Homogous and analogous traits

1.      a. homologous trait: four toes

Cat: The cat (Felis catus), also known as the domestic cat or housecat to distinguish it from other felines and felids, is a small furry domesticated carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests. Cats have been associated with humans for at least 9,500 years, and are currently the most popular pet in the world. Owing to their close association with humans, cats are now found almost everywhere in the world. (Wikipedia)

Lion: The lion is a species of the genus Panthera and its closest relatives are the other species of this genus: the tiger, the jaguar, and the leopard. Until the late Pleistocene, about 10,000 years ago, the lion was the most widespread large land mammal after humans. (Wikipedia)

      b. Homologous traits are those which species have in common because they have descended from a common ancestor. For instance, every species of cat has the homologous trait of possessing only four toes on its hind foot, because every member of the cat family descended from a common feline ancestor. The greater the number of such traits that two species share, the more closely they are related. A cat and a lion have more homologous traits between them than a cat and a human, for example—so cats and lions are more closely related, biologically.

c.    Feline was the common ancestor of these two species

d.    Lion, cat

2.      a. analogous trait: incisor teeth

Beaver: The beaver (genus Castor) is a primarily nocturnal, large, semi-aquatic rodent.  A beaver's teeth grow continuously so that they will not be worn down by chewing on wood. Their four incisors are composed of hard orange enamel on the front and a softer dentin on the back. The chisel-like ends of incisors are maintained by their self-sharpening wear pattern. (Wikipedia)

Elephant: Elephants are large land mammals in two genera of the family Elephantidae: Elephas and Loxodonta. Elephants' teeth are very different from those of most other mammals. Over their lives they usually have 28 teeth.The two upper second incisors: these are the tusks. Tusks in the lower jaw are also second incisors. These grew out large in Deinotherium and some mastodons, but in modern elephants they disappear early without erupting. (Wikipedia)

b. Consider the teeth of the beaver and the elephant. The gnawing front teeth of the beaver and the tusks of the elephants are both basically incisor teeth. While inherited in a basic form from an ancestor common to the beaver and the elephant, these teeth have been greatly modified by evolutionary mechanisms into the seemingly dissimilar teeth we see today in the beaver and the elephant.

c. I did not find common ancestor in my research.

d. Beaver, elephant

Protein Synthesis

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Historical Influence on Darwin - Thomas Malthus

"In October 1838, that is, fifteen month after I had begun my systematic inquiry, I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long- continued observation of the habits of animals and plants, it at once struck me that under these circumstances favorable variations would tend to be preserved and unfavorable ones to be destroyed. The results of this would be the formation of a new species. Here, then I had at last got a theory by which to work" (Charles Darwin, from his autobiography, 1876).

Charles Darwin was influence by many philosophers, economists and writers. One of his main influenced was Thomas Malthus, who wrote "Essay on the Principle of Population" (1798) The central theme of his essay was that human population growth would always overpower food supply growth, creating perpetual states of hunger, disease and struggle. So there will be competition and the most fit will get the food, reproduce, and spread their genes. The natural, ever present struggle for survival caught the attention of Darwin, and he extended Malthus' principle to the evolutionary scheme. Darwin considered that some of the competitors in Malthus' perpetual struggle would be better equipped to survive. Those that were less able would die out, leaving only those with the more desirable traits. Through his research Darwin concluded that this ongoing struggle between those more and less fit  to survive would produce a never-ending progression of changes in the organism. In its simplest form, this is evolution through natural selection.
Thomas Malthus's work helped inspire Darwin to refine natural selection by stating a reason for meaningful competition between members of the same species. He saw the concept relative to all species not just humans.
I believe that Charles Darwin couldn't  have developed his theory of natural selection without theories of Malthus, because before reading Malthus' ideas, Darwin had thought that living things reproduced just enough individuals to keep populations stable. He realized that the population theory could be applied to all aspects of organic life and provided a solid base in which natural selection could be studied.
Darwin had strongly believed in Malthus' theory and he used the population theory to help explain his own theory about natural selection in his book.

The church had extremely influenced on people in England in 19th century. Darwin knew that his theory which did not depend on supernatural processes would create problems. His ideas provoked a harsh and immediate response from religious leaders in Britain. They argued that his theory directly contradicted many of the core teaching of the Christian faith.
Darwin's work has helped fuel intense debates about religion and science then and now, so it's worthwhile to consider what his own religious beliefs were.

www.usmp.berkeley.edu/histrory/malthus.