Evolution
Beagle Trip
On Darwin’s Voyage on the Beagle, he did many things. He made readings and observations about the history of the earth, such as the formation of mountains and glaciers. He found that the earth is very, very old. The idea he developed that lead into his theories of evolution was that gradual processes can affect the earth and cause big changed.
He studied many animals of the South American flavor, and specifically many animals of the Galapagos Islands. He found that animals on different islands were similar, but differed from animals on the mainland. He reasoned that all life was related.
Theories
Darwin developed two major theories:
environment will survive and produce more offspring.
Evidence
There are many types of evidence that support the theory of evolution.
Fossil evidence shows changes in organism seen in their fossils. Artists often render what the actual animal would look like, based on its fossil.
Geographic distribution will show species with similar characteristics. An example of this would be the Galapagos finches all sharing similar characteristics, but still showing differences.
Homologous structures are actual animals-- not just their fossils-- that show relation between each other.
Embryonic evidence is when similarities are found between embryos of different species. Very early embryos are very similar.
Molecular evidence is similarities in the DNA and chemical make up of a species.
Vestigial evidence is when structures left over after change show relation to the new, changed structures.
Evolutionary/Genetic Patterns
Evolutionary Patterns
Adaptive radiation happens when species share a common ancestor. At one point during that ancestor’s history, it split off into multiple species.
Punctuated equilibrium is when a creature has a very long period of stability where it does not change, or stasis, and then goes through a short burst of change.
Genetic Patterns
Macroevolution shows changes from generation to generation in the frequency of alleles.
The Hardy-Weinberg equilibrium happens when a population does not change or evolve and the frequency of alleles remains constant.
There are different types of genetic drift, changes to a gene pool due to change in the environment. A bottleneck effect is when a natural disaster drastically diminishes alleles and frequency. A founder effect is when a new colony is formed, along with a new gene pool.
History of Life
Long ago people believed that organisms came directly from matter in an abiogenetic creation. This was called the Theory of Spontaneous Generation. Three major scientists of the 17th, 18th, and 19th centuries each helped to disprove this theory.
In 1668 Francisco Redi proved that meat did not give birth to flies. He attracted flies with jars of meat and studied the patterns of the eggs laid in the jars.
In 1767 Lazarro Spallanzani found that microbes could be killed by boiling them. He also found that microbes did not spontaneously generate from jars, but that they came from the air.
In 1864 Louis Pasteur proved that microbes did not come from the air, but that they came from cells on dust particles that were floating in the air.
A theory as to how the universe was created is the big bang theory. In the beginning, all matter was in a very dense, rightly packed area. A cosmic explosion caused this are to expand, creating the universe.
Finches
We studied why suddenly 40% of the finches on an island of the Galapagos suddenly died. It was found that natural selection had occurred. Finches with rounded, dull beaks died and finches with stronger, sharper beaks lived. This happened because the finches with more powerful beaks had an advantage in getting food.