Origin of Life There is no unanimous agreement on a theory about the origin of life. Any record would have been erased during the long history of turmoil on the Earth's surface.
Origin of Life There is no unanimous agreement on a theory about the origin of life.
However, it is known that it must have happened between 4. Some relevant information about this subject is presented in the followings: The Environment - Four and a half billion years ago, the proto-Earth was completing its formation.
It was still covered with a thick layer of molten lava. A grazing collision occurred with the subsequent appearance of a transient ring around the Earth that rapidly become the Moon. Small cometary impacts persisted until about four billion years ago. The still dense atmosphere had time to stabilize and slowly cool, above oceans which were at first very hot, then tepid.
The number of lagoons and shallows, alternately covered and uncovered by the ebb and flow of the seas, was very great, because the tides were gigantic with the Moon at least three times closer than at present.
There was Figure Origin of Life [view large image] only one place of constancy and nourishment - a warm spring in the relative safety of the deep ocean floor. It was the only habitable zone at that time for very simple life. The Materials - The raw materials in the atmosphere of early Earth consisted mainly of nitrogen and traces of other molecules as shown in Figure a.
The oxygen concentration started to rise only at about 3. The composition is markedly different from those exist in the atmosphere of the outer planets see Table and in the inter-stellar molecular clouds where hydrogen is the dominant constituent.
Figure b shows the Figure a Atmospheric Composition Figure b Prebiotic Materials progression from inorganic molecules to simple organic molecules, to more complex organic compounds and eventually toward life.
Another essential ingredient is water. It is the fluid that transports the molecular components from one place to another and facilitates the chemical reactions that keep life going. Water serves as a supporting and cleansing fluid, bearing nutrients to where they are needed and taking away wastes.
Furthermore, water is the general purpose solvent for dissolving organic molecules.
If molecules are to be broken down and reconstructed in a controlled way, if information codes are to be translated into working molecules and if information storages are to persist over a long period, only water can satisfy the requirement of providing such a solution in the ranges of temperature and pressure on Earth.
Recent researches indicate that the hydrogen bonds in water may play a role on the folding of proteinand the binding of protein to DNA. The high water content in our body has suggested to many biologists that life on Earth arose in the oceans.
In fact, there is a rough correspondence between the content of such elements as calcium and potassium in seawater and in blood and tissues. It is thought that living systems tend to incorporate the primitive environment, so that their internal surroundings would tend to resemble the familiar conditions of the early history of life, a possibility first glimpsed by the 19th century French physiologist Claude Bernard.
Figure a Water [view large image] In Stanley Miller mixed substances such as water, molecular hydrogen, methane, and ammonia in a flask. After passing electrical discharge as input energy to this mixture, the assembly rearranged into a host of organic molecules as shown in Figure b including amino and nucleic acids - the building blocks of life.
Since the experimental environment is not exactly the same as the atmosphere of the early Earth note the presence of CO2it could be that those organic molecules were produced in either localized spots on Earth where the Figure b Prebiotic Chemistry [view large image] chemical composition may be different from the global environment, or they might come from outer space.
For example, the Murchison meteorite 1 contains similar organic matter as produced in the experiment. Note that glycine and alanine are the most abundant amino acids in both cases.
Recent research indicates that they are probably the earliest building blocks for life. Meanwhile, astronomers have detected more than different kinds of organic molecules by in the giant molecular clouds where stars and planets are born.
These range from the simple two-atom molecules such as nitric oxide NOto the large cyanopentacetylene HC11N with chain of 11 carbon atoms. Bythe number of molecular species found in space has increased to about by various means of detection Figure c.
It is not known how some of the more complicated arrangements can be formed in the cold-dark inter-stellar space. One suggestion proposes quantum tunneling to overcome the energy barrier in the process of formation. Figure c Molecules in Space [view large image] The materials of life can be summarized into one category - the reduced organic compounds.
The process of reduction stores energy while the carbon in organic substance provides a versatile building block. There are many theories on the source of such materials, such as lightning in the atmosphere, and delivery by comets as discussed above.
Another suggestion is from the hydrothermal vents located near the mid-ocean ridge. Hydrocarbons are produced when CO2 in ocean water meets H2 in the spring water from the mould Figure d according to the formula:As human beings, we need to eat living things for energy.
Other organisms are able to make their own food. Autotrophs can provide energy sources for themselves as well as for those of us who can't. Calcification A dry environment soil-forming process that results in the accumulation of calcium carbonate in surface soil layers. Calcite Mineral formed from calcium nationwidesecretarial.com mineral found in limestone.
Calcium Carbonate. Microbial metabolism is the means by which a microbe obtains the energy and nutrients (e.g. carbon) it needs to live and nationwidesecretarial.comes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics.
The specific metabolic properties of a microbe are the major . Organisms are placed into these categories based on similarities or common characteristics. Some of the characteristics that are used to determine placement are cell type, nutrient acquisition, and reproduction.
The two main cell types are prokaryotic and eukaryotic nationwidesecretarial.com types of nutrient acquisition include photosynthesis, absorption, and ingestion.
Microbial metabolism is the means by which a microbe obtains the energy and nutrients (e.g. carbon) it needs to live and nationwidesecretarial.comes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics. The specific metabolic properties of a microbe are the major factors in determining that microbe's ecological niche.
The glossary that follows assumes a definition of ecology--the study of interactions between organisms and their environment--much wider than what fits under the field's habitual statistical nationwidesecretarial.cominism and ecopsychology are mentioned, for example, as are terms from organic gardening and permaculture.