What type of molecule is produced by virus-infected cells to communicate to non-infected cells the presence of a virus?

One of Darwin's infamous lines of evidence regarding evolution is biogeographical evidence. Biogeographical, when broken down basically means how the biology (bio in biogeography) of organisms on Earth (geo in biogeography) migrated and moved across from their original place. Darwin used this as a line of evidence because he studied the movement or migration of certain species to gain an understanding on the changes within the environment, which due to natural selection, would eventually alter the species' traits. An example of biogeography would be fossils, and how there were different species on different parts of the world as well as species that went extinct due to environmental changes.

Darwin's second line of evidence for the theory of evolution would be adding onto biogeography in a sense where it, in and of itself, would be considered evidence regarding changes. Fossils are preserved or saved remains or skeletons of a used-to-be living organism. Fossils are a great way not only to track changes but also to discover possible new species that might not have been alive during Darwin's days. By carefully examining the evidence and information a single or numerous fossil gives Darwin, he could clearly, depending on the clarity and amount of remain within the fossil, see changes in bone structure.

Darwin's last line of evidence for the theory of evolution is anatomical evidence. Anatomical evidence is build upon the findings of fossils and comparing them to species that are alive today. Anatomical evidence allows common ancestry to be identified by looking and comparing similar traits to a pre-existing   organism to one today. One can also find the differences between the two organisms that are being compared to see if there is a relationship at all.

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