Oxygen and Life

Bio Lab 101 Smithsonian Laboratory Early Atmosphere 1. How abundant was oxygen in the early atmosphere? The earth’s early atmosphere contained only small amounts of free oxygen, produced by the reaction of water vapor with sunlight. The oxygen rich atmosphere that developed later and on which oxygen breathing life now depends was result of the origin and spread of organisms capable of photosynthesis. 2. What evidence do scientists have that the oxygen content of our atmosphere has increased since the earth’s origin?By looking at the rustiness of ancient rocks, scientists attempt to trace the evolution of oxygen in the atmosphere. 3. Why is oxygen more abundant in the atmosphere today? spread of organisms that did photosynthesis. 4. What are stromatolites? stramolites are laminated mound like structures that generally form in shallow water through the growth of microscopic blue-green algae and bacteria. 5. What do scientists think is implied by the presence of stromatoli tes in Precambrian rock?May of the algae and bacteria that build modern stramolites are photosynthesis. 6. What is ozone and how is it produced? Ozone screens out most of the ultra violet radiation from the sunlight. Ozone forms through the action of ultra violet radiation on oxygen in the upper atmosphere and many scientist reason that their layer could have formed only after oxygen from photosynthesis began to accumulate. 7. Why is the ozone important to life today? The ozone is important to life because it acts as a shield from the harmful effects of direct radiation. . What effect did increased levels of oxygen in the atmosphere have on early life forms? Created a threat because of the early life form because their environment polluted by their oxygen reducing neighbors whose internal chemistries could resist oxygen toxic free. Banded Iron Formation 1. What is banded iron Rock that contains oxidized iron, iron chemically combined with oxygen. 2. When did these formations become common? Formed in ancient years. About 2. 2 billion years ago. 3. What is the significance of these formations?Pebbles and cobbler show that liquid water was present on the surface of the earth, and ion oxides indicate free (uncombined) oxygen was also present, though at very low levels. The Oldest Rocks: Remnants of a Youthful Earth 1. How old are the oldest rocks on earth? The oldest rocks on earth date back to 3800 million years ago. 2. What evidence of life do these ancient rocks contain? the presence of oxygen to the activity of oxygen producing organisms, therefore life was far along. 3. Is this evidence great enough to allow scientists to conclude that life indeed existed during this period?No because the physical processes in the atmosphere could also have produced free oxygen and in some rocks residues that contain carbon have a make up similar to living matter but these residues to may have purely chemical origin. The Earliest Traces of Life 1. When do scientists think lif e originated on Earth? Between 4600 million years ago to 3500 million years ago. 2. What are the oldest fossils and how old are they? The oldest fossils on record are stromatolites, which date back to 3500 million years ago. The Precambrian 1.When did the first cells with nuclei appear? 3800 million years ago 2. Fossils of multicellular animals are from what time period? The fossils of multicellular animals date back to the Precambrian time period. 3. In what era did all of these events take place? The events listed above took place at the beginning of the Cambrian period to the end of the Paleozoic era. Origin of Life 1. What elements are most prevalent in living organisms? The six elements most prevalent in living organisms are carbon, hydrogen, nitrogen, oxygen, phosphorous and sulfur. . Were these elements present in the infant solar system? The only element out of the six listed above that was present in the infant solar system was hydrogen. It also had helium. 3. What circumst ances may have fostered the development of chains of amino acids and nucleotides? The circumstances that may have played a part in the development of these chains were the conditions in which they were formed. They formed in small ponds that periodically heated and dried, leaving traces of these water molecules that would play a part in producing the chains. . What are the characteristics of the ancestors of living cells and what could they â€Å"do†? The ancestors of living cells, also known as the â€Å"forerunners†, were single celled, with a ring shaped coil of DNA. They would gather into clumps, absorb smaller molecules, rearrange them, and released them as waste products. 5. Why is water important to life? Water is the medium in which biochemical reactions occur, playing an extreme importance in creating and sustaining life here on earth. 6. What are the â€Å"true† hallmarks of life? omplicated network of energy producing an energy consuming reactions plu s the ability of the entire system plus the ability of the entire system to produce itself was the hallmark of true life. 7. What molecular evidence do scientists have that all life is at least distantly related and has a common ancestor? The possible varieties of proteins are virtually unlimited even for the primitive proteins life ferredoxin. If one calculates the possible combinations of percent amino acids along a ferredoxin chain of fifty four links the result is a number more potential variations than there are atoms in the known universe.Drspite the vast possibilities portions of amino acids sequences are similar or even identical in proteins from organisms as dissimilar as humans being and bacteria. Since it is unlikely that this could occur by chance, scientist interpret this to mean that all life is at least distantly related and shares common origin. 9. What conditions are thought to have existed on primitive earth that favored the origin of life? The conditions on primit ive earth that favored the origin of life included an atmosphere rich in carbon dioxide and water vapor.Also, hot springs and small bodies of water formed the chemical building blocks of life. Single Celled Life 1. What are cherts? Cherts are sedimentary rocks that are fine grained, silica rich microcrystalline, cryptocrystalline, or micro-fiborous that contain fossils. 2. How old are these fossils? The fossils within cherts are between 2100 and 1800 million years old. 3. Were these prokaryotic or eukaryotic? These fossils within cherts are prokaryotic. 4. What evidence for eukaryotic (and possibly multicellular) life is found in the Greyson shale?The evidence for multicellular/eukaryotic life within the Greyson shale is found in the dark features of a samples surface. They are large, organized, and in a spiral shape, which represent the characteristics left behind of a eukaryotic organism. 5. How old is the shale? The shale is 1300 million years old. Multi-celled Life 1. Describe t he Ediacaran Fauna: Fossils of soft bodied organisms that lived mre than 570 million years ago occur in the sandstone deposit on the edicora hills of South Australia. 2. How old are these fossils? The fossils within the Ediacara Fauna are 570-670 million years old.