Biology 120                 Ecosystems: Energy Flow, Human Impact                 R. Irwin

Ecosystems:


Productivity of different biomes:
 
Biome Mean Primary Productivity per Area (tonnes/km2) Area (106km2) Mean Global primary productivity
(109tonnes)
Terrestrial:
Tropical Rain Forest   2200  17  37.4
Temperate Deciduous Forest   1200 7  8.4
Taiga  800 12 9.6
Temperate Grassland  600 9 5.4
Desert  90 18 1.6
Cultivated Land  650 14 9.1
Aquatic:
Open Ocean  125 332 41.5
Coral Reefs & Algal Beds  2500 0.6 1.6
Swamp & Marsh  2000 2 4

Human Impacts:

PRACTICE QUESTIONS:

1. The community of species within an area, plus the abiotic factors with which organisms interact in the area, is called a(n) ____________________________.
2. All organisms that are the same number of energy "steps" away from the energy source of an ecosystem are said to belong to the same _______________________.
3.  The trophic level of animals that eat animals that eat plants is called the ____________________.
4.  What is the ultimate fate of the energy that plants convert into biologically useful (chemical bond) energy?  What is the ultimate source of this energy?
5.  Why do we require continuous input of energy from the sun -- why can't we just recycle the energy that plants have already converted into biologically useful (chemical bond) energy?
6. The trophic level of organisms that get energy from dead, decaying organisms is called the _______________________.
7.  The total amount of sun energy that is converted into biologically useful chemical bond energy by the plants in an ecosystem in some period of time is called the _______ ______________ of that ecosystem.  The total amount of sun energy that plants convert into new plant growth in an ecosystem in some period of time is called the ________ _________________ of that ecosystem.
8.  Which is bigger, the net productivity or the gross productivity of an ecosystem?  Why -- what happens to the energy present in one but not present in the other?
9. As we look at higher and higher trophic levels in an ecosystem, the amount of energy in each trophic level:
a. increases as energy is added from the many lower levels
b. decreases as energy is lost as heat
c. stays the same because the amount of energy available from the sun stays the same
10.  When humans cut down forests to grow crops, how does this affect the productivity of the ecosystem?  How will this in turn affect the amount of species that can be supported by the energy present in an area?  What impact does this have on so-called "greenhouse gasses" in the atmosphere?  What impact is it expected to have on global climate change?
11.  Which terrestrial (on land) ecosystem type has the highest rate of productivity per area?  Which terrestrial (on land) ecosystem type has the highest global rate of productivity? Are these the same?  Why/why not?
12. Which aquatic ecosystem type has the highest rate of productivity per area?  Which aquatic ecosystem type has the highest global rate of productivity?  Are these the same?  Why/why not?
13. When toxic compounds are added to communities, what happens as they are passed from trophic level to trophic level of organism?  Why does this happen?  Which trophic level is most likely to be adversely affected by the addition of toxic compounds?
14.  Why is increasing CO2 in the atmosphere predicted to increase global temperature?  What are some possible problems with increasing global temperature?