1) The process of photosynthesis, performed by plants, algae, and some bacteria, is responsible for producing the oxygen we breathe.

2) The blue whale is the largest animal to have ever existed, with an average length of about 82 feet (25 meters).

3) The study of fossils is called paleontology, and it helps us understand the history of life on Earth and the process of evolution.

4) The first successful human heart transplant was performed by Dr. Christiaan Barnard in 1967.