What is the function (purpose) of the valves which connect the heart chambers? allows blood to flow between the two atria
allows blood to flow from the atria to the ventricle
prevents blood from flowing into the atria when ventricle pumps
allows blood to flow between the two ventricles

In what for do plants utilize nitrogen? why do they need nitrogen?

Match the functions to the cell types ? contraction and relaxation. conducting electrochemical signals fighting diseases carrying genetic material

80 points pls brainliest 1. what does a red shift mean? blue shift? 2. describe the big bang theory. according to this theory, how old is the universe? 3. scientists believe the universe is expanding. what is the evidence that supports this? 4. describe a nebula. 5. describe the 3 types of galaxies. what is a barred spiral galaxy? 6. what is a light year? how far is alpha centauri from earth? 7. describe the universal law of gravitation. be sure to include gravitational force between two objects. 8. describe the planets’ orbits around the sun. 9. what is the asteroid belt? where is it located? 10. describe rotation and revolution of earth. what determines an earth day and year? 11. how do galaxies exist? 12. compare and contrast the inner and outer planets. 13. what causes the seasons?