1. Ecology (Gk. "home"): The study of interactions of organisms with their abiotic and biotic environment.
   Interactions include those among living things, and those between living things and their nonliving environment.
2. Interactions occur at all levels
   At every level: cellular, organismal, community, global. We, and all living things, are in constant interaction with our environment and are effected by the quality of that interaction. Examples are ubiquitous.

1. Population growth
   -
1. J-shaped curve (exponential growth)
   22.1 Exponential Growth
   
1. Occurs when resources for growth and reproduction are unlimited
   Reproduction is out of control, unlimited.
2. Result: a species approaches a maximum rate of growth
   The only population that presently demonstrates something close to exponential growth is that of humans.
2. S-shaped curve (logistic growth)
   22.2 Logistic Growth
   
1. Growth levels due to limiting factors at the carrying capacity of the environment
   Limiting factors: availability of resources, predation, etc..
2. Result: numbers of individuals within a population are in balance with limiting factors
   (= environmental resistance)
   Population is maintained at the carrying capacity of the environment. (The capacity for an environment to sustain life; when all the limiting factors are taken into account.) Example: predation: predators thrive when the prey population is thriving, but when the predators thrive to the point of diminishing the prey population, their own population becomes limited. So there must be a balance between predator and prey populations.
3. Factors limiting or regulating population growth
   These factors determine carrying capacity/serve as population controls, and can be either biotic or abiotic factors:
1. Density-dependent factors
   Factors that are the result of population size/density.
1. Growth-limiting (mortality) factors increase in effect on population as the number of individuals increase in the population.
   22.3 Kaibab Deer
   
2. Examples: competition for food; disease; predation; parasitism
   Important: what are the two 'lessons' to be learned from Dr. Cates' Kaibab Deer example? (bottom-right blanks in diagram 22.3: from lecture: I hope you were there.)
2. Density-independent factors
   Factors that don't arise from population size that effect it.
1. Growth-limiting (mortality) factors that do not vary in effect on population as number of individuals increases in the population
   
2. Examples: severe changes in temperature, wave action of intertidal zone, freezing ice storms, hurricanes, volcanic eruptions
   
2. Unifying concepts in Ecosystem Ecology:
   -
1. Ecosystems defined:
   All the interactions in an area, both biotic and abiotic interactions.
2. Energy flow through ecosystems
   Matter cycles, ENERGY FLOWS.
1. First law of thermodynamics
   Energy cannot be created nor destroyed, (only transformed.)
2. Second law of thermodynamics
   Entropy: when energy is transformed it loses quality.
3. Consequences of energy flow
   Heat is lost with every energy transformation, (be it biotic or abiotic). 22.4 Energy Flow
   
1. Energy flow (10% rule)
   (The 10% is only a rough estimate.) Only around 10% of energy is transferred between trophic levels (producers--primary consumers--secondary consumers--tertiary consumers). The other 90% is lost as heat. So if you started with 1,000 calories of energy at the producer level (plants), a primary producer would be able to obtain 100 of those calories, a secondary consumer only 10, and a tertiary consumer, only 1 calorie of the original 1,000; the rest was lost as heat along the way.
2. Effect on numbers of individuals
   There are fewer individuals at the higher trophic levels (more producers than primary consumers, more primary consumers than secondary consumers, etc..)
4. Energy dynamics of living systems
   -
1. Autotrophs and heterotrophs
   
2. Food chain
   22.5 Food ChainsA food chain is a linear representation of who eats who.
   
3. Food web
   22.6 Food wwWeb
   A food web includes the dyanmics of various food chains, demonstrating the flow of energy (food) in an ecosystem.
1. Producers
   All consumers are ultimately dependent upon producers for energy.
2. Consumers
   Heterotrophs are consumers: primary, secondary, tertiary. (Which are we? We can be any: primary consumers when we eat plants; secondary consumers when we eat animals that eat plants; tertiary consumers when we eat animals that have eaten animals.)
3. Decomposers-detrivores
   Feed on dead/decaying matter. Examples: rolley-polleys (pill bugs), fungi, etc.. These are important in returning nutrients (nitrogen, phosphorour, etc.) into biotic tissues; thus playing a role in the cycling of the material composition of life.
4. Biological magnification
   22.7 Biomagnification
   The accumulation of toxins in the ecosystem. Example: we spray plants with DDT. Consumers eat the plants and other consumers that have eaten the plants. As we move up in trophic levels, the concentration of the toxin (DDT in this example) increases. Other toxins that are biologically magnified: mercury, pesticides, etc.. The accumulation of harmful chemicals in living tissues has serious consequences at every level.
5. Cycling of matter through ecosystems
   
1. Water cycle
   Examine the following diagrams: 22.8 Water Cycle
   
2. Carbon cycle
   22.9 Carbon Cycle
   
6. Ecosystem change
   Ecosystems do change, and in a very orderly way: succession: the orderly replacement of one species (or a group of species) by another. Much of succession is driven by abiotic factors: temperature, ph of the soil, etc..
   
1. Primary succession
   Orderly replacement that begins with bare rock or soil. (Example: the first organims to inhabit a particular rocky area may be lichens, which may alter the immediate environment to become more conducive to other species as well, and the cycle continues.
2. Secondary succession
   Secondary succession begins with an ecosystem that has been disturbed (example: an ecosystem disturbed by fire. There is an orderly succession of plant life that follows the burning down of a forested area.) Another example: lava flow.

22.10 Matter Cycles / Energy Flows
And remember: animals flow to the rhythm of the land.