|MadSci Network: Environment & Ecology|
Hi Sarah, For the answer let's ignore the deep sea hot water vents and just talk about above ground ecosystems. The energy flow is all about food, making it and eating it. For a typical above ground ecosystem the first energy source is the sun. Plants, some bacteria, and algae can use this energy (photons of light within a narrow range of wavelengths) plus, water and carbon dioxide to make simple sugars (food). This process is called photosynthesis. The sugars are in turn used to provide energy and building blocks to make more complex compounds. The plants that photosynthesize are called producers, everything else is a consumer. For the plant to grow it uses energy from the sun to do it and in a sense you can say a plant represents that energy. A primary consumer is a plant eater (herbivore - cow, bacteria, fungus, etc.). A plant eater grows by using the energy that is stored in the compounds of a plant. There is a certain amount of waste (it takes energy to break chemical bonds and make new ones etc.), but there is enough energy left over for the organism to survive and grow. As a rule of thumb, an herbivore will gain a kilogram for every 10 kilograms it eats when it is young and growing actively. Secondary consumers eat primary consumers and the energy flow continues through them. Again about 10 kg of gazelle will allow a young lion to grow about 1 kg. You can imagine that when the lion dies, another animal (vulture) will come and eat it, again transferring the energy in the ecosystem. You can go crazy trying to figure where all the energy in an ecosystem goes. But what is important is remembering that photosysthesis allows organisms to capture the sun's energy and everything else ultimately gets its energy (food) from eating the plant or eating something that ate the plant. If the plants are aquatic in a bog, enventually they can end up as coal. If we burn that coal we will get back some of the sun's energy that has been in long term storage. Hope this little bit has been helpful. It's a big and interesting field. I looked at a textbook - Biological Science, An ecological appoach (BSCS Green Version) 6th edition. Kendall/Hunt publishing co. Iowa. for inspiration. It's the best biological science textbook I have ever seen and I recommend it highly. Cheers, Steve Seefeldt
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