Sponge: Set up Cornell Notes on pg. 47

Topic: C.2 Gersmehl Diagrams and ecosystems

Essential Question: Explain the differences between an open and closed ecosystem.

BIOZONE: None

Textbook: None

C.2 Gersmehl Diagrams and ecosystems

Key Vocabulary:Gersmehl DiagramClosed Ecological ecosystemDisturbance Hypothesis

Explain the differences between an open and closed ecosystem.

• 46 Gersmehl Diagram: Key

Gersmehl Diagram: Rainforest Gersmehl Diagram: Taiga

Disturbance Hypothesis graph

Gersmehl DiagramsGersmehl diagrams describe energy flow and nutrient recycling of different biomes• A common method of demonstrating the cycling of nutrients within

the main “stores” of an ecosystem

Gersmehl Diagrams

• Arrows of varying thickness represent nutrient transfer

• Circles of varying sizes represent the size of the nutrient stores

Included in the diagrams:• Input- nitrogen, carbon, minerals

• Output- loses of nutrients by leaching and runoff

• Flows- such as leaf and needle fall from biomass to litter, and uptake of nutrients from the soil

Skill

• Construction of Gersmehl diagrams to show the inter-relationships between nutrient stores and flows between taiga, desert and tropical rainforest

Construct a Gersmehl Diagram: RainforestAlways read the information first!• Biomass is the main store of nutrients because the tropical rainforest has tall,

dense vegetation with many layers and multiple species• Precipitation (P): rainfall is high all year• Litter has a very small store of nutrients because of the high rate of

decomposition• Soil has a very small store of nutrients because of leaching and low soil fertility• Weathering (W) is rapid because of high heat and humidity• Leaching (Le) is high because of high rainfall (Leaching is the process of

extracting minerals from a solid by dissolving them in a liquid)• Runoff (R) is high due to such large amounts of rain, that the soil cannot absorb

it at all

Construct a Gersmehl Diagram: Rainforest• Biomass is the main store of nutrients because

the tropical rainforest has tall, dense vegetation with many layers and multiple species

• Precipitation (P): rainfall is high all year• Litter has a very small store of nutrients

because of the high rate of decomposition• Soil has a very small store of nutrients because

of leaching and low soil fertility• Weathering (W) is rapid because of high heat

and humidity• Leaching (Le) is high because of high rainfall

(Leaching is the process of extracting minerals from a solid by dissolving them in a liquid)

• Runoff (R) is high due to such large amounts of rain, that the soil cannot absorb it at all

Use this model to help you set up your G. Diagram

Middle L p. 46

Construct a Gersmehl Diagram: Rainforest• Biomass is the main store of nutrients

because the tropical rainforest has tall, dense vegetation with many layers and multiple species

• Precipitation (P): rainfall is high all year• Litter has a very small store of nutrients

because of the high rate of decomposition• Soil has a very small store of nutrients

because of leaching and low soil fertility• Weathering (W) is rapid because of high heat

and humidity• Leaching (Le) is high because of high rainfall

(Leaching is the process of extracting minerals from a solid by dissolving them in a liquid)

• Runoff (R) is high due to such large amounts of rain, that the soil cannot absorb it at all

Construct a Gersmehl Diagram: Taiga• Litter is the largest store of nutrients

because of the low rate of decomposition as a result of low temperatures

• Run-off is high. The ground is still frozen when the snow is melting

• Biomass is relatively low because conifers have only one layer of needles and there is no undergrowth

• Transfer from biomass to litter is high because of the constant supply of needles falling from coniferous trees

• Soil stores are very small. Poor soil is formed from glacial deposits and so there is low soil fertility

• Weathering of rocks is slow because of the cold

Use this model to help you set up your G. Diagram

Middle R p. 46

Construct a Gersmehl Diagram: Taiga• Litter is the largest store of nutrients

because of the low rate of decomposition as a result of low temperatures

• Run-off is high. The ground is still frozen when the snow is melting

• Biomass is relatively low because conifers have only one layer of needles and there is no undergrowth

• Transfer from biomass to litter is high because of the constant supply of needles falling from coniferous trees

• Soil stores are very small. Poor soil is formed from glacial deposits and so there is low soil fertility

• Weathering of rocks is slow because of the cold

Application

• Consideration of one example of how humans interfere with nutrient cycling

An example of humans interfering with nutrient cycling

• Collapse of marine fisheries as a result of overfishing and habitat loss has affected nutrient cycling in the marine environment

• The role of fish as nutrient recyclers is critical

An example of humans interfering with nutrient cycling

• Eighty percent of the nutrients that are used by primary producers are supplied by fish

• Removal of fish in areas where nitrogen is low will affect primary production by plants

• This has a negative effect on the herbivores in that community– Ex: Estimates of nitrogen excretions rates for grey snapper in the Bahamas

were 456% higher in unfished area. The excretion rates of phosphates were 451%

– The sea grass beds that are the key habitat for young fish may be affected by this lack of recycled nutrients

Ecological Systems

• Most ecosystems are open– Light enters and is trapped by plants– Herbivores eat the plants and their

feces fertilizes the soil– Minerals may be leached by water

after rain and be carried down river to a new ecosystem

Understandings

• In closed ecosystems energy but not matter is exchanged with the surroundings

A Closed Ecosystem• A closed ecological system (CES) does

not rely on exchange of matter with its surroundings

• Waste products must be used by at least one other species– Urine, feces, and CO² must be converted

into O², food, and H₂O

• This involves at least one autotroph which can use waste products to make food (as long as sunlight is available)

Biosphere 2

• Large research facility owned by University of AZ

• Experiments carried out weekly while humans live in the closed environment

Bio-Dome• Bio-Dome is a 1996 American comedy film

• Parody of Biosphere 2

• The plot of the film revolves around two clumsy, dim-witted slackers who, while on a road trip, look for a toilet stop in what they believe is a shopping mall, which in fact turns out to be a "bio-dome", a form of a closed ecological system in which five scientists are to be hermetically (completely) sealed for a year.

A Closed Ecosystem• No natural system on Earth is considered to be a closed system

– BUT…the entire planet can be thought to be almost closed– Large amounts of light energy enter the Earth and eventually return

to space as heat, but matter is not exchanged.

Understandings

• Disturbance influences the structure and rate of change within ecosystems

Disturbances influence the structure and rate of change in an ecosystem

• A disturbance is a new environmental condition that affects the structure and rate of change in an ecosystem

• Natural– Fire/flood/wind/insect invasion

• Humans- unnatural– Clearing a forest/ building a homes or

a road/plowing a field

Disturbance Hypothesis

In 1975 Joseph Connell proposed a new idea• Disturbance hypothesis:

Disturbance is a common phenomenon and can actually have a BENEFICIAL effect on species diversity in a community– Ex: forest fire

Disturbance Hypothesis Graph

Make observations about the graph. What do you notice?

Disturbance Hypothesis GraphMake observations about the graph. What do you notice?

• Low disturbances will cause a decline in diversity– Only the species that are the best

competitors will dominate• High levels of disturbance lower diversity

– Only a few species can complete their life cycle between disturbances

• Intermediate levels of disturbance, are the most effective at maintaining diversity – There is enough time between disturbances

for a number of species to colonize an area & slows the growth of dominant species

Bottom p. 46

Skill

• Investigation into the effect of an environmental disturbance on an ecosystem

Guidance

• Examples of aspects to investigate in the ecosystem could be species diversity, nutrient cycling, water movement, erosion, leaf area index, among others