Questions & Answers

Keywords included selection, anagenesis, mutation, cladogenesis, speciation, adaptation, change over time, dispersal, .... All are important, but as the discussion proved very difficult to test, and the keywords often come with implicit assumptions.

I did not see keywords like neutral evolution & drift (important for 'silent site' mutations and to evaluate molecular data), self organisation (this is where evolution gets either very difficult or nearly religious, but consider the stability of predator-prey systems, Lotka-Volterra systems), co-evolution, species or group selection (I did not miss that one in particular!).

1a) Define a species!

All groups seemed to have a lot of fun with this. Definitions generally centred on reproductive isolation, geographic isolation and genetic or morphologic similarity. These were variations of the 'biological species concept' of Ernst Mayr (evolutionary systematist). Invariably we found, the definition 1) makes a species of something we do not view as a species (Parisians live in a restricted area, are morphologically similar, and able to leave fertile off-spring), or 2) excludes many organisms from being a member of a species (asexual organisms like bacteria; differentially reproducing/non-reproducing closely related individuals like ants/bees/wasps in a colony; sexual but effectively self-fertilising organisms like peas).

There is no good answer to this (except species don't exist). Consider the 'species' of marguerite and the 'species' of Mytilus edulis (blue mussel). They are two groups, each of very similar animals with common evolutionary history (all marguerites have a common ancestor and all Mytilus edulis have a common ancestor), so each group is definable, but there is no special property of that kind of group. Look at this simplified tree:

If A and D are two individuals of marguerite, you can define the group 'marguerite' as: A and D, their last common ancestor and all of its descendants. Then 'marguerite' will be A, B, C, and D (plus lots of others). This group is defined only by common evolutionary history, not by properties of the individuals or of the group. Similarly, Mytilus edulis (or anything else) can be defined as two (or more) individuals, their last common ancestor and all descendants of that ancestor. You get rid of the rigid hierarchy, .... superfamily, family, genus, species ...., and get groups with stable (invariant) definitions.

2) Phrase your views of evolution as testable hypotheses and suggest experiments that can refute your hypotheses. This is difficult! You can make functional or historic hypotheses and tests.

Functional:

Keyword: selection.

Hypothesis: If selection works in evolution, we observe different reproductive success in individuals with different properties (characters).

Experiment: Find individuals with different properties and measure their reproductive success over time and interpret the result in view of the differences.

For example birth weight (the weight of an individual at birth) is believed to be under strong selection for an ideal, intermediate weight. Low birth weight usually means premature birth and risk of death, high birth weight may cause brain damage during birth; there is selection for an intermediate weight. Note, it is difficult to actually make experiments and test everything!

Historic:

Keyword: co-evolution

Hypothesis: two groups of organisms co-evolve, for example a group of parasites evolve with a group of hosts.

Experiment: make independent phylogenies (trees) of hosts and of parasites. If they co-evolve, they have the same branching pattern. Note the alternative is hosts evolve and parasites evolve independently, and have another evolutionary pattern (phylogeny).

3). Find 3 examples of evolutionary statements about a specific organism or group of organisms in your books.

We did not get far that way. I wanted you to find something like:

a) The rachidian is reduced in Mumbo jumboensis.

b) The diverse habitats of the Faraway Islands fostered a rapid speciation of Mumbidae.

c) A reduced osphradium in Mumbo jumboensis is an adaptation to ...

d) Groups with crawl-away larvae speciate more readily than those with planctonic larvae, because of limited dispersal.

- and see whether there is an analysis of data or it is just a convenient explanation (it usually is). Biologists often treat evolution as 'the fun stuff' that you can not analyse; this is the standard explanation that is never questioned and never tested. I hope to have given you a feeling of, evolution - pattern as well as process - is indeed testable: you can phrase explicit hypotheses, you can analyse specific data, you can apply reproducible methods, and refute or accept hypotheses.