Paul Ralph Ehrlich (born 29 May 1932) is an American biologist and educator who is the Bing Professor of Population Studies in the department of Biological Sciences at Stanford University and president of Stanford's Center for Conservation Biology. By training he is an entomologist specializing in Lepidoptera (butterflies), but he also a prominent ecologist and demographer. Ehrlich is best known for his dire warnings about population growth and limited resources. Ehrlich became well-known after publication of his controversial 1968 book The Population Bomb. In the years since many of Ehrlich's predictions have proven incorrect, but he stands by his general thesis that the human population is too large and is a direct threat to human survival and the environment of the planet. He is also known for the famous Simon–Ehrlich wager, a bet about the trend of prices for certain metals that he made in 1980 with, and lost to, economist Julian Simon.

Ehrlich was born in Philadelphia, Pennsylvania. His father was a shirt salesman, his mother a Greek and Latin scholar. He earned a bachelors degree in zoology from the University of Pennsylvania in 1953, an M.A. at the University of Kansas in 1955, and a Ph.D. in 1957 at the University of Kansas, supervised by the prominent bee researcher C.D. Michener. During his studies he participated in surveys of insects on the Bering Sea and in the Canadian Arctic, and then with a National Institutes of Health fellowship, investigated the genetics and behavior of parasitic mites. In 1959 he joined the faculty at Stanford, being promoted to professor of biology in 1966. He was named to the Bing Professorship in 1977, and he is president of the Center for Conservation Biology at Stanford University. Additionally, Ehrlich is a fellow of the American Association for the Advancement of Science, the United States National Academy of Sciences, the American Academy of Arts and Sciences and the American Philosophical Society.

 Paul Ehrlich (help·info) (14 March 1854 – 20 August 1915) was a German scientist in the fields of hematology, immunology, and chemotherapy, and a Nobel laureate. He is noted for discovering the syphilis treatment salvarsan, the first drug targeted against a specific pathogen; and for his research in autoimmunity, calling it "horror autotoxicus". He coined the term chemotherapy and popularized the concept of a magic bullet.

Paul Ehrlich was born into a Jewish family in Strehlen, in the German Kingdom of Prussia, Province of Silesia (now in Poland). As a schoolboy (inspired by his cousin Karl Weigert who owned one of the first microtomes), he became fascinated by the process of staining microscopic tissue substances. He kept that interest during his studies at the universities of Breslau, Straßburg, Freiburg im Breisgau and Leipzig.

In his dissertation at the University of Leipzig, he picked up the topic again ("Contributions to the Theory and Practice of Histological Staining", Beiträge zur Theorie und Praxis der histologischen Färbung). He married Hedwig Pinkus (then aged 19) in 1883. The couple had two daughters, named Stephanie and Marianne. After his clinical education and habilitation ("The Need of the Organism for Oxygen", Das Sauerstoffbedürfnis des Organismus) at the Charité in Berlin in 1886, he received a call from Robert Koch to join the Institute of Infectious Diseases in Berlin (1891).

Tom Turner is an English landscape architect,garden designer and garden historian teaching at the University of Greenwich in London. He is the author of books and articles on landscape and gardens and is the editor of the Garden History Reference Encyclopedia CD and the online Gardens Guide. Educated at the Universities of St Andrews and Edinburgh, he studied landscape architecture under Frank Clarke.