1. C.2 Communities and Ecosystems pt 2
Essential idea: Changes in community structure affect and are affected by organisms.

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

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

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

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

6. 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 =
Animal
FCR
Beef Cattle
5 - 20
Pigs
Sheep
4 - 6
Poultry
Salmon
The lower the FCR the more efficient the method of food production.

7. C.2.A1 Conversion ratio in sustainable food production practices.
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
Animal
FCR
Beef Cattle
5 - 20
Pigs
Sheep
4 - 6
Poultry
Salmon
How ethical are the practices that lead to a low FCR?
What is more important, efficient food production or the ethical treatment of animals?

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

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

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

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

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

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

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

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

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

17. C.2.S1 Comparison of pyramids of energy from different ecosystems.
Net productivity of different ecosystems varies greatly
To understand why analyse the energy pyramids of the different ecosystems.
source of data:

18. C.2.S1 Comparison of pyramids of energy from different ecosystems.
Reasons for high net productivity of an ecosystem
1. High primary productivity (by producers) means more energy is available to the ecosystem.
2. The higher the efficiency of energy transfer between trophic levels the higher the net productivity. Energy transfer is typically 10%.
(5 trophic levels)
3. Higher the primary productivity and greater the efficiency 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.
(4 trophic levels)

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

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

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

22. C.2.S4 Analysis of data showing primary succession.
Use the examples to analyse data showing primary succession
Changes over time in total plant species richness over time at select sites on Mount Saint Helens, WA

23. Examples of secondary succession caused by disturbance to ecosystems
C.2.U6 Disturbance influences the structure and rate of change within ecosystems.
Examples of secondary succession caused by disturbance to ecosystems
Disturbance can be natural or caused by human activity
A stable deciduous forest community
A disturbance, such as a wild fire, destroys the forest
The fire burns the forest to the ground
The fire leaves behind empty, but not destroyed, soil.
Grasses and other herbaceous plants grow back first.
Small bushes and trees begin to colonize the area
Fast growing evergreen trees develop to their fullest, while shade-tolerant trees develop in the understory.
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.

24. Ways of measuring the effect of succession include: Species diversity
C.2.S5 Investigation into the effect of an environmental disturbance on an ecosystem.
Your investigation could compare a site undergoing secondary succession with a primary ecosystem. This could be extended to look at the various stages of secondary succession if local sites allow.
Ways of measuring the effect of succession include:
Species diversity
Stem/Seedling density
Biomass
Canopy coverage / light intensity at the surface
Depth/Volume of leaf litter
Soil nutrient levels
Possible opportunities would include:
Abandoned settlements/fields
Fields recovering after fire damage
Fire breaks in woodland

25. the flow of water or gases
C.2.U5 In closed ecosystems energy but not matter is exchanged with the surroundings.
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.

26. 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.
Harvesting of crops
Biomass (including phosphates and nitrates) removed from the agricultural ecosystem
phosphates added to the agricultural ecosystem
Agriculture
phosphates added to the agricultural ecosystem
Water run-off (leaching) from agricultural fields results in build-up of phosphates and nitrates in waterways and leads to eutrophication.
Phosphates and nitrates removed from the agricultural ecosystem and added to adjacent aquatic ecosystems
Nitrate fertiliser produced from atmospheric Nitrogen
(by the Haber process)