The history of an idea - natural selection Flashcards
Was Darwins book controversial?
The origin of species is a very controversial book which sold out instantly.
What is the biological species concept as defined by Ernst Mayr?
“species are groups of interbreeding natural populations that are reproductively isolated from other such groups” – Ernst Mayr
This means that a species is defined by potential reproductive partners for an individual. And the gene pools of certain species are inaccessible to other species.
What is the great chain of being?
Plato and aristotle say that there is a smooth gradation between minerals and God. Says that man is above animals.
This idea suggests a relationship between things whcih inhabit the world.
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What are Judeo-Christian ideas?
The idea that each organism has been individually created at a point in time and species are therefore unchanging.
Believes that any relationship comes only from the fact that the ‘creator’ was the same for each species
What are known as the classical ideas of life?
“Judeo-Christian” ideas and “The great chain of being.” Maybe “natural theology”?
What is natural theology?
A branch of religious thought which sought to define the nature of God by studying the natural world, created in the 19th century from William Paley.
What did William Paley argue?
In 1802, William Paley argued that living things were complicated and must have been designed.
He used the ‘watchmaker analogy’ – a complex object like a watch must be designed and cannot arise by accident, so must have had a designer.
He argued that living things are also complex, therefore they are designed and must have a ‘designer’ – i.e. God
Who started the binomial system of classification?
Carolus Linnaeus started the binomial system of classification eg. Homo sapiens.
What did Carolus Linnaeus believe?
Linnaeus at first thought that species were fixed from the Creation but later began to consider that species within a genus may have arisen since the creation
Modern classification is still based on Linnaeus’ system.
What does classification imply?
Classification implies a relationship:
What happens when we try to classify things?
Once we begin to classify things it is natural that we find hierarchical relationships in that classification
Look at the diagram – it is obvious to us that cats and dogs are more alike than either are to mice – it is also obvious that mice and voles are more alike than any other grouping here
Yet all of these groups also share similarities compared to more distantly related groups e.g. fish, insects, plants
We get something looking like a family tree.
What do relationships imply?
Relationships imply ancestry.
What does a family tree imply?
The diagram looks similar to a family tree, but a family tree implies that each of the branches of the tree has a common ancestor where the branches meet.
What was Erasmus Darwins view of evolution?
Erasmus Darwin’s view of evolution was one of life ‘striving’ for improvement. These ideas were current in the thinking of pioneers of the Industrial Revolution – the Lunar Society
What actually IS evolution?
Evolution is descent with modification.
What is an example of descent with modification?
The modern horse is believed to have descended via intermediate species from Hyracotherium (from 55 million years ago).
Over time, the leg bones of this animal are modified across the species, eventually resulting in the leg of the mordern horse
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What did Cuvier champion as an explanation for the presence of fossils?
Cuvier championed catastrophism as an explanation for the presence of fossils of extinct animals
He argued that a series of floods explained extinction - the biblical flood was seen as one of these possible events.
What did Archbishop Ussher calculate?
Archbishop Ussher calculated the age of the earth on the basis of calculating genealogies in the Old Testament – he came to the conclusion that the earth was created on Sunday, 23rd October 4004BC
What did Charles Lyell do?
Charles Lyell, in his ‘Principles of Geology’ set out the theory of uniformitarianism – the earth was shaped by gradual accumulation of deposits forming rock which were then eroded
It put the age of the earth as possibly millions of years
The huge extension of the earth’s age gave scope for evolution to have occurred
What is Lamarckism?
An early believer in evolution, Lamarck proposed that evolution occurred by the inheritance of acquired characteristics
according to Lamarck’s theory:
giraffes began as short necked animals
living with a food source high in the canopy
an ancestral giraffe stretched its neck
as it reached more food it left more young
the young inherited their parent’s stretched neck, they stretched … and so on….
What would Lamarckism mean for cells?
– it would mean that each of your cells contained information gained in your lifetime which is then passed to your offspring
What was Weismanns rat experiment?
Weissmann’s rat experiment was designed to debunk Lamarck – chop the tail off generation after generation of rats – they’ll still be born with tails
What was the state of play in December 1831?
HMS Beagle set sail to map the coast of South America.
Charles Darwin voyaged as a naturalist and companion to the Captain.
- It was becoming accepted that the earth was old – very old
- Evolution had begun to be sought as an explanation for the fossil record and the interrelatedness of various organisms by radical thinkers
- But…evolution was still a minority belief (Darwin at this time did not believe in ‘transmutation’)
- There was no accepted way in which evolution could occur
What did Darwin find on his journey (1)?
1) One major piece of evidence that led Darwin to reject the fixity of species was the “succession of types”
With the help of Richard Owen – the foremost palaeontologist in Britain at the time – Darwin’s fossils of the South American megafauna were shown to be related to modern day armadillos and tree sloths. Glyptodont is related to Armadillos. Megatherium is related to sloths.
Darwin later cited this as evidence of descent with modification.
What did Darwin find on his journey (2)?
2) Darwin then collected specimens in the Galapagos – was told that the tortoises varied between islands. Collected mockingbirds and finches – but forgot to label where he found them!
What did the variation of mockingbirds between islands allow darwin to realise?
It was the recognition that the mockingbirds varied between islands that gave Darwin the idea that evolution had happened since the arrival of an ancestral mockingbird to the Galapagos long ago.
