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What Darwin Never Knew
Transcript of What Darwin Never Knew
Charles Darwin was offered a place on the British Navel ship the H.M.S. Beagle whose mission was to survey the waters around South America
One port of call on Darwin's voyages proved more important than all the others: The Gallapagos Islands. This cluster of 13 isolated islands lies 600 miles of the coast of Ecuador, in the Pacific Ocean
Originally, there must have been just one type of bird on the Galapagos, but over time it had diversified into many kinds, with different beak shapes; the same for tortoises. One type of tortoise must have turned into many kinds, with different shells depending on which island they lived on
Darwin had an amazingly bold idea: The Tree of Life- that ALL species were connected
Ultimately one type of creature could be transformed into something utterly different. A process Darwin called "descent with modification"
The pattern that Darwin saw was that creatures that survived were those best adapted to the specific environments that they lived in
Darwin realized that variation must be the starting point for change in nature. In any generation, the animals in a litter are never quite the same. And in the wild, such a tiny variation might be the difference between life and death.
The DNA molecule is one of the real secrets of life. It is a perfect system for storing the vast amounts of information that is necessary for building all kinds of creatures.
Mutation is a critical ingredient in the recipe for evolution. Without mutation, everything would stay constant, generation after generation. Mutation generates variation, or differences between individuals
People were freaked out by the relatively small number of genes. It's down to 23 thousand protein coding genes in a human genome.
Body plan genes determine where the head goes; where the limbs go, and what form they may take: whether they are arms, legs or wings
It is not the genes you have but how you use them that creates diversity in the animal kingdom
Switches are not genes!
They don't make stuff like hair, cartilage, or muscle, but they turn on and off the genes that do.
After hunting through a vast stretch of DNA, Darwin found a section of DNA that had mutated. Lake stickleback fish did not have the genes that make spikes found on ocean stickleback fish.
While studying the different beaks on the different finches of the Galapagos Islands, Darwin discovered that while the beaks had the same genes there were differences in timing and intensity
Everything goes back to Darwins idea of the tree of life. All life forms are ultimately related and have diversified and changed over billions of years so now they look completey different
If Darwin were correct, then somewhere there had to be a fossil that was part fish but had the beginnings of legs.
The Tiktaalik fit this idea. Most of the body was fish like and covered in scales.
However, it also had an arm like fin or perhaps a fin like arm that had the same bone structure of every four limbed animal.
Hox genes are found in all complex animals from the velvet worm dating back 600 million years to the modern human. In all that time the letters of their DNA has remained virtually unchanged.
Hox genes determine the placement of all parts of an animal. Where the front and back are going to be, the top and bottom, where the eyes are placed, how many fingers and toes they are going to have.
Amazingly, in ALL four limbed animals (even humans) exactly the same genes create the long upper arm bone
Given the obvious differences between humans and chimps you may expect DNA to be drastically different. However, the DNA is almost 99% identical.
One percent may not seem like much but that is 30 million A's, T's, C's, and G's worth of DNA
Basically, you can make massive changes, by making small changes. Changing only a couple of DNA letters around can have a profound effect.
If you could ask Charles Darwin any question what would you ask him? Why would you ask him that?