Please answer the question correctly

(30 points)

How does the study of genetic disorders such as pku biologists understand normal alleles?

Which of the following is a reason why early living organisms on earth could not have survived on the surface? 1. the lack of an ozone layer 2. the lack of oxygen in the atmosphere 3. the fact that these organisms were single-celled

When fossil fuels are burned, carbon dioxide is released. how does this gas impact the environment?