Period 2 Anagenesis

Anagenesis is when a population of an entire species changes into something different genetically without a split in the gene tree. It is also known as phyletic change, or just simply evolution.

This article discusses t"In Britain before the industrial revolution, the white form of the moth predominated; pollution from smokestacks darkened the environment, however, and the exposed the white moths to predators. Black forms came to dominate instead of white. Since the change occurred within the species, this is anagenesis." ( This is an example of anagenesis.

he resistance that species gain to antibiotics through genetics. HIV is a very quickly evolving virus because of its method of replicating itself. It replicates in high rates of mutations that allow the virus to assume new forms. After years of infection and treatment, HIV patients carry a unique version of the virus because of it evolving resistance to the bacteria. This is what makes it hard to find a cure. Evolution by natural selection transform the population into a new sort of creature that is more resistant to the drug. Horse Flies and DDT are a good example because within a decade, horse flies became resistant. DDT was thought to be one of the most powerful drugs in 1939.

Speciation is when a lineage splits into two species. Darwin explains this. For speciation to occur, many many many mutations must accumulate before two populations become separated and this process takes thousands of generations, time one single scientist cannot observe. Though it takes a long time for it to occur, it can end abruptly when the last critical changes occur. It is much harder to witness, then anagenesis and is more rare and elusive. Although, fruit flies have been discovered to show speciation by scientists William Rice and George Salt. The fruit flies produced two different types of fly species after thousands of generations in different environments. They adapted and passed those adapted traits onto offspring to eventually change the species so much that it was no longer the same as the original. If you have a problem with fruit flies, visit The Bug Squad:

Darwin wrote a a book in 1859 called The Origin of Species. This book was different because it showed and easy to understand explanation of how evolution worked, including anagenesis.

Anagenesis is the first part of the evolutionary process. This is when one single species is transformed.

"Evolution can take place by anagenesis, in which changes occur within a lineage, or by cladogenesis, in which a lineage splits into two or more separate lines. Anagenetic evolution has doubled the size of the human cranium over the course of two million years; in the lineage of the horse it has reduced the number of toes from four to one." (Britannica Online)

"The opposite of anagenesis, cladogenesis, is when a species splits into two genetically-distinct populations adapted to different ecosystems or survival strategies. The ancestral population of a species that has changed through anagenesis is, by definition, extinct. (Cladogenetic evolution does not require the ancestor to be extinct.)" (

n. A pattern of evolution that results in linear descent with no branching or splitting of the population. from this just describes what goes on in the changing of time and how it is believed to have come this far.

Through this anagenesis there is speciation:the formation of new species as a result of geographic, physiological, anatomical, or behavioral factors that prevent previously interbreeding populations from breeding with each other. this also helps organisms find their niche in their ecosystem.

Because of these things the world is now so diverse and the world is always changing. This makes scientist job in life very hard but yet again exciting. Charles Darwin thought of this idea and has helped move it along through this book the origin of species this has enhanced science and other famous scientists have based their ideas oft this book like Alfred Wallace yet help made it their own.

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