1. Population Dynamics & Cycles in Nature

2. Population Dynamics Population- a group of organisms of the same species that occupy a given area and reproduce If environmental conditions are “favorable,” then the number of individuals in population should increase from one generation to next Population density = # of organisms/area

3. Population Size-Growth Rate Birth rate- # individuals born Death rate- # individuals die Immigration- # individuals that move in Emigration- # individuals that move out If… BR + I = DR + E EQUILIBRIUM BR + I > DR + E INCREASING BR + I < DR + E DECREASING

4. Exponential Growth Exponential growth- starts out slowly but then grows rapidly to infinitely high numbers Represented by “J curve” This does NOT describe real populations forever Something always limits growth eventually

5. Factors Affect Growth Rate Limiting Factors: factors that stop populations from reaching their biotic potential Space Water Nutrients Competition Disease Natural disasters

6. Logistic Growth Logistic Growth : Population growth that levels off due to environmental resistance. Real populations can only grow exponentially for short spans. More realistic. Seen as a “ S-curve ” on a graph

7. Carrying Capacity Carrying Capacity- Total # of individuals that can be supported by the environment in a particular area. The Earth has 7 billion people…how many more can it support? World Population http://www.youtube.com/watch?v=9_9SutNmfFk

8. Cycles in Nature Cycling maintains homeostasis (balance) in the environment. Matter is constantly recycled. 3 Cycles to Investigate: 1. Water Cycle 2. Carbon Cycle 3. Nitrogen Cycle

9. Water Cycle Evaporation: Liquid Gas Condensation : Gas Liquid Precipitation : Rain, Snow, Sleet, Hail Transpiration: process through which plants lose water vapor through leaves Ground Water: water within the earth

10. Water Cycle

11. Carbon Cycle Carbon © is the molecule of life (proteins, carbs, fats, and other important molecules) Autotrophs use photosynthesis Convert CO 2 into energy-rich molecules Autotrophs or Heterotrophs use carbon molecules for growth & energy ( Cell Respiration ) CO 2 is released into the atmosphere Decomposition- breakdown of dead organisms and waste, returning carbon to the soil and atmosphere. Fossil Fuels- dead organisms that are buried in sediment; formed by pressure. Combustion: the burning of fossil fuels.

12. Carbon Cycle

13. Nitrogen (N) Cycle Air 78% (N 2 ), organisms cannot use Nitrogen in that form. Lightning & certain bacteria convert Nitrogen in air into more useable forms for plants and animals. Nitrogen fixation- convert atmospheric nitrogen (N2) into ammonium (NH4+) which can be used to make organic compounds like amino acids (proteins). Nitrogen-fixing bacteria: Some live in a symbiotic relationship with plants of the legume family (e.g., soybeans, clover, peanuts).

14. Nitrogen (N) Cycle Herbivores eat plants – convert N- containing plant proteins into N – containing animal proteins N returned to soil in urine (excess N) & when organism dies Plants reuse these N molecules Bacteria act on these molecules & put N back into the air

15. Nitrogen Cycle