1. Biology is a Hierarchy
Every level of biological organization is built on the level below it.
Cells cooperate in tissues.
Tissues cooperate in organs.
Organs cooperate in organ systems.
Organisms, Populations, Etc.

2. Figure 45.6 A Food Web in the Yellowstone Grasslands
Energy flows, but matter is recycled

3. Productivity
Primary productivity: the total amount of energy converted into biologically useful forms by producers.

4. Trophic Efficiency
 Within a food chain, only ~10% of energy at any trophic level will be passed on to the next trophic level.

5. Many complex symbiotic relationships exist in an ecosystem
feedback control systems play a role in the functioning of these ecosystems

6. Many adaptations of organisms are related to obtaining and using energy and matter in a particular environment

7. The level of variation in a population affects population dynamics

8. Population ability to respond to changes in the environment is affected by genetic diversity.
Species and populations with little genetic diversity are at risk for extinction.
Examples
California condors – recovery program started with 20 birds
Bananas
All bananas are clones
The Gros Michel variety was affected by Panama disease (a fungus) in the 1950s
The current variety, Cavendish, is resistant to the disease, but Panama disease has since mutated and is becoming a problem again.

9. Genetic diversity allows individuals in a population to respond differently to the same changes in environmental conditions.
Examples?
Variation and frequency is modeled by which equation?
p2 + 2pq + q2 = 1

10. The diversity of species within an ecosystem may influence the stability of the ecosystem.
Tl;dr: everything I just said about populations, also applies to ecosystems

11. Natural and artificial ecosystems with fewer component parts and with little diversity among the parts are often less resilient to changes in the environment