Ecology 2 Energy Flow in Ecosystems
Biodiversity • Biodiversity is the variety of organisms in a given area. • Physical factors (abiotic) have a big influence on biodiversity. • Ex: Low temp or Low water = Low biodiversity Sahara Desert Forest
Sunlight Without a constant input of energy, living systems cannot function. Sunlight is the main energy source for life on Earth. Did you know that of all the sun’s energy that reaches the Earth, less than 1% is used by living things? This small amount is enough to produce as much as 3.5kg of living tissue/square meter/year
Producers Only plants, some algae, and certain bacteria can capture energy from sunlight or chemicals and use that energy to produce food. These organisms are called autotrophs (or producers).
Photosynthesis/Chemosynthesis • Photosynthesis • Photosynthetic Autotrophs use light energy to power the conversion of CO2 and H2O into O2 and carbohydrates—organic molecules that store energy. • Chemosynthesis • Chemosynthetic Autotrophs (all of which are bacteria)use chemical energy to produce carbohydrates. This process relies on the energy in bonds such as Hydrogen Sulfide.
Consumers • Many organisms (including animals, fungi, and many bacteria) cannot harness energy directly like autotrophs. • These organisms acquire energy from other organisms.
Loss of Energy • When a zebra eats 20 lb. of grass, the zebra does not gain 20 lb. Why not? • Where did the energy go?
Energy in an Ecosystem • Energy is stored at each link in a food web, but the amount available becomes less at each level.
The 10 percent rule • When a zebra or a caterpillar eats grass, some of the energy is stored in the zebra or caterpillar. • Most of the energy, however, does not stay with the zebra. • As the zebra uses energy from the grass to run and grow, the energy is changed to heat energy.
90% Energy is lost as heat • The zebra does not keep 90% of the energy it gets from the grass. • Only about 10% of the energy from the grass becomes part of the zebra’s body. • This amount of stored energy is all that is available to organisms at the next trophic level that eat the zebra.
Energy Pyramid • A diagram that shows an ecosystems’ loss of energy. • Each layer in the energy pyramid represents one trophic level. • The lowest level, the producers, have the most energy.
Energy Pyramid • Herbivores have less energy and make up the second level. • Carnivores that feed on herbivores make up the higher level. • The energy stored at each level is about 1/10th the energy stored in the level below.
Top Carnivores are Rare • Big predators are rare compared to herbivores. • A lot more energy is required to support a single predator than a single herbivore. • Many ecosystems do not have enough energy to support a large population of predators.
Carrying Capacity • The largest population that an ecosystem can support at any given time.