led to more involved mammalian parenting behaviors and increased female participation, in addition to the great investment that females have in gestating offspring. Larger simian males are more likely to become dominant, and dominant males often get the most and best food and have enhanced reproductive rights, as females are attracted to them. Virtually all monkey and ape societies are male-dominated, and the modern ideal of human females freely choosing their mates (or, perhaps more importantly, non-dominant males choosing their mates, if they get to mate at all) is rarely in evidence in monkey and ape societies, and is a new phenomenon for humans. The phenomenon of attractive women mating with rich and powerful men has deep roots in the simian evolutionary journey.
An important evolutionary principle is organisms' developing a new feature for one purpose and then using that feature for other purposes as the opportunity arose. As complex life evolved in the newly oxygenated seafloors, several immediate survival needs had to be addressed. To revisit the , if an oxygen-dependent animal did not have access to oxygen, it meant immediate death. Obtaining oxygen would have been the salient requirement for early complex life that adopted aerobic respiration , which is how nearly all animals today respire. While animals in low-oxygen environments have adapted to other ways of respiring (or perhaps in the first place), they are all sluggish creatures and would have quickly lost in the coming arms race. , which is a critical connective tissue in animals, requires oxygen for its synthesis, and was one of numerous oxygen-dependencies that animals quickly adopted during the Cambrian Explosion.
Essay on importance of animals and birds in our life
Since the most dramatic instances of speciation seem to have happened in the aftermath of mass extinctions, this essay will survey extinction first. A corollary to is that if any critical nutrient falls low enough, the nutrient deficiency will not only limit growth, but the organism will be stressed. If the nutrient level falls far enough, the organism will die. A human can generally survive between one and two months without food, ten days without water, and about three minutes without oxygen. For nearly all animals, all the food and water in the world are meaningless without oxygen. Some microbes can switch between aerobic respiration and fermentation, depending on the environment (which might be a very old talent), but complex life generally does not have that ability; nearly all aerobic complex life is oxygen dependent. The only exceptions are marine life which has adapted to . Birds can go where mammals cannot, , for instance, or being , due to their . If oxygen levels rise or fall very fast, many organisms will not be able to adapt, and will die.
They appear in ancient cave paintings, ..
There is also evidence that life itself can contribute to mass extinctions. When the eventually , organisms that could not survive or thrive around oxygen (called ) . When anoxic conditions appeared, particularly when existed, the anaerobes could abound once again, and when thrived, usually arising from ocean sediments, they . Since the ocean floor had already become anoxic, the seafloor was already a dead zone, so little harm was done there. The hydrogen sulfide became lethal when it rose in the and killed off surface life and then wafted into the air and near shore. But the greatest harm to life may have been inflicted when hydrogen sulfide eventually , which could have been the final blow to an already stressed ecosphere. That may seem a fanciful scenario, but there is evidence for it. There is fossil evidence of during the Permian extinction, as well as photosynthesizing anaerobic bacteria ( and ), which could have only thrived in sulfide-rich anoxic surface waters. Peter Ward made this key evidence for his , and he has implicated hydrogen sulfide events in most major mass extinctions. An important aspect of Ward’s Medea hypothesis work is that about 1,000 PPM of carbon dioxide in the atmosphere, which might be reached in this century if we keep burning fossil fuels, may artificially induce Canfield Oceans and result in . Those are not wild-eyed doomsday speculations, but logical outcomes of current trends and , proposed by leading scientists. Hundreds of already exist on Earth, which are primarily manmade. Even if those events are “only” 10% likely to happen in the next century, that we are flirting with them at all should make us shudder, for a few reasons, one of which is the awesome damage that it would inflict on the biosphere, including humanity, and another is that it is entirely preventable with the use of technologies .