Evolution and Genetics Come Together

Question 1

Give an example (or a few) of reasons why people questioned Darwinism.

Answer 1

Any of the following:

• Swamping of variants
• New mutations can’t be good
• Earth isn’t old enough
• Fossil record has directionality
• Fossil record has gaps

Question 2

What model did Hugo de Vries propose in his book “Mutation Theory”?

Answer 2

Saltationism. New species evolve in single-generation jumps.

Question 3

What did Hugo de Vries observe when he self-pollinated Oenothera lamarckiana? What about when he crossed them?

Answer 3

Self-pollination: bred true (AxA = A)

Crossed: varied offspring (AxB = C,D,E)

Question 4

According to Hugo de Vries, why was there no swamping of gene variants?

Answer 4

Because saltationism resulted in offspring which were not intermediate.

Question 5

According to Hugo de Vries, was natural selection creative? What accounted for new variation?

Answer 5

No, but saltationism could produce new variations.

Question 6

According to Hugo de Vries, why did fossils appear to exist in a progressive series?

Answer 6

Because advantages could build on advantages according to saltationism.

Question 7

According to Hugo de Vries, why were there gaps in the fossil record?

Answer 7

Because there are no intermediate forms in his model of saltational evolution.

Question 8

Why were all of Hugo de Vries observations of Oenothera lamarckiana pretty much worthless?

Answer 8

Because O. lamarckiana has a super weird reproductive cycle/mechanism. His conclusions only applied to this plant.

Question 9

Who proposed a recent version of Hugo de Vries’ saltational evolution? How did this work?

Answer 9

Richard Goldschmidt proposed that there existed “hopeful monsters” which evolved radical new advantageous traits and somehow survive to pass these on.

Question 10

Describe “orthogenesis”.

Answer 10

An alternative model of evolution which relies on a species having an internal drive to evolve. can supposedly build up “evolutionary momentum” (ex: Irish Elk).

Question 11

Describe “neo-Lamarckism”.

Answer 11

A more modern revival of the inheritance of acquired characteristics.

Question 12

How did Hardy and Weinberg approach Mendelian genetics?

Answer 12

By taking a populational approach, asking how frequencies of factors change in a population over generational time.

Question 13

What did Soviet evolutionary biology excel at in the 1920s-30s?

Answer 13

Agricultural genetics and the study of genetic variation in natural populations.

Question 14

How did Soviet biologists figure out where species originated?

Answer 14

Assumed (correctly) that it would be the area with the greatest variability in a species.

Question 15

Who were some of the people involved in the modern synthesis?

Answer 15

Any of:

• Ronald A Fisher
• JBS Haldane
• Sewall Wright
• Theodosius Dobzhansky
• Ernst Mayr
• George Gaylord Simpson

Question 16

What was proved by the modern synthesis? Give a few examples.

Answer 16

Any of:

• No inheritance of acquired characteristics
• Mutation
• Persistence of recessive alleles
• Recombination
• Gene interactions
• Particulate inheritance explains quantitative traits
• No blending inheritance at gene level

Question 17

What would happen to genes without crossing over (sexual reproduction)?

Answer 17

Muller’s ratchet. An accumulation of deleterious mutations over time.

Question 18

What did the modern synthesis suggest regarding gene interactions that Mendel did not conclude?

Answer 18

That traits are the result of several genes interacting, rather than a gene controlling each trait.

Question 19

What is meant by a “quantitative trait”? Give an example.

Answer 19

A measurable phenotype which depends on the influence of many genes (ex: height).

Question 20

Does natural selection need to be intense to have an impact?

Answer 20

No, even small differences that are maintained over time can be selected for.

Question 21

In addition to natural selection, what does the modern synthesis suggest as alternative causes of evolution?

Answer 21

Genetic drift and gene flow (+others I’m sure).

Question 22

Contrary to Richard Goldshmidt, what does the modern synthesis propose?

Answer 22

That there is no barrier between microevolution and macroevolution.