Which unit of geologic time is the oldest? cenozoic mesozoic ordovician precambrian

Will mark branliest. the theory of plate tectonics was developed with the contribution of scientists from many different disciplines. which of the following is a contribution from geophysicists?

Be in this im starting a with you so if you want you can get a partner for this. but basically im going to assign you guys a biome and you have to have a big sheet paper and you will turn it into 4 squares. the top right square is will be a drawing square for a drawing you will make of your biome. the top left square is about the biomes plants and drawings of them. the bottom left square is about the biomes animals. the bottem rights square is about the description of the biome. leave a comment or an answer and i will assign biomes. if your request one thats the one you get. send me a link to the project and i will grade ! im not a teacher btw.

Why has two different alleles for the same trait?