Ecosystem Structure
3.5-3.6
Boundaries of Ecosystems Overlap
and Change
 It is difficult to define the exact boundaries of
an ecosystem.
 All ecosystems are connected to others
around them.
 All ecosystems on the earth are connected to
one another to form the biosphere.
 A change in the ecosystem may affect many
others.
 When one population is affected by abiotic
factors, many others are in the same
community are affected at the same time.
Most Communities Have More
Producers than Consumers
 One of the most important abiotic factors that
affects relationships in community is energy.
 Without the sun, there would be no green
plants, no herbivores, and no carnivores.
 There are few ecosystems that get their
energy from another source.
 A communities size is limited by the amount
of energy available for its producers.
 The gross primary productivity is the amount
of chemical energy fixed by photosynthesis.
 The flow of energy and the amount of mass in
a community is like a pyramid.
 The loss of energy from a food chain can be
represented by an energy pyramid.
 Each level of the pyramid has 1/10 of the
energy of the level below it.
 Only about 1/1,000 of the chemical energy
used by producers can flow through a threeconsumer food chain to a top predator.
 When humans eat they act as a top level
consumers.