Ecosystems maintain themselves by cycling energy and nutrients obtained from external sources

Ecosystems maintain themselves by cycling energy and nutrients obtained from external sources

An example of the concept of energy flow through trophic levels of a food chain.

1st Law of Thermodynamics2nd Law of Thermodynamics

1st Law = Energy is neither created or destroyed.

In nature energy comes in as sunlight, passes along as biomass, and exits as heat bit by bit.

The amount of energy within a system is constant. The form of the energy however changes.

Two basic processes must occur1. Cycling of chemical elements2. Flow of energy

1. Transfer- Basic flow through a system. Change in location of energy or matter○ Ex. Water rushing down a hill

2. Transformation- A new product is created. Change of state (solid, liquid, gas). ○ Ex. Water evaporating into water vapor

Producers transform light energy from the sun into chemical energy (photosynthesis)

Consumed and transferred to other organisms (respiration)

Eventually dead organism are broken down by decomposers and nutrients are returned to the soil.

Energy is lost as heat to the atmosphere during this process but is not lost to the system.

2nd Law = Energy goes from a concentrated form into a dispersed form.

Available energy decreases with time as order takes energy.

Energy transfer is not 100% effective.

There is less and less available energy in each successive level.

The entropy of an isolated system not in equilibrium will tend to increase over time.

In other words, the randomness (entropy) of the universe is always increasing

Entropy is a measure of the amount of disorder in a system.

An increase in entropy arising from energy transformations reduces the energy available to do work.

When energy conversions take place they are not 100% efficient and some energy is wasted as heat energy.

Within any food web the amount of energy that is found in the producers is much more than that found in the top carnivores (tertiary etc…).

As energy is transferred and transformed from one organism to the next (moves up the trophic levels) energy is lost as heat.

When a loin chases a zebra, the zebra attempts to escape, changing stored chemical energy into useful work

During its attempt to escape some of the stored energy is converted to heat and lost from the food chain.

Energy = work + heat (and other wasted energy)

Calculating the percent of energy transferred

Divide energy from the second trophic level by the energy from the first trophic level.

Multiply by 100

Pour 1000 mL of tap water into the 1000 mL beaker. Add 2 drops of food coloring to the water and swirl. The water in this beaker represents the energy found in the first trophic level (producers)

Line up 3 clear cups. How much energy was transferred from trophic level one to trophic level 2?

Pour that percentage from the 1000 mL into the first cup.

How much energy was transferred from the second trophic level to the third?

Pour that percentage from cup one into cup two.

Repeat for the fourth trophic level/cup three.

Flow of energy through a ecosystem can be shown as an Ecological Pyramid

Equilibrium refers to a state of balance in an ecosystem Steady state Static

Steady-state equilibrium – Maintains a stable system due to constant flow of inputs and outputs

Steady-state equilibrium refers to an ecological system because such a system requires inputs and outputs in order to function. .

Static equilibrium - doesn't’t apply to natural systems as there are no inputs or outputs so no change occurs.

Static – always in balance Inanimate objects

Stable – Returns to balance after disturbance Rubber

Unstable – Achieves new balance after disturbance Car Crash

A system that is an unstable equilibrium and faces a disturbance will not return to the original equilibrium and establish a new one.

As long as there is sunlight, plants can perform the process of photosynthesis, however when night time comes, plants must adopt a new equilibrium to produce food, this equilibrium is known as respiration.

Ecosystems are said to be “Self-regulating”

Each contain feedback mechanisms which function to maintain the system in its equilibrium state. Positive Negative

Negative Feedback – dampens effects and promotes return to stability Predator-prey relationships

Positive Feedback – Amplifies change and leads to deviation from stability Temperature and greenhouse gases

The capacity of an ecosystem to respond to a disturbance. 

Absorb disturbance without shifting to an alternative state and losing function and services. conditions

Disturbances can include Fires Flooding Windstorms Insect population explosions Deforestation Fracking Pesticide

Some disturbances can significantly affect an ecosystem and can cause an ecosystem to reach a threshold beyond which some species can not recover.

Reduction of biodiversitionExploitation of natural resourcesPollutionLand-use

Positive Feedback tends to amplify and drive a system toward a tipping point

Minimum amount of change within a system that will destabilize it, causing it to reach a new equilibrium or stable state.

At a particular moment in time, a small change within a global climate system can transform a relatively stable system to a very different state of the climate

Identifying what phenomena are capable of passing tipping points can be tricky.

“Tipping elements” is used to describe large-scale components of the Earth System which may be subject to tipping points. Arctic Sea Ice Ice Sheets El Nino Amazon Rain Forest