16/05/2007 · Origin of Photosynthesis ..
photosynthesis A. sunlight is absorbed by chlorophyll in a leafB. carbon dioxide is taken in from the airC. water is transported from the rootsD. glucose is synthesized and distributed throughout the plantE. oxygen is released
The Origin of Photosynthesis - Astrobiology Magazine
A historical view of the buildup of atmospheric oxygen concentration since the beginning of the sedimentary record (3.7 109 ybp) can be worked out by making use of the fact that the carbon in the product of the above reaction has a slightly lower C13 content than does carbon of inorganic origin. Isotopic analysis of carbon-containing sediments thus provides a measure of the amounts of photosynthetic O2 produced at various times in the past.
Free oxygen is never more than a trace component of most planetary atmospheres. Thermodynamically, oxygen is much happier when combined with other elements as oxides; the pressure of O2 in equilibrium with basaltic magmas is only about 107 atm. Photochemical decomposition of gaseous oxides in the upper atmosphere is the major source of O2 on most planets. On Venus, for example, CO2 is broken down into CO and O2 . On the earth, the major inorganic source of O2 is the photolysis of water vapor; most of the resulting hydrogen escapes into space, allowing the O2 concentration to build up. An estimated 2 1011 g of O2 per year is generated in this way. Integrated over the earths history, this amounts to less than 3% of the present oxygen abundance. The partial pressure of O2 in the prebiotic atmosphere is estimated to be no more than 103 atm, and may have been several orders of magnitude less. The major source of atmospheric oxygen on the earth is photosynthesis carried out by green plants and certain bacteria:
implications regarding the origin of photosynthesis
The definition of photosynthesis is the process through which plants use water and carbon dioxide to create their food, grow and release excess oxygen into the air.
The process of photosynthesis produces oxygen
An ecosystem consists of the whole community of living organisms (biocenosis), the abioticcomponent of a certain environment (biotope) and their relationships.
The relationships essentially consist in a flux of substances which pass from thenon-living components to living ones and in a flux of energy which passes from thephotosynthetic organisms (plants) to the herbivorous animals, then to carnivores. Thewastes and the dead organisms are then decomposed by the micro-organisms which brake downthe substances back to simple components, in a full cycle.
1 - With a shovel in a field or in a wood, dig a square hole of about half a meter (1 1/2feet) square and about 40 cm (18") deep. Describe the non-living components of thesoil and all forms of life you find: roots, earthworms, snails, centipedes, spiders,crickets, etc. To complete the description of the ecosystem of the soil, look forinformation on the role of each of these organisms and the relationships with the otherforms of life of this environment.
2 - In similar way you have studied the soil ecosystem, you can analyze other ecosystemssuch as the ones in a forest, pond, shore, or desert.
G. and L. Durrell (2) can be useful, or there are many other books on this matter.
An Illustration of a Soil Ecosystem
Protocols for a Soil Ecosystem Approach for Characterizing Soil Biodiversity
Internet keywords: soil ecosystem.
The oxygen produced during photosynthesis comes ..
Let us see now how protists and other little animals of ponds react to alteration to theirenvironment.
1 - Some microscopic algae, like the euglena, search out light (phototaxis) and to do thisthey use an organelle sensible to the light, named stigma. With a dark paper, cover thebottom part of a test tube holding a culture of euglena. The part of the test tube exposedto light should become green, rich with algae. Make the same experiment with othermicroscopic algae and with protozoa.
2 - Add two or three drop of distilled water to a little water drop collected in a pondand watch what happens to the protists. Very probably you will see them inflate and thenexplode. This occurs because of the different saline concentration inside and outside theprotists and the osmotic pressure which is produced inside their cells.
3 - Protists are sensitive to most chemicals and generally they react by running away; insome cases instead they approach them (chemotaxis). Prepare some microscope slides withprotists and observe through the microscope their behavior when you add acidic substances(i.e.: vinegar), basic substances (i.e.: backing soda), glucose, salt, sparkling water(rich of CO2), broth, milk, tiny grain of cheese, dyes, etc. At thebeginning use very low amounts of these substances, then increase their concentration.
4 - From a pond or an aquarium, collect a hydra and place it on a microscope slide with apair of water drops. Observing this tiny polyp through the microscope, probably you willsee some sucker shaped microorganisms (trichodina) moving on its body. Watch what happensafter adding a little drop of vinegar to their water! Trichodina will escape from thehydra and probably die. Hydra itself will have launched many of its harmful paralyzingdarts.
5 - Submit protists to different stimulus such as light, temperature, electric field(about 5 V in DC). In this last case, some protists will gather on the cathode (thenegative - pole). Also amebas are inclined to move towards the cathode. Change thepolarity of the current and observe the behavior of the protists.
Internet Keyword: phototaxis chemotaxis protists.