Microevolution

NOTE: This post is for Saturday's D block class and Monday's B block class

What is it? How does it differ from macroevolution?

Microevolution is evolution on a small scale—within a single population. A population is a group of individuals who reproduce together in the same area at the same time. The neat thing about microevolution is we can see in our life time. Today we looked at two different case studies one about mussels and one about crickets.

Musseling in on Evolution

The Asian shore crab invaded the eastern coast of the U.S. about 15 years ago and began foraging on the native blue mussel, which, at the time, had no defenses against the exotic, aggressive crab. But these days, the blue mussel responds to the crab’s presence by building up a thicker shell over the course of a few months. That extra buttressing helps thwart the crab's attacks — and makes the mussel a harder nut to crack!

The blue mussel The Asian shore crab

For the full story, click here.

Quick Evolution Leads to Quiet Crickets

Attack of the flesh-eating parasitoid maggots!! Mutant mute crickets run rampant in tropical paradise!! The headlines may sound like a trailer for a cheap horror flick — but in fact, these sensationalist sound bites accurately describe the situation on the Hawaiian island of Kauai. The "flesh-eating parasitoid maggots" are the offspring of the fly, Ormia ochracea, which invaded Hawaii from North America, and the mutant crickets are the flies' would-be victims. The flies follow the chirps of a calling cricket and then deposit a smattering of wriggling maggots onto the cricket's back. The maggots burrow into the cricket, and emerge, much fatter, a week later — killing the cricket in the process. But this fall, biologists Marlene Zuk, John Rotenberry, and Robin Tinghitella announced a breakdown in business-as-usual in this gruesome interaction: in just a few years, the crickets of Kauai have evolved a strategy to avoid becoming a maggot's lunch — but the strategy comes at a cost...

On the left is a typical field crick like those on Kauai, and on the right are the parasitic maggots of Ormia ochracea inside such a cricket.

To read the full story, click here.

Homework: Find an article or case study that discusses microevolution in a specific organism. Be prepared to explain the case to the class as well as answer questions about the case. On Thursday, 2.21, you will have a quiz on evolution, so start studying!