Evolutionary stories

Burke Museum April 26

The evolutionary stories of ths weeks trip to the Burke museum of natural history revolved around the topics of Sex, treachery, and death.
The sex in evolution was vividly displayed by song birds, and birds of paradise in the museum collection, where the males were usually the more brghtly colored. One of many morphologic distincions of males that can happen as a result of sexual selection, another example being sexual dimorphsm.
The death aspect of death in evolution gave insight into how the burke museum can use their inventory of very old collections of birds to retroactively study the population dynamics of population of different species, a very useful tool.
Treachery provided some interesting cases to study within the context of evolution. Over time, parasitic relationships have led to a sort of coevolutionary arms race between those being parastized, and those seeking to gain an advantage. One way this happens is in the disguising of eggs. As Richard Dawkins put it there could be a gene for making your eggs look like the eggs of the bird who you want to raise your offspring for you, and there could be a gene in that bird for recognizing intruder eggs. Both genes have selective pressure for passing on their on genetic info.
The very interesting case study of treachery comes ith Cowbirds, for hom there has been a proposed mafia hypothesis that suggests that these birds ho parasitize a wide range of nests in a given year, will return to the nests of small birds whom it parasitized to check up on whether they are raising the cobird young, and if not, punish the host in a way that would take an impressive amount of memory. This theory is supported by the fact that the cowbirds brains increase in capacity or size during mating season. Hoever an alternative theory suggests that it is simply beneficial for cowbirds to terrorize as many birds nests as possible to encourage those birds to re-nest and provide more opportunities for the cowbird to parasitize them.

Posted on June 5, 2012 02:58 PM by robertmarsh