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Lecture 11

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University of Toronto St. George

Lecture 11 -The evolution of morphological body parts first arose during the Cambrian explosion, in particular hard exoskeletons for protections, and sensory features such as antennae -They were relatively immobile; they sat, swam but did not move as quick as modern animals -The diversity of this period had animals completely different -Predation first arose during this period as well, found by the trilobite fragments in the stomache of the undiscovered “terror of the trilobites” -The causes of the Cambrian explosion were explained by the environmental factors, but in addition the HOX/HOM genes which were regulatory genes that changed the structures of an organism’s body -The switch from sulfur-consuming anaerobic photosynthesis to aerobic photosynthesis allowed for the deposition of oxygen into the environmental atmosphere -A mass extinction of cyanobacteria, since oxygen was toxic to these protozoic organisms -Respiration of oxygen was considerably more efficient than anaeorobic respiration -The process of fermentation, which was anaerobic, yielded much less energy than cellular respiration which used cellular respiration -The rise of animals because of this, which were incapable of producing their own food, and had an increased metabolic rate, first arose -As a consequence, predators arose due to the rise of animals -The shells indicated that it was defense against predation, in particular perfectly rounded holes rather uneven “decay” holes -Molecular clock genes are genes which can be identified, and which can indicate how long ago animals have been separated from each other -The role of chance in evolution, can be seen through background extinctions and mass extinctions -Background extinction is one which happens through natural selection and evolution -However, mass extinctions take place over a relatively short-period of time and leads to Mass die-outs -About 65 million years ago, the Cretatious-Tertiary period saw a mass die-out, 50-80% of organisms including most if not all large animals died out -An asteroid is believed to have hit the Earth, causing this -At the cretaceous-tertiary boundary, there have been discovered a thick deposit of iridium -Iridium is quite rare in the Earth’s crust, but are common in meteorites, and many areas around the world have shown 30x the concentration normally found -In addition, there are shock crystals, produced by high-impacts, around meteorite sites all around the Earth - The debate was quite controversial until the 1990s, until the discovery of a geophysical technique in Yucatan had discovered it -The die-out did not entirely happen at once, rather the ecological fallout occurred over many thousands of years -Mammals survived due to their original, nocturnal, small scavenger lifestyles Lecture 12 -The evolution of humans from apes, begun 5.4 million years ago, based on the use of molecular clocks -Bonobos are unique among apes, through their hypersexuality and their matriarchal societies -The last common ancestor of chimpanzees and humans were known to be similar to chimpanzees, and had a basis of culture -The karyotype of the species, the study of chromosomes are known to be different -C
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