Homology and analogy

A house cat and a human are homologous. They both share a very similar bone structure in the forearms. The radius bones in both cats and humans are homologous. Cats come from the feline family and are quadrupeds. They walk on all four limbs. They use their homologous forearms in very different ways than humans. Humans come from the ape family and are bipedal. They use their forearms for grabbing and carrying and not for walking or jumping like cats.

    

A duck and a duck billed platypus are analogous. They both have bills on their face and webbed feet. Other than these two similarities they share almost nothing in common. Ducks are birds and can fly. Duck billed platypus' can't fly and come from the ornithorhynchus family, they are also much better swimmers. Ducks have feathers and their counterpart platypus do not. Although they share analogous traits they are nothing alike.
  

Protein Synthesis

AGGTATTGTACCAACCGAACGTCTGAAGTGTGAGCTTGATCCGGCAGGT

Historical influences on Darwin

I believe that the person most influential on Darwin's theory of natural selection was Jean Baptiste Lamark.  Jean Baptiste Lamark hypothesized that a species changed over time. He believed that a species was not fixed into it's current state, rather that it could pass on traits to the next generation. This contribution in my opinion could have given Darwin all the fuel he needed to stoke the fires of his natural selection theory. Lamark believed that a giraffe that was regularly stretching his neck to reach leaves then it would pass that long neck trait on to it's offspring and over many generations of this, the giraffes would be born with longer necks.
Darwin's theory's are very similar to Lamark's in many ways. Darwin believed that a species would adapt to it's environment and over  time evolve into a new species. Survival of the fittest works very similarly to Lamarks ideas about the giraffes. The video used an example about humming birds evolving longer beaks to reach nectar in deeper flowers. The two examples are very close.
I believe although Lamark's ideas might have been invaluable to Darwin's theory's, it would not have been possible for Darwin to come to his same conclusions. Darwin observed life and nature. Life and nature are brimming with examples of natural selection. The instrumental factor in my opinion was observing it for himself. As a student of nature Darwin would have observed and been familiarized with many species of plants and animals. His trip to the gallopagus islands put him in a unique position to view many of the same or similar species on such a remote corner of the globe. His observation and having the remarkable brain power to understand what he saw would have given him a chance regardless of prior theories.
At the time the church was adamantly against ideas that contradicted their creationist beliefs. This made it difficult on Darwin who was faced with a tough decision. He was a proper man of high society and didn't want to go against the church but at the same time he was a man of science. His scientific research had led him to an important discovery that could get him ostracized. It was a difficult decision that did not come quickly and was not well received at first. Fortunately when someone puts out such a controversial theory contradictory to the church others will quickly try and falsify it. The good fortune in this case was they only further supported Darwin's claims.

 http://evolution.berkeley.edu/evolibrary/article/_0/history_09