Interesting Related Facts

by Nicole Cipri

This chapter is a free excerpt from Quicklet on Neil Shubin's Your Inner Fish.


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  • Shubin mentions that the earth’s atmosphere reached its current levels of oxygen about one billion years ago. What he didn’t mention was why: ancient forms of cyanobacteria experienced a population boom. Cyanobacteria use photosynthesis, which creates oxygen as a waste product.
  • Cyanobacteria formed some of the oldest fossils available, called stromatolites. There are still living stromatolites in the world. Some can be found in Shark Bay, off the western coast of Australia.
  • While there has been talk of tetrapods “invading” or “conquering” land, it was probably more of a tactical retreat. Tiktaalik was probably an unwieldy swimmer, and even less steady on land. It likely came ashore only to escape from predators.
  • Humans and other animals actually carry two sets of DNA: one contained in their cells’ nucleus, which is inherited from both parents, and another contained in the cells’ mitochondria, which is inherited solely from the mother.
  • Nearly all multicellular creatures have mitochondria in their cells, which convert the oxygen we breathe into energy for the cells. Scientists theorize that mitochondria were once separate creatures, but were absorbed by a larger prokaryote. Rather than being consumed, the two organisms formed a symbiotic relationship.
  • Plants also have mitochondria, but they use them as a kind of secondary energy system. Plants mainly get their energy from chloroplasts, which transform light into energy through photosynthesis.
  • The Burgess shale collection of fossils, first discovered in 1909 by Charles Walcott, gives us a strange glimpse into Cambrian life. Many of the species are remarkably well-preserved, with even their soft-tissue visible. While some of the creatures are obvious predecessors of current creatures, others bear no resemblance to any known group of animals, living or extinct.
  • Placozoa are such strange and unique creatures, they have been placed into their own phylum. By contrast, all vertebrates belong to a single phylum.
  • Creationists have long argued that there are not enough transitional fossils to support the theory of evolution. They also argue that human organs, such as the eye, are far too complex to have evolved on their own. Maybe they should read Shubin’s book?
  • Despite creationists’ denial, fossils of transitional species keep popping up, including Tiktaalik.
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