Chapter 3 Botkin and Keller Flashcards
What is a system?
a set of components, or parts, that function together as a whole
ex: organism, city, river, the earth
What is an open system and give examples:
in an open system, some energy or material (solid, gas or liquid) moves into or out of the system
Ex: the ocean, water moves into the ocean from the atmosphere and out again
All real systems that we deal with in the environment are open to the flow of matter, energy and information
What is a closed system and give examples:
No matter moves in or out of the system. Energy and and information nmvoes around in the system but does not go in our of of the closed system
ex: the earth’s atmosphere
What is a static system?
A static system has a fixed condition
Ex: a birthday balloon attached to a pole - it stays in one place
What is a dynamic system?
A dynamic system changes, often continually over time.
ex: a hot air ballon, moves in response to the wind and air density
What is classical stability?
A kind of static system, but has a constant condition, and if it disturbed from that condition, it returns to it once the disturbing factor has been removed
Ex: pendulum on a grandfather clock that swings back and forth
Is the population, ecosystem and earths biosphere a static system?
It was believed so before, but the more it is studied, the clearer it becomes that these ecological systems are dynamic systems, and require change
What are the two important distinctions of open systems?
steady state or non steady state
What is a steady state system?
The inputs are equal to the outputs, so the amount stored within the system is constant
In ideal example is a dam or lake into which water flows in and out
Does forcing systems into steady state work?
it fails most often, it is difficult to force natural ecological and environmental system into s steady state
Ex: Missouri River
What is the idea of “the balance of nature”
The idea that our natural environment, when left undisturbed by people, tent toward some sort of steady state
Also called dynamic equilibrium
What is a definition of an ecosystem?
communities of organism and their nonliving environment in which nutrients and other chemicals cycle and energy flows
What can cause disruption to the “steady state”?
Primary human intervention, but even when humans no not interfere with the natural environment it does not stay steady for long due to natural disturbances
Can systems stay steady state forever?
No, changes over time will happen due to natural disturbances
forests, rivers and coral reefs can be affected by storms, fires or floods
What is average residence time?
How long, on average, a unit of something of interests to us will remain in a reservoir
Ex: how much water can be stored for how long in one reservoir
What is feedback?
Feedback occurs when the output of a system (or a compartment in a system) affects its input - this can be negative or positive
Ex. human temperature
What is negative feedback?
a way of feedback to self-regulates according to input (important for steady-state-systems)
humans sweat (output) to cool down in hot weather (input)
What is positive feedback?
this occurs when an increase in output leads to a further increase of the output - it is vicious cycle. Destabilizing
Best example is a forest fire
Examples of people’s use of the environment that leads to positive feedback?
Off-road vehicles cause soil erosion
Can systems have both positive and negative feedback?
Hell yeah, like the human population in large cities
Positive feedback on the population size happens when people move there for work and higher standards of living, and more people means more opportunities - more migration
Negative feedback occurs in the form of increased air and water pollution, disease and crime
Is negative feedback always desirable?
No, despite being the “self-regulating” feedback, it is not always what you want - it depends on the system and the potential changes
What is a flow?
the amount transfered
what is a flux?
rate of transfer per unit time
What is a linear flow?
in a linear flow process, if you add the same amount of anything to a compartment in a system, the change will always be the same, no matter how much you have added before and no matter what else has changed about the system and its environment
what are nonlinear flow processes?
the effect of adding a specific amount of something changes depending on how much has been added before
nonlinear process often have lag time or delays
Ex: something fills up (like drinking water)
What is lag time?
Lag time is the delay between a cause and the appearance of its effect.
we can fail to recognize the change and know what is the cause and what is the effect. We can also come to believe that a possible cause is not having a detrimental effect, when in reality the effect is only delayed
What is exponential growth?
Change is exponential when it increases or decreases at a constant rate per time period, rather than by a constant amount.
Looks like a J-shape
What is doubling time?
The doubling time is the time necessary for the quantity being measured to double. A useful rule is that the doubling time is approximately equal to 70 divided by the annual percentage growth rate
What is overshoots?
when growth exceeds the carrying capacity - results in a collapse
What are some examples of irreversible consequence?
Good examples of this are soil erosion and the harvesting of old-growth forest.
With soil erosion, there may be a long lag time until the soil erodes to the point where crops no longer have their roots in active soil that has the nutrients necessary to produce a successful crop. But once the soil is eroded, it may take hundreds or thousands of years for new soil to form, and so the consequences are irreversible in terms of human planning.
What is the idea of environmental unity?
the idea that it is impossible to change only one thing; everything affects everything else.
illustrated by the ideas of urbanization
What is the idea of uniformitarianism?
the idea that geological and biological processes that occur today are the same kinds of processes that occurred in the past, and vice versa. Thus, the present is the key to the past, and the past the key to the future.
we can assume that in the future the same physical and biological processes will operate, although the rates will vary as the environment is influenced by natural change and human activity
Who introduced the idea of uniformitarianism?
James Hutton in 1785 - father of geology
