Life on Earth 1 Flashcards
Discuss the implications of the existence of organic molecules in the cosmos for the origin of life on Earth.
Murchison Meteorite, VIC, Aus, 1969.
- 19/92 amino acids identified were also found on Earth.
- This suggested that the source of organic molecules for the origin of life originated from outside the earth.
- However, there is still very little evidence for the existence of organic molecules in the universe or cosmos.
The theories presented by Haldene and Oparin in 1923 did not provide much evidence for the existence of organic molecules until the experiments of Urey and Miller in 1953. Although it is was proved that organic molecules could be formed from inorganic molecules, there is still no evidence for the mechanism that forced complex organic compounds to change to early life forms.
Identify the relationship between the conditions of early earth and origin of organic molecules.
The early earth was a hostile environment. Due to the high temperatures at the earth’s centre and volcanic activity, there was much outgassing of toxic molecules, some of which being water, methane (CH4), Ammonia (NH3), Hydrogen (H2), Nitrogen (N2) and Carbon Dioxide (CO2).
The atmosphere was anoxic - no free oxygen. All oxygen were bound within compounds such as water and carbon dioxide. This also lead to no ozone layer, allowing UV light to penetrate earth.
Early earth’s atmosphere:
- water vapour
- hydrogen
- methane
- ammonia
These provided the environment for the formation of organic molecules. The sun, lightning and hot springs, volcanoes, radioactivity in the crust and impact of meteorites provided energy.
Organic molecules are thought to form 4 bya and became the building blocks of life.
These molecules react rapidly with oxygen. If oxygen had been initially present at the start of their formation, the molecules would have reacted too quickly and not built up in the concentrations necessary for the formation of larger molecules.
Describe two scientific theories relating to the evolution of the chemicals of life and discuss their significance in understanding the origin of life.
Special creation: whereby everything was created by a supernatural force i.e. God. Science cannot disprove or prove this as this event cannot be repeated in experimentation or observed.
Comozoan/panspermia: life arrived from Earth from somewhere else.
- It is thought that Earth was heavily bombarded by meteorites in the past.
- Tests have shown that various organic molecules and amino acids are present in some meteorites.
- The Murchison Meteorite contained 19 amino acids that resembled some of Earth’s.
Biochemical evolution/ chemosynthetic theory: where life originated on Earth.
- Haldane and Oparin (1923) suggested that organic molecules could be formed from inorganic molecules.
- The oceans with lightning were an organic soup.
- Urey and Miller (1953) made an experiment that simulated the conditions of what early Earth was like to see if organic molecules could be formed from inorganic molecules. It was a success.
Gather information from secondary sources to describe the experiments of Urey and Miller and use the available evidence to analyse the:
- reason for their experiments
- the results for their experiments
- the importance of their experiments in illustrating the nature and practice of science
- contribution to the hypothesis about the origin of life
Also describe the significance of the Urey and Miller experiments in the debate on the composition of the primitive atmosphere.
Experiment apparatus:
A closed system was set up and powerful electric sparks were discharged into a glass chamber containing ammonia, hydrogen and methane. Water vapour from another glass chamber of water that was being boiled entered the glass chamber with the gases and electric sparks as it evaporated. As it condensed, it was collected into a separate flask. The resulting substance was tested after one week of continuous cycling.
Reason for experiments:
- to support and test the theories of Oparin and Haldene about the components of Earth’s early atmosphere and to see whether organic molecules could be formed from inorganic molecules.
Results of experiments:
- Organic molecules and amino acids were formed from inorganic molecules.
Importance of experiment in showing how science is done:
- there needs to be quantitive proof to prove theories
- numerous organic molecules were produced in a simulated experiment which modelled the theory
Contribution to the hypothesis about the origin of life on Earth:
- Supported Haldene’s and Oparin’s theories about early Earth’s atmosphere and that complex organic molecules (which may be the origin of life on Earth) can be produced naturally from inorganic molecules
Identify changes in technology that have assisted in the development of an increased understanding of the origin of life and evolution of living things.
Electron microscope development: lead to the understanding of structures at a molecular level, the remains of micro-organisms and mineral nature of early rocks.
Radiometric dating: the principle of superposition, stratigraphic correlation. Developed for dating the relative ages of fossils and surrounding rock material.
Seismology: provided knowledge about the structure of the Earth and the characteristics of earthquakes.
Geology: determined the position of meteorites and volcanoes, the fossil record and geological history of the Earth.
Geophysics: used the concept of continental drift and sea floor spreading (magnetic surveys) to indicate properties of the Earth’s structure and age.
Atomic absorption spectrophometry: used to measure the concentration of metal elements in rock materials relative proportions of stable isotropes - determines absolute age of fossils.
X-ray crystallography: determines the structure of an immense variety of molecules and compounds.
Radioactive tracing: measures the speed of chemical processes.
Gas and liquid chromotology: chemical separation technique. Used to isolate molecules for further study.
Engineering developments: enabled space and deep sea exploration.
Amino acid and nucleotide sequencing: comparisons with ancient organic material and present biological compounds.
Biochemical analysis: DNA. Comparative studies of different organisms.
Genetic engineering: used to increase understanding of relatedness between organisms and possibly evolutionary pathways.
Samples from outer space: analysis has led to theories about the origin of life on earth and enabled examination for possible origins of organic molecules.
