This edition: Biology & Evolution
Humans are biological organisms that have a place in the natural world. To understand what it means to be human we need to understand how we became human. The video introduces the topic of biology by looking at an important evolutionary force, natural selection, and how it has affected a species of fox living on islands off the California coast. Next, the ultimate source of variation is discussed as the hereditary material, DNA, is examined. Genes, alleles, and proteins are discussed as part of normal human physiology, including their role in inherited genetic diseases. How the hereditary material is distributed to offspring is the focus of meiosis, by which sex cells are formed. Crucial here is that different combinations lead to variation between each sex cell. Mutations give rise to new variations upon which natural selection can act. In the final segment of the video, population genetics is showcased. A human case of natural selection, the sickle-cell trait, is highlighted. Non-Darwinian forces of evolution, gene flow and genetic drift are explored, and the video ends with a discussion of how evolutionary forces can change a population.