Evolution + Genetics Come Together

Question 1

When did questions about Dawinism/natural selection become prominent?

Answer 1

c. 1900-1910

Question 2

What was the basis for the question about Darwinism: ‘wouldn’t new variants be swamped and disappear before natural selection could act?

Answer 2

blending inheritance implies that the blending of traits would lessen the variation in a population and natural selection would be too slow to act on it

Darwin inferred introduction of variation but didn’t know about mutation and how variation was introduced so he couldn’t explain it

Question 3

What was the basis for the question about Darwinism: all new genetic variants must be deleterious as had been seen in labs. So where did adaptive variants come from? How was natural selection creative and creating populations better adapted?

Answer 3

all the lab experiments in early genetics works were showing that variation and mutations were negative/deleterious

Question 4

What was the basis for the question about Darwinism: aren’t the sun and earth too young for the slow process of natural selection to have produced the diversity existing?

Answer 4

Lord Kelvin’s critique based on his estimates of gravitational collapse and the age/resources of the sun

Question 5

What was the basis for the question about Darwinism: Why do fossils show a progressive series from lower to higher strata when natural selection doesn’t include directionality?

Answer 5

maybe there is another driver of evolution that is not natural selection which does act with directionality

Question 6

What was the basis for the question about Darwinism: why are there gaps and jumps in the fossil record?

Answer 6

natural selection is not step-wise, but this question suggests that evolution is

the fossil record was incomplete and still is

Question 7

Who proposed the Mutation Theory in the 20th century?

Answer 7

Hugo de Vries (1901-03) in his book the Mutation Theory

Question 8

Which organism did de Vries work on to study the mutation theory?

Answer 8

evening primrose, O. lamarckiana

Question 9

What were de Vries’ observations when studying evening primrose?

Answer 9

1. he found 2 strains of the plant growing wild outside Amsterdam
2. he self-pollinated them and they bred true but when he crossed them, they produced different sized offspring

Question 10

What did de Vries conclude about his observations of his crosses of evening primrose / his model?

Answer 10

he thought that because the offspring didn’t represent the parents, a new species had evolved and could not be crossed to produce the parents

new species evolve in single-generation jumps = abrupt

Question 11

What is saltationism?

Answer 11

de Vries’ model of evolution based on single-generation jumps

Question 12

How did de Vries mutation theory answer the swamping of new variants question about Darwinian evolution?

Answer 12

mutations create variability that are so significant and different from the parents that they constitute naming describing a species

Question 13

How did de Vries mutation theory answer the selection creative force question about Darwinian evolution?

Answer 13

maybe natural selection was just for elimination and mutations are the creative force which generates new variety

Question 14

How did de Vries mutation theory answer the young earth question about Darwinian evolution?

Answer 14

because he observed abrupt changes, his model didn’t need the earth or sun to be old to support high diversity

Question 15

How did de Vries mutation theory answer the fossils showing a series question about Darwinian evolution?

Answer 15

progression was inherent to his model (adding new variety and forming new species) that natural selection wasn’t - people thought this was represented by fossils

Question 16

How did de Vries mutation theory answer the gaps in the fossil record question about Darwinian evolution?

Answer 16

mutation showed a step-wise evolution into new species

Question 17

What was the problem with de Vries’ model of evolution?

Answer 17

he used O. lamarckia, evening primrose, which is a highly exceptional plant

it has a very unique and complex chromosomal make up

he tried to replicate his work on other plants but couldn’t and it took a long time for geneticists to understand why primrose worked

Question 18

What is a more recent example of saltation evolution?

Answer 18

Richard Goldschmidt (1940) thought microevolution doesn’t lead to macroevolution and large genetic jumps are needed for explaining speciation

there were special variants that are more extreme than regular variation

Question 19

What were Goldschmidt’s ‘jumps’ called?

Answer 19

‘hopeful monsters’ that may have an advantage

he understood that hybridization can be mistaken as an evolutionary jump and a dramatic phenotypic change can occur but is not necessarily beneficial

Question 20

What is orthogenesis?

Answer 20

a model of evolution based on evolutionary lineages having an inherent direction which has been determined by internal drivers, not natural selection

lineages can grow, develop and senesce under the weight of an evolutionary momentum that natural selection can’t reverse

Question 21

What did orthogenesis suggest? how is this different from natural selection?

Answer 21

suggests an innate drive to evolve and that mutation is being pushed in a direction - suggests evolution is a runaway train until it crashes because natural selection cannot reverse any variation

natural selection suggests an external driver and does not include directionality

Question 22

Is orthogenesis accepted today?

Answer 22

no, the runaway train analogy has been disproved, natural selection can delete maladaptions

Question 23

What is Neo-Lamarckism?

Answer 23

another model of evolution in the 20th century

brought back Lamarck’s ideas about acquired inheritance - based on experiments that seemed to suggest this occurred in plants not being watered reproducing offspring with thicker leaves

Question 24

What approach did Hardy and Weinberg (1908) take to Mendelian genetics?

Answer 24

they took a populational approach by asking how Mendelian factors increase or decrease in frequency over time

Question 25

Who was GH Hardy (1877-1947)?

Answer 25

an English mathematician who studied population genetics by building off of Mendelian genetics

Question 26

Who was Wilhelm Weinberg (1862-1937)?

Answer 26

a German physician who studied population and evolutionary genetics by building off of Mendelian genetics

Question 27

How did Hardy and Weinberg work? What did they accomplish?

Answer 27

they worked independently but came to the same conclusions

they took Mendelian genetics out of the lab and instead focused on population genetics (how does a new population arise given the Mendelian ratios?)

Question 28

Which country had strong evolutionary biology and genetics work in the 1920s-30s? what aspects did they specialize in?

Answer 28

the Soviets

specialized in agricultural genetics and study of genetic variation of natural populations

Question 29

Who is an example of a well known and influential Soviet evolutionary biologist and geneticist of the 20th century?

Answer 29

Theodosius Dobzhansky

Question 30

What does the Modern Synthesis (1920-40s) refer to?

Answer 30

the synthesis/bringing together of evolution and genetics

Question 31

Who were the major players involved in the modern synthesis or bringing together evolution and genetics?

Answer 31

among others

Ronald A Fisher (1890-1962)
JBS Haldane (1892-1964)
Sewall Wright (1889-1988)
Theo Dobzhansky (1900-1975)
Ernst Mayr (1904-2005)
George Gaylord Simpson (1902-1984)

Question 32

What did the works of the modern synthesis demonstrate for genetics and Darwinian evolution?

Answer 32

principles of new genetics could explain Darwinian evolution

Question 33

How did the banishing of acquired inheritance support Darwinian evolution?

Answer 33

experiment cutting mouse tails and breeding repeatedly did not produce offspring with shorter tails as would be expected if acquired inheritance existed

no internal drivers of evolution - only external = natural selection

Question 34

How did evidence for mutation support Darwinian evolution?

Answer 34

the introduction of new genes/traits via mutations could account for the speed of natural selection to produce the biodiversity that exists today

Question 35

How did the persistence of recessive variance support Darwinian evolution?

Answer 35

this removed the idea of blending inheritance or intermediates

genes can persist in a genome without expression in that generation but may express in a future generation

Question 36

How did evidence for recombination support Darwinian evolution?

Answer 36

recombination of chromosomes during cell division accounts for variability that evolution via natural selection can act on

Question 37

How did understanding gene interactions support Darwinian evolution?

Answer 37

genes can interact to cause unique phenotypes = most characters are not expressed or coded for by a single gene, often it is multiple genes in pathways

Question 38

How did particulate inheritance support Darwinian evolution?

Answer 38

continuous inherited variation can be explained by particulate inheritance

this was an ongoing debate, whether it was this way around or the opposite

we can understand quantitative, continuous traits (ex. weight, height) through discrete inheritance (not a continuous fluid or something)

Question 39

How did learning that genes are not influenced by blending inheritance support Darwinian evolution?

Answer 39

sometimes a phenotype appears to be a blend or intermediate, but its genotype is not blended

Question 40

How did the modern synthesis show that selection doesn’t need to be large to be important?

Answer 40

people used to think that the selection advantage had to be large to be important and to persist in a population, but Mendelian genetics showed that small variance is still important

Question 41

How did the modern synthesis enlarge the set causes of evolution?

Answer 41

people working on this developed the theories of

genetic drift as a random force acting on gene frequency in a population

understood migrations as important to gene flow and genetic structure of a population

Question 42

How did the modern synthesis argue there was no barrier between micro- and macroevolution?

Answer 42

macroevolution is additive to microevolution as seen at the genetic level where small changes over time can lead to new species

Question 43

Who (or what) was the unsung hero of 20th century genetics?

Answer 43

the fruit fly!

Question 44

How does the chapter from ‘Fly’ describe the differences between Dobzhansky and Morgan?

Answer 44

Dobzhansky was a fan of Morgan’s genetics but

Morgan didn’t agree with a lot of evolutionary thought and dismissed it as speculative and non-scientific

Dobzhansky did not see the conflict between experimentalist/natural dichotomy and thought they were complimentary

Question 45

Why was it weird that Morgan wrote 3 books with ‘evolution’ in the title?

Answer 45

he was known for objecting evolutionary ideas and was convinced that natural selection was dead

Question 46

Which famous scientist can be attributed to diminishing natural selection’s reputation in evolutionary biology?

Answer 46

Thomas Hunt Morgan

Question 47

When did Darwinian natural selection experience a renaissance?

Answer 47

in the 1930s when evidence began accumulating from multiple sources

Question 48

What did the author of ‘Fly’ attribute Morgan’s inability to accept natural selection?

Answer 48

his misconception of genetic variability in natural populations

Morgan was a die hard experimentalist and not a trained field/naturalist

he thought mutant flies could arise in natural populations as they did in his lab, but called them ‘aberrations’ from the wild type

he thought wild populations were genetically homogenous

Question 49

What did genetics do for evolution and the origin of species?

Answer 49

made it more credible and acceptable by a broader audience

Question 50

What other species of fruit fly did genetics popularize? how?

Answer 50

D. pseudooboscura - Dobzhansky crossed this S. American fly with a N. American one and observed partial reproductive isolation (male offspring were sterile, females were fertile) –> led Dobzhansky to believe that SMALL genetic changes can lead to reproductive barriers causing new species

important in unifying evolution with genetics

Question 51

what caused the slow diminishment of the ‘fly group’ in Morgan’s lab?

Answer 51

Sturtevant’s reaction to Dobzhansky staying in Pasadena and rejecting the professorship at Texas and then Calvin Bridges suddenly and tragically died

in combo with the impending retirement of Morgan without naming a successor = competition

Question 52

How was Dobzhansky influential to the modern synthesis?

Answer 52

his work with fruit flies, demonstrating that different populations had different gene frequencies and can reproduce but not always produce viable offspring, supported Darwinian evolution and natural selection and solidified it as part of evolutionary thinking = gene flow leads to reproductive barriers and new species

Question 53

How does this book describe Calvin Bridges?

Answer 53

people found him very likeable

‘flamboyance, generosity and gullibility’

Dobzhansky said ‘he possessed a divine spark’

he was unconventional and kinda wild? he left his wife and kids, got a vasectomy and lived sexually promiscuous lifestyle which some attribute to his death (syphilis)