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Evolution - Coggle Diagram
Evolution
Darwinian Evolution
Who was Charles Darwin?
Early Life: Charles Darwin was born in Shrewsbury England in 1809 to a wealthy family of physicians. His father wanted him to follow the family legacy, but Darwin found medical practices at the time gruesome, and he dropped out of medical school to become a member of the clergy. Here he met John Henslow, a professor who helped him attend the HMS Beagle voyage lead by Captain Fitzroy. The HMS Beagle is where Darwin conducted the majority of his research.
The HMS Beagle Expedition: The HMS Beagle Expedition lasted a total of 5 years and sailed around the world, to places including South America, Australia and the Galapagos. Darwin attended this expedition researching thousands of different species and started to notice the similarities between certain species. Using the theories of Malthus, Lyell, etc. Darwin began to develop the theory of evolution.
Darwin soon after his expedition settled down and slowed on his research while still going around lecturing about his ideas on evolution and natural selection. Many were pushing him to publish his ideas, but he was hesitant to go forward until a man named John Wallace approached him asking to use his research for a publication on the theory of evolution. Darwin refused and realizing someone might steal his credit for evolution he wrote the book "Origin of Species" in 1859 which discussed his theory of natural selection and evolution.
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Who came before Darwin?
Aristotle was a philosopher (384-322 BC) who was titled the "Father of Biology" due to his early contributions to the field. He viewed species as unchanging and perfect as designed by God. Developed the idea of Scala Naturae, a ladder where life forms are arranged by increasing complexity.
Linnaeus was a physician (1707-1778) who developed the binomial naming system for living organisms and started grouping species together by similarities.
Cuvier was a paleontologist (1769-1832) who expanded on Linnaeus' naming system and introduced the theory of extinction.
Hutton and Lyell (1800s) proposed Earths geologic features were a result of gradual mechanisms and theorized Earth was very old, contrary to the leading theory at the time.
Lamark was a French biologist (1744-1829) who rivaled Darwin and theorized an opposing mechanism for evolution "use and disuse". He argued that species who used parts of their body more often lead to development in these traits from generation to generation. Characteristics acquired during an organism's life would be passed onto their offspring,
Evolution of Populations
Genetic Variation
Genetic Variation: differences in individuals in the composition of their genes or other DNA sequences, often reflected by phenotypic differences. Without genetic variation, evolution cannot occur in a population.
Genetic variation starts at the whole gene level and can be quantified as the average percent of loci that are heterozygous (2 different alleles for that locust)
Genetic Variation origination from gene mutation, gene duplication, or any other processes that introduce new alleles.
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Frameshift Mutation: Insertions or deletion of bases that are not in multiples of 3 which alters the reading frame of the genetic code
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The presence of heterozygous individuals is good for the species as it protects them if the dominant or recessive allele becomes less favorable in that environment
Hardy Weinburg Equation
Hardy Weinburg Equation lets us assess allele frequencies in a population and determine if a population is evolving
Hardy Weinburg only works if these assumptions are true: NO Mutations, NO Gene Flow, Population must be very large, Mating must be random, Natural selection is not changing the population, and the allele tested is NOT sex linked.
P = frequency of dominant allele (B)
q = frequency of the recessive allele (b)
p^2 = frequency of homozygous dominant individuals (BB)
q^2 = frequency of homozygous recessive individuals (bb)
2pq = frequency of heterozygous individuals (Bb)
Gene Drift and Flow
Gene Drift: Chance events that cause allele frequencies to fluctuate unpredictably from one generation to the next, predominately in small populations. Can lead to a loss of genetic variation in populations and harmful alleles to become fixed.
Founder Effect: When a few individuals are isolated from a larger population and establish a new gene pool
The Bottleneck Effect: When a sudden change in environment such as a natural disaster results in a dramatic reduction in the population causing allele frequencies to change
Gene Flow: The transfer of alleles into or out of a population due to the movement of fertile animals and their gamete. Reduces the genetic differences between populations and introduces new alleles.
