1. Cycles in the Environment Populations and Biodiversity
Ecology 2.0
Cycles in the Environment
Populations and Biodiversity

2. The Water Cycle Evaporation: water turns from liquid to a gas
Transpiration: water from a plant turns to a gas
Warm humid air rises & cools to form a liquid again to make clouds (condensation)
Precipitation: water falls as any form
Groundwater: water that soaks into the ground
Runoff water: water that does not soak into the ground

3. Carbon Cycle Carbon is released in several ways:
As CO2 from respiration
Decaying material releases heat and CO2
Burning fossil fuels
Volcanic activity
Plants use the carbon (C) from CO2 to make it into glucose and release O2.

4. Oxygen Cycle Oxygen (O2) is needed for respiration
Plants produce O2 during photosynthesis and release it into water and the air
Consumers take in O2 during respiration and let it out as CO2.

5. Nitrogen Cycle Nitrogen is needed to make protein
78% of air is nitrogen in the form of N2
Gaseous N2 must be fixed (converted to solid forms) so that it can be absorbed or eaten.

7. How does Nitrogen Cycle?
Lightning can make N2 bond to water in the air, and it will come down with rain.
Bacteria in the soil can change N2 into NH3 (ammonia)
Animals eat plants containing nitrogen and excrete it as NH3 in urine
Decomposition puts ammonia in the soil
Ammonia is converted into NO2 (nitrites) and NO3 (nitrates)
Plant roots absorb nitrates
Bacteria can convert nitrates back into N2 and return it to the atmosphere

8. Histograms: a special type of graph used to represent the changing population of a certain country
Negative Population Growth
The children are outnumbered by the adults. Average of less than two children per family.
Positive Population Growth
The children outnumber the adults of child-bearing age. More than two children per family.
Zero Population Growth
The children are fairly equal to the number of child-bearing adults. Average of two children per family.

9. Histograms: Positive Growth
Developing countries usually show positive growth.
The aged make up a very small population.
Health care may be inaccessible to many, or may be of poor quality.
Economy may not be stable.
Most of population lives at poverty level.
War may be a factor that affects young adult male population

10. Histograms: Zero Growth
The population is relatively stable, neither growing nor shrinking.
Developed countries
Good health care.
Good sized elderly population
Stable economy
Most families are middle-class

11. Histograms: Negative Growth
Population will experience decrease in near future due to fewer children being born.
Well developed countries.
Larger elderly population
Typically “rich” country.
Future may be economically iffy – aging population relies on government health and pension programs that are supported by taxes of working people.

12. Histograms Affected by 3 things: Number of births Number of deaths
Number of individuals that enter or leave a population.

13. GROWTH CURVES
By looking at the growth of a population graphically, how does it occur?

14. Exponential Growth
Exponential growth ~ Occurs when individuals in a population reproduce at a constant rate.
Occurs when there are unlimited resources.
Graph shows a J-shaped curve.
This occurs until a limit on a resource is reached

15. Logistic Growth
Logistic Growth~ Occurs when a population slows its growth after a period of exponential growth.
Occurs when a limiting factor is introduced.
Graph shows an
S-shaped curve.
Carrying capacity ~
Shown at the point where the curve flattens out.
The maximum number of individuals in a population that can be supported by an ecosystem.

16. Limiting Factors: Anything that limits the size of a population
Density dependent limiting factors ~ A factor that depends on population size.
Disease
Parasites
Predators
Competition
Density independent limiting factors ~ Any large-scale factor that can affect a population that doesn’t depend on the number of individuals.
Natural disaster (Earthquake, flood, tornado, etc.)
Long term change in weather