Photosynthesis

  • The process mostly takes place in the chloroplasts of plant leaf mesophyll cells
  • The energy for photosynthesis comes from light
  • Light energy is converted to chemical energy by chlorophyll
  • There are two sets of reactions, light dependent and light independent
  • Photosynthesis is affected by temperature, light intensity, light wavelength and carbon dioxide level
  • All living things depend on the organic molecules synthesized by plants as a result of photosynthesis
  • Photosynthesis is the most important chemical process on earth – it provides food and energy for all living creatures who eat the plants that rely on this process to produce their food (glucose).
  • More than half (70%) of the world’s oxygen is produced by phytoplankton photosynthesis in the world’s oceans.
  • Thirty percent (30%) of the world’s oxygen is produced in the rainforest.
  • There are two types of chlorophyll.
  • In 2005, scientists discovered that special bacteria deep in the ocean (where no sunlight could reach) were conducting photosynthesis using very faint light from hydrothermal vents.  This could mean other life exists deep in the ocean or even on other planets!
  • Researchers have discovered a sea slug that eats algae but does not digest it fully.  Instead, the remaining algae continue to conduct photosynthesis inside the slug and to contribute to the energy of the slug.
  • Photosynthesis is the reason conifers and other pine trees grow in a cone shape.  This shape allows more needles to be exposed to the sun, which enables the tree to grow taller.
  • One of the trees in Africa (the Tumbo Plant) has only two wide leaves but can live for over 1,000 years with little rain water.
  • The first scientific evidence for photosynthesis was found in the late 18th Century by chemists Joseph Priestley and Jan Ingenhousz. They noticed that a plant could revive a mouse from suffocation in an enclosed jar, using sunlight. 
  • The plant did not care about the mouse. It was only occupied with performing photosynthesis to make itself grow.
  • Organisms that make their own food out of sunlight are called photoautotrophs.
  • Oxygen is the usual waste product of modern photosynthesis.
  • It also produces all the carbon compounds that make up living cells.
  • Plants are the most familiar photoautotrophs, but they did not develop the technology themselves. They acquired it
  • Before photosynthesis evolved, Earth’s atmosphere consisted of water vapour, methane, ammonia and other gases, but not oxygen. 
  • The earliest fossil of a filamentous organism thought to perform photosynthesis is about 3.5 billion years old.
  • In order to perform photosynthesis, bacteria had to build a complex metabolic pathway involving the green pigment chlorophyll and requiring at least 17 steps.
  • Early photosynthesis did not involve oxygen and had minimal effect on the atmosphere
  • About 2.7 billion years ago cyanobacteria adopted a version of photosynthesis that oxidized water to produce O2. At first, dissolved iron absorbed most of the oxygen.
  • Billion years ago all the iron became saturated. Oxygen began accumulating in the atmosphere. It was toxic to anaerobic organisms and wiped out most life on Earth. This event is known as the Oxygen Catastrophe. It set the stage for the ascendance of eukaryotes, the more complex aerobic organisms including plants, fungi, and animals. It is theorized that one early eukaryote absorbed a cyano bacteria but instead of digesting it, began a symbiotic relationship. This was the first plant.
  • That individual cyanobacteria became the first chloroplast, the organelle that performs photosynthesis in all plants and algae.
  • Practically all chloroplasts are derived from that single event more than 1 billion years ago.
  • One species of amoeba succeeded in replicating the experiment more recently. It contains chloroplasts closely resembling a different variety of free-living cyanobacteria.
  • Lichens (like in the top photo) are the symbiotic compound of a fungus with either a green alga (a simple plant) or a cyanobacteria.
  • The fungus provides protection and chemical nutrition while the green partner provides solar energy for both organisms. Various fungi have followed this same strategy independently numerous time to survive in extremely cold, arid and nutrient-poor environments
  • A number of invertebrates have developed symbiotic relationships with photosynthetic organisms. This practice is widespread among sponges, corals, and sea anemones, which harbour algae or bacteria in their bodies.
  • Certain sea slugs feed on green algae and then incorporate their chloroplasts into their cells. Photosynthesis can keep the slugs alive for extended periods.
  • Green algae also live in the eggs of a species of salamander and help the embryo develop. So far this is the only documented example of a vertebrate forming photosynthetic symbiosis.

Must Read:

Ecosystem

Food Chain and Food Web

Renewable energy

1 COMMENT

Comments are closed.