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Transcript
Evolution Dr. James R. Whitfield, Ph.D Evolution "Nothing in Biology Makes Sense Except in the Light of Evolution” - Theodosius Dobzhansky What is Evolution? Evolution is the process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth. What is Evolution? Evolution is the process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth. Evolution is the story of the origin of life and the formation of the vast biodiversity on Earth Origin of Life The Universe is old – about 20 billion years old! Origin of Life The Universe is old – about 20 billion years old! When we look out at the stars we are looking millions of years and trillions of miles into the past Origin of Life The Universe is old – between about 14 and 20 billion years old When we look out at the stars we are looking millions of years and trillions of miles into the past However, no matter how long we look at those stars we are limited in how far back we can actually see – the light from the oldest stars simply has not had enough time to reach us yet! The Big Bang The Big Bang theory is the prevailing cosmological theory attempting to explain the origin of the Universe. The Big Bang The Big Bang theory is the prevailing cosmological theory attempting to explain the origin of the Universe. It describes a single huge explosion, unimaginable in physical terms resulting from tremendous heat and pressure The Big Bang The Big Bang theory is the prevailing cosmological theory attempting to explain the origin of the Universe. It describes a single huge explosion, unimaginable in physical terms resulting from tremendous heat and pressure As the universe continued to expand it cooled down The Big Bang This cooling allowed for the formation of subatomic particles and then simple elements such as hydrogen and helium (the two most abundant elements in the Universe today) The Big Bang This cooling allowed for the formation of subatomic particles and then simple elements such as hydrogen and helium (the two most abundant elements in the Universe today) Over the next few billions years cooling and gravity allowed for the formations of galaxies. Our galaxy – The Milky Way formed about 4.5 billion years ago The Early Earth There was no atmosphere on the early Earth The Early Earth There was no atmosphere on the early Earth Water vapor (H2Ov), ammonia (NH3), methane(CH4) , carbon monoxide (CO), and carbon dioxide (CO2) The Early Earth There was no atmosphere on the early Earth Water vapor (H2Ov), ammonia (NH3), methane(CH4) , carbon monoxide (CO), and carbon dioxide (CO2) UV light broke up the water vapor into hydrogen and oxygen. The oxygen combined with ammonia and methane to form more water, carbon dioxide and ozone (O3) The Early Earth As the planet continued to cool the water vapor continued to condense and fall as rain The Early Earth As the planet continued to cool the water vapor continued to condense and fall as rain The rain eventually filled in the depressions on the Earth forming the oceans The Early Earth As the planet continued to cool the water vapor continued to condense and fall as rain The rain eventually filled in the depressions on the Earth forming the oceans Life first appeared about 500 million years later or about 4 billion years ago HOW? The previous slide said life appeared 500 million years ago but it does not say anything about how HOW Now that’s the big question! Theories on the Formation of Life Some scientists believe that life came from outer space Theories on the Formation of Life Some scientists believe that life came from outer space The early Greeks believed that “spores” transported life from planet to planet Theories on the Formation of Life Some scientists believe that life came from outer space The early Greeks believed that “spores” transported life from planet to planet This “Theory of Panspermia” is still believed by many scientists today Theories on the Formation of Life For a long time people believed in the “Theory of Spontaneous Generation” – that life appeared form nowhere Theories on the Formation of Life For a long time people believed in the “Theory of Spontaneous Generation” – that life appeared form nowhere However Franscisco Redi and later Louis Pasteur proved that this theory was incorrect Theories on the Formation of Life Pasteur proposed the “Theory of Biogenesis” which states that, “Omne vivum ex vivo” all life come from life Theories on the Formation of Life Pasteur proposed the “Theory of Biogenesis” which states that, “Omne vivum ex vivo” all life come from life If you remember one of the principle of the modern cell theory states that, “omni cellulae e cellula” all cells come from cells Pasteur’s Experiment Theories on the Formation of Life Oparin and Haldane proposed that the frst life could have come from preexisting, non-living organic molecules (RNA, proteins, etc,..) and that the formation of life was preceded by chemical evolution Theories on the Formation of Life Oparin and Haldane proposed that the frst life could have come from preexisting, non-living organic molecules (RNA, proteins, etc,..) and that the formation of life was preceded by chemical evolution i.e., the formation of diverse organic molecules from inorganic components Theories on the Formation of Life In 1953 Stanley Miller and Harold Urey at the University of Chicago (Chicago, Illinois, USA) designed an experiment to recreate the conditions present on the early Earth in a laboratory setting Theories on the Formation of Life They created an electric discharge into a flask containing, methane, water vapor, ammonia, and hydrogen Theories on the Formation of Life They created an electric discharge into a flask containing, methane, water vapor, ammonia, and hydrogen They observed the formation of amino acids – which as we know are the building blocks of proteins, which build organelles, which build cells, … Millers Flask Theories on the Formation of Life Other researchers performing similar experiments have been able to produce, sugars, glycoproteins, and fats Theories on the Formation of Life Other researchers performing similar experiments have been able to produce, sugars, glycoproteins, and fats The theory that chemical evolution proceeded biological life is now generally accepted However However None of these experiments have answered how the first self replicating metabolic life arose However None of these experiments have answered how the first self replicating metabolic life arose Miller and Urey simply said, “given the conditions in the early atmosphere the building blocks of life could develop” But We do know that the first non-cellular “life” could have originated about 3 billion years ago But We do know that the first non-cellular “life” could have originated about 3 billion years ago That is was probably large RNA molecules, proteins and polysaccharides But We do know that the first non-cellular “life” could have originated about 3 billion years ago That is was probably large RNA molecules, proteins and polysaccharides The first cellular life did not appear until about 2 billion years ago But We do know that the first non-cellular “life” could have originated about 3 billion years ago That is was probably large RNA molecules, proteins and polysaccharides The first cellular life did not appear until about 2 billion years ago These were unicellular, prokaryotes that lived in a watery environment Biogenesis This version of biogenesis that the first form of life slowly arose through evolutionary forces from non-living molecules is generally accepted today However, this is only the beginning Biogenesis This version of biogenesis that the first form of life slowly arose through evolutionary forces from non-living molecules is generally accepted today However, this is only the beginning We now need to look at how these first unicellular organisms could have evolved into the complex biodiversity of today The Modern Theory of Evolution Many religious beliefs hold the theory of “Special Creation” The Modern Theory of Evolution Many religious beliefs hold the theory of “Special Creation” This idea of creationism is laid out in the Christian Bible in the Book of Genesis The Modern Theory of Evolution Many religious beliefs hold the theory of “Special Creation” This idea of creationism is laid out in the Christian Bible in the Book of Genesis Proponents of this theory believe that 1- All living this we see today were created as they are now – perfect and unchanged 2- The diversity we see now was as it was in the past and will be in the future 3- The Earth is about 6,000 years old (your book says 4,000) The Modern Theory of Evolution These ideas were strongly challenged based on the Work of Charles Darwin and the observations he made while travelling on the H.M.S. Beagle The Modern Theory of Evolution These ideas were strongly challenged based on the Work of Charles Darwin and the observations he made while travelling on the H.M.S. Beagle Darwin concluded that existing life forms show similarities to varying degrees not only among themselves but with long extinct life forms The Modern Theory of Evolution He further concluded that there had been extinctions of life forms in the past and that new life forms arose at various periods in the history of the Earth. The Modern Theory of Evolution He further concluded that there had been extinctions of life forms in the past and that new life forms arose at various periods in the history of the Earth. There had been a gradual evolution of life forms Darwin’s Theory Darwin theory can be summarized as Darwin’s Theory Darwin theory can be summarized as Natural selection Darwin’s Theory Darwin theory can be summarized as Natural selection Descent with Modification Darwin was Influenced by Thomas Malthus Natural Selection Natural selection states that within any population there will be built in variation. This variation will allow some individuals to survive better than other. These organisms will outbreed the other members of the population and produce more offspring with the desired characteristics Natural Selection Natural selection states that within any population there will be built in variation. This variation will allow some individuals to survive better than other. These organisms will outbreed the other members of the population and produce more offspring with the desired characteristics This is called fitness Descent with Modification Descent with modification simply means that as organisms reproduce mutations will occur. Any mutation that is beneficial and increases an organisms fitness will stay in the population. Given the immensity of time the slow accumulation of mutations will lead to the formation of new species Descent with Modification Descent with modification simply means that as organisms reproduce mutations will occur. Any mutation that is beneficial and increases an organisms fitness will stay in the population. Given the immensity of time the slow accumulation of mutations will lead to the formation of new species It does not mean that the original organism will go extinct Descent with Modification Million of years ago men and monkeys shared a common ancestor. Then a branch came we went one way but the monkeys continued on the way they were Not Accurate The Other Player Alfred Wallace was a contemporary of Darwin. He independently developed his own Theory of Evolution while working in the Malay Archipelago. Darwin was hesitant to publish his work (because of the social and political ramifications) however upon learning of Wallace’s work he felt compelled to publish first Evolution Before Darwin Prior to Darwin Evolution was discussed and tried to be explained by French Naturalist – Jean Baptiste Lamarck. Lamarck proposed that evolution was driven by use and disuse. He believed that traits could be acquired during ones lifetime and then passed on. For example, giraffes could acquire longer necks because they needed to browse high in tress. Once they got this longer neck they could pass on the trait to their offspring. This theory is no longer believed The Evidence for Evolution Fossils – the remains (of usually the hard parts or organisms) preserved in stone The Evidence for Evolution Fossils – the remains (of usually the hard parts or organisms) preserved in stone Rocks form sediment. A cross section of the Earths crust indicates the arrangement of the sediment over very long periods of time The Evidence for Evolution Fossils – the remains (of usually the hard parts or organisms) preserved in stone Rocks form sediment. A cross section of the Earths crust indicates the arrangement of the sediment over very long periods of time Different sediments contain different fossils The Evidence for Evolution Fossils – the remains (of usually the hard parts or organisms) preserved in stone Rocks form sediment. A cross section of the Earths crust indicates the arrangement of the sediment over very long periods of time Different sediments contain different fossils The Evidence for Evolution We can see that life forms vary over time, that they become extinct and that new forms of life have appeared in Earth’s history Relative vs Absolute Dating Relative dating simply states that this is older or younger than that but gives no indications as to its actual age Relative vs Absolute Dating Relative dating simply states that this is older or younger than that but gives no indications as to its actual age Absolute dating using such techniques as radioactive carbon dating, Potassium – Argon dating (K-Ar) or Uranium – Lead dating (U-Pb) uses half-life techniques to determine the absolute age of objects The Evidence for Evolution Comparative anatomy and morphology show similarities and differences between today’s organisms and those from the past The Evidence for Evolution Comparative anatomy and morphology show similarities and differences between today’s organisms and those from the past From this we can determine the presence (or lack of) a common ancestor The Evidence for Evolution Comparative anatomy and morphology show similarities and differences between today’s organisms and those from the past From this we can determine the presence (or lack of) a common ancestor Homologous structures – The forelimb pattern of whales, bats, humans and cats all show similar bone structure but have different functions The Evidence for Evolution Therefore a homologous structure is a structure that looks the same but does different things – It demonstrates a common ancestor and divergent evolution The Evidence for Evolution Analogous structures represent the opposite scenario. These are structures that look different but do the same thing. For example a bird and butterfly wing are anatomically very different but they both enable flight. This represents convergent evolution The Evidence for Evolution Similar habitats often result in the selection of similar adaptive features in different groups of organisms but toward the same function. Consider whales and sharks they have not had a similar common ancestor for tens of millions of years (or more) but because of where they live they have evolved to have similar body types The Evidence for Evolution Similarities in protein and gene function among diverse organisms give clues to common ancestry The Evidence for Evolution One argument for evolution that your book makes that most sources do not is that through artificial selection man has created new species (both plants and animals) in a few hundred years then why could it not happen in nature over a few million years Industrial Melanism The peppered moth is an example of industrial melanism. Prior to the industrial revolution in England. The white variant of the moth was most common with lesser amounts of the melanised version. The moths lived on the near-white lichens that covered the trees. As the Industrial revolution progressed the trees became black from coal-fired plants. The population of black moths increased as being this color gave them a competitive advantage (they were harder to spot) and the white moth population declined. Several years after the passage of the clean air acts as the trees returned to the normal color there was a shift once again toward white moths (Remember – no variant was totally wiped out) Vestigial Structures Vestigial Structures A vestigial structure is a structure that had a function at one time but no longer does. Some examples in humans include the wisdom teeth, pinnae cartilage of the ear and eyebrows While most people consider the appendix to be a vestigial structure there is some controversy about this Plica semilunaris Adaptive Radiation There is an expression that says, “Nature abhors a vacuum” Adaptive Radiation There is an expression that says, “Nature abhors a vacuum” This means that wherever life can exist – life will exist Adaptive Radiation There is an expression that says, “Nature abhors a vacuum” This means that wherever life can exist – life will exist Some examples of this are the plants present in the Hawaiian Islands, The finches of the Galapagos Islands and the marsupials od Australia Adaptive Radiation In each of these situations you had ancestral stock that radiated outward as various mutations allowed them to take advantage of diverse habitats – Consider how the beaks of the finches are adapted to the types of seeds found in different areas Mechanisms of Evolution Darwin was a gradualist. He believed that mutations were small and random but moved in one direction Mechanisms of Evolution Darwin was a gradualist. He believed that mutations were small and random but moved in one direction Hugo deVries was a proponent of Saltation which states that large mutations could occur rapidly, leading to the formation of a new species in a single generation Mechanisms of Evolution Stephen J. Gould proposed a theory called “Punctuated Equilibrium” which stated that organisms stayed stable for veru long periods of time and then for any number of reasons orgnaisms went through rapid periods of evolution (100,000s of years to a few million) and then returned to a period of stability for many millions of years Hardy – Weinberg Equilibrium Hardy-Weinberg can be used to determine the frequency of a particular allele in a population Hardy – Weinberg Equilibrium Hardy-Weinberg can be used to determine the frequency of a particular allele in a population Hardy-Weinberg provides a snapshot of that population Hardy – Weinberg Equilibrium HWE states that the alleles in a population will remain constant from generation to generation in the absence of other evolutionary influences. Hardy – Weinberg Equilibrium Hardy-Weinberg requires a variety of conditions to be met in order for it to be used (as you will see HWE) is more of an intellectual exercise than an actual thing. HWE requires that Hardy – Weinberg Equilibrium Populations be large Hardy – Weinberg Equilibrium Populations be large That there be no immigration or emigration from the population Hardy – Weinberg Equilibrium Populations be large That there be no immigration or emigration from the population All mating’s be random (No mate selection) Hardy – Weinberg Equilibrium Populations be large That there be no immigration or emigration from the population All mating’s be random (No mate selection) There are no mutations Hardy – Weinberg Equilibrium Populations be large That there be no immigration or emigration from the population All mating’s be random (No mate selection) There are no mutations All organisms are equally fit Hardy – Weinberg Equilibrium HWE – is an algebraic formula that states: p + q =1 where p2 + 2pq + q2 = 1 So if p = represents the Homozygous dominant phenotype, pq represents the heterozygous phenotype and q represents the recessive phenotype, then Hardy – Weinberg Equilibrium .6 + .4 = 1 and (.6)2 + 2(.6)(.4) + .42 = 1 .36 + .48 + .16 = 1 Therefore 36% of the population is AA 48% of the population is Aa 16% of the population is aa A change in the frequency of the alleles in the population would be interpreted as evolution