The word extinction carries an awful weight as it signifies the very end of a specific lineage – the last member of a given species dying. It is hard to imagine even though we are currently living in a time in which the number of extinctions is rapidly accelerating due to our own species’ activity on the planet. At the same time extinctions are a normal aspect of the pattern of life on Earth. The rate of exctinctions over evolutionary time pulsates in a mesmerizing ebb and flow with peaks that occasionally reaches an extinction rate of more than 90% based on the fossil record. Regardless, there seems to be a steady rate of background extinction that has occured over time. Our task this week is to understand the concept of extinction and the different processes that partake in the end of a species. Simultaneously, we also approach the concept of radiations, i.e. the process that leads to a rapid increase in the diversity of species. From an evolutionary perspective the connection between radiation and extinction is a very interesting one as an understanding of its dynamic connection can allow us to elucidate the patterns of biodiversity on Earth over time.

The goal this week is to discuss patterns of extinction and radiation of species:

Is there a pattern to the extinction events as perceived from the empirical evidence from the fossil record? What are possible causes of the major extinctions? The minor ones? Does extinction occur all the time? Why? Do species vary in their time on Earth? Can the evolutionary process prepare a species for surviving extinction events? On the other side of the coin – can one argue that there are events leading to a rapid increase in diversity of species? What conditions favor such radiations? Are there any connections between extinctions and radiations? Do you think that we are currently living in a time period that future biologists may refer to as a mass extinction event, the so called sixth mass extinction?

Choose a topic (see above), do some further research and write a thoughtful, analytical and comprehensive post (by Thu at the latest). You are, of course, expected to examine the works of the other students and respond to them in a thoughtful and creative fashion. Your task is to trigger a debate originating from the original post so try to be creative in your responses. You can agree or disagree as long as you provide a solid argument. Post at least three responses to the posts of other students over the week.



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