### system:

Natural system
* All natural systems have tiny amounts of mercury.
* Many natural systems affect wildlife survival and population fluctuations.
* are a complex interaction of living and nonliving parts
  - heterogeneous, most subsurface systems markedly so
  - resilient because their complexity has been evolving for billions of years
* can operate just fine without human behavioral systems.
* do have the capacity to reuse waste, but that capacity is limited.
* have little opportunity to adapt to climate change
  - two types of food webs-grazing and detritus
* rely on nutrients from slowly decomposing leaves, plants, branches and creatures.
* remove phosphorus through absorption onto soil particles.
* s are complex and hence require complex models to explain their behavior.

Navigation system
* Most navigation systems use time and distance to figure location.
* Some navigation systems use south as the reference plane.
* are the biggest lifesavers for airplanes.

### system:

Nervous system
* All nervous systems contain glial cells.
* are body parts
  - found in most multicellular animals, but vary greatly in complexity
  - highly organized collections of neurons and supporting cells
  - part of bodies
  - solid objects
* can change.
* consists of two main divisions.
* contains neurons and cells called glia.
* has simple brain of paired ganglia, and ventral nerve cord.
* is brain located in dorsal cavity and spine in vertebral canal.
* perform primarily analog computations, and quantize the computed result.
+ Nerve, Nerve Structure: Anatomy of the nervous system
  * Nervous system contains neurons and cells called glia. Glia cells keep the neurons safe and healthy. Neurons take messages to and from the CNS to the rest. The dendrite and axon are fibers that go out from the cell body. Axons take information 'away from' the cell body. Dendrites take information to the cell body.

Neural system
* consist of layers of neurons which are connected to each other
  - one or more interconnected layers of neurons
* is the intellect, memory and activity of a human being.

### system:

Open system
* Open System Is a system where both matter and energy can cross the boundary of the system.
* architecture An architecture whose specifications are public.
* are common in nature
  - dynamic systems that interact with and respond to their environment
  - systems that interact with their environment
  - very common in the physical environment
* evolve while closed systems decay.
* foster a marketplace of content rather than a competition for market share.
* lack capillaries and the blood perfuses through the tissues of the animal's body.

Operational system
* allow an organization to function.
* are like the heart, lungs, arms and legs of an organization.

Optical system
* All optical systems contain both imaging and non-imaging or illumination systems.
* are also useful for capturing movement of actual animals
  - more complex than electrical systems
* have problems with occlusion caused by one body part blocking another from view.
* make use of the visible-light portion of the electromagnetic spectrum.
* require nanometre scale apertures and light guides.
* use either natural or artificially generated guide stars to detect the distortions.

Organ system
* All organ systems interact and are interdependent
  - to make an organism
* Every organ system has different functions and physical characteristics.
* Most organ systems are operational in the fetus by four to six months.
* Some organ systems have their own internal control systems instead of, or in addition to, hormones.

Organic system
* fluctuate near stationary states.
* have molecular recognition abilities that have had a long time to evolve.
* use composts, manures, and biological pest controls.

Parasympathetic system
* innervates the fundus and stimulation causes sustained contraction.
* promotes normal responses including slowing down heartbeat.