1. Succession The change in the composition of species over time
A disturbance (removes some individuals or biomass from a community) alters resource availability
Primary succession occurs on substrates that never previously supported living things (volcano, glacier)
Secondary succession occurs when a habitat was destroyed by a damaging event (Fire, forest clear-cutting, abandoned lots )
Community composition and structure may change radically in response to changes in abiotic and biotic conditions.
The important feature of a disturbance (any event that removes some individuals or biomass from a community) is that it alters some aspect of resource availability.
The impact of disturbance is a function of three factors:
Type of disturbance.
Frequency of disturbance.
Severity of disturbance
Most communities experience a characteristic type of disturbance, and in most cases, disturbances occur with a predictable frequency and severity.
This is called a community's disturbance regime.
Early successional communities are dominated by species that are short lived and small in stature, and that disperse their seeds over long distances.
Late successional communities are dominated by species that tend to be long lived, large, and good competitors for resources such as light and nutrients.
The specific sequence of species that appears over time is called the successional pathway.

2. Pioneer Species
The first organisms to colonize a newly exposed habitat
r-selected
Good dispersal capability
Tolerant
Devote most energy to reproduction & little to competitive ability
Ex: lichens, mosses, grasses, weeds
Eventually replaced by Climax Community
K-selected
Ex: perennial grasses, shrubs, trees
R-selected: opportunistic, fast growing, quickly reproduce
Tend to be “weedy”; weeds are plants adapted for growth in disturbed soils.
Early successional species devote most of their energy to reproduction and little to competitive ability.

3. Productivity Primary Productivity Gross Primary Productivity (GPP)
The rate at which photosynthetic organisms produce organic compounds in an ecosystem
Gross Primary Productivity (GPP)
The total amount of photosynthesis
Net Primary Productivity (NPP)
The energy that remains to be invested in growth and reproduction
NPP = GPP - Respiration
All ecosystems share a characteristic pattern: The total biomass produced each year is greatest at the lowest trophic level and declines at higher levels.
The amount of biomass produced at each subsequent trophic level must be less than the amount at the previous level.

4. The Pyramid of Productivity
NPP results in biomass (energy available to next level)
Efficiency of biomass transfer between trophic levels is only about 10 percent.

5. In general, NPP on land is much higher than it is in the oceans, as more light is available to drive photosynthesis on land than in marine environments.
The terrestrial ecosystems with highest productivity are located in the wet tropics.
Marine productivity is highest along coastlines, and it can be as high near the poles as it is in tropics.

6. Biomagnification
Certain molecules increase in relative concentration as they are transferred between trophic levels.
Examples: DDT, toxaphene (insecticide)

7. Biogeochemical Cycle Elements move between abiotic and biotic systems
Reservoirs = major storage locations
Assimilation = incorporation of elements into plants and animals
Release = return of elements to environment
Nutrients are the link between the biotic and abiotic factors of an ecosystem.
Reservoirs: The major storage locations
Assimilation: The processes through which each element incorporates into terrestrial plants and animals
Release: The processes through which each element returns to the environment

8. Decomposition
Converts the nutrients in soil organic matter to an inorganic form
Limits the rate at which nutrients move through an ecosystem
Releases nutrients tied up in intact tissues
Rate influenced by
Abiotic conditions (ex: moisture, temperature, O2)
Quality of detritus as a food source for decomposers (bacteria, fungi, archaea)
Until decomposition occurs, nutrients stay tied up in intact tissues.
The rate is influenced by two factors:
Abiotic conditions such as oxygen availability, temperature, and precipitation.
The quality of the detritus as a nutrient source for the fungi, bacteria, and archaea that accomplish decomposition.

9. The Water Cycle -In oceans, evaporation exceeds precipitation
The global water cycle begins with the evaporation of water out of the ocean and precipitating back into it.
Evaporation exceeds precipitation.
When this water vapor moves over the continents, it is augmented by water transpired by plants.
Precipitation falls on the continents.
The cycle is completed both by water that moves from the land to the oceans via streams and by groundwater—water that is found in soil.
Humans are affecting the water cycle in many ways.
One of the most direct ways is in groundwater storage and the replenishment of groundwater.
The water table, the upper limit of saturated soil, is dropping on every continent.
-In oceans, evaporation exceeds precipitation
-Water vapor moves over land, gains transpired water
-Precipitation falls on land, water moves back to oceans
-Many human effects, ex: water tables are dropping

10. The Nitrogen Cycle
Nitrogen needed to manufacture all amino acids and nucleic acids
-Nitrogen needed to manufacture amino and nucleic acids
-Nitrogen fixation = conversion from N2 to NH3 (ammonia),
A usable form by plants
Soil-based bacteria
-Denitrification = conversion from nitrogen-based compounds to N2

11. -Leads to decreased species diversity in terrestrial ecosystems
Human-fixed nitrogen in the form of fertilizers, nitric oxide from burning fossil fuels, and cultivation of certain crops is having a major effect on the nitrogen cycle.
Adding nitrogen to terrestrial ecosystems usually increases productivity. But overfertilization with nitrogen can cause anoxic “dead-zones” in aquatic ecosystems, and can lead to a decrease in species diversity in terrestrial ecosystems.
-Overfertilization with nitrogen can cause anoxic “dead zones” in aquatic ecosystems (algal blooms & high decay)
-Leads to decreased species diversity in terrestrial ecosystems

12. The Carbon Cycle -Incorporation via photosynthesis (CO2 → sugar)
In both terrestrial and aquatic ecosystems, photosynthesis is responsible for taking carbon out of the atmosphere and incorporating it into tissue.
Cellular respiration, in contrast, releases carbon that has been incorporated into living organisms to the atmosphere, in the form of carbon dioxide.
-Incorporation via photosynthesis (CO2 → sugar)
-Release via cellular respiration (sugar → CO2)

13. Human Impact On The Carbon Cycle
Adding excess CO2 to the atmosphere
Burning of Fossil Fuels
Intensive agriculture
Deforestation
CO2 is a greenhouse gas
Traps heat radiated from Earth
Linked to global climate change
Industrialized countries burn excessive quantities of fossil fuels
Increases in the amounts of greenhouse gases have the potential to warm Earth’s climate by increasing the atmosphere’s heat-trapping potential.
Earth is facing the most traumatic episode of environmental change in human history. The trauma has two sources: the massive loss of species and global warming.
Two factors are responsible for the human impacts on ecosystems:
The rapid increase in human population.
The rapid increase in human resource use.
Residents of industrialized countries, though relatively few in number, burn extraordinary quantities of fossil fuels and thus are largely responsible for global warming.

14. Productivity Changes Human impact altering NPP
Increase on land (more photosynthesis)
Rising temperatures, increased rainfall in tropics, increased fertilization
Decrease in oceans (lower water density)
Altered currents prevent uprising of nutrients
Land increase due to factors that increase photosynthesis - rising temperatures, increased rainfall in the tropics, and CO2 fertilization
Ocean decrease due to change in water density (altered currents, less likely for nutrient rich water in the benthic zone to mix with upper layers)