Introduction to Evolution Essay

Topic 1

1. A – Thomas Malthus - Malthus wrote about the struggle for survival and its relationship to the fact that the food supply is limited, but animals, if permitted by other circumstances, will continue to breed until there are too many for the available food, at which time they will compete for scarce resources. This got Darwin thinking about natural selection and the concept of biological fitness, and ultimately, to how natural selection, coupled with spontaneous mutations, could shape the characteristics of the survivors through succeeding generations, and how this could account for the diversity among the species and their evolution over sufficient periods of time.

B - Lyell's new book, Principles of Geology (1830-3), profoundly influenced Darwin. Lyell offered not just a new geology but a new way of understanding nature. Lyell showed how tiny, slow, gradual and cumulative change over immense periods of time could produce large changes. Natural, visible, non-miraculous causes should be sought to explain natural phenomenon. Darwin had the opportunity to witness all of these forces, such as erosion, earthquakes and volcanoes, during the Beagle voyage and he became convinced that Lyell's views were correct. Darwin made several very important discoveries about the geology of South America, volcanic islands and the origins of coral reefs by building on Lyell's ideas.

Gould and Eldredge: Punctuated Equilibrium - natural selection was incorrect, evolution only happens at a rapid rate, organisms may not share common ancestors.

Gradualism
Based on Geology and the findings of James Hutton and Charles Lyell, gradualism is the idea that large changes are actually the culmination very small changes that build up over time. This is seen often in geologic processes and when Charles Darwin first began formulating his Theory of Evolution, he adopted this idea for how evolution happens over very long time periods.
The fossil record is a piece of evidence that supports this view. There are many transitional fossils that show structural adaptations of species as they transform into new species. The geologic time scale helps show how the species have changed over the different eras since life began on Earth.
Punctuated Equilibrium
The other generally accepted hypothesis for the rate of evolution is called punctuated equilibrium. Punctuated equilibrium is based on the idea that we cannot see changes in a species, so there must be very long periods of no changes of species. That is the equilibrium part of punctuated equilibrium. However, we do know that species do change, so there has to be a period of time where those changes occur. Punctuated equilibrium asserts these changes over a relatively short amount of time "punctuating" the long periods of equilibrium.
At this time, neither hypothesis is considered more correct than the other. More evidence will be needed before either gradualism or punctuated equilibrium will be declared the actual mechanism for the rate of evolution.

Topic 2

1. Some alleles becoming more common and others becoming less common over time, creating evolutionary change

2.

Founder effect Bottleneck

|Small # of species gives rise to new population |Change in gene pool after dramatic decrease in population size, |
| |starvation, disease, human activities, natural disasters |
|Founders carry alleles and bring them to the new population |factors kill victims rather unselectively so the small surviving |
| |population does not represent the better adapted individuals |
|Concept is gene pool change from larger population where founders came|Certain alleles are overrepresented and some

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