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The facts of evolution come from observational evidence of current processes, from imperfections in organisms recording historical common descent, and from transitions in the fossil record. Theories of evolution provide a provisional explanation for these facts. [1] Each of the words evolution, fact and theory has several meanings in different ...
As fossilization is an uncommon occurrence, usually requiring hard body parts and death near a site where sediments are being deposited, the fossil record only provides sparse and intermittent information about the evolution of life. Evidence of organisms prior to the development of hard body parts such as shells, bones and teeth is especially ...
Aging is therefore presumed to be a byproduct of evolution, but why mortality should be selected for remains a subject of research and debate. Programmed cell death and the telomere "end replication problem" are found even in the earliest and simplest of organisms. [35] This may be a tradeoff between selecting for cancer and selecting for aging ...
In this way, a population of mutant cells, called a clone, can expand in the neoplasm. Clonal expansion is the signature of natural selection in cancer. Cancer therapies act as a form of artificial selection, killing sensitive cancer cells, but leaving behind resistant cells. Often the tumor will regrow from those resistant cells, the patient ...
This innovation causes a major burst of animal coevolution. First freshwater pelomedusid turtles. Earliest krill. 120 Ma Oldest fossils of heterokonts, including both marine diatoms and silicoflagellates. 115 Ma First monotreme mammals. 114 Ma Earliest bees. [94] 112 Ma Xiphactinus, a large predatory fish, appears in the fossil record. 110 Ma
The first cause of cancer was identified by British surgeon Percivall Pott, who discovered in 1775 that cancer of the scrotum was a common disease among chimney sweeps. [ citation needed ] The work of other individual physicians led to various insights, but when physicians started working together they could draw firmer conclusions.
A former college dean who dedicated years of her life to researching a cure for cancer was gunned down on a walking trail near campus last week and her killer is still on the loose, leaving a ...
Scientist Otto Warburg, whose research activities led to the formulation of the Warburg hypothesis for explaining the root cause of cancer.. The Warburg hypothesis (/ ˈ v ɑːr b ʊər ɡ /), sometimes known as the Warburg theory of cancer, postulates that the driver of carcinogenesis (cancer formation) is insufficient cellular respiration caused by insult (damage) to mitochondria. [1]