EXAM 3 EVOLUTION TB OUTLINE CHAPTER 22 22 1 EVOLUTION EVOLUTION changes in allele frequencies over time aka genetic changes NATURAL SELECTION a type of evolutionary force in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits We can view evolution in two related but different ways o Pattern revealed by facts and observations about the natural world what is happening change how is this occurrence taking place o Process the mechanisms that produce the observed pattern of DARWIN S FIVE THEORIES Evolution has happened Darwin had plenty of evidence for this All life has a common ancestor Darwin had very little evidence on this since he didn t know what genes or DNA was The diversity of life is the result of a series of splits in the lineage family tree of living things first of Darwin s main contributions Natural selection is the primary mechanism driving evolutionary change However there were others that contributed too genetic drift and gene flow second of Darwin s main contributions Evolution occurs gradually over time it could happen rapidly or slowly it depends DARWIN S EVIDENCE FOR HIS THEORIES Homology a collection of fossils that can help show consistent The fossil record patterns of an organisms lineage and help trace it ancestors but these structures may have different functions within these species when different species share the same structures due to common o Embryology was used to help determine this o Convergence morphological similarities with the same functions among species due to natural selection and NOT due to common ancestry therefore two organisms experiencing this aren t technically related Island species species that are either similar to the mainland ones or unique from them determined after his experiences on the Galapagos islands EXAM 3 EVOLUTION TB OUTLINE o Continental islands islands attached to the mainland that tend to have organisms similar to those on the mainland organisms that are unique and different from those on the mainland islands separate from the mainland that tend to have o Oceanic islands Endemic unique to that place and occur nowhere else species occurring only in a specific place and are Selective breeding another in order to make them more useful when humans choose which organisms to mate with one BASIC PRINCIPLES OF NATURAL SELECTION There has to be a variety of phenotypes present among a population There has to be an association between the phenotype and fitness o I e organism X has a phenotype that copes best with the environment therefore making it the most fit individual There has to some sort of change in the environment There has to be a genetic basis to the given traits of a population since natural selection acts directly on phenotypes which indirectly affects genotype IN ORDER FOR NATURAL SELECTION TO DO ANYTHING TO A POPULATION THERE HAS TO BE SOMETHING FOR IT TO WORK WITH HENCE THE REQUIREMENTS ABOVE SCIENTISTS AND THEIR IDEAS Darwin drew from the work of other scientists that were studying fossils the remains traces of organisms from the past o Fossils can provide a glimpse of some of the organisms that populated the earth at the time that the layer containing that specific fossil was formed o The older the fossils were the more dissimilar they were to current life forms One of the scientists inferred that extinctions must have been a common occurrence in the history of life His explanation for this is catastrophism the principle that events in the past occurred suddenly and were caused by mechanisms different from those operating in the present so according to the scientist s speculation each layer of rock containing a fossil represented a catastrophe like a flood that led to the extinction of many species EXAM 3 EVOLUTION TB OUTLINE o In contrast other scientists proposed that change took place through the cumulative effect of slow but continuous processes Charles Lyell came up with a principle of Uniformitarianism which stated that mechanisms of change are constant over time He also came up with the idea that the same geological processes that occurred in the past are still occurring today o Based on influences from other scientists Darwin then concluded that geologic changes must result from slow continuous actions rather than the widely accepted age of a few thousand years therefore showing that Earth is way older than what was originally thought During Darwin s time several naturalists suggested that life evolves as environments change o One of them named Lamarck is remembered for his inaccurate idea that 1 acquired traits are passed down through generations in an organism s lifetime and 2 that the more used body parts or organs are the stronger and larger they are while the ones that aren t really used deteriorate due to under use Our understanding of traits today disproves both of Lamarck s ideas 22 2 DARWIN S VOYAGE He joined the beagle as the captain s companion Primary mission of voyage to chart poorly known stretches of the South American coastline Darwin took many notes on the specimens and he also collected some of his own o The fossils he found although clearly different from living species were distinctly south American in their resemblance to the living organisms of that continent After observing an earthquake s effects on fossils of rocks from the ocean being found high in the mountains Darwin then understood more of what Lyell was saying that the physical evidence seen doesn t support the idea that earth is only a few thousand years old THE PART OF THIS VOYAGE THAT HAD THE MOST IMPACT ON DARWIN WAS THE GALAPAGOS ISLANDS o Some species that he found were unique to individual islands while others were found on two or more adjacent islands o However most of the Galapagos species were not found anywhere else in the world A concept called endemic EXAM 3 EVOLUTION TB OUTLINE So Darwin hypothesized that maybe the species found there were colonized by those from the South American mainland and then they just diversified leading to new species on these islands ADAPTATIONS Darwin observed many examples of adaptations inherited characteristics of organisms that enhance their survival and reproduction in specific environments o But then he began to perceive adaptation to the environment and the origin of new species as closely related processes Therefore his explanation of how adaptations come about arise centered on
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