A sick cow has trouble walking and getting up. What are the Signs of BSE in Cows?Ī common sign of BSE in cows is incoordination. Without knowing it is there, the cow’s body cannot fight off the disease. The body of a sick cow does not even know the abnormal prion is there. For reasons that are not completely understood, the normal prion protein changes into an abnormal prion protein that is harmful. Most scientists think that BSE is caused by a protein called a prion. Neurologic means that it damages a cow’s central nervous system (brain and spinal cord). Progressive means that it gets worse over time. BSE is commonly called “mad cow disease.” What is BSE?īSE is a progressive neurologic disease of cows. "Bovine" means that the disease affects cows, "spongiform" refers to the way the brain from a sick cow looks spongy under a microscope, and "encephalopathy" indicates that it is a disease of the brain. I’ve reproduced some of them here as a slide show, and below.The word BSE is short but it stands for a disease with a long name, bovine spongiform encephalopathy. The book is also accompanied by some remarkable paintings by Quade Paul. These programs turned out to be supremely evolvable–with relatively minor mutations, they could give rise to new forms. Animals evolved genetic programs for turning a single egg into a complex body. The animal kingdom became both physically and ecologically complex.īut the diversity of the Cambrian had another source: the DNA of the animals themselves. As the environment changed, new kinds of animals evolved that could occupy new niches. The animals changed their environment–burrowing animals, for example, pierced the sea floor with countless tunnels. As predators emerged, their prey became better defended with spikes and shields the predators in turn became even deadlier. The stage was set for big, active creatures to evolve. Erwin and Valentine explain how the Earth was undergoing drastic changes in the millions of years leading up to the flowering of the animal kingdom, with global ice ages and a burst of oxygen flooding the oceans. The so-called Cambrian Explosion probably had many fuses. Two of the leading experts on the period, Doug Erwin of the Smithsonian Institution and James Valentine of Berkeley have collaborated on a new book, The Cambrian Explosion: The Construction of Animal Biodiversity, in which they synthesize evidence, both old and new, about this exceptional chapter in animal evolution. In the 24 years since then, scientists have learned a lot more about the Cambrian. Many people have become familiar with this period of evolution through Steven Jay Gould’s 1989 influential book, Wonderful Life. But the Cambrian fossil record is also rife with forms only distantly related to animals on Earth today, some of which were so weird that the sight of a reconstruction of the creatures made scientists burst out laughing. Many of the oldest known members of living animal groups–including our own–appear during the Cambrian Period. And then, around 520 million years ago, the fossil record of animals starts to roar like a firehose switched from a trickle to full blast. Some were recognizable members of living groups of animals, while others were so bizarre that paleontologists suspect they belonged to long-extinct lineages. Over the next 100 million years or so, new kinds of animals emerged. Those earliest animals may have been like today’s sponges, rooted to the sea floor and filtering food particles from the water. Paleontologists have found traces of animal life dating back at least 635 million years.
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