Click to edit Master subtitle style 29/09/2016 Ecosystems

29/09/2016 We’ve worked our way up the hierarchy… From individuals to populations to communities and finally to ecosystems. Ecosystems includes the living and non-living (biotic and abiotic) parts of a natural community.

29/09/2016 Ecosystems are complex communities of animals and plants that interact in many ways. Seen from another view, though, ecosystems are quite simple, and have the simple function of converting the sun’s energy into heat energy. It all starts with light energy, which plants use to build sugar molecules. In other words, light energy is converted to chemical energy. From that point on in the food web, the chemical energy is used for the process of life. Finally all the energy is transformed to heat energy.

29/09/2016 Food Chains and Food Webs This is the path of energy, or ‘what eats what’ in nature. Trophic refers to food. Each step is a trophic level Plants and algae (single-celled plants) produce chemical energy from sunlight. They are called primary producers. They are called autotrophs because they make their own food.

29/09/2016 animals eat plants to get this energy. These animals are called herbivores or primary consumers. All consumers are also called heterotrophs because they eat other life forms.

29/09/2016 Other animals eat the herbivores. These are the predators or secondary consumers.

29/09/2016 Animals that eat other predators are called third-level or tertiary consumers.

29/09/2016 Some animals feed from several different trophic levels. For example, bears eat plants, herbivores and carnivores. These animals are called omnivores.

29/09/2016 Finally, decomposers or detritivores eat dead plant and animal matter. Included here are many insects, fungi, worms and bacteria.

29/09/2016 Put it all together and… You have a food chain if only one species is in each trophic level. More typical though, is a complex ‘web’ of species, Called a food web.

29/09/2016 Food webs exist in every ecosystem that has good biodiversity. There are several ‘pathways’ for the nutrients and energy to take. It all starts with producers and ends with decomposers, though.

29/09/2016 Energy Flow in Ecosystems At every trophic level (producers are the first, herbivores are the second, etc.) the organisms in that level use about 90% of the chemical energy for living. That energy is lost as heat and is not available to the next trophic level. This creates an ‘energy pyramid’. In this example, how much of the chemical energy created by the kelp is available to the Giant Sea Bass?

29/09/2016 Solution 100% of the chemical energy produced by the kelp is available to itself. It uses 90%. 10% is available to the sea urchin. It uses 90%. 1% is available to the sheephead. It uses 90%. 0.1% is available to the Giant Sea Bass.

29/09/2016 Nutrient (Chemical) Flow The energy in an ecosystem needs to constantly be replenished by the sun’s energy but the nutrients (phosphorous, nitrogen, carbon, etc. are recycled through the biogeochemical cycles we’ve discussed. Plants are the primary producers that bring the energy and nutrients into the food web. They create the primary productivity of the ecosystem. All of the living organisms in an ecosystem make up the biomass of the ecosystem.

29/09/2016 Disturbed Ecosystems Ecosystems in stable environments achieve a balance (or equilibrium) in which things don’t change very much. When a natural or man-made disturbance occurs, the ecosystem is thrown out of balance. Over time, it can return to balance through the process of ecological succession.