2.  Ecology is the study of the interactions between organisms and their environment. ◦ Interdependence is a key theme found throughout ecology. ◦ Living things depend on each other in complex ways for survival. ◦ Ecological models can be used to study this complexity.

3.  The hierarchy of environmental organization from largest to smallest is: Biosphere, Ecosystems, Communities, Populations, and Organisms. ◦ Biosphere —thin zone of the Earth that supports life. ◦ Ecosystem —all living and nonliving parts of an ecosystem  Biotic factors—living organisms  Abiotic factors—nonliving parts.

4. ◦ Community—all the organisms living in a certain area. Example: pond community ◦ Population—all the organisms of the same species living in the same area. Example: frogs in a pond

5.  Two strategies exist to deal with fluctuations in environments. ◦ Conformers—organisms who do not regulate their internal conditions; they change with the environment. Ex: ectothermic animals ◦ Regulators—organisms that use energy to control some of their internal conditions. Ex: endothermic animals

6.  Sometimes, adjusting isn’t possible and organisms must temporarily escape. Ex: Lizard hiding in the shade Seed dormancy or animal hibernation Migration

7.  Sunlight is the main source of energy in most ecosystems  Energy flows from sunlight through producers (make food) and consumers (eat food)

8.  Photoautotrophs— use solar energy (photosynthesis) to produce sugar  Chemoautotrophs— use energy stored in inorganic molecules (chemosynthesis) to produce carbohydrates

9.  Consumers—get food by eating other organisms or organic wastes. (Heterotrophs)  Four types: Herbivores—eat producers Carnivores—eat other consumers Omnivores—eat producers and consumers

10.  Detritivores--feed on “wastes” (dead plants, animal wastes, and dead animal carcasses.) ◦ A few are specifically classified as decomposers because they cause decay and return important nutrients to the soil. Detritivores Decomposing Detritivores

11.  Energy flow through an ecosystem can be illustrated using trophic levels (shows an organism’s position in a sequence of energy transfers)  1 st level = producers  2 nd level = herbivores  3 rd and higher levels = predators

12.  Consumers are also grouped into feeding or trophic levels according to the foods they eat.  Many organisms feed at more than one level, especially omnivores. C 1 —first level consumers: eat plants C 2 —second level consumers: eat C 1 consumers C 3 —third level consumers: eat C 2 consumers

13. C1C1 C2C2 C3C3 A food chain is a model of the flow of energy through the Organisms of an ecosystem.

14.  Food web —many food chains combine to form a food web.  Gives more information. ◦ The members can be identified by their trophic level. ◦ Many organisms function on more than one trophic level. Which is a producer? Which are C 1 consumers? Which are C 2 consumers? Which is a C 3 consumer? Which is a C 4 consumer?

15. A complex food web from an aquatic ecosystem

16.  An energy pyramids --show how the amount of energy available decreases at each level of the food chain.

17.  Many of the abiotic factors in an ecosystem pass through cycles that allow the substances to be used and reused.  Four important cycles of abiotic substances include: ◦ Water cycle ◦ Carbon cycle ◦ Nitrogen cycle ◦ Phosphorus cycle

18.  Water passes through both living and nonliving parts of the environment. The water cycle is maintained by evaporation, transpiration, condensation and precipitation.

19.  Photosynthesis and cellular respiration form the basis of the carbon cycle.  In the past 150 years, atmospheric carbon dioxide has risen more than 30%..mostly due to the burning of fossil fuels

20.  Air is 78% nitrogen gas. Most organisms cannot use nitrogen in this form.  Nitrogen-fixing bacteria change nitrogen gas into nitrates which can be used by living things to make proteins and nucleic acids. ◦ Live in the soil and on the roots of certain plants (beans, peas, clover and alfalfa). ◦ Receive carbohydrates from plants and produce nitrogen for plants ◦ Release extra nitrogen into the soil.  Decomposers--make the nitrogen from decaying organisms and wastes available in the soil by turning it to ammonia (NH 3 ) which changes in the soil to ammonium (NH 4 + ) in a process called ammonification.  Soil bacteria turns ammonium into nitrites (NO 2 - ) and nitrates (NO 3 - ) in a process called nitrification. Plants can use the nitrates and then animals can eat the plants.  Anaerobic bacteria return nitrogen to the air by breaking down soil nitrates in the process of denitrification.

22.  Phosphorus is necessary for healthy bones, teeth, and the formation of DNA and RNA.  The erosion of rocks is important in adding phosphorus to the soil and water.  Excreted wastes and decaying organisms also add phosphorus to soil and water.  Plants absorb phosphorus. Animals get phosphorus from plants.