1. 2.3 The Balance of the Matter and Energy Exchange
(pages 53 – 61)

2. The Earth is an Open and a Closed System
The Earth is a closed system in relation to matter and an open system in relation to energy. There is a constant input of energy into the biosphere and a constant output of radiant energy (heat) to space.

3. The amount of sunlight that is received by an ecosystem affects the amount and the type of productivity of an ecosystem.
Productivity: the rate at which an ecosystem’s producers capture and store energy within organic compounds over a certain length of time.
Commonly measured in terms of energy per area, per year; (J/m2/a)
Productivity is the rate at which organisms produce new biomass. Productivity can also be expressed in terms of biomass of vegetation added to an ecosystem per year; (g/m2/a).

4. Comparing productivity of ecosystems in terms of (A) the percentage of Earth’s surface and (B) average net productivity. Net productivity here is the total amount of radiant energy that is transformed to chemical energy by producers, minus the amount used by the producers during cellular respiration.

5. What factors affect the productivity of an ecosystem?

6. Productivity varies among ecosystems; the rate of productivity depends on many variables:
number of producers present in the ecosystem

7. Productivity varies among ecosystems; the rate of productivity depends on many variables:
the amount of light and heat available (solar radiation)

8. Productivity varies among ecosystems; the rate of productivity depends on many variables:
the amount of rainfall the system receives

9. Productivity varies among ecosystems; the rate of productivity depends on many variables:
the amount of available nutrients

10. Answer the Questions…
Question 1. Explain how increased amounts of sunlight can have both positive and negative effects on productivity.
Question 2. What are two major factors (other than available nutrients) that can limit productivity?

11. Gaia Hypothesis
Organisms must maintain an internal balance to remain healthy (homeostasis). The Gaia hypothesis considers homeostasis on a global level. The Gaia hypothesis states:
“the entire range of living matter on Earth from whales to viruses and from oaks to algae could be regarded as constituting a single living entity capable of maintaining Earth’s atmosphere to suit its overall needs and endowed with faculties and powers far beyond those of its constitute parts”.

12. Answer the Question…
Question 3. State the Gaia hypothesis in your own words.

13. Human Activities and the Natural Balance
Dead zones are regions or lakes or oceans in which aquatic life has suffocated due to algal blooms. Dead zones can occur seasonally in response to the turn-over of nutrient-rich waters in warmer temperatures.
Human activities often account the occurrence of dead zones.

14. Each red dot on the map represents a marine “dead zone”
Each red dot on the map represents a marine “dead zone”. What does the location of the red dots tell you about the possible causes for marine “dead zones”?

15. Dead zones are regions or lakes or oceans in which aquatic life has suffocated due to algal blooms. Dead zones can occur seasonally in response to the turn-over of nutrient-rich waters in warmer temperatures.
Human activities often account the occurrence of dead zones.

17. How do the nutrients make it to the ocean?
Nutrients can leach from soil into rivers by rain.
Sewage discharged into large bodies of water contain high levels of phosphorus and nitrogen - promoting algal blooms
Surface run-off from livestock operations carry nutrient rich wastes into water ways.
Surface run-off from fertilized agricultural land and residential lawns can enter rivers and oceans.

18. Answer the questions…
Question 4. How can an increase in available nutrients cause a dead zone to form in deep waters? Trace the steps involved from an increase in nutrients  to the decrease in aquatic biodiversity.

19. Question 5. Wetlands are often called the “kidneys” of the environment
Question 5. Wetlands are often called the “kidneys” of the environment. Based on your knowledge of human physiology, what do the kidneys do? How do you think this relates to the discussion of excess nutrients in the water ways?

20. The Biosphere’s Solution
The kidney filters harmful substances out of the bloodstream, ensuring that concentrations of these substances stay within safe limits.
Solutions to environmental problems are often discovered in the biosphere itself. Because wetlands (marshes, swamps and bogs) are permanently saturated with water, they act as large filters.

21. How Wet Lands Work