The earliest bacterium-like organisms proliferated, giving rise to a great variety of forms, some of which were capable of photosynthesis. From these arose the oxygen-producing cyanobacteria approximately 3 billion years ago. Bacteria are called prokaryotes, meaning literally “before the nucleus.” They contain a single, large molecule of DNA not located …

Darwin’s theory of evolution is now over 140 years old. Darwin articulated the complete theory when he published his famous book On the Origin of Species by Means of Natural Selection in England in 1859. Biologists today are frequently asked, “What is Darwinism?” and “Do biologists still accept Darwin’s theory …