If a blood vessel is damaged, chemicals begin a chain reaction that causes platelets to stick to the vessel wall. The platelets release more chemicals that accelerate the clotting process. This process ends once the vessel wall has been repaired by a clot. this is an example of what?

A. a positive feedback loop

B. a negative feedback loop

C. thermoregulation

D. osmosis

List two modern organisms that have pentameral symmetry

Which are reasons cells undergo cell division?

20 point pls brianliest 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?