Amolecule that can be used as a molecular clock has a neutral mutation rate of one mutation per 20 million years. how many years ago did two species share a common ancestor if the molecules found in these two species differ by a total of six mutations? 60 million years 120 million years 100 million years 30 million years

Before the can be observed by using a transmission electron microscope, cells are sliced into very thin sections. what disadvantage does this procedure present in the study of cellular parts

One of the reasons that stars are so large is because

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?