Ecosystems maintain themselves by cycling energy and nutrients obtained from
external sources. At the first trophic level, primary producers (plants, algae, and some
bacteria) use solar energy to produce organic plant material through
photosynthesis. Herbivores—animals that feed solely on plants—make up the
second trophic level. Predators that eat herbivores comprise the third trophic
level; if larger predators are present, they represent still higher trophic
levels. Organisms that feed at several trophic levels (for example, grizzly
bears that eat berries and salmon) are classified at the highest of the trophic
levels at which they feed. Decomposers, which include bacteria, fungi, molds,
worms, and insects, break down wastes and dead organisms and return nutrients
to the soil.
On average about 10 percent of net energy production at one trophic level is
passed on to the next level. Processes that reduce the energy transferred
between trophic levels include respiration, growth and reproduction,
defecation, and nonpredatory death (organisms that die but are not eaten by
consumers). The nutritional quality of material that is consumed also
influences how efficiently energy is transferred, because consumers can convert
high-quality food sources into new living tissue more efficiently than
low-quality food sources.
The low rate of energy transfer between trophic levels makes decomposers
generally more important than producers in terms of energy flow. Decomposers
process large amounts of organic material and return nutrients to the ecosystem
in inorganic form, which are then taken up again by primary producers. Energy
is not recycled during decomposition, but rather is released, mostly as heat
(this is what makes compost piles and fresh garden mulch warm).
http://www.learner.org/courses/envsci/unit/text.php?unit=4&secNum=3
external sources. At the first trophic level, primary producers (plants, algae, and some
bacteria) use solar energy to produce organic plant material through
photosynthesis. Herbivores—animals that feed solely on plants—make up the
second trophic level. Predators that eat herbivores comprise the third trophic
level; if larger predators are present, they represent still higher trophic
levels. Organisms that feed at several trophic levels (for example, grizzly
bears that eat berries and salmon) are classified at the highest of the trophic
levels at which they feed. Decomposers, which include bacteria, fungi, molds,
worms, and insects, break down wastes and dead organisms and return nutrients
to the soil.
On average about 10 percent of net energy production at one trophic level is
passed on to the next level. Processes that reduce the energy transferred
between trophic levels include respiration, growth and reproduction,
defecation, and nonpredatory death (organisms that die but are not eaten by
consumers). The nutritional quality of material that is consumed also
influences how efficiently energy is transferred, because consumers can convert
high-quality food sources into new living tissue more efficiently than
low-quality food sources.
The low rate of energy transfer between trophic levels makes decomposers
generally more important than producers in terms of energy flow. Decomposers
process large amounts of organic material and return nutrients to the ecosystem
in inorganic form, which are then taken up again by primary producers. Energy
is not recycled during decomposition, but rather is released, mostly as heat
(this is what makes compost piles and fresh garden mulch warm).
http://www.learner.org/courses/envsci/unit/text.php?unit=4&secNum=3
Assignments
iib_mastery_checklist.docx | |
File Size: | 42 kb |
File Type: | docx |
dissolved_oxygen__primary_prod_activity1.pdf | |
File Size: | 341 kb |
File Type: |
energy_flow_in_ecosystems.pptx | |
File Size: | 3184 kb |
File Type: | pptx |
the_oceans_invisible_forest1.pdf | |
File Size: | 339 kb |
File Type: |