Chapter 55 - 56
I. Trophic Relationships in Ecosystems
A. Trophic levels
– 1. Primary producers (autotrophs) support all other organisms in an ecosystem.
– 2. Primary consumers (herbivores) eat autotrophs.
– 3. Secondary consumers (carnivores) eat herbivores.
– 4. Tertiary consumers eat other carnivores.
– 5. Detritivores eat dead stuff and waste.
B. The trophic structure of an ecosystem describes its feeding relationships.
C. A food chain shows a straight line feeding relationship within an ecosystem.
D. A food web shows the complex feeding relationships within an ecosystem.
II. Energy Flow in Ecosystems
A. Primary productivity is the amount of sunlight that is converted into chemical energy
by the autotrophs within an ecosystem over a period of time.
1.Gross primary productivity is the total productivity of an ecosystem-but not the total
energy since some energy that is produced, must be used for cellular respiration.
2.Net primary productivity is the total productivity minus the energy used for cellular
B. Trophic efficiency refers to the % of energy that is transferred from one level to the
III. Nutrients Cycle Through Ecosystems
A. The Water Cycle
B. The Carbon Cycle
C. The Nitrogen Cycle
D. The Phosphorus Cycle
VI. The Human Impact
A. Biological magnification occurs when toxins become concentrated in the tissues of
animals as they move up through trophic levels.
– top level carnivores are most affected.
B. The Greenhouse Effect is a warming of the earth which may be caused by increased
CO2 released as a byproduct of human activities.
C. The exploding human population has had a major impact:
– 1.habitat destruction
This is the single biggest issue
– 2.extinction of species
– 3.increased pollution
• D. The rapid and unceasing growth of the human population is the most urgent
and serious problem facing our earth.
• I. The Biodiversity Crisis
• A. The current rapid loss of biodiversity is an urgent problem.
– Population densities of migratory birds in the US have dropped 50% in the last
– More than 1/4th of all plant species in the US are in danger of becoming extinct.
• Biodiversity hot spots are areas with high #’s of threatened or endangered species.
• B. The major threats to biodiversity are :
• 1.Habitat destruction(the greatest threat).
– Accounts for 73% of extinctions, 93% of coral reefs are damaged
• 2. Introduced(nonnative) species cause extinctions by:
• a. Out-competing native species.
• b. Reducing biological diversity.
– Starlings, house sparrows, pigeons, fire ants, nile perch, Kudzu
• 3.Overexploitation of wildlife (due to excessive hunting)
• C. Biodiversity may save our lives…
• -if it isn’t gone before we “get it”!
• D. Species Conservation
• 1. Endangered species are in danger of extinction.
• 2. Threatened species are likely to become endangered.
• 3. Populations that have been split up, form pockets of individuals called
metapopulations. Each metapopulation has different challenges in its’ fragmented
• 4.Edges and movement corridors influence biodiversity and survival of species.
– Abrupt edges formed from human activities upset the fragile balance of the
– E. Restoration Ecology
• 1. Restoration ecology is concerned with returning damaged ecosystems to their natural