Which of the following was most likely responsible for the fact that organic molecules no longer form spontaneously on earth?
a. organisms began to photosynthesize
b. earth's surface temperature cooled.
the study of biology is important because it focuses on
a. the animals of the earth
b. the development of human forms
c. the interactions of all living things d. the functions of the human body

1) A. The primitive earth had a lot of UV radiation. Photosyntesis originated O2 and O2 reacts generating O3 (ozone). The ozone layer prevents a lot of UV radiation to reach inorganic molecules and provide them with a lot of energy. Without that intense UV radiation, inorganic molecules cannot convert into organic molecules (because no other source of energy provides enough energy for that process).

2) C. Biology does not focus only on animals, less still will it focus only on humans. Biology studies all living organisms in every aspect: development, functions, interactions, evolution. Biology can be divided in several areas: physiology, which studies functions of each part of an organism (which can be an animal, a plant, a bacteria, etc); anatomy, which describes the organism's structure. Or we can divide it according to which organisms it studies - there we have: botany (plants), zoology (animals), microbiology (bacteria and fungi). Another area describes how an organism interacts with the environment and with other organism - that is called Ecology. And another area is Evolution, which describes how an organism changes over time (several generations) and becomes a different organism, and relates that with the origin of life.