Year: 2022

THE NON-DISRUPTED. “Some large-scale patterns withstood one or more of the Big Five extinctions with little disruption. These include the continued dominance of reefs by rugose and tabulate corals and stromatoporoid sponges across the Ordovician-Silurian boundary, the escalation of morphological responses seen in molluscan shells to increased predation intensity across the end-Cretaceous boundary, the prolonged Paleozoic decline of trilobites, and the onshore-offshore expansions and retreats of a number of post-Paleozoic marine orders.” https://lnkd.in/epHhn4i) View in LinkedIn

MINOR SETBACKS. “Other trends suffer setbacks—presumably owing to the contrast between mass extinction and “normal” selectivities—but then resume their long-term trajectories.” https://lnkd.in/epHhn4i) View in LinkedIn

DEAD CLADE WALKING. “Clade survival is no guarantee that preextinction trends will persist or be reasserted in the postextinction setting. Each extinction has examples of clades that survived the extinction event only to fall into a marginal role or eventually disappear (dead clade walking).” http://www.pnas.org/content/98/10/5393.full/Donnie) View in LinkedIn

FAILURE TO CROSS. “The intervals after mass extinctions tend to be significantly enriched in taxa that failed to cross the next stage boundary, relative to other intervals before the extinction event; in other words more clades that survived a mass extinction tend to dwindle or disappear shortly after the event than would be expected by chance.” https://lnkd.in/epHhn4i) View in LinkedIn

DIVERSITY EXPLOSIONS. “The most dramatic and creative evolutionary role of mass extinctions is the promotion of postextinction diversifications, typified most vividly by the exuberant radiation of the mammals after the demise of the dinosaurs and other reptilian clades at or near the end-Cretaceous boundary.” https://lnkd.in/epHhn4i) View in LinkedIn

SO ENDS this first of two weekend Fragments on extinctions versus diversity explosions during the history of life. The staggering facts that 99% of life that ever existed has gone extinct, amounting to an estimated 5 billion species, are a snapshot of both the robustness of life, and that it hangs like a thread in the flow of time. Looking around at the diversity around us, it seems hard to fathom. But each expansive radiation of life post-extinction takes about 5 million years, as we will see next weekend. Breathtaking numbers. View in LinkedIn

ADAPTIVE DEATH. "How could an inherited trait that promotes death, rather than survival, possibly be adaptive?" https://lnkd.in/ecP3KMX View in LinkedIn

PROGRAMMED ORGANISMAL DEATH. "This review was motivated by the observation that diverse organisms apparently have such active, internal death-promoting mechanisms and by the subtle and difficult conceptual issues that understanding the evolution of this kind of trait raises." https://lnkd.in/ecP3KMX View in LinkedIn

HIGHER LEVEL SELECTION. "If death is the function of programmed organismal death (i.e., if programmed organismal death is an adaptation for promoting death), then programmed organismal death must be selected for at a level other than the organism level." https://lnkd.in/ecP3KMX View in LinkedIn

SELF-INFLICTED DEATH. "Two main categories of putative programmed organismal death: senescence in macro-organisms and programmed cell death in unicellular microorganisms." https://lnkd.in/ecP3KMX View in LinkedIn