What do scientists study to figure out how long it takes the sun to make one rotation on it's axis?

Adistinctive characteristic of mammals that is not observed in other vertebrates is

When does an organism become an adult during a life cycle? a)before metamorphosis is complete b)after producing offspring c)after development is complete d)before gametes fuse

Which of the following is true about the introduction of a non-native species to an environment? (a) they usually adapt quickly so they can have a positive affect on the environment. (b) they can disrupt the environment and cause much damage and devastation to native species. (c) they usually become predators in a food chain and to keep prey populations under control. (d) because the native species are better-adapted to the environment, the non-native species always end up dying out.