Which best describes tropic relationship in ecosystems?

Which of the following is one of the four conditions necessary for natural selection to occur in a population? fewer organisms are born than the habitat can support mutation does not occur organisms have identical characteristics variation is inherited

Which of the follow describes a disadvantage secondary sources have compared to primary sources?

There are fewer than 100 naturally occurring elements in the universe, but there are millions of different unified substances. explain how this can be true.