2. Organisms and Their Environment Ecology: the study of how organisms interact w/their environment. Includes Abiotic (nonliving) features Temperature, sunlight, rain, rocks, and ponds. Biotic (living) features Other living things

3. Species Interaction in Communities W/in communities, species interact in different ways. Keystone Species: species that plays a critical role in maintaining the structure of an ecological community. Otters: Regulate sea urchin pop. which eat kelp Otter help to keep enough kelp for all other species to use

4. Community Interactions Competition Two species in a community compete for the same resource. Niche: total set of biotic and abiotic resources it used w/in a community. Species compete when their niches overlap. Symbiosis Two species live in close association w/one another. Parasitism Relationship that is good for one member and bad for the other.

5. Commensalism One species benefits but does not affect the other. Mutualism Both species benefit.

6. Energy Flow in Ecosystems All living things need energy. Biomass- amount of organic matter in an ecosystem. Only about 10% of the energy at one level of the food chain becomes available to the next level of the food chain. 10,000 kg 1000 kg 100 kg

7. Materials Cycling in Ecosystems All substances move around Earth, going back and forth between tissues of living organisms and the abiotic world. Biogeochemical cycles 3 Major cycles Water Evaporation Condensation Precipitation Infiltration

9. Carbon Cycle Enters through photosynthesis, and fossil fuels. Becomes available to other consumers as it moves up food chain. Returned through respiration and break down of organic molecules.

10. Nitrogen Cycle Bacteria convert nitrogen gas to ammonium and then to nitrates that can be absorbed by plants. Moves up the food chain. Returns when it is converted back to nitrogen gas by other bacteria.

11. Phosphorous Cycle Not common in biosphere. Stored in rock and soil, and in ocean sediments. As these wear down, phosphate is released. Plants absorb, washes into streams. Moves through food web.

12. Change in an Ecosystem Ecological Succession: how the community of species living in an ecosystem changes over time. Two types: Primary succession Colonization of bare land w/no soil. When volcanoes create new land Secondary succession Begins when existing life in a habitat is destroyed, but soil remains. Fires

13. Population Studies Four factors determine how population size changes over time. Birth rate, death rate, rate of immigration into pop. and rate of emigration out of the pop. Exponential Growth Occurs when a pop. Grows @ a fixed rate per amount of time. Happens when pop. have unlimited resources Pop. eventually crashes.

15. Logistic Growth Happens when pop. growth slows as it approaches the habitat’s carrying capacity. Maximum number of individuals or max population density a habitat can support.

16. Populations Studies Continued.. Non-Native Species: a species living outside of its native range arrived by humans. (Accidental or Deliberate) Positives New crops for food Negatives New species don’t have natural predators so they can take over an environment. Bull frog- Colorado Asian clam- Colorado Burmese Python Black Rat

17. Human Population Growth More than 7 billion people live on Earth today. Has grown exponentially until recently. Will we be able to continue this growth forever? Scientist believe that the world human population will peak @ around 10 billion soon after the year 2050.

18. Age-Structure Diagrams Show population of a country broken down by gender and age group

19. Crazy Facts Population of the U.S. on March 27, 2008 was 314,882,811. One birth every 8 seconds. One death every 12 seconds. Net migration into the U.S. is 1 person every 46 s. Total= 1 person in the U.S. every 15 s.