BioKnowledgy C.2 Communities and ecosystems

C.2 Communities and Ecosystems

Essential idea: Changes in community structure affect and are affected by organisms.

Between the two coral heads is a crown of thorns sea star. These predators graze the corals. If too successful they will change the community structure of the reef so that it becomes dominated by algae rather than coral. This in turn forces the sea star to migrate to other reefs where coral dominates the community structure.

By Chris Paine

https://bioknowledgy.weebly.com/

https://bioknowledgy.weebly.com/

Understandings

Statement Guidance

C.2.U1 Most species occupy different trophic levels in

multiple food chains.

C.2.U2 A food web shows all the possible food chains in a

community.

C.2.U3 The percentage of ingested energy converted to

biomass is dependent on the respiration rate.

C.2.U4 The type of stable ecosystem that will emerge in an

area is predictable based on climate.

C.2.U5 In closed ecosystems energy but not matter is

exchanged with the surroundings.

C.2.U6 Disturbance influences the structure and rate of

change within ecosystems.

Applications and Skills

Statement Guidance

C.2.A1 Conversion ratio in sustainable food production

practices.

C.2.A2 Consideration of one example of how humans

interfere with nutrient cycling.

C.2.S1 Comparison of pyramids of energy from different

ecosystems.

C.2.S2 Analysis of a climograph showing the relationship

between temperature, rainfall and the type of

ecosystem.

C.2.S3 Construction of Gersmehl diagrams to show the

inter-relationships between nutrient stores and

flows between taiga, desert and tropical rainforest.

C.2.S4 Analysis of data showing primary succession.

C.2.S5 Investigation into the effect of an environmental

disturbance on an ecosystem.

Examples of aspects to investigate in the

ecosystem could be species diversity, nutrient

cycling, water movement, erosion, leaf area

index, among others.

C.2.U2 A food web shows all the possible food chains in a community.

There can be more than one producer in a food web, and consumers can occupy multiple positions (trophic levels)

A food web is a diagram that shows how food chains are linked together into more complex

feeding relationships within a community

http://ib.bioninja.com.au/_Media/food_web_med.jpeg

http://ib.bioninja.com.au/


http://ib.bioninja.com.au/_Media/food_web_med.jpeg

C.2.U1 Most species occupy different trophic levels in multiple food chains.

http://i-biology.net/


C.2.U1 Most species occupy different trophic levels in multiple food chains.



C.2.S3 Construction of Gersmehl diagrams to show the inter-relationships between nutrient stores

and flows between taiga, desert and tropical rainforest.

http://commons.wikimedia.org/wiki/File:Nutrient_cycle.svg

Gersmehl diagrams were first developed in 1976, by P.F. Gersmehl, to show the

differences in nutrient flow and storage between different ecosystems

Sinks for nutrient storage:• Biomass (flora and fauna)• Litter• Soil







Nutrient inputs into the ecosystem:• Nutrients dissolved in raindrops• Nutrients from weathered rock

Nutrient outputs (losses) from the ecosystem:• Nutrients lost through surface runoff• Nutrients lost through leaching





When used to analyse a particular ecosystem:• Diameter of sinks are proportional

to the mass of nutrients stored in each sink

• the thickness of the arrows are proportional to the rate of nutrient flow



Flows between the sinks:• Littering (including withering, defoliation,

excretion, unconsumed parts left over, dead bodies of animals, and so on) *

• Decomposition of the litter into inorganic nutrients, which are then stored in the soil

• Nutrient uptake by plants

Human interactions are not considered – do not confuse littering with dropping trash

*




• Litter (pine needles) is the main store

• Slow rate of nutrient transfer between stores

• Soil is the main store• Slow rate of nutrient

transfer between stores (except for the transfer from biomass to litter)

• Biomass is the main store (soil is nutrient poor)

• Fast rate of nutrient transfer between stores

tagia(temperate forest)

desert tropical rainforest

Image source: Allott, A. (2014). Biology: Course companion. S.l.: Oxford University Press.

C.2.U3 The percentage of ingested energy converted to biomass is dependent on the respiration

rate.




rate.




rate.




rate.




rate.



C.2.A1 Conversion ratio in sustainable food production practices.

In commercial (animal) food production, farmers measure the food conversion ratio (FCR). It is a measure of an animal's efficiency in converting feed mass into the desired

output. For dairy cows, for example, the output is milk, whereas animals raised for meat, for example, pigs the output is the mass gained by the animal.

It is calculated by:

mass of the food eaten (g)

(increase in) desired output (g)

(per specified time period)FCR =

http://en.wikipedia.org/wiki/Feed_conversion_ratio

Animal FCR

Beef Cattle 5 - 20

Pigs 3 - 3.2

Sheep 4 - 6

Poultry 1.4 - 2

Salmon 1.2 - 3

The lower the FCR the more efficient the method of food production.


C.2.A1 Conversion ratio in sustainable food production practices.


Animal FCR

Beef Cattle 5 - 20

Pigs 3 - 3.2

Sheep 4 - 6

Poultry 1.4 - 2

Salmon 1.2 - 3

A good (low) FCR is obtained by minimising the losses of energy by respiration, for example:• Restricting animal movement• Slaughtering the animal at a young

age (older animals have higher FCRs as they grow more slowly)

• Optimising feed so it is efficiently digested

How ethical are the practices that lead to a low FCR?What is more important, efficient food production or the ethical treatment of animals?


C.2.S1 Comparison of pyramids of energy from different ecosystems.




























source of data: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/NetProductivity.html

To understand why analyse the energy pyramids of the different ecosystems.

Net productivity of different ecosystems varies greatly

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/NetProductivity.html


1. High primary

productivity (by producers) means more energy is available to the ecosystem.

3. Higher the primary productivity and greater the

effeciency of energy transfer mean that more energy is available at high trophic levels. This can support longer the food chains, hence and more trophic levels increasing net productivity. Ecosystems rarely have more than 4 or 5 trophic levels.

2. The higher the

efficiency of energy transfer between trophic levels the higher the net productivity. Energy transfer is typically 10%.

Reasons for high net productivity of an ecosystem

(4 trophic levels)

(5 trophic levels)

C.2.U4 The type of stable ecosystem that will emerge in an area is predictable based on climate.

Biome is a geographical area that has a particular climate and sustains a specific

community of plants and animals (i.e. a type of ecosystem)

Biosphere is the total of

all areas where living things are found (i.e. the totality of biomes)

• The main factors affecting the distribution of biomes is temperature and rainfall• These factors will vary according to latitude and longitude, elevation and proximity to the sea• Temperature is influential because it affects the rate of metabolism – the phases in the life cycles

of many organisms are temperature dependent• In the same way, the availability of fresh water (both in the soil and in rivers and lakes) is critical to

the growth and nutrition of organisms• Rainfall and warmer temperatures are more common near the equator and less common at the

poles

http://ib.bioninja.com.au/options/option-g-ecology-and-conser/g2-ecosystems-and-biomes.html





The six major types of biome/ecosystem are outlined in the table below






The six major types of biome/ecosystem are outlined in the table below





C.2.S2 Analysis of a climograph showing the relationship between temperature, rainfall and the

type of ecosystem.

http://cispatm.pbworks.com/f/1209212862/biome_graph.jpg

n.b. The biomes in regions within the dashed line are strongly influenced by other factors (e.g. seasonality of drought, fire, animal grazing).

A climograph is a diagram which

shows the relative combination of temperature and precipitation in an area.

This modified climograph (first developed by Robert Whittaker) shows the stable ecosystems/biomes that arise as a result of the relative combination of temperature and precipitation.

It is a graphical representation of the biome summary table (last slide).


C.2.S2 Analysis of a climograph showing the relationship between temperature, rainfall and the

type of ecosystem.


n.b. The biomes in regions within the dashed line are strongly influenced by other factors (e.g. seasonality of drought, fire, animal grazing).

A climograph is a diagram which

shows the relative combination of temperature and precipitation in an area.

This modified climograph (first developed by Robert Whittaker) shows the stable ecosystems/biomes that arise as a result of the relative combination of temperature and precipitation.

It is a graphical representation of the biome summary table (last slide).






http://bcs.whfreeman.com/thelifewire/content/chp55/55020.html










Changes over time in total plant species richness over time at select sites on Mount Saint Helens, WAhttp://www.nature.com/scitable/knowledge/library/succession-a-closer-look-13256638

Use the examples to analyse data showing primary succession

http://wps.pearsoncustom.com/wps/media/objects/2128/2179441/28_03.html

http://www.nature.com/scitable/knowledge/library/succession-a-closer-look-13256638

http://wps.pearsoncustom.com/wps/media/objects/2128/2179441/28_03.html

C.2.U6 Disturbance influences the structure and rate of change within ecosystems.


1. A stable deciduous forest community2. A disturbance, such as a wild fire, destroys the forest3. The fire burns the forest to the ground4. The fire leaves behind empty, but not destroyed, soil.5. Grasses and other herbaceous plants grow back first.6. Small bushes and trees begin to colonize the area7. Fast growing evergreen trees develop to their fullest,

while shade-tolerant trees develop in the understory.8. The short-lived and shade intolerant evergreen trees

die as the larger deciduous trees overtop them. The ecosystem is now back to a similar state to where it began.

http://en.wikipedia.org/wiki/File:Secondary_Succession.png

Examples of secondary succession caused by disturbance to ecosystems

Disturbance can be natural or caused by human activity


http://en.wikipedia.org/wiki/File:Secondary_Succession.png

C.2.S5 Investigation into the effect of an environmental disturbance on an ecosystem.

Your investigation should compare a site undergoing secondary succession with a primary ecosystem. This can be extended to look at the various stages of secondary succession if local sites allow.

Possible opportunities include:• Abandoned settlements/fields• Fields recovering after fire damage• Fire breaks in woodland

Ways of measuring the affect of succession include:• Species diversity• Stem/Seedling density• Biomass• Canopy coverage / light intensity at the

surface• Depth/Volume of leaf litter• Soil nutrient levels

http://en.wikipedia.org/wiki/File:NASAburningbrazil.jpg

http://en.wikipedia.org/wiki/File:NASAburningbrazil.jpg

C.2.U5 In closed ecosystems energy but not matter is exchanged with the surroundings.

http://cdn.pickchur.com/wp-content/uploads/2013/02/bottle_ecosystem.jpg

Most natural ecosystems are ‘open ecosystems’. They can exchange energy and matter with adjacent ecosystems or environments. Examples of matter exchange are:• migration of animals• harvesting of crops• the flow of water or gases

Closed ecosystems, such as mesocosms(4.1.S2) and the Biosphere 2 project are closed ecosystems. Although energy can be exchanged (most commonly through the entry of light and the loss of heat), matter remains in the system. Water and nutrients are cycled within the ecosystem.

Closed ecosystems are of interest to Scientists as they provide insight in how extra-terrestrial habitats can be setup and maintained.

http://upload.wikimedia.org/wikipedia/commons/1/13/Biosphere_2_-_1998_a.jpg

http://cdn.pickchur.com/wp-content/uploads/2013/02/bottle_ecosystem.jpg

http://upload.wikimedia.org/wikipedia/commons/1/13/Biosphere_2_-_1998_a.jpg

C.2.A2 Consideration of one example of how humans interfere with nutrient cycling.

Humans practices can accelerate the the flow of matter into and out of ecosystems. This by implication (and often design) alters the nutrient cycling in ecosystems.

Phosphate mined and

converted to fertiliser.

Nitrate fertiliserproduced from

atmospheric Nitrogen

(by the Haber process)

Agriculture

Harvesting of crops

Water run-off (leaching) from

agricultural fields results in build-

up of phosphates and

nitrates in waterways and

leads to eutrophication.

Bibliography / Acknowledgments

Jason de Nys





http://www.slideshare.net/jasondenys



Education

BioKnowledgy C.2 Communities and ecosystems