[Music] hi welcome back to free size lessons.com UK by the end of this video you should be able to describe the processes that take place in the carbon cycle you should then be able to describe the role of decomposers now I should point out that many students think that the carbon cycle is tricky but I promise you it's not as difficult as it looks the first key fact that you need to know is that the carbon cycle starts with carbon dioxide in the atmosphere now there's only one way that carbon can enter the carbon cycle and that's by photosynthesis remember that in photosynthesis carbon dioxide's combine with water to make the sugar glucose photosynthesis uses light energy and is carried out by plants so remember that photosynthesis is the only way that carbon can enter the carbon cycle carbon dioxide returns back to the atmosphere by aerobic respiration and remember that every single living organism cows out respiration now I need to make one thing clear respiration and breathing are not the same thing never use the word breathing when you mean respiration so remember that the carbon cycle involves two key processes photosynthesis which burns carbon into the cycle and respiration which returns carbon back to the atmosphere so I'm going to take you now through the carbon cycle and it's important that you learn this okay so here's the carbon dioxide in the atmosphere plants and algae take in carbon dioxide from the atmosphere in photosynthesis the carbons used to make carbohydrates fats and proteins which make up the cells of plants and algae now plants and algae respire so some of the carbon is released back to the atmosphere as carbon dioxide plants and algae can be eaten by animals and then these animals can be eaten by other animals like this at this point the carbon that was in the plants becomes part of the carbohydrates fats and proteins in the cells of animals just like plants animals respire so some of the carbon is released back to the atmosphere as carbon dioxide animals release waste products such as feces and eventually all animals and plants die so now we've got carbon and waste products and in dead remains the waste products aren't dead remains are then broken down by decomposing microorganisms for example bacteria and fungi and when decomposes carry out respiration the carbon in the waste undead remains is returned to the atmosphere as carbon dioxide decomposes are extremely important as they cycle materials through an ecosystem as well as returning carbon to the atmosphere as carbon dioxide they also release mineral ions to the soil now under certain conditions for example a lack of oxygen decomposes cannot function effectively and if this happens then the carbon in dead remains can slowly be converted to fossil fuels and over many millions of years a large amount of carbon has been trapped underground as fossil fuels however over the last 200 years humans have been burning huge amounts of fossil fuels for example coal and oil and compost and fossil fuels is releasing a large amount of carbon dioxide back to the atmosphere remember you'll find plenty of questions on the carbon cycle in my revision workbook and you can get up by clicking on the link above [Music]