Evidence for Evolution Chapter 13 PDF

Evidence for Evolution  Paleontology The first observed evidence for evolution was in the fossil record. New organisms were being discovered in the fossil record – Close to all of these organisms have been extinct Geological timesc...

Evidence for Evolution  Paleontology The first observed evidence for evolution was in the fossil record. New organisms were being discovered in the fossil record – Close to all of these organisms have been extinct Geological timescale – Has had many different hypotheses, all proven wrong until radioactive dating was discovered – Earth is 4.6 billion years old  Geological Eras Time periods which are marked by mass extinction events. – 65 Million years ago non-avian dinosaurs went extinct (Birds are considered by many scientists to be directly related to dinosaurs) – 248 million years ago nearly all of life went extinct Between 90-97% of life  Fossils Fossils form by many different methods, but all are rare processes Compression: involves sediment below and on top of a dead organism resulting in remains being left behind. Petrifaction: results from the hard body portions of the organism being replaced by minerals in the soil Imprints leaves an outline or imprint of the organism  How old are fossils? Relative dating: It is based upon the principle of superposition Lower layers of the earth are generally considered to be older than higher layers. – Doesn’t give an actual date, but does give chronological information Absolute dating: based upon radiometric dating – See next slide  Radiometric Dating (fig. 12.6) Radiometric dating gives an actual time period – Does give a range of dates as inherent errors in the experiment have to be accounted for Radioactive isotopes change their atomic structure in a set time pattern. – Carbon14: C14 to N14 good for up to 40,000 years – Potassium-Argon is good for the 100 million and billion year range  Missing Links In Charles's Darwin’s Origin of Ambulocetus sp. Species he devoted a couple chapters to challenges he saw in his theory. One being the lack of Archaeopteryx sp. “transitional fossils”. At the time there was little discovery, since then we have discovered lots of transitional Tiktaalik fossils.  Biogeography The study of the geographical distribution of organisms Theory of Plate Tectonics describes the mechanisms of the motions of the surface of the earth – Mechanism which helps describe earthquakes – Helps to explain the distribution of the fossil record  Island Biogeography Islands have a unique for of biogeography. – Reptiles, arthropods (insects, spiders, etc), and birds are the most successful animal colonizers Reptiles usually become larger Birds often become flightless – Mammals and amphibians have a rough time colonizing islands. Mammals often become smaller Often involve rapid evolution because the first organisms have no competition to evolve into new niches – Adaptive Radiation (p. 282 Chapter 13)  Anatomical structures Biological evolution has led to anatomical similar patterns amongst organisms which are closely related to one another Next three slides – Homologous Structures Fig. 12.10 – Vestigial Structures Fig. 12.11 – Analogous Structures Fig. 12.13  Homologous Structures Anatomical structures which share the same evolutionary origin – Have the same genetics involved with their development – Have the same embryonic development The forelimbs of tetrapods (amphibians, reptiles, birds/dinosaurs, & mammals) all have the same structure, same genetic origin, and same embryological origin – One bone-two bone-and a blob of bones (legs and arms) Tetrapod Comparison  Homology of Genetics PAX6 gene produces a transcription factor: – A Transcription factor is a RNA produce that controls how other genes are transcribed – Affects the development of eyes among bilaterian animals. As diverse as arthropods, mollusks, and vertebrates  Vestigial Structures Organs which use to have a biological function but have lost their function through time – Pilo erector muscles raise the hairs on our body. Use to be used for two functions: 1.) body warmth 2.) make us look bigger No longer can function because we lost a lot of our body hair, but the muscles are still present – Whales and some snakes till have pelvic structures from when they had 4 limbs. Whale Pelvic Structures Because whales evolved from terrestrial tetrapods, they still have the genetics for the pelvic structure. They have yet to have evolved a true tail structure. Their Fluke (the tail) is made of fat tissue.  Analogous Structures Structures which appear the same but come from different evolutionary origin. Generally have the same function. – Will have a different embryonic development and genetics – Example wings in birds and wings in insects Convergent evolution is when a particular structure is successful and evolves in separate groups of organisms – The streamlined shape of marine mammals and fish; eyes have evolved several times in several different groups  Marsupials and Placental Mammals Mammals have three main groups: the Placental, the Marsupial, and the Monotremes. Marsupials were dominant in Gondwondaland while the Placentals were dominant in Laurasia When North American and South American made contact the Placentals of Laurasia won out.  Embryonic Development Evolution can be traced through embryonic development of organisms Organisms which are more closely relate will have similar embryonic development. Fig 16.16 Homeotic: a gene which if it changes then the development of the organism change – Usually these are regulatory genes which control other genes during development of the organism the differences in humans and chimpanzees is caused by homeotic differences.  Ernst Haeckel A German naturalist of the 19th century Studied comparative embryogenesis (the embryonic development) Drew pictures of various organisms to compare with one another – Fudged his data to make his examples look more alike – Unfortunately put a negative connotation on comparative embryogenesis His research has been discarded, but replaced with more accurate research.  Comparative Molecular Biology Evolution can be traced in the DNA, RNA, and proteins of organisms Organisms with similar patterns in their DNA, RNA, and proteins are more closely related to one another – Not just functional genes, but pseudogenes and transposons as well An example is the cytochrome c gene as illustrated in fig. 12.19  Case of the missing Chromosome Humans and chimpanzees are very closely related, but humans have one less pair of chromosomes than do chimpanzees. How is this possible? Evolutionary theory would predict that humans would have a fused pair of chromosomes (two chromosomes which became one) which would match with a pair of independent chromosomes in the chimpanzee – Chromosome no. 2 in the human genome has two centromeres and a telomere (the stretch of DNA which is found on the end of chromosomes) in the center of the chromosome. This is where evolution as a theory made a prediction and it was supported with what was observed Human vs Chimpanzee Karyotype We designated two of the chimpanzee’s chromosomes as 2A and 2B, because they have the same genes as our second chromosome All of the other apes have chromosomes 2A and 2B as a part of their genome.  Vitamin C (Not in your book) Most mammals have a functional gene which allows for the individual to produce their own vitamin C. Humans and the other apes (Chimpanzees, Bonobos, Gorillas, and Orangutans) are incapable of producing their own vitamin C We all have the same gene, but it is dysfunctional. All of the great apes (including humans) have the same 6 mutations which led to the gene being dysfunctional – This is another piece of evidence which supports all the great apes have a common ancestor. – If we all had different ancestors then on would suspect that the random nature of mutations would lead to each group having their own mutations, no the same 6. Evolutionary Tree of the great apes The 6 mutations occurred before the split between the population which would become the orangutans and the population which would eventually lead to gorillas, humans, chimpanzees, and bonobos.  Molecular Clock This is a method of determining when to groups of organisms diverged from one another. Two piece of knowledge have to be met. – Rate of mutations for a particular gene Not all genes mutate at the same rate – The mutations which exist between the two individual groups of organisms If both pieces of knowledge are met, then one can argue that these two individual groups diverged from one another at a certain date Still very shaky  Darwin’s Finches Ecologists, Peter and Rosemary Grant, from Princeton university have a multi-decade research project involving the finches found in the Galapagos Island – Famously named Darwin’s Finches, though Darwin never really studied the finches as much as other birds They have seen speciation take place within the thirty years they have done their work. – They have also noticed changes in the beak structure of the finches