Wed, 15 May 2013
Ammonoids are a diverse group of cephalopods, a group of molluscs that include squid, octopuses, cuttlefish and nautiloids. They lived for over 300 million years (from the Early Devonian – the end Cretaceous) and survived multiple mass extinctions. They finally succumbed to the mass extinction event at the end of the Cretaceous, the same event that killed the Dinosaurs. Ammonoid fossils are found abundantly around the world and offer palaeontologists a exceptional opportunity to study the evolution, life history and ecology of these fascinating invertebrates. Today we will be talking to Dr Kenneth De Baets from the Palaeontology Section, GeoZentrum Nordbayern about what we can learn about ammonoid ecology from the study of their fossils, and what this tells us about the evolution of living cephalopods.
Wed, 1 May 2013
One of the most significant events in Earth’s history has been the oxygenation of its atmosphere 2.45–2.32 billion years ago. This accumulation of molecular oxygen in Earth’s atmosphere was so significant that it is now commonly known as the Great Oxidation Event (GOE). The long-reaching effects of the GOE were literally world-changing; the compositions of the atmosphere and hydrosphere were altered, and through various redox reactions (where atoms have their oxidation state changed), the nature of the continents and global climate changed too. However, and perhaps from an anthropocentric viewpoint, the most important effect would be upon the biosphere: the GOE paved the way for the evolution of aerobic (oxygen respiring) organisms, including our earliest ancestors.
It is possible to track the GOE through geochemical traces left in the rock record. However, one thing we're still uncertain about is whether or not this event represents either a sharp increase in oxygen production or a reduction in oxygen sinks - the jury is still out on that one. With this level of ambiguity over the dynamics of the GOE, it may be a little surprising to know that there has been a long-standing consensus on how the oxygen was actually produced: photosynthetic organisms called cyanobacteria (blue-green algae, so named after the pigment they produce).
In this episode we discuss with Dr. Bettina Schirrmeister (University of Bristol) about the evolution of cyanobacteria and the role they played in the GOE.