Some scientists believe that life on Earth began about 3.5 billion years ago. What do they base this belief on?​

How can you approximate the number of calories required to keep you in energy balance?

Use the phylogenetic tree to the right to determine which statement below is true. organisms a and f are not related. organism e is more closely related to organism b than organism f. organisms c and d are more closely related than organisms a and b. phylogenetic trees

Hemoglobin is a proton that carries oxygen around the body what is hemoglobin made from