Modern Synthesis

Question 1

3 things for Darwin’s theory

Answer 1

• variation in a trait
• variation needs to produce differential success in reproduction
• variation is inheritable

Question 2

Darwinism

Answer 2

Natural selection acts on continuous variation

Question 3

Jumps or mutation theory

Answer 3

Evolution proceeded by large leaps (rather than small variations over a long time) and o

Question 4

Two competing explanations

Answer 4

Biometricians (Darwinian evolution) and mendelians (opposed Darwinian evolution)

Question 5

Biometricians

Answer 5

Analysis of data from natural populations (height, shore crab breadth)

Found a normal distribution curve (observed continuous variation)

Question 6

Mendelian’s

Answer 6

Controlled lab experiments

Observed discontinuous variation (saw really obvious difference in phenotypes eg. Flower of hamster colour)

Argued Darwin’s idea didn’t work: selective value on small variations ineffective

Question 7

The mutation theory

Answer 7

Hugo de Vries early 1900s

Noticed different forms of evening primrose that produced new varieties, introduced term ‘mutation’, argued mutations led to very different forms (discontinuous variation) that could lead to evolution.

This was Mendelian opposition to darwinism

Question 8

Up until 1906 who was winning

Answer 8

Mutation theory and Mendelism was winning versus Darwinian

Question 9

William castle

Answer 9

Took rats at extreme ends of distribution

Showed that you could enlarge the distribution of variation available (huh?)

Shows the variation

Question 10

Nilsson-Ehle

Answer 10

Found multiple loci can control colour

Experiments of wheat and oats

Lots of loci controlling something like colour = looks like continuous variation (Darwinian)

Question 11

Thomas Morgan

Answer 11

Counted bristles drosophila have

Showed Mendelian factors could produce small variations in character

Question 12

What did castle show?

Answer 12

Can select on continuous variation to outside original range

Question 13

What did Nilsson-Ehle’s crossing experiments show?

Answer 13

Characters can be controlled by several loci (polygenic)

Question 14

What did Morgan’s work on drosophila show?

Answer 14

Mendelian factors could produce small variations in character

Question 15

What is population genetics theory

Answer 15

System of mathematic tools that allows you to predict what happens to genes over the time

Question 16

Restating the theory of NS

Answer 16

Genes code for phenotypes
Phenotypes are heritable
Can have different forms of genes (alleles) which is the variation Darwin is talking about
Combine this with selection = restated theory of natural selection in genetic terms.

Question 17

What does the mathematic framework of natural selection show

Answer 17

Can show how long natural selection will take

Question 18

Why was the mathematical framework of NS good

Answer 18

It answered things Darwin hadn’t been able to answer

Question 19

Example of use of mathematical framework of NS

Answer 19

Is it worth him trying to select out long horns?

• cattle with long horns (males)
• Farmer wants to know if it’s worth him trying to select our long horns and how long it will take
• can tell farmer how many generations he has to select to make sure the horns disappear from the generation

Question 20

Explain history of natural selection theory after origin was published (2 things)

Answer 20

1. After origin of species 60-70 years of controversy. (Darwinism - Biometricians VS mutation theory - Mendelism)
2. Theory and data showed these competing ideas weren’t in conflict (actually two parts of the same idea).

Question 21

How did Darwinism and Mendelism become one idea

Answer 21

(a) Mendelian inheritance can produce continuous variation

(b) natural selection can act via Mendelian genetics

Question 22

Who was Mary Anning XX

Answer 22

Paleontologist

Discovery of several dînas use fossils

Question 23

How could the genetics approach be viewed as reductionist

Answer 23

In reality natural selection is working on big organisms but we only look at gene frequencies etc and genetics

Question 24

What’s the link between genetics + selection and the appearance of design ?

Answer 24

Process of gene level selection leads to the appearance of an organism as designed

(Increase in gene frequencies,as you collect best genes in population you think of the best adapted organism as the one that’s collects all the best genes)

Question 25

What was the beauty of this genetic explanation as to why organisms become highly adapted ?

Answer 25

Means we can now explain why organisms look as if they’re designed without needing to invoke an actual designer

Question 26

What does he say about fitness

Answer 26

Cant measure fitness directly because difficult

• so have to choose proxies for fitness
• eg. Weight correlates with survival which correlates with how many offspring you have which correlates with fitness

Question 27

What are four things that can cause change in gene frequencies

Answer 27

Genetic drift
Migration
Mutation
Natural selection

Question 28

What did the Biometricians think?

Answer 28

Natural selection acted on continuous variation

Question 29

What did the Mendelians think?

Answer 29

They thought selecting small variations over time was ineffective

They observed so continuous variation and favoured the mutation theoryv

Question 30

What was the mutation theory ?

Answer 30

That mutations led to variations which suddenly appeared (discontinuous forms) and these could then lead to evolution

This theory became the Mendelian opposition to Darwinism

Question 31

How did data and theory help resolve the debate over Darwinism VS the mutation theory?

Answer 31

Castle - showed you could select on continuous variation to outside the original range

Nilsson-Ehle - used crossing experiments between wheats and oats to show that characters can be controlled by multiple loci

Thomas Morgan - work on drosophila showed Mendelian factors could produce small variations in character

Question 32

Does NS act at a genetic or individual level? XXX

Answer 32

XXXX?

NS acts on a genetic level to produce an indivise with the best genes

Question 33

Is natural selection evolution?

Answer 33

Natural selection is a mechanism of evolution