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Evidence of Evolution

Pre-IB Bio 1
by

Sanjay Chandrasekhar

on 2 May 2011

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Transcript of Evidence of Evolution

Evidence From Biogeography The Theory of Uniformity or Uniformitarianism The Theory of Uniformity was theorized by Charles Lyell and it states that gradual, repetitive changes shaped the Earth. These changes include Earthquakes, Volcanoes, and other natural phenomena which slowly change the world. This theory received much criticism from"scholars" that believed the Earth was only 6,000 years old, and based on Lyell's calculations, the changes would have taken millions of years to form. Plate Tectonics The Theory of Plate Tectonics is basically that the world is made of constantly moving "plates" right below the crust of the Earth. There are oceanic plates and continental plates, and these plates make up all of the land we humans see everyday. There are 7 major plates, which are the African Plate, The Antartic Plate, The Eurasian Plate, the Indo Australian Plate, The North American Plate, the Pacific Plate, and the South American Plate. All the landmasses of the earth were once a single body known as Pangea, and all the water together was known as Pantholassa. Gradualism Gradualism is a theory that states that all profound changes in history and geography are a result of cumulative, but very slow processes. This theory was later incoorporated in the theory of Uniformitarianism. Evidence From Comparative Morphology Comparative Morphology Many animals in our world have very different features than us, but many of their structures are the same, such as human arms and whale flippers. Why is this? It is because of of comparative morphology. Since it is theorized that all plants and animals came from a single ancestor, then there will be similar traits in all the animals and plants, such as arm/fin structure. Morphological Divergence Morphological divergence is the changing of traits of animals and plants from their original ancestor. These traits diverge, or go seperate ways throughout time in order to better adapt animals and plants to their surroundings. This adaptation is part of the reason the world is as it is today. Convergent Morphology Morphological convergence is the exact opposite of morphological divergence, it refers to the traits that stayed the same in animals overtime. The function these animals or plants are similar, but the structure is not always. Models for Speciation Allopatric Speciation Allopatric refers to the "different lands" each species occupies. When one species lives in two different places, then overtime, the species will adapt to their surrounding, and speciation will eventually occur, and the two species can no longer reproduce together. The way and pace one species can be isolated from itself is unique. It could happen from a quick natural disaster, forcing half of a species into one place, while the other goes somewhere else to survive, or it could gradually happen overtime. All of this is evident in islands, in which finches and other animals and plants slowly evolve to the surroundings. Sypatric Speciation Sometimes, speciation occurs without an actual barrier being present. An example are cichlids in Africa, who present different mitochondrial DNA between nearby streams and lakes. Because of the size of this lake, both species have to live in the same location. Polyploidy Polyploidy is the inheritance of three or more of each type of chromosome due to improper separation of chromosomes during meiosis or mitosis. When plants are polyploid, a new species is instantaneously created. Dosage compensation prevents most polyploid animals because it regulates the level of gene expression. Parapatric Speciation When the daughter species of two different population form a border between the two populations. When these species breed together, they produce hybrid offspring, similar to both previous species. Patterns of Speciation and Extinction Cladogenesis and Anagenesis Cladogenesis is when a population slowly adapt to different circumastances and go in their own respective directions.
Anagenesis is when a species goes down an unbranched line, so basically new species are formed directly from the old one, and the species are very similar to each other. Speciation models Evolutionary Trees are used to show the relationships between species even after they have branched off of each other.
The Gradual Model is used to show slow changes overtime in species using a tree diagram and each time a new species is created, a branch comes off at a slight angle.
The Punctuation Model shows dramatic speciation followed by slow peaceful times without any speciation. Adaptive Radiation Adaptive Radiation is when many evolutionary processes happen quickly and they form new species. Basically, it is when one species rapidly creates multiple new species with different morphological and physiological traits. Adaptive Zones Adaptation happens for different reasons.
Physical Access is when adaptive zones open up and there is a whole evolutionary tree in that zone.
Evolutioary Access is when species gain traits in order to better use the environment to further their species.
Ecological Access is when better suited organisms displace or "kick out" the previously resident species. Extinction Extinction is when a species dies out because of a lack of adaptation to an environment, which is sometimes caused by localized environmental changes.
Usually, these extinctions are caused by catastrophic events, such as natural disasters. Analogous Structures Analogous structures occur when species with no common ancestor have similar traits with similar functions. Basically, these two different species evolved seperately, which furthers the theory of evolution. Species adapt to the surroundings, so two completely different species in the same environment might have the same traits in order to survive.
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