What has to happens in order to natural selection to occur

List charasteristics of athenosphere

According to this food web which of the following would be considered primary consumers

Food webs - transferring energy and matter from one level to another. here you see four food webs. one or more are incorrect. which food web(s) show the correct sequence of organisms, from start to top level consumer? a) a b) d c) c d) a and d