Evolution I
There is grandeur in this view of life…C. Darwin, On the Origin of Species
1859
The Evolution of an Idea
“would it be too bold to imagine, that all warm-blooded animals have arisen from one living filament, which THE GREAT FIRST CAUSE endued with animality”E.Darwin, Zoonomia vol 3 1794
Erasmus Darwin painted by Joseph Wright of Darby
Lamarck: Transmutation of Species
Jean-Baptiste Lamarck
Life becomes more complex over time
Adaption occurs via use and disuse
Changes to an individual during its lifetime are inherited by its offspring
Natural Theology
Most people thought that all species had been created independently and had fixed forms
The living world was thought to have been created by a benevolent god giving each species a specific function in the natural world
Study of the natural world was thought to illuminate god’s creation and benevolance
Parasitic Wasps : Benevolence in action?
A Clergyman in the Making?
Charles Darwin
Born 1809 to a wealthy doctors family
Studied Medicine at Edinburgh before transferring to Cambridge to take a bachelors degree At Cambridge he became interested in geology and natural historyAfter graduation he had to wait a few years before he could be ordained into the church
Ice ages in Wales
Cwm Idwal and the Ogwen Valley. A classic post glacial landscape
In the summer of 1831 he travelled through wales with the geologist Adam Sedgwick becoming convinced of the gradual origin of the landscape
Robert Fitzroy
Vice-Admiral Robert Fitzroy RN.
From an aristocratic Family (Uncle was Lord Castlereagh)
Master and Commander of HMS Beagle in 1831
Went on to become the second governor of New Zeeland in the 1840’s
Was a skilled geographer and survayor
Developed the science of metrology and published the first weather forecasts
Fitzroy’s OfferFitzroy was given command of HMS Beagle to complete the survey of the South American coast started some years before
He was worried that the length and distance from home would take its toll on his mental health and wanted a social companion
He was looking for a gentleman geologist/naturalist who could pay his own expenses to take part in the voyage
Darwin’s tutor at Cambridge suggested him and his uncle Joseph Wedgewood persuaded his father to let him go
The Voyage of HMS Beagle
Dec 1831 to Oct 1836
The Galapagos Islands
Giant Tortoises
San Cristobel North Isablea South Isablea
Darwin’s Finches
Coral Islands
Return to EnglandOn his return to England Darwin settled to analyzing his notes and specimens with the help of others in particular Sedgwick, Robert Owen and John Gould
Gould identified the birds collected in the Galapagos as finches not the mixture of families Darwin had identified
Fossils collected in Patagonia were identified by Owen as extinct mega-fauna
He married his cousin Emma Wedgwood and Settled in Gower Street, London before moving to Down House in Kent.
Malthus: An Essay on the Principle of Population
Population
Food Supply
Reverend Thomas Malthus
Pigeon Fancying Racing Homer Frillback
English PouterFantail
Artificial Selection The fancy pigeons like breeds of dog and farm animals and plants are breed to give desired characteristics
Individuals showing the wanted feature well and few unwanted features are crossed
In the next generation the offspring showing the wanted features best are again crossed
Over time the wanted feature (fan like tail, large crop, speed) will increase and the breed changes form
The Struggle for ExistenceTo keep the numbers of a population stable each adult pair needs to raise 2 offspring to adulthood in their lifetime
Each breeding pair actually produces many more offspring than this yet population numbers remain more or less stable
Most of the offspring die of starvation, disease or predation before they reach maturity
Only a small number survive and breed in their own turn
Natural SelectionAll individuals show some variation from the species norm
Most individuals die before reaching adulthood
Those showing most adaptation to the environment are most likely to survive and breed
Over time the species will change to become more adapted to the environment
So if the environment changes the species change to make its self more suited to the new conditions
Adaptive Radiation
Blistering BarnaclesDarwin wanted to write a description of all barnacle species living and extinct in the world
After 10 years of work he finished a description of all the barnacles living in the waters of Great Britain and some of the more important fossil species
Alfred Russell Wallace
Born 1823 to a relatively poor family
Worked as a surveyor in the 1840’s before becoming a professional naturalist
Travelled widely in South America and the Malay Archipelago
Became an expert on the geographical distribution of animals as well as evolution
Animal Collecting
Wallace made his living by collecting animal specimens for sale to collectors
From 1848 to 1852 he travelled in the Amazon Basin collecting animals but lost most of his specimens when his homeward bound ship sank
From 1854 to 1862 he undertook a second expedition to the east indies (Malaysia and Indonesia)
The Wallace Line In the North West the fauna is Asian e.g. tigers, elephants and orang-outangs
To the south west it is Australian eg marsupials.
Change of Forms Published “On the Law which has Regulated the Introduction of New Species” in 1855
This outlined some work on distribution of species and suggested new species arose close to existing ones
In 1857 or 1858 during a bout of Malaria in the Borneo jungle Wallace re-read Malthus and developed a theory of natural selection
Wallace’s Letter
“if Wallace had my MS. sketch written out in 1842, he could not have made a better short abstract! Even his terms now stand as heads of my chapters. Please return me the MS., which he does not say he wishes me to publish, but I shall, of course, at once write and offer to send to any journal.”Charles Darwin in a letter to Charles Lyell
In early 1858 Wallace wrote to Darwin proposing a mechanism for the emergence of new species and asked for Darwin’s comments
Two papers one by Wallace and one by Darwin were read to the Linnaean Society in July 1858 with an introduction by Lyell and Huxley
On the Origin of Species by Natural Selection
Darwin wrote the Origin between July1858 and March as a “short” abstract of his ideas
1250 copies of the first edition were sold on or before the day of publication, the 3000 copy second edition was sold out before the end of January 1860
The book describes artificial and natural selection and some of the main lines of evidence Darwin had for developing the theory
What is a Species?A species is a group of individuals with a common form and life style
Each species occupies an ecological niche
Individuals of a species can breed with other individuals of the same species and produce fertile offspring
A species is a population of individuals that can and do interbreed with each other
Populations that stop interbreeding can become separate species
Natural Selection
Only individuals well adapted to the environment survive
Only traits carried by surviving individuals are present in the next generation
Over time individuals become more adapted to their environment and change form to become new species
Common Descent
All living things descend from previous living species
As time passes species change into one other forms
All living things come from 1 single common ancestor and this form has been altered by variation and natural selection to give the adapted forms we see around us
It is this common descent that has given rise to the common features that make classification possible
There is no progress in evolution only change
The Age of the Earth
Landscapes are formed by constant simple geological processes going on today
These include sedimentation, erosion, volcanism and earthquakes
While climate and events may change the processes do not
To form the structures in the landscape takes time and so the earth is 100’s of millions of years old at least (actually around 4.5 billion years old)
The Fossil Record
Structural Homology
Embryology
Human
Dog Cat
Darwin Photo
Evolution of the Eye
A Sequence of intermediate forms leading to the structure of the eye
Each form can be found in different extant species
FitnessFitness is a measure of how well an individual is adapted to its environment
This has nothing to do with “strength” but is measured by reproductive success and survival
The longer you live and the more children, nieces and nephews the greater your fitness to the environment
The Oxford Debate: Survival of the Fittest
Samuel Wilberforce, Bishop of Oxford
Thomas Henry Huxley
The Descent of Man“light will be thrown on the origin of man and his history” C. Darwin, Origin of Species 1859
Sexual SelectionAn Individual that survives 2 years and has 10 offspring is “fitter” than one that survives 10 years and has 2 offspring
As well as competing for resources individuals also compete for mates
Males can evolve a feature solely because females find it attractive and visa versa
The Problem of Inheritance If natural selection is to produce evolution variation must be inherited
Also a small amount of variation must be able to spread through a population
An even mixing of characteristics will lead to variation being “averaged out” of a population not retained
Neo-DarwinismThe combination of mendelian population genetics with natural selection is known as the “neo-Darwinian synthesis”
This combination is the main current theory of evolution and we will look at these ideas and the evidence for them in the next lecture