MITOCHONDRIA WERE ONCE FREE-LIVING ORGANISMS
Three of these entries, including this one and not counting the time piece, are starting to get us to the very bottom of evolution now:
"Most significantly, we [the oak and humans] both use precisely the same code for translating nucleic acid information into protein information, as do virtually all the other creatures on the planet,*" writes Sagan, but in a footnote he adds a very interesting piece of information.
[Footnote] "*The genetic code turns out to be not quite identical in all parts of all organisms on the Earth. At least a few cases are known where the transcription from DNA information into protein information in a mitochondrion employs a different code book from that used by the genes in the nucleus of the very same cell. This points to a long evolutionary separation of the genetic codes of mitochondria and nuclei, and is consistent with the idea that mitochondria were once free-living organisms, incorporated into the cell in a symbiotic relationship billions of years ago. The development and emerging sophistication of that symbiosis is, incidentally, one answer to the question of what evolution was doing between the origin of the cell and the proliferation of many-celled organisms in the Cambrian explosion." (COSMOS, Sagan, p. 38)
GET YOUR MIND AROUND THIS AND AROUND AND AROUND
As for me, I didn’t know keeping time was quite this complex. I just look at the clock hands in the clock face on the wall.
"Average Earth time, officially known as TDB (for barycentric dynamic time, using French word order) is the astronomers' time scale. It is the time that would be kept by a hypothetical cesium clock at sea level on a fictitious Earth that swings around the Sun at a constant speed in a perfect circle, in an otherwise empty Solar System. (The arcane world of precision timekeeping is populated by nearly as many hypothetical clocks as real ones!) This time scale is obtained by correcting real clock readings for the seasonal variation, plus a smaller correction for the effect of the Moon on the Earth's motion." —Robert March in an essay "Does Anybody Know The Right Time?" in the collection of science writing called MYSTERIES OF LIFE AND THE UNIVERSE edited by William Shore
WE'RE ALL SPONGERS
We're getting down to sponges now, we're getting to the bottom of things. I've been plowing through this book for the longest time, but still to go are 100 more pages. I'm taking a lot of time to work on my algebra class also. Contemplate what Dawkins calls "landmark".
"The evolution of multicellular sponges from single-celled protozoa is one of the landmark events in evolution. . . ." Dawkins, THE ANCESTOR'S TALE, p. 486
HATE TO TELL YOU THIS, BUT NOT ONLY HAVE WE BEEN SPONGES,
WE'RE ALSO ALL ASSHOLES AT ONE TIME OR ANOTHER
"Gastrulation is something that all animals do early in their life. Typically, before gastrulation, an animal embryo consists of a hollow ball of cells, the blastula, whose wall is one cell thick. During gastrulation the ball indents to form a cup with two layers. The opening of the cup closes in to form a small hole called the blastopore. Almost all animal embryos go through this stage, which presumably means it is a very ancient feature indeed. You might expect that so fundamental an opening would become one of the two deep holes in the body, and you'd be right. But now comes the big divide in the animal kingdom, between the Deuterostomia (every pilgrim who arrived before Rendezvous 26, including us) and the Protostomia (the huge throng who are now joining at Rendezvous 26).
"In deuterostome embryology, the eventual fate of the blastopore is to become the anus (or at least the anus develops close to the blastopore). The mouth appears later as a separate perforation at the other end of the gut. The protostomes do it differently: in some, the blastopore becomes the mouth, and the anus appears later; in others, the blastopore is a slit that subsequently zippers up in the middle, with the mouth at one end and the anus at the other. Protostome means 'mouth first'. Deuterostome means 'mouth second'.
"This traditional embryological classification of the animal kingdom has been upheld by modern molecular data. There are indeed two main kinds of animal, the deuterostomes (our lot) and the protostomes (them over there)." —Richard Dawkins, THE ANCESTOR'S TALE, pp. 377-378