BIO 4113 – Evolutionary Biology Introduction
“….a beautifully simple and easily understood idea – evolution by natural selection – can be scientifically tested in all these fields. It is one of the most powerful ideas in all areas of science, and is the only theory that can seriously claim to unify biology.”
Evolution: change in living things by descent with modification. The change may be range from DNA sequences to behavior.
Evolution depends on external environmental change and on random genetic changes. That means that the future course of evolution is unpredictable, unless we can specify future conditions. Another aspect: evolution of life has proceeded in branching pattern, with the tremendous variety of modern species being descended from a common ancestor.
Adaptation – a critical concept. Living things show adaptations.
Natural Selection: Simply put, some kinds of individuals in a population tend to contribute more offspring to the next generation than do others. Provided that the offspring resemble their parents, any attribute of an organism causing it to leave more offspring than average will increase in frequency in the population over time. The composition of the population will then change.
Diderot Maupertuis Darwin was not the first to question the idea that species were fixed, although it was certainly the commonly held belief at his time.
The French naturalist Jean-Baptiste Lamarck put forward the idea that species changed over time in 1809 in his book Philosphie Zoologique. His process, though, was very different from that imagined by Darwin fifty years later. Lamarck suggested the idea of transformism. He did not suggest that lineages branched and went extinct.
Lamarck’s Theory actually had two parts: • Transformism • Inheritance of Acquired Characteristics.
Friction between Lamarck and the highly influential Georges Cuvier had a great influence on thinking through the early part of the 19th Century. Cuvier
Charles Darwin 1809-1882
Shrewsbury, England Charles Darwin was born on February 12, 1809, in Shrewsbury, England. Interestingly, another man was born on the same day in a log cabin in Kentucky. That man was Abraham Lincoln.
The Darwin family home was called “The Mount”. It was here that Darwin was born, and where his father practiced medicine.
Charles father, Robert Waring Darwin, was a prominent physician in Shrewsbury.
Erasmus Darwin (1731-1802 Organic life beneath the shoreless waves Was born and nurs’d in ocean’s pearly caves: First forms minute, unseen by spheric glass, Move on the mud, or pierce the watery mass; These, as successive generations bloom, New powers acquire and larger limbs assume; Whence countless groups of vegetation spring, And breathing realms of fin and feet and wing.
Shrewsbury School Charles was educated at home until the age of nine. He then attended Shrewsbury School, a boarding school located about a mile from his home, until he was sixteen.
In 1825, Charles entered the University of Edinburgh in Edinburgh, Scotland, to study to become a physician.
“The instruction at Edinburgh was altogether by lectures, and these were intolerably dull, with the exception of those on chemistry….to my mind there are few advantages and many disadvantages in lectures as compared with reading…. Dr. _____ made his lectures on human anatomy as dull as he was himself, and the subject disgusted me.” Charles Darwin 1876
In 1827, Charles gave up the study of medicine and began studying for a career in the clergy at Christ’s College of Cambridge University.
During his time at Cambridge, Darwin was an “adequate” student, but busied himself with many other activities. He became fascinated with natural history. He was particularly fascinated with the intrigued by the enormous diversity of beetles.
Darwin was influenced by a Professor of Botany (and clergyman), John Stevens Henslow. Henslow persuaded Darwin to become interested in Geology. “I fully believe a better man never walked this earth.” Charles Darwin to Joseph Hooker regarding John Stevens Henslow. John Henslow 1851
Henslow arranged for Darwin to accompany Adam Sedgwick on a field trip studying the geology of Wales in 1831. This stimulated Darwin’s interest in geology. Adam Sedgewick
In 1831, Henslow arranged for Darwin to be interviewed for a position on board the HMS Beagle
Darwin was interviewed by Robert Fitzroy, and was offered a position as a “volunteer” naturalist on board the Beagle. Captain Robert Fitzroy of the HMS Beagle
South American sketch from Beagle voyage The Beagle’s primary mission was mapping and exploring the coast of South America.
On the voyage, Darwin read Lyell’s Principles of Geology. It persuaded him that the earth was very ancient. Charles Lyell Author of Principles of Geology
The Galapagos Darwin was particularly influenced by observations made in the Galapagos Islands, some 500 miles off the coast of Ecuador.
Pinnacle Rock The Galapagos are a group of volcanic islands, isolated from the South American mainland.
The islands are inhabited by a diverse group of organisms that differ from those found on the mainland. Marine iguana
On his return, Darwin married his cousin Emma Wedgewood. They had ten children, with seven surviving to adulthood. Charles with his daughter
In 1842, the Darwins moved to Down House in Kent, about sixteen miles from London. Darwin never left the British Isles again.
He spent much of his time in his study, working on his ideas. Darwin’s microscope
Darwin became one of the world’s leading authorities on a wide range of topics, including barnacles…… …. and volcanic islands.
“I happened to read for amusement Malthus on Population and, being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved and unfavourable ones to be destroyed.” Darwin, on reading Malthus’ Essay on the Principle of Population in 1838. “ Thomas Malthus
In 1844, Darwin received a manuscript from Alfred Russell Wallace, a young naturalist who was working in the Malay Archipelago.
The monumental new idea in Origin of Species was not the idea that species had evolved. The enormous step that Darwin took was the suggestion of a mechanism by which evolution could take place.
Darwin’s ideas were immediately controversial in the public eye, although most scientist’s were quickly convinced of the validity of his arguments.
One of the better arguments against Darwin’s theory was that it lacked a satisfactory theory of heredity. In fact, Darwin preferred a “blending” theory of inheritance. In truth, such a mechanism of inheritance would work against evolution by natural selection.