Review session

Question 1

(Kassen)
what is the paradox of diversity, and how can it be resolved? illustrate your answer with ref to examples given from microbial experiments

Answer 1

The paradox of diversity is:
Natural selection should eliminate all but the fittest type, yet species regularly co-exist

Resolving the paradox: (Spatial variation)
The envr is heterogeneous, meaning for different condtions of growth , the envr has many different niches,
Selection will eliminate diversity within the niche , distinct specialist phenotypes are favoured in different niches

Example:
pseudomonas fluorescense !
spatial variation in drug availability (ciprofloxacin), diversification of P fluorescens in unshaken (spatially structured) microcosm , competition between nalidicic acid and tetracycline resistant strains of E.coli

Question 2

what is the difference between “hard” selection and “soft” selection

Question 3

What is the different variation for generalist and specialists

Answer 3

generalists = temoral variation
specialists = spatial variation

Question 4

(Larson)
How does phenotypic plasticity may promote high levels of evolvability?

Answer 4

phenotypic plasticity, allows for spatial variation on adaptive landscapes, which can provide different sources for evolution.

so provides a range where phenotypes can change over different environments .

It is a way to bypass developmental bias !

allows organisms to explore phenotypic space without permenant change, which can then be canalised and get fixed (evolution)

ex:
fins to limbs thanks to plasticity
or
Hsp90 in drosophila trait phenotypically determined turned genotypic determined!

phenotypic plasticity implies that many phenotypes are not linked through pleiotropy, this suggests high degrees of modularity/parcelation (low levels of integration), that will facilitate higher rates of evolution

Question 5

(Larsson)
Using examples from class, write a short essay to defend the argument that modularity at the genomic level can be associated with modularity at the phenotypic level.

Answer 5

modularity is the fuel to diversification ! drives evolution at the micro scale, freedom from constraint

a good example are the Hox genes, GRNs

Proper answer:
genomic modularity often translates to gene regulatory network modularity , often translates to morphogenetic modularity, often translates to adult phenotypic modularity

genes are that are modular within the genome (eg Hox genes) will drive developmental processes within discrete modules (heart, Uterus, limb) and these phenotypic units are modules at the phenotypic level