I will add that it is highly important that every teacher should, for his or her own sake, be qualified and required to teach in all three parts of the Trivium; otherwise Masters of Dialectic, especially, might find their minds hardening into a permanent adolescence. For this reason, teachers in preparatory schools should also take Rhetoric class in the public schools to which they are attached; or, if they are not so attached, then by arrangement in other schools in the same neighborhood. Alternatively, a few preliminary classes in rhetoric might be taken in preparatory school from the age of thirteen onwards.
I noticed several crippling weaknesses in all alternative energy efforts that I was involved with or witnessed. Most importantly, when my partner mounted his efforts, people participated primarily to serve their self-interest. While the pursuit of mutual self-interest is the very definition of politics, self-interested people were easily defeated by organized suppression, although the efforts usually self-destructed before suppression efforts became intense. Another deficiency in all mass free energy efforts was that most participants were scientifically illiterate and did not see much beyond the possibility of reducing their energy bills or becoming rich and famous. Once the effort was destroyed (and they are, if they have any promise), the participants left the alternative energy field. Also, many lives were wrecked as each effort was defeated, so almost nobody was able or willing to try again. Every time that my partner rebuilt his efforts, it was primarily with new people; few individuals lasted for more than one attempt.
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Land colonization was perhaps the Devonian’s most interesting event. The adaptations invented by aquatic life to survive in terrestrial environments were many and varied. Most importantly, the organism would no longer be surrounded by water and had to manage . Nutrient acquisition and reproductive practices would have to change, and the protection that water provided from was gone; plants and animals devised methods to protect themselves from the Sun’s radiation. Also, moving on land and in the air became major bioengineering projects for animals. Breathing air instead of water presented challenges. The pioneers who left water led both aquatic and terrestrial existences. Amphibians had both , and arthropods, whose exoskeletons readily solved the desiccation and structural support problems, evolved to replace their gills, which were probably book gills.
in the late Carboniferous. Arthropods became dominant predators once again, although cephalopods patrolled the reefs as apex predators. at that time, although the succeeding Devonian Period has been called the Golden Age of Brachiopods. As oxygen levels rose, trilobites lost segments and, hence, gill surface area, which may have been an ultimately extinctive gamble. When the Devonian extinction happened during anoxic events, trilobites steeply declined and thereafter only eked out an existence until the Permian extinction finally eliminated them from the fossil record. Fish began in the Silurian, which was a great evolutionary leap and arguably the most important innovation in vertebrate history. Jaws, tentacles, claws… features were advantageous, as animals could more effectively manipulate their environments and acquire energy. On land the colonization began, as mossy “forests” abounded, and made their appearance, although they were generally less than a hand-width tall when the Silurian ended, and nothing reached even waist-high.
The twin ideas of efficiency and resilience are important. Efficiency is about getting more for less, particularly energy. Although aerobic respiration’s energy efficiency allowed for to develop, they end up creating interactions and dependencies, and the entire structure can lose its resilience when compared to simpler systems. Remove one part of the food chain and the entire ecosystem can collapse, and it can be part of the chain, from top to bottom. Making systems more efficient, as the last bits of energy are wrung from the system, reduces their resilience to the real world’s surprises. That dynamic is probably a key contributing factor of mass extinctions during the eon of complex life. Modern ecosystems studies are making the connections clear and are being applied to the dynamics of human civilizations; work has been seminal in this regard. Complex ecosystems pass through of exploitation, conservation, release, and reorganization, and three dimensions of interaction are involved: potential, connectedness, and resilience. In general, simple systems are more stable than complex ones, which is another reason why any , if there were any, would have been far less cataclysmic than those of complex life.
The Carboniferous also marked the rise of reptiles, which between 320 and 310 mya. The very term has become rather informal with the rise of , as birds and mammals descended from “reptiles” but are not called that. The term refers to groupings such as reptiles, in which part of the clade is not classified in the named group; clades (beginning with the last common ancestor and including all descendants) are tidier and scientists often prefer them. Although the issue, as usual, is controversial today, it seems that and reptilian ancestors may have descended from different groups of tetrapods, and some seemingly added to the controversy. But the idea that reptiles are is still prominent. Most importantly, reptiles were the first , a clade that includes birds and mammals, which do not need to lay their eggs in water and allowed reptiles to . Reptiles then colonized niches previously unavailable to amphibians. The first reptiles were small and ate insects, and laying eggs in trees may have been a solution to arboreal life. Seed plants and amniotes could reproduce on dry land, and their success greatly expanded terrestrial ecosystems.
works for animals that are no more than a couple of millimeters thick, but for larger animals a respiration system was necessary. The rise of the arthropods has been an enduring problem for paleobiologists. Why was the arthropod so successful, particularly in the beginning? Segmented animals dominated Cambrian seas, and segmentation provides for repeated features. Segments obviously became important for locomotion but, for arthropods, segmentation appears to have conferred the more important advantage of distributed oxygen absorption. Each trilobite leg had an attached gill, and leg motion constantly drew fresh oxygenated water over each gill. Arthropods never developed the kinds of lungs that vertebrates have, or the pump gills of fish and other aquatic animals. Early arthropods breathed by moving their legs. Peter Ward’s recent hypothesis is that segments were first used for respiration, to provide a large gill surface area, and using the segments for locomotion came later. For trilobites, the same functionality that pushed water over gills was also coopted for food intake. Also, the leg-mounted gill was necessary because of an arthropod’s body armor; oxygen could not be absorbed through tough exoskeletons.
The issue of avian and dinosaurian air sacs and when they evolved has been the focus of a rancorous dispute that was only recently resolved and hinged on the hollow parts of bones, which is a phenomenon called . The controversy involved dinosaur bone pneumaticity and how it may have been related to birds. In a , it was shown that birds have their most important air sacs where nobody thought they were, near a bird’s tail, not its head. Not only that, pneumatic bones are all related to the air sac system, and birds have the same pneumatic bones as saurischian dinosaurs did. The obvious implication is that the air sac system evolved in theropods and sauropods, when dinosaurs first appeared. If the air sac system appeared with the first dinosaurs, it is one more big reason why dinosaurs prevailed over the less respiratorily gifted therapsids. Such a highly effective respiration system evolving in a low-oxygen environment is a tantalizing hypothesis.