Did the control of fire to , ? Or did merely use it to begin dominating the world? Was cooking the seminal event in the appearance of humans? Those questions may not be definitively answered in my lifetime, and led to the somewhat uncertain title of this chapter. Highly transformative developments coincided with the appearance and dispersal of , which was a radical break from all that came before – biologically, technically, and culturally – and strongly implies great cognitive enhancements. I believe that the control of fire and cooking would leave deep cultural and biological impacts on the human journey, and because barely changed during its nearly two-million year tenure on Earth, both in biology and in Acheulean artifacts, I favor Wrangham’s hypothesis, at least until the Next Big Finding. Just as Einstein said that and that his theories would one day become obsolete, but that their best parts would survive in the new theories, I suspect that significant aspects of Wrangham’s hypothesis will live on in successor hypotheses, and other scientists have been following Wrangham’s lead.
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.
Free Earth Essays and Papers - 123helpme
Here is a brief summary of this essay. Ever since more than three billion years ago and about a billion years after the Sun and Earth formed, organisms have continually invented more effective methods to acquire, preserve, and use energy. after three billion years of evolution and, pound-for-pound, it used energy . The story of life on Earth has been one of , and in turn influencing them. During the eon of complex life that began more than 500 million years ago, there have been many brief for some fortunate species, soon followed by increased energy competition, a relatively stable struggle for energy, and then cleared biomes and set the stage for another golden age by organisms adapted to the new environments. Those newly dominant organisms were often marginal or unremarkable members of their ecosystems before the mass extinction. That pattern has characterized the journey of complex life over the past several hundred million years. among some animals, which provided them with a competitive advantage.