The fossil record shows that the types of living things on Earth changed over time. Which fossil would most likely be found in the oldest rock layer?

If bacteria are much too small to see, what is one reason why can we see colonies in the petri dishes that have plenty of food to eat after only a few days?

Ihave no idea how to solve these. plus there's another question that is 2) a 10 kilogram meteorite is collected in space and brought back to earth. it is composed of 1.25 kg of uranium-238 and 8.75 kg of lead-206. how many u-238 half lives have passed? what is the approximate age of the meteorite?

Which structure in the cardiovascular system connect arteries to veins?