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DEATH FITNESS IN UNICELLULAR ORGANISMS. "There is considerable experimental evidence for fitness advantages from programmed organismal death to clonal kin groups of cells of species usually considered to be ‘unicellular’. These fitness advantages may represent a significant source of selection pressure." https://lnkd.in/ecP3KMX View in LinkedIn

CAMBRIAN PUZZLE. “Abrupt appearance of major bilaterian clades in the fossil record during the first three stages of the Cambrian Period has puzzled the scientific world since 1830s.” https://lnkd.in/ehHwFGP View in LinkedIn

ALTRUISTIC BEES. "One familiar example occurs in honeybee workers, which commit suicide each time they sting invaders in defense of their hive. Similarly, these workers altruistically commit suicide in ways that apparently function to prevent the spread of disease within the hive. In these cases, there is little mystery concerning function or evolution. Kin selection, or equivalently, selection among colonies, is a powerful force shaping the evolution of eusocial insects." https://lnkd.in/ecP3KMX View in LinkedIn

NOT PROGRAMMED. "General explanations for organismal senescence are varied and contentious, and the idea that iteroparous senescence is “programmed” is not the majority view." https://lnkd.in/ecP3KMX View in LinkedIn

SO ENDS this topic of mass extinctions. It is a remarkable history of boom and bust events in life’s history, from great abundance to hanging by a thread. What is evident, is that it is hard to snuff life out, even in the face of cataclysmic events. Some life forms will survive. Even when you look at the growth and survival of seedlings, there is an evident force to survive at all costs in any conditions. Life is a fiercely determined force. View in LinkedIn

COMPLEX AND UNPREDICTABLE. “The evolutionary response to mass extinction is slow on human time scales, difficult to predict owing to the contingencies of postextinction conditions including the identity and evolutionary dynamics of the survivors, and geographically heterogeneous.” http://www.pnas.org/content/98/10/5393.full/Donnie) View in LinkedIn

FORCE OF CHANGE. “Extinction itself promotes biotic interchange. Asymmetries in ancient biotic interchange generally appear to reflect geographic differences in extinction intensity. The end-Cretaceous extinction shows, however, that although biotic interchanges pervade the postextinction world, simple linear relationships can break down to produce unexpected source-sink patterns.“ http://www.pnas.org/content/98/10/5393.full/Donnie) View in LinkedIn

NO GUARANTEES. “Survivorship during mass extinctions need not be closely related to many aspects of biological success as measured during “background” times.” http://www.pnas.org/content/98/10/5393.full/Donnie) View in LinkedIn

ONGOING EVENTS. “Mass extinctions happen. The fossil record provides ample evidence that even the more widespread and species-rich clades, ecosystems, and biogeographic provinces are not infinitely resilient.” http://www.pnas.org/content/98/10/5393.full/Donnie) View in LinkedIn

CONCLUSION. “I would not go far wrong in saying that the most dramatic evolutionary effects of mass extinctions can be epitomized in just four words: they remove successful incumbents.” http://www.pnas.org/content/98/10/5393.full/Donnie) View in LinkedIn