. on the cell wall d. around the mitochondria

What was the land like over 500 million years ago? what was under the sea?

The pressurized plants and fungi mentioned in the video have some surprising similarities. what differences would you expect them to have?