Yeast cells, plant cells, and mammal cells all share many similarities in cell signaling. This provides evidence that: a. cell-signaling mechanisms are only found in organisms that use methods of sexual reproduction
b. intercellular communication evolved as a way for multicellular organisms to coordinate cell functions
c. eukaryotic cells use signal transduction pathways while prokaryotic cells use a more primitive form of signaling
d. signal transduction pathways appeared in cells before the evolution of multicellular organisms

When analyzing tree rings, what do scientists assume a thin ring indicates?

Human genes only differ by less than percent. a. 1 b. 6 c. 11 d. 16

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?