L7

Question 1

Modern Evolutionary Synthesis
Huxley 1942

Evidence??

Answer 1

Life evolves through evolution by natural selection and, to some degree, genetic drift.

paleontology, systematics, genetics

Question 2

Problems with Modern Synthesis

Answer 2

• how do plastically complex traits arise from genes that were selected for a given trait?
• is phenotypic variation and plasticity just non-adapted noise?
• how does genetic response to environment evolve?

Question 3

Confusion/controversy with Modern Synthesis

1 - gradual change

Answer 3

Quantitative mean shifts are common but not ubiquitous. How can you explain multimodality? Shouldn’t it condense to unimodality through selection or diverge and cause speciation?

DEVELOPMENTAL RESPONSES MUST BE KEY - TAKES STRAIGHT TO NEW FITNESS PEAK

Question 4

Confusion/controversy with Modern Synthesis

2 - the conservation of development

Answer 4

Change is deviation from genetic predisposition - huge work to break coadapted gene complexes - true at species level but not at phenotypic level. Is development a facilitator of change or a constrainer? If latter, how do new species even evolve?

IS IT NOT INEVITABLE THAT NEW SPP EVOLVE THROUGH ENV EFFECTS ON GENE SWITCHES DURING DEVELOPMENT CREATING RADICALLY DIFFERENT PHENOTYPES?

Question 5

Confusion/controversy with Modern Synthesis

3 - proximate/ultimate

Answer 5

Proximate causes of variation have nothing to do with evolution?

Question 6

Confusion/controversy with Modern Synthesis

4 - continuous vs discrete variation

Answer 6

Darwin’s idea is based on continuous - how can big phenotypic changes evolve so quickly if random mutation and selection are the main evolutionary driver? And how can you get big differences in phenotype without big genotype differences?

Question 7

Confusion/controversy with Modern Synthesis

5 - but what is under selection? Genotype or phenotype?

Answer 7

Daphnia - spines vs no spides is phenotypic not genetic. If daphnia were always exposed to predators you would get mean change in phenotype without genotype change. Is this evolution??

Question 8

Resolve the problems

Answer 8

• NS can only affect genes that are expressed with measurable phenotypic consequences - suggests selection acts on phenotypes?
• Novelties arise from reorganisation of dev. pathways given changing evolution
• Genes are followers not leaders

Question 9

Genetic assimilation

Answer 9

Introduction of beneficial genes into existing selection on phenotypes arises through developmental canalisation (selection on a single outcome)