7 - Evolution of Life in PPT - Department of Physics

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STEPS IN THE ORIGIN OF LIFESIMPLE ORGANIC MOLECULES (MONOMERS) WERE PRODUCED VIA CHEMICAL REACTIONS AND/OR DELIVERED VIA COMETARY IMPACTS. SIMPLE ORGANIC MOLECULES COMBINED TO MAKE LONG POLYMERS SOME OF THE LONG POLYMERS MUST HAVE BEEN SELF-REPLICATING (LIKE DNA). POLYMERS WERE ENCLOSED INSIDE A “CELL” THAT WAS SEPARATED FROM ITS ENVIRONMENT BY A MEMBRANE.

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MUTATIONSCHANGES IN THE SEQUENCE OF BASES IN DNA DUE TO MISTAKES IN DNA REPLICATION. THESE INCLUDE: A MISTAKE IN WHICH THE WRONG BASE IS INSERTED INTO A GROWING DNA STRAND. FOR EXAMPLE, IF THERE IS A C IN THE TEMPLATE STRAND, A G SHOULD BE ATTACHED TO IT, BUT AN A MAY BE ATTACHED INSTEAD. THE C AND A WON'T STICK TOGETHER AS WELL AS THE C AND G WOULD. A SINGLE BASE THAT IS ADDED OR DELETED A SEQUENCE OF SEVERAL BASES THAT IS DUPLICATED OR DELETED NOTE: IF BASES ARE ADDED OR DELETED, THIS CAUSES THE STRAND WITH MORE BASES TO LOOP OR BULGE OUTWARD FROM THE OTHER STRAND.

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MUTATIONSMUTATIONS OCCUR BECAUSE OF: RANDOM MISTAKES LESS OFTEN THAN ONCE PER BILLION BASES EXPOSURE TO: HIGH ENERGY PHOTONS (ULTRAVIOLET, X-RAYS, OR GAMMA RAYS)‏ OTHER HIGH ENERGY PARTICLES CERTAIN CHEMICALS (“MUTAGENS”)‏

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MUTATIONSWHAT IS THE EFFECT OF A MUTATION? REMEMBER THAT THE DNA IS PART OF A GENE THAT CODES FOR A PARTICULAR PROTEIN. THEREFORE, WHAT IS THE EFFECT ON THE PROTEIN? SOMETIMES THERE IS NO EFFECT AT ALL ON THE PROTEIN BECAUSE OF THE REDUNDANCY IN THE GENETIC CODE. (RECALL THAT SEVERAL CODONS OFTEN CODE FOR THE SAME AMINO ACID.)‏ SOMETIMES A SINGLE AMINO ACID IS REPLACED BY A DIFFERENT AMINO ACID. SOMETIMES A WHOLE STRING OF AMINO ACIDS ARE REPLACED BY DIFFERENT ONES. ADDITIONALLY, SOMETIMES THERE IS A CHANGE IN THE WAY THE PROTEIN IS FOLDED. (THIS IS CAUSED BY A CHANGE IN THE AMINO ACID SEQUENCE.) PRODUCTION OF THE PROTEIN MAY BE STOPPED ALTOGETHER.

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MUTATIONSSOME MUTATIONS HAVE IMPORTANT EFFECTS, AND OTHERS DO NOT. OF THOSE THAT DO HAVE IMPORTANT EFFECTS: MOST RESULT IN CHANGES ARE HARMFUL TO THE ORGANISM BECAUSE A PROTEIN DOESN'T FUNCTION PROPERLY. AS A RESULT, THE ORGANISM MAY DIE, OR BECOME SICKER, WEAKER, SLOWER, DUMBER, OR LESS ATTRACTIVE TO THE OPPOSITE SEX. HOWEVER, OCCASIONALLY A MUTATION IS BENEFICIAL TO THE ORGANISM, BECAUSE THE ALTERED PROTEIN DOES A BETTER JOB OR CAN TAKE ON SOME NEW ROLE. THIS CAN MAKE THE ORGANISM HEALTHIER, STRONGER, FASTER, SMARTER, OR MORE ATTRACTIVE TO THE OPPOSITE SEX.

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MUTATIONSDO MUTATIONS GET PASSED ON TO AN ORGANISM'S OFFSPRING? FOR MUTATIONS THAT HAPPEN IN MOST CELLS OF A MULTICELLULAR ORGANISM, THE ORGANISM ITSELF MAY BE AFFECTED (CANCER, FOR EXAMPLE), BUT THE CHANGE IS NOT PASSED ON TO THE ORGANISM’S OFFSPRING. IF A MUTATION HAPPENS IN AN EGG OR SPERM CELL OF A MULTICELLULAR ORGANISM, OR IN A SINGLE-CELLED ORGANISM, THEN IT IS PASSED ON TO THE ORGANISM’S SUBSEQUENT OFFSPRING.

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EVOLUTION THE RESULT OF MUTATIONS THAT HAVE BEEN PASSED ALONG TO OFFSPRING, AND THEN ARE OPERATED ON BY NATURAL SELECTION NATURAL SELECTION: IF THE MUTATION IS HARMFUL, THE ORGANISM HAS REDUCED REPRODUCTIVE SUCCESS. IT MAY DIE BEFORE REPRODUCING AT ALL, OR HAVE FEWER OFFSPRING, OR HAVE OFFSPRING THAT DIE , ETC. AS A RESULT, THE MUTATION TENDS TO BE “SELECTED AGAINST” OR WEEDED OUT OF THE POPULATION. IF THE MUTATION IS BENEFICIAL, THE ORGANISM HAS GREATER REPRODUCTIVE SUCCESS. IT HAS A LARGER NUMBER OF OFFSPRING, OR OFFSPRING THAT ARE HEALTHIER OR MORE LIKELY TO SURVIVE AND REPRODUCE THEMSELVES. AS A RESULT, THE MUTATION IS “SELECTED FOR” OR PREFERENTIALLY RETAINED IN THE POPULATION.

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EVOLUTION AS A RESULT OF NATURAL SELECTION, ORGANISMS OFTEN BECOME STRONGER, FASTER, OR MORE INTELLIGENT WITH TIME. ORGANISMS WITH APPROPRIATE MUTATIONS CAN OFTEN MOVE INTO NEW ENVIRONMENTS THAT THEIR ANCESTORS COULD NOT LIVE IN. WHEN ENOUGH ORGANISMS WITH SIMILAR MUTATIONS ACCUMULATE WITHIN A GROUP, THEY CAN BRANCH OFF TO EVENTUALLY FORM A NEW SPECIES (ESPECIALLY IF THEY HAVE MOVED INTO A NEW ENVIRONMENT). REMEMBER THAT SOME MUTATIONS ARE NEITHER BENEFICIAL NOT HARMFUL. THESE LEAD TO VARIATION AMONG INDIVIDUALS WITHIN A SPECIES, IN TERMS OF CHARACTERISTICS LIKE EYE COLOR, HAIR COLOR, AND SKIN COLOR.

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EVIDENCE FOR EVOLUTION OBSERVATIONS “AFTER THE FACT” OF THE EFFECTS OF EVOLUTION: CLOSELY RELATED SPECIES OCCUPYING DIFFERENT ENVIRONMENTS – APPEARS THAT THEY HAD A COMMON ANCESTOR EXAMPLE: FINCHES IN GALAPAGOS ISLANDS OBSERVED BY DARWIN SIMILARITIES IN DNA SEQUENCES BETWEEN RELATED SPECIES – THE CLOSER THE EVOLUTIONARY RELATIONSHIP, THE MORE SIMILAR THE DNA SEQUENCES EXAMPLE: HUMANS SHARE 98% OF OUR DNA SEQUENCES WITH CHIMPANZEES MANY MORE, TOO NUMEROUS TO LIST

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EVIDENCE FOR EVOLUTION OBSERVATIONS OF EVOLUTION OPERATING IN “REAL TIME”: COLD VIRUSES ONCE YOU RECOVER FROM A COLD, YOU ARE THEN IMMUNE TO FUTURE INFECTIONS BY THAT SAME VIRUS. SOMETIMES, YOU MAY GET A COLD, PASS IT ON TO FRIENDS OR RELATIVES, AND THEN GET IT BACK FROM ONE OF THEM. THIS COULDN'T HAPPEN UNLESS THE COLD VIRUS HAD MUTATED OR EVOLVED. DEVELOPMENT OF ANTIBIOTIC RESISTANCE IN BACTERIA WHEN BACTERIA ARE EXPOSED TO AN ANTIBIOTIC, MOST ARE KILLED. THOSE BACTERIA WITH A MUTATION GIVING THEM RESISTANCE PREFERENTIALLY SURVIVE AND REPRODUCE. EVENTUALLY MOST OF THE BACTERIA ARE RESISTANT TO THE ANTIBIOTIC. (OVERUSE OF ANTIBIOTICS HAS MADE THIS PROBLEM MORE SERIOUS.)

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EVIDENCE FOR EVOLUTION OBSERVATIONS OF EVOLUTION OPERATING IN “REAL TIME”: CHANGE IN COLORATION OF MOTHS IN EUROPE DURING THE INDUSTRIAL REVOLUTION MOTHS WERE ORIGINALLY LIGHT-COLORED IN ORDER TO BLEND IN WITH LIGHT-COLORED TREE TRUNKS ON WHICH THEY RESTED. POLLUTION FROM BURNING COAL MADE TREE TRUNKS DARKER IN COLOR, AND PREDATORS COULD MORE EASILY SEE AND EAT LIGHT-COLORED MOTHS. MOTHS WITH A MUTATION FOR DARKER COLOR PREFERENTIALLY SURVIVED AND REPRODUCED, UNTIL MOST MOTHS WERE DARK-COLORED. NOTE: “REAL TIME” OBSERVATIONS OF EVOLUTION IN ACTION ARE VERY DIFFICULT TO MAKE FOR “HIGHER” ORGANISMS THAT REPRODUCE SLOWLY. THEY ARE MORE APPARENT IN ORGANISMS THAT REPRODUCE QUICKLY.

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DIVERSITY OF LIFE ON EARTHTHE RESULT OF EVOLUTION IS AN ENORMOUS DIVERSITY OF SPECIES. HOW ARE LIVING ORGANIMS CLASSIFIED? THE CLASSIFICATION SCHEME SHOULD TELL US SOMETHING ABOUT HOW VARIOUS SPECIES EVOLVED.

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CLASSIFICATION OF LIFELIVING THINGS ARE CLASSIFIED BY: (IN ORDER FROM MOST GENERAL TO MOST SPECIFIC)‏ CELL TYPE DOMAIN KINGDOM PHYLUM CLASS ORDER GENUS SPECIES LET’S LOOK AT CELL TYPES, DOMAINS, AND KINGDOMS, THE MOST BASIC OR MOST GENERAL CATEGORIES.

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TWO CELL TYPESPROKARYOTIC CELLS MANY (BUT NOT ALL) SINGLE-CELLED ORGANISMS ARE OF THIS CELL TYPE CELL HAS NO NUCLEUS OR ORGANELLES DNA FORMS A SINGLE STRAND OR LOOP CELLS ARE USUALLY SMALLER EUKARYOTIC CELLS SOME SINGLE-CELLED ORGANISMS AND ALL MULTICELLULAR ORGANISMS (INCLUDING ALL ANIMALS AND PLANTS) ARE OF THIS CELL TYPE CELL HAS A NUCLEUS AND ORGANELLES DNA IN CHROMOSOMES IN THE NUCLEUS CELLS ARE USUALLY LARGER

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ORGANELLES STRUCTURES WITHIN A EUKARYOTIC CELL THAT ARE SEPARATED FROM THE REST OF THE CELL BY MEMBRANES. THESE INCLUDE: MITOCHONDRIA CARRY OUT CHEMICAL REACTIONS THAT RELEASE ENERGY PROVIDE A SOURCE OF ENERGY FOR THE CELL FOUND IN ALL EUKARYOTIC CELLS CHLOROPLASTS FOUND IN CELLS OF PLANTS (BUT NOT ANIMALS)‏ CARRY OUT PHOTOSYNTHESIS CO2 + H20  O2 + FOOD

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MITOCHONDRIA AND CHLOROPLASTSCONTAIN DNA THAT IS SEPARATE FROM THE DNA IN THE NUCLEUS. MITOCHONDRIAL DNA AND CHLOROPLAST DNA THIS DNA CONTAIN FUNCTIONAL GENES THIS DNA REPLICATES ITSELF WHEN THE CELL DIVIDES THE SEQUENCE OF BASES IN MITOCHONDRIAL DNA RESEMBLES THOSE IN CERTAIN BACTERIA. THIS PROVIDES A CLUE TO THE EVOLUTIONARY ORIGIN OF ORGANELLES.

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MITOCHONDRIA AND CHLOROPLASTSPROKARYOTIC CELLS ARE SIMPLER THAN EUKARYOTIC CELLS. THEREFORE, THE FIRST CELLS WERE UNDOUBTEDLY PROKARYOTIC. HOW DID THE FIRST EUKARYOTIC CELLS EVOLVE? AN IMPORTANT STEP WAS THE ORIGIN OF MITOCHONDRIA AND CHLOROPLASTS. THEORY: ONE PROKARYOTIC CELL WAS ABSORBED BY ANOTHER (THIS IS HOW THEY EAT) OR INVADED THE OTHER (PERHAPS TO INFECT IT WITH A DISEASE). PORTIONS OF THE CELL THAT WAS ABSORBED REMAINED IN THE “HOST” CELL AS MITOCHONDRIA OR CHLOROPLASTS. THE ENERGY PROVIDED BY THE ORGANELLE GAVE THE HOST CELL A SELECTIVE ADVANTAGE.

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THREE DOMAINS OF LIFE PROKARYOTIC CELLS SINGLE-CELLED SOME CARRY OUT PHOTOSYNTHESISPROKARYOTIC CELLS SINGLE-CELLED INCLUDES MANY EXTREMOPHILESCELLS ARE EUKARYOTIC INCLUDES BOTH SINGLE-CELLED AND MULTICELLULAR ORGANISMS INCLUDES ALL “HIGHER” ORGANISMS NOTE: DNA EVIDENCE SUGGESTS THAT ORGANELLES IN EUKARYOTIC CELLS PROBABLY RESULTED FROM BACTERIA THAT WERE ABSORBED BY ARCHAEA

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CLASSIFICATION OF LIFETWO CELL TYPES PROKARYOTIC CELLS (SIMPLER)‏ EUKARYOTIC CELLS (MORE COMPLEX)‏ THREE DOMAINS BACTERIA (PROKARYOTIC CELLS)‏ ARCHAEA (PROKARYOTIC CELLS)‏ EUKARYA (EUKARYOTIC CELLS)‏ FIVE KINGDOMS WITHIN DOMAIN EUKARYA PROTISTA (SINGLE-CELLED EUKARYOTES)‏ MONERA (SINGLE-CELLED EUKARYOTES)‏ FUNGI (MULTICELLULAR EUKARYOTES)‏ PLANTS (MULTICELLULAR EUKARYOTES)‏ ANIMALS (MULTICELLULAR EUKARYOTES)‏ FURTHER SUBDIVIDED INTO PHYLA, CLASSES, SPECIES, ETC.

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CAMBRIAN EXPLOSIONAN ENORMOUS AND SUDDEN INCREASE IN THE DIVERSITY OF LIFE ON EARTH ALL BASIC “BODY PLANS” AMONG ANIMALS, SUCH AS CHORDATES (INCLUDES VERTEBRATES) AND ARTHROPODS (INCLUDES INSECTS AND CRUSTACEANS) DEVELOPED THEN LASTED FROM ABOUT 545 TO 500 MILLION YEARS AGO WHY? MAYBE OXYGEN LEVELS IN THE ATMOSPHERE REACHED A CRITICAL LEVEL NEEDED TO PROVIDE ENOUGH ENERGY FOR MORE COMPLEX ORGANISMS “SNOWBALL EARTH” PERIOD ENDED, AND WARMING OF EARTH OPENED UP NEW ECOLOGICAL NICHES MAYBE GENETIC COMPLEXITY OF ORGANISMS REACHED A CRITICAL LEVEL, ALLOWING MANY NEW MUTATIONS AND RESULTING VARIATION MAYBE ALL OF THE ABOVE

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CHRONOLOGY OF LIFE ON EARTH4.0-4.6 BYA CHEMICAL EVOLUTION, NO LIFE YET 3.8-4.2? FIRST PROKARYOTIC CELLS 3.6 BACTERIA / ARCHAEA SPLIT 2.1 FIRST EUKARYOTIC CELLS 2.0-2.4 OXYGEN LEVEL IN ATMOSPHERE STARTS TO RISE GRADUALLY 1.0 FIRST MULTICELLULAR ORGANISMS

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CHRONOLOGY CONTINUED545 MYA ”SNOWBALL EARTH” ENDS, OXYGEN LEVEL BECOMES CLOSE TO CURRENT LEVEL, CAMBRIAN EXPLOSION 475 FIRST PLANTS ON DRY LAND 400 FIRST AMPHIBIANS 300 FIRST REPTILES 250 FIRST MAMMALS 65 EXTINCTION OF LARGE DINOSAURS 2-6 AUSTRALOPITHECUS (HUMAN ANCESTOR)‏ 100 TYA HOMO SAPIENS, MODERN HUMANS

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Last Updated: 8th March 2018

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