History of Evolutionary Thought

Question 1

Special Creation

Answer 1

• Each organism originated independently
• Each organism has remained the same since the time of creation
• All organisms were created recently

Question 2

Aristotle

Answer 2

“Great Chain of Being”

Question 3

Carolus Linnaeus

Answer 3

He
- Established conventions for naming organisms in mid-1700s - taxonomy
- Sharp discontinuities between species
- Argued that species are immutable (unchanging)

Question 4

Nicolaus Steno

Answer 4

He
- Discovered fossils by observing an old sharks teeth
- Rock layers (strata) provide a record of earth’s history
- Study of strata = stratigraphy

Question 5

Georges Buffon

Answer 5

• Creatures were made up of ‘particles’ that came together at the start of life
• The ‘particles’ make up an ‘internal mould’ that determined the nature of a species
• As a species moved to a new place its particles could change
• First hints of evolution

Question 6

Greek Philosophers

Answer 6

• Tried to explain nature through material principles - the basis of scientific thought

Question 7

Jean-Baptiste Lamarck

Answer 7

• First detailed theory of evolution
• Species change through time by inheritance of acquired characteristics

Question 8

Importance of Lamarck’s ideas

Answer 8

He
- Recognized that life forms are connected
- Recognized that there is variation in traits
- Recognized that inheritance is an important aspect of adaption
- Provided a mechanism for evolution

Question 9

Charles Robert Darwin

Question 10

Voyage of the Beagle

Answer 10

• Collected many fossils and living organisms
• Uniformitarianism: Natural processes that can be observed and show responsibility for events in the past

Question 11

Darwin’s observation #1

Answer 11

• Lots of diversity of similar forms
  - He thought he had collected wrens, blackbirds, and finches - they
  were all finches!
• Nearby islands had different species - why?
• Species seemed to fit well with their environments

Question 12

Darwin’s observation #2

Question 13

Darwin’s observation #3

Answer 13

Fossils were recognizably associated with extant fauna but yet wee dramatically different
- ‘Law of Succession’ - fossils and living organisms from one area were similar to each other but different from those in other areas
- Observed previously

Question 14

Darwin’s observation #4

Answer 14

• Humans, seals, bats, and other mammals look superficially different
• Closer examination indicates similar bone arrangements
• Similarities are due to common ancestry (homologies)?

Question 15

Darwin’s conclusion

Answer 15

Species were not specially created but instead evolved through descent with modification

Question 16

Taxonomy

Answer 16

The practice and science of categorization
- Species
- Genus
- Family
- Order
- Class
- Phylum
- Kingdom

Question 17

1700 Geology and Paleontology

Answer 17

• Geologists accepted that rocks form very slowly
  - Earth must be old
• Fossils differed from species seen today - species can go extinct
• Similar fossils tended to be found in similarly aged layers of rock with different ones in newer layers - species appear and disappear
• Gradual changes in geology appear to be explained by processes we see today

Question 18

Darwin’s postulates

Answer 18

• Individuals within species are variable
• The variations are, at least in part, passed from parents to offspring
• In every generation, some individual are more successful at surviving and reproducing
• Survival and reproduction are not random, but are determined by the traits’ variation

Question 19

Darwin’s Logic

Answer 19

The critical ingredients for evolution by natural selection

Question 20

Darwin’s contribution

Answer 20

• Natural selection as a mechanism
• Population thinking
• The non-constancy of species
• The descent of all organism from common ancestors
• The gradualness of evolution
• The multiplication of species

Question 21

Darwin’s big knowledge gap

Answer 21

• How variations are passed on to offspring (Genetics!) There was no concrete idea on ‘inheritance’ at the time
• His natural selection theory was challenged
• How variability was generated in populations (Mutation!)
• There was a lack of knowledge on mutations
• The relative short age of the Earth (15 - 20MY) does not allow for slow and gradual changes to accumulate (4.5 billion years!)
• They believed the earth was ALOT younger than it was

Question 22

Evolution after Darwin

Answer 22

• In 1900 rediscovery of Mendel’s work with peas led to alternative explanations (rather than natural selection)
• In 1930/40 scientists joined ideas and concepts to form a New vison of evolution: “Modern Synthesis”

Question 23

Mutationism

Answer 23

A mutation is any change in the DNA sequence in a cell. Mutations cause discrete variation which results in new species

Question 24

Fruit flies

Answer 24

They have a very simple genetic structure and a quick reproduction rate - easy to see pros and cons of certain mutations

Question 25

Competing theories

Answer 25

Saltationism: Evolution proceeds in major steps by abrupt transformation Neo Lamarckism: Evolution is coordinated addition of developmental stages in a species, not natural selection Orthogenesis: Characteristics of organisms are directed towards pre-determined goals These theories have no mechanisms proposed - which is important in proving evolution theories

Question 26

Modern Synthesis (1937-

Answer 26

- Scientists joined ideas/concepts from genetics, paleontology, and systematics into a new vision of evolution (Scientist dream team) They took parts from all the older theories and built off them to create this theory - Mendelian and population genetics were applied to the process of Natural Selection - The 'Synthesis' emphasized the interaction among random mutation, natural selection, genetic drift, and gene flow in microevolution - It was suggested that these evolutionary processes were sufficient to account for macro-evolution

Question 27

Principles of the synthetic theory

Answer 27

- Mutations are rare, amplified by recombination - Allele frequency change by genetic drift and natural selection - Natural populations are variable; natural selection is intense - Geographic population of a species are often adaptive; continuum of degree of differentiation of populations - Fossil records include examples of gradual changes

Question 28

Recombination

Answer 28

Pieces of DNA are broken and recombined to produce new combinations of alleles