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 to produce as much as 3.5kg of living tissue/square meter/year 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 CO 2 and H 2 O into O 2 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.

Autotrophs

Hydrothermal Vents

Consumers  Many organisms (including animals, fungi, and many bacteria) cannot harness energy directly like autotrophs.  These organisms acquire energy from other organisms.

Food Chain

Food Web

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 1/10 th 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.