Principles of BiologyThe Heterotroph HypothesisPrimitive Conditions on the EarthEons of TimeSlide 5Slide 6Synthesis ReactionsSlide 8Miller's ExperimentSlide 10Aggregates of Organic MoleculesSlide 12Slide 13CoascervatesAnaerobic RespirationDevelopment of AutotrophsAerobic RespirationEndosymbiosisSlide 19Slide 20Geologic Time ScaleThe Geologic Time ScaleSlide 23Slide 24Glaciations of the QuaternaryThe Fossil RecordSlide 27Early MammalsFossil Record of Early HumansSlide 30ProconsulProconsul africanusEarly Pleistocene HominidsAustralopithecus afarensisSlide 35Slide 36Slide 37Australopithecus transvaaliensisSlide 39Slide 40Homo habilisSlide 42Middle Pleistocene HominidsHomo erectusSlide 45Slide 46Slide 47Slide 48Homo sapiens neanderthalisSlide 50The Late PleistoceneEvolutionary Trends in PrimatesSlide 53Biological TaxonomySlide 55Slide 56Topics for Third ExamThe EndPrinciples of BiologyByFrank H. Osborne, Ph. D.EvolutionThe Heterotroph Hypothesis•According to the heterotroph hypothesis, the first organisms to develop were heterotrophs.•The autotrophic organisms developed after the heterotrophic ones.Primitive Conditions on the Earth•The age of the Earth is thought to be 4.5 x 109 (4.5 billion) years. Evidence for this estimate comes from the measurement of the decay of Uranium. This time is divided into four eons. •In the earliest eon, there was a reducing atmosphere, much heat, lightning (electrical discharge), ultraviolet (UV) light from the Sun and radiation.Eons of Time Eon Duration (Millions of Years)Hadian 4500-4000Archaen 4000-2500Proterozoic 2500- 600Phanerozoic 600-TodayPrimitive Conditions on the Earth•There was no ozone layer in the earliest days of the Earth. To form an ozone layer requires oxygen. Oxygen is the waste product of photosynthesis. Photosynthesis did not develop until after the formation of the first eukaryotic cells, about 2.5 billion years ago. Therefore, without an ozone layer, UV light came all the way down to the surface.Primitive Conditions on the Earth•There are no rocks found so far that go back to the formation of the Earth. Geological processes of erosion, transport and depostion have worn away the original rocks.•There have been rocks found in Canada and Australia that are dated in the range of 3.9 - 4.1 billion years.Synthesis Reactions•A reducing atmosphere of ammonia (NH3), methane (CH4), hydrogen (H2) and water (H2O) has been shown to be able to produce such molecules as urea, hydrogen cyanide, organic acids and other molecules under laboratory conditions by random synthesis reactions with each other.Synthesis Reactions•There was no oxygen in the early atmosphere but there was some CO2 present. The molecules produced experimentally in Miller's spark discharge apparatus were similar to biological molecules. For example, amino acids were found.Miller's ExperimentAggregates of Organic Molecules•Aggregates are collections of organic molecules that may have formed along the shorelines of primitive seas where the molecules were exposed to ultraviolet light.•Radiation on rocks causes them to heat up. There is evidence that when organic molecules are heated together dry, they react.Aggregates of Organic Molecules•Fox took dry amino acids and heated them together. Water was released that condensed on the inside of the test tube at the top. This condensation resulted from reactions between the amino acid molecules. Thus the origin of the term "condensation reaction."Coascervates•Certain larger aggregates (coascervates) might have begun to divide after reaching a certain size. Experiments have shown that CH4, NH3, and H2O can yield bases like those found in DNA.Anaerobic Respiration•Fermentation is found in all cells, not only the anaerobic bacteria but even those that use aerobic respiration. So, anaerobic respiration must have developed first. The first organisms probably got their energy by fermenting organic molecules that were dissolved in the water.Development of Autotrophs•Some organisms must have developed the means by which to perform photosynthesis. The resulting release of oxygen over time led to the formation of the oxidizing atmosphere we have today.Aerobic RespirationThose organisms that could tolerate and use oxygen went on to become aerobic. It is thought that eukaryotic cells developed as a result of one kind or prokaryote living inside another.Endosymbiosis•This explanation is called the endosymbiotic theory. According to this explanation, mitochondria that we have today were originally a form of prokaryote that had a knack for producing energy.•Similarly, chloroplasts are thought to have resulted from other prokaryotes that could trap solar energy.Endosymbiosis•Evidence for this theory comes from the fact that mitochondria and chloroplasts have their own DNA molecules, independent of the DNA in the chromosomes of the nucleus of the cell. This DNA is closely related to bacterial DNA, not nuclear DNA.Endosymbiosis•Also, mitochondria and chloroplasts have their own ribosomes. These ribosomes are closely related to bacterial ribosomes and are distinctly different from the cytoplasmic ribosomes.Geologic Time ScaleGeologic Time Scale•Geologic time is divided into eras, periods and epochs.•Mainly the distinctions are based on fossil evidence.The Geologic Time Scale•Life began in the proterozoic eon, about 2.5 billion years ago.•This is also known as the Pre-Cambrian era. Each era is a subdivision of an eon. Each era is also further subdivided into periods. The periods correspond to major divisions in geologic (and biologic) history.The Geologic Time Scale•Geologists use biology as evidence for different periods. Up until the discovery of radioactivity in 1895, there was uncertainty about the age of the Earth or different layers of rocks.The Geologic Time Scale•Geologists then and now use fossils to indicate information about the age and history of various rocks. The most recent period, the one we are in now, is known as the Quaternary Period.Glaciations of the Quaternary•There were four major glaciations (ice ages) in the Quaternary period. The earliest ice age began 600,000 years ago. •Others occurred beginning at 500,000 years and 250,000 years. The last one began at 70,000 years and ended 20,000 years ago.The Fossil Record•The oldest rocks are over 3.5 billion years old. Fossils are the remains of living things or are objects that were made