Energy Flow in Ecosystems Chapter 5
The ultimate source of energy for almost all organisms is the Sun
Life depends on the Sun • Energy from the sun enters an ecosystem when a plant uses sunlight to make sugar molecules in a process called photosynthesis – plants, algae and some bacteria capture solar energy which starts a series of chemical reactions that require CO2 and water and then produce carbohydrates. Other organisms consume these carbohydrates and use the energy stored in them. • When animals eat plants, some energy is transferred from the plant to the animal.
The plant is the producer – an organism that makes its own food – also known as autotrophs. The animal is the consumer – an organism that gets its energy by eating other organisms – also known as heterotrophs
An exception to the rule: Deep-ocean Ecosystems • The bottom of the ocean is teaming with life with large communities of organisms living near thermal vents. They exist in total darkness, where photosynthesis does not occur. Bacteria that feed on hydrogen sulfide make their own food and serve as producers are called chemosynthetic– other underwater organisms eat the bacteria which support a thriving ecosystem
Types of Consumers in an Ecosystem • Consumers that eat only producers are called herbivores. Ex. Cows • Consumers that eat other consumers only are called carnivores. Ex. Lions • Consumers that eat both plants and animals are called omnivores. Ex. Humans • Consumers that get their food by breaking down dead organisms are called decomposers or detritivores. Ex. Bacteria and fungi – they return nutrients in rotting material to the soil, water, and air
Cellular Respiration– the process of breaking down food to yield energy • Your body gets energy out of food by using oxygen. You breathe to break down food. By breaking down the food, your body obtains the energy stored in food • Cellular Respiration: C6H12O6 + 6 O2 6CO2 + 6 H2O + energy • Photosynthesis:6CO2 + 6 H2O + energy C6H12O6 + 6 O2 • This energy consumers obtain through cellular respiration helps to make more body tissues, fight diseases as well as daily activities like walking, breathing, thinking, etc. Any excess energy obtained and not used is stored as fat.
Energy Transfer Every time an organism eats another organism, a transfer of energy occurs. We can trace the transfer of energy as it travels through an ecosystem by studying food chains, food webs and trophic levels. They tell us how energy is transferred and how much is transferred
Food Chains and Food Webs • Food chain – a sequence in which energy is transferred from one organism to the next as each organism eats another organism • Because feeding relationships in ecosystems are more complicated that a simple food chain we use • Food webs – shows the many possible feeding relationships in an ecosystem
Trophic Levels • Each step through which energy is transferred in a food chain is known as a trophic level – each time energy is transferred from one organism to another, some of the energy is lost as heat and less energy is available to organisms at the next trophic level. Some energy is lost during cellular respiration – organisms use the remaining energy to carry out life functions – about 90% of energy at each trophic level is used in these ways. Only 10% of the energy stored gets transferred to the next trophic level