Botkin Chapter 4 - The Big Picture: Systems of Change

system

*set of components that function together as a whole a set of components that are linked and interact to produce a whole. for example, the river as a system is composed of sediment, water, bank, vegetation, fish, and other living things that all together produce the river

four reasons why solving environmental problems can be difficult

- exponential growth - long lag times - irreversible changes - chains of linked events often occur (env unity)

methods of studying global change (3)

- monitoring - geological history - modeling

Philosophy 101 had 50 students the first day of class. However, the class has a reputation for being an easy A, and the enrollment is unlimited. The # of students has increased a an avg rate of 5% per class day. What is the doubling time of the enrollment in the class

14 class days Td=70/5%per class day= 14 class days

The balance in your bank account is $1200. You have a monthly income of $600 and month expenses of $600. Calculate the ART of dollars in your account:

2 months; ART=S/F=$1200/$600per month=2months

A 1000 liter fish tank has a pump to filter and re-circulate the water. The water in the tank has a residence time of two hours. What is the rate of throughput due to the pump?

500L/hr ART=S/F 2hrs=1000L/F F=500L/hr

A hypothetical strain of bacteria doubles every two minutes (exponential growth). One single bacterium was put in a sealed bottle at 8:00 AM, and the bottle was filled at exactly 10:00 AM. What time was the bottle half full?

9:58AM

linear process

W/respect to systems, refers to the addition or subtraction of anything to a compartment ina system where the amount will always be the same, no matter how much you have added before and what else has changed bout the system and the environment. For example, if you collect stones from a particular site and place them in a basket and place one stone per hour, you will have placed 6 stones in 6 hours and 24 in 24 hours, and the change is linear with time.

*species

a group of individuals capable of interbreeding

*population

a group of individuals of the same species living in the same area or interbreeding and sharing genetic information

feedback

a kind of system response that occurs when output of the system also serves as input leading to changes in the system

average residence time (ART)

a measure of the time it takes for a given part of the total pool or reservoir of a particular material in a system to be cylced through the system. When the size of the pool and rate of throughput are constant, ART is the ratio of the total size of the pool or reservoir to the avg rate of transfer through the pool. ART= S/F *short RT= vulnerable to change; easy to go back to equillibrium *long RT= less vulnerable to change, hard to fix

equilibrium

a point of rest. at equilibrium, a system remains in a single, fixed condition and is said to be in equilibrium (compare w/steady state)

environmental unity

a principle of environmental sciences that states that everything affects everything else, meaning that a particular course of action could lead to a string of events. Another way of stating this idea is that you can't do only one thing

dynamic equilibrium

a steady state of a system that with negative feedback will return to a quasi-equilibrium state following disturbance

classical stability

a system characterized by constant conditions that, if disturbed from those conditions, will return to it once the factor that disturbed the system has been removed

closed system

a system in which there are definite boundaries to mass and energy and thus exchange of these factors with other systems does not occur

positive feedback

a type of feedback that occurs when an increase in output leads to a further increase in output. this is sometimes known as a vicious cycle, since the more you have, the more you get

negative feedback

a type of feedback that occurs when the system's response is in the opposite direction of the output. Thus negative feedback is self-regulating.

open system

a type of system in which exchanges of mas or energy occur with other systems

*biota

all organisms of all species living in an area or region up to and including the biosphere, as in "the biota or the Mojave Desert" or "the biota in that aquarium"

*ecosystem

an ecological community and its local, nonbiological community. an ecosystem is the minimum system that includes and sustains life. it must include at least an autotroph, a decomposer, a liquid medium, a source and sink of energy, and all the chemical elements required by the autotroph and the decomposer

balance of nature

an environmental myth that the natural environment, when not influenced by human activity, will reach a constant status, unchanging over time, referred to as an equilibrium state

A system with a greater input that output would experience:

an increase in storage

which of the following is associated with natural systems that have long residence times (for example, underground aquifers) a) throughput is greater than pool size b) difficulty in flushing out pollutants once they are introduced c) the system is quickly polluted and quickly cleaned d) the system is quickly polluted but slowly cleaned e) short regeneration times following periods of greater output than input

b) difficulty in flushing out pollutants once they are introduced

materially closed system

characterized by a system in which no matter moves in and out of the system, although energy and information may move across the system's boundaries. For example, Earth is a materially closed system for all practical purposes

dynamic system

characterized by a system that changes often and continually over time

nonlinear process

characterized by system operation in which the effect of adding a specific amount of something changes, depending upon how much has been added before

A chemical spill has occurred on the shore of a lake in an area where the underlying aquifer is widely used as a drinking water supply. The pollutants threaten to flow into both the surface water and the groundwater. The residence time of water in the lake is short, and the residence time in the groundwater is long. Which of the following statements is correct? a) pollutants will quickly invade the lake and will linger there the longest b) pollutants will quickly invade the groundwater and will linger there the longest c) pollutants will quickly invade the groundwater, but will linger longest in the lake d) pollutants will quickly invade the lake, but will linger longest in the groundwater e) there is no cause for alarm

d) pollutants will quickly invade the lake, but will linger longest in the groundwater

The tendency of an ecological system to remain relatively stable over a long period of time, even though much material and energy is entering and leaving the system is an example of:

dynamic equilibrium

simply stated, the principle of environmental unity states that:

everything affects everything else

exponential growth

growth in which the rate of increase is a constant percentage of the current size; that is, the growth occurs a constant rate per time period

*biosphere

has several meanings. one is that part of a planet where life exists. on earth it extends from the depths of the oceans to the summits of mountains, but most life exists within a few meters of the surface. A second meaning is the planetary system that includes and sustains life, and therefore is made up of the atmosphere, oceans, soils, upper bedrock, and all life

considering inputs and outputs from ti, the pool will be in a steady state when:

input equals outputs

Change that tends to stabilize a system is called:

negative feedback

Consider a situation where increased solar radiation reaches the Earth's surface and raises the ocean temperature. This results in more evaporation, which produces more clouds. The increased cloud cover reduces the amount of solar radiation that reaches the surface of the Earth. This is an example of:

negative feedback

A______type of feedback mechanism functions as a ____________process for the system as a whole.

negative; stabilizing or self-regulating

static system

neither system elements nor the system itself changes much over time in relation to the environment.

overshoot and collapse

occurs when growth in one part of a system over time exceeds carrying capacity, resulting in a sudden decline in one or both parts of the system

Gaia hypothesis

states that life manipulates the environment for the maintenance of life, for example: algae floating on near the surface of the ocean influence rainfall at sea and the carbon dioxide content of the atmosphere, which affects the climate of the planet. These types of processes are seen by some as a type of physiological self-regulation.

flow

the AMOUNT of material transferred within a system

flux

the RATE of transfer of material within a system per unit time

lag time

the delay in time between the cause and appearance of an effect in a system

uniformitarianism

the principle stating that processes that operate today operated in the past. therefore, observations of processes today can explain events that occurred in the past and leave evidence, for example, in the fossil record or in geologic formations

doubling time

the time necessary for a quantity of whatever is being measured to double. (Td=70/growth rate%)

*ecological community

this term has two meanings (1) a conceptual or functional meaning: a set of interacting species that occur in the same place (sometimes extended to mean a set that interacts in a way to sustain life). (2) an operational meaning: a set of species found in an area, whether or not they are interacting

The premise that the natural forces are acting today are the same as those that were acting in the past is known as:

uniformitariansim

steady-state system

when an input equals output in a system, there is no net change and the system is said to be in a steady state. a bathtub with water flowing in and out at the same rate maintains the same water level and is in a steady state (compare with equilibrium)

output

with respect to basic operation of system, refers to material or energy that leaves a particular storage compartment

input

with respect to basis concepts of systems, refers to material or energy that enters a system