ADDENDA
i) The Roles of Photosynthesis.
Photosynthesizers have played a vital role in the Earth's life support system. They have:-- * extracted Carbon from the atmosphere;
- * released oxygen into the atmosphere;
- * preserved water on Earth;
- * created sedimentary rocks;
- * created the stratospheric ozone layer;
- * disposed of Wildlife wastes and created fertile soils;
- * provided food for a vast array of Wildlife;
- * formed habitats for an increasingly fabulous biodiversity; and,
- * stabilized the climate.
ii) The Photosynthetic Common Denominator.
The common denominator between the white cliffs of dover, concrete, plastics, banded iron formations, the himalayas - is that they were all made by Photosynthesis.
iii) The Various Types of Photosynthesizer.
The Earth's Photosynthesizers consists of Bacteria (in the oceans, wetlands, topsoil), Algae (in the oceans) - Coral reefs; Plants - Grasses (both terrestrial and marine), Trees (terrestrial and mangrove); and some Animals.I: Prokaryotic (Bacterial) Photosynthesizers.
The first Photosynthesizers were oceanic bacteria which derived their hydrogen from hydrogen sulphide, "To reduce Carbon dioxide from the air into the hydrogen rich Carbon compounds of cells, microbes needed a source of electrons. An excellent early source of electrons was gaseous hydrogen ..."; "The first organisms to exploit it (Photosynthesis) were bacteria which obtain their hydrogen mainly from hydrogen sulphide (H2S) or organic acids, and their Carbon and oxygen from Carbon dioxide. The bacteria lived in water (as their descendants do to this day), and obtained the raw materials for Photosynthesis from the water.""The simplest prokatyotic cells (single cells or chains of cells, with no nucleus) derived their food and energy by fermentation. Later, they became photosynthetic and resembled modern blue-green algae that build colonial structures and are recognized throughout the geological record as stromatolites."
II: Eukaryotic Protoctists.
"Bacterial Photosynthesis was followed by another version of the process, using a different kind of chlorophyll, and it was this type of Photosynthesis that led to the evolution of green Plants. The essential difference is that in Plant Photosynthesis the hydrogen is obtained, not from hydrogen sulphide, but from the photolysis (breakdown using light energy) of water."; "Today the green and purple sulfur bacteria still use hydrogen sulphide as their electron donor in photosynthesis. In the early days photosynthesis was largely dependent on a steady source of hydrogen sulphide, and the gas was converted into yellow sulphur deposits on the ground or into globules in the water that were later oxidized to make ocean sulphate. But now, as water replaced hydrogen sulphide as the largest reserve of electrons for photosynthesis, oxygen began to build up in the atmosphere."The first forms of eukaryotes (organisms which have nucleated cells) were Protoctists, "Protoctists - all the eukaryotes that are neither Animals, plant, nor fungi - include ciliates, amoebae, malarial parasites, slime molds, plankton, seaweeds and single-celled photosynthetic swimming microbe such as euglena. While most are harmless, protoctists cause many tropical diseases (chagas disease, giardiasis, malaria, and african sleeping sickness), red tides, and major crop and Animal infestations. Because nearly all phytoplankton are protoctists, they also form the basis for the ocean food chain." Some Protoctists became Photosynthesizers when they absorbed Photosynthesizing bacteria into their cells and turned them into organelles, "Oxygen released by photosynthesis slowly transformed the atmosphere .. This was accomplished by capture, a rape of a cell, as bacteria were tucked inside the larger cell, complete with their special skills. Photosynthesizing bacteria became photosynthesizing organelles."
Foraminifera.
"Although 'merely' protoctists, foraminifera are one of the most diverse groups of fossil forming small organisms. An astounding variety of magnificent shells are made by these complex single-celled beings, some 40,000 different species which have evolved in the last 520 million years."Coccolithophorids.
"The most numerous of these (shell-forming) organisms are algae - plants, although they move about as animals do - known as coccolithophorids. Their calcareous plates are called 'coccoliths'. Coccolithophorids became very abundant some 200 million years ago and have remained so ever since."III: Plants.
Tracheophytes and Bryophytes.
"Land plants have followed two main strategies. The plants that developed xylem, roots, and efficient systems for circulating water are the vascular plants, the abundant tracheophytes. A different route was taken by the bryophytes, which survive as mosses, hornworts, and liverworts."
The Types of C3 and C4 Plants.
C3 Plants include Wheat, Rice, Barley, Oats, Potatoes, Sugar Beet, Soya beans, sweet Potatoes, cassava, Bananas, Coconuts, Chickpeas, cotton, roses, strawberries, most fruits and vegetables, and Trees.C4 Plants include Maize, Cane Sugar, Millet and Sorghum, and grasses. "There is nothing more superficially ordinary than grass. It is a flowering plant, although its wind pollinated flowers are scarcely conspicuous .. However, grass is a special herb. The appearance of grasses in the tertiary was of crucial importance to the modern mammal fauna, for many of the animals that figure prominently in human history feed, predominantly, upon grass. Grasslands finally took over large tract of the world during the miocene .. the great grasslands, savannah, prairie and pampas, date back to this period."
The Differences beteen C3 and C4 Plants.
"There are two main groups of plants with different systems for capturing Carbon dioxide through Photosynthesis. The first, C3 Plants, are so designated because the first product in the sequence of biochemical reactions involved in photosynthesis has three carbon atoms. These Plants include Wheat, Rice, Barley, Oats, Potatoes, Sugar Beet, Soya beans, sweet Potatoes, cassava, Bananas, Coconuts, Chickpeas, and most fruits and vegetables. They react positively to increased Carbon dioxide levels leading to greater growth and increased yields .. The second group, C4 Plants, in which the first product has four Carbon atoms, is less responsive to increased Carbon dioxide levels. C4 crops include Maize, Cane Sugar, Millet and Sorghum. C4 crops are mainly tropical and are grown most widely in africa. Many of the world's major pasture grasses are also C4 Plants, so the carrying capacity of the world's major grasslands is not likely to benefit significantly from Carbon dioxide fertilization."; "Most of the main crop plants are described as C3 plants and these might give increased yields (with increased concentrations of atmospheric carbon). This group includes wheat, rice, potatoes, barley and cassava, which between them make up over 50% of global crop production. Another group of plants form oxaloacetic acid, a four carbon molecule, when they fix Carbon dioxide. They do not react so positively to increased concentrations of Carbon dioxide. They belong to the C4 group and examples include maize, sugar cane and sorghum, which have about a 20% share in world food crop production. Most Trees are C3 Plants, but again increased stress due to climatic changes may more than wipe out any extra growth resulting from higher Carbon dioxide levels."; "Ancient plants such as cotton, wheat, roses and strawberries, classified as C3, go back to 300 million years when the Earth's atmosphere contained much less carbon dioxide. More recent plants, C4s such as maize, sorghum and sugar cane, are 40-50 million years old and more adapted to modern conditions."; "Not surprising is the emergence in the Miocene, some 10 million years ago, of a new type of green plant able to grow at lower Carbon dioxide concentrations. These plants have a different biochemistry and are called C4 plants to distinguish them from the mainstream C3 plants. The C4 plants are able to Photosynthesize at much lower carbon dioxide levels than older C3 plants. The new C4 plants include some, but not all grasses, whereas trees and broad leaved plants generally use the C3 cycle." (James Lovelock).
IV: Animals.
"Photosynthetic animals are well known (for example, elysia, Plachobranchus, convoluta roscoffensis ...)."
V: The Range of Photosynthesizers.
Since the formation of the Earth the number and range of Photosynthesizers has increased substantially. The first Photosynthesizers were Bacteria, then Protoctists, then simple Plants. Over the last 300-400 million years, some of these Plants have diversified into the wide range of different Trees which exist today. Paradoxically, the most recent Photosynthetic innovation has been the increase in the number of grasses. .. "of the 380,000 species of plant, about 250,000 are 'higher' plants in evolutionary terms. There are two main groups (of plants): the angiosperms (enclosed-seeded) which include the flowering plants; and the much less numerous gymnosperms (naked seeded) which include the conifers and the more primitive, palm like cycads. Of the other 130,000, in order of evolutionary development,- 10,000 are ferns, horsetails and clubmosses;
- 16,000 mosses and liverwort;
- 50,000 fungi;
- 18,000 lichens; and
- 25,000 algae, a group which includes seaweeds."
VI: The Process of Photosynthesis.
All Photosynthesizers are Bacteria.
All Photosynthesis is carried out by Bacteria whether they are independent or have become absorbed into the structure of Protoctists/Plants. It has been proposed that .. "Plants are green because their intended victims, the chloroplasts that began as oxygen-producing cyanobacteria, resisted death by ingestion."
Plants feed on Sunlight, Water and Gases.
"Plants use chlorophyll to capture Carbon dioxide from the atmosphere, converting it into plant tissue and energy-rich compounds such as starch and sugar."; "In essence, a plant taps the energy of sunlight to make carbohydrate out of carbon dioxide and water. The plant then uses this carbohydrate for energy, and as a building material to synthesize proteins, fats, and all the complex chemicals of life, drawing also on minerals in the soil."; "Another way to make a living that early bacteria seem quickly to have developed is using the sun to drive chemical reactions. Even dim sunlight can be absorbed by large coloured molecules called pigments, and the captured energy can then be used to break hydrogen loose from some simple compound, to be united with carbon dioxide and form carbohydrates."
The Danger of Oxygen.
"Primitive bacteria do not use water, H2O, as their source of hydrogen. (The oxygen released if they stripped hydrogen from water would burn their cells). .. several groups of bacteria began to synthesize complex molecules - enzymes - that could capture oxygen within their cells and then safely escort these lethal molecules outside their cell walls before any damage was done."
The Carbon Isotopes involved in Photosynthesis.
"Photosynthesis preferentially uses the lighter isotope of carbon (12C) and therefore leaves the CO2 of the surface waters enriched in 13C. Surface dwelling planktonic foraminifera therefore have relatively heavy 13C values. The 13C of benthic foraminifera is lighter because deep waters contain the 12C liberated by the oxidation of organic matter formed at the surface and because Photosynthesis does not occur at these depths."; "Carbon has two stable isotopes, 12C and 13C, the first very slightly lighter than the second. When living organisms use it, they tend to select the lighter isotope, which costs fractionally less energy to absorb. This means that when sedimentary rocks are found to contain more than the usual ratio of 12C to 13C, it was some form of life that must have altered the balance. Some of the oldest rocks on Earth (were) laid down 3.8 billion years ago. Some chemical analyses suggest there is a 12C surplus in these rocks, and if this is true life must have put it there. As evidence of Photosynthesis it would be startling because it comes a mere 200 my at most after the Earth grew cool enough to live on."
iv) Index of Terms.
Prokaryotes
The first life forms on Earth were Prokaryotes. These micro-organisms have no nucleated cells.Eukaryotes.
All eukaryotes have nucleated cells - whether Protista, Fungi, Plants or Animals.Angiosperms.
These are flowering plants which are enclosed-seeded.Gymnosperms.
Gymnosperms were the first big Trees on Earth.They are naked seeded Plants which include theConifers and Cycads.
Metazoan.
Multicellular Animal life.
Anaerobic/Anoxic.
Organisms which live in environments free of oxygen.
Cyanobacteria - stromatolitic carbonates.
Cyanobacteria are blue green photosynthesizing Bacteria which build colonial structures known as stromatolites.
Ediacaran faunas.
First appeared in precambrian times roughly 1bya-570mya. Ediacaran faunas have no hard parts, no CaCO3 skeletons.
v) Four Types of Being.
"Different carbon and energy sources are used to make cell tissues of living organisms.
Autotrophs.
An organism that uses CO2 present in the environment or generated from some other compound, as the source of cellular carbon is an autotroph.
Heterotrophs.
An organism that uses organic carbon compounds (such as methane) as sources of cellular carbon is a heterotroph.
Phototrophs.
An organism that can use light as the energy source is a phototroph and
