Category: Uncategorized

HARDER TAKES LONGER. "The eukaryotic cell originated by the most complex set of evolutionary changes since life began: eukaryogenesis. Their complexity and mechanistic difficulty explain why eukaryotes evolved two billion years or more after prokaryotes." http://www.pnas.org/content/112/33/10278.full View in LinkedIn

PROTEIN TRANSPORT MACHINERY. "Nowack and Grossman reported that three genes encoding components of photosystem I that have been transferred to the nucleus of the (eukaryotic) amoeba Paulinella chromatophora produce cytosol-synthesized proteins that are imported back into chromatophores." http://www.pnas.org/content/112/33/10278.full View in LinkedIn

PURELY RHETORICAL? "Overall, we question whether premises of existing theories about the uniqueness of eukaryogenesis and the greater evolutionary potential of eukaryotes have been objectively formulated and whether, despite widespread acceptance that eukaryogenesis was “special,” any such notion has more than rhetorical value." http://www.pnas.org/content/112/33/10278.full View in LinkedIn

ANOTHER CONTRARY FINDING. "In just the last few years, however, at least one endosymbiont not genealogically related to mitochondria and plastids has been shown to (likely) have independently evolved protein transport machinery." http://www.pnas.org/content/112/33/10278.full View in LinkedIn

SO ENDS this further consideration of spider webs, and a prelude to the next weekend that largely deals with the subject of web geometry. Not only must webs be strong, and be composed of various silks, but they must also ensnare the prey with durable stickiness that does not dry out. The chemical manufacture and extrusion of these materials that polymerize outside the body from internal organs that operate at ambient temperatures and pressures is today beyond the capability of chemists; companies like DuPont and BASF have had to abandon this project. https://www.acs.org/content/acs/en/pressroom/presspacs/2014/acs-presspac-march-5-2014/synthetic-spider-silk-strong-enough-for-a-superhero.html View in LinkedIn

EVOLUTIONARY BOTTLENECK. "In this century, it is probably the evolution of mechanisms for importing necessary proteins into organelles that is taken as the most difficult, eukaryogenesis-limiting step." http://www.pnas.org/content/112/33/10278.full View in LinkedIn

CONTRARY FINDING. "Another is the recent discovery that the mealybug endosymbiotic β-proteobacterium Tremblaya harbors the γ-proteobacterial endosymbiont Moranella, on which it is absolutely dependent for complementation of many of its missing genes (it retains only 120!). This finding tells us that prokaryotes can acquire other prokaryotes as endosymbionts without first developing eukaryote-like phagotrophy." http://www.pnas.org/content/112/33/10278.full View in LinkedIn

TRANSITIONS. "First, the parts of a new whole may retain some independence with respect to their ability to reproduce. Second, interdependence of parts is emphasized as a threshold that must be crossed for a new type of individual to have truly evolved. Both are what we see in the case of the eukaryotic cell." http://www.pnas.org/content/112/33/10278.full View in LinkedIn

KIN VERSUS FOREIGN. "It is uncontroversial that eukaryogenesis involved the fusion of two taxonomically distinct units to form a new type of cell. Eukaryogenesis can thus be distinguished from evolutionary transitions based on the integration of closely related units (as in the evolution of multicellularity)." http://www.pnas.org/content/112/33/10278.full View in LinkedIn

NO SINGLE EVENT. "Margulis, a champion of endosymbiotic theory, argued for the community perspective on the eukaryotic condition. Symbiotic mergers similar to eukaryogenesis, she insisted, are ubiquitous in the history of life. As a result, our understanding of evolutionary processes requires the radical revision, perhaps abandonment, of many traditional neo-Darwinian ideas." http://www.pnas.org/content/112/33/10278.full View in LinkedIn