Energy and Food webs Flashcards
Define productivity, GPP, respiration and NPP.
Productivity- rate of production of biomass.
1) Gross Primary productivity (GPP)- entire/total photosynthetic output.
2) Respiration- energy used for metabolic maintenance.
3) Net primary productivity (NPP) - Production remaining after respiration- which may then be allocated to either growth or reproduction.
NPP = GPP - R
Photosynthetic organisms only grow whenn GPP > R.
Examples of productivity
Tropical rainforests- highly productive. NPP exceeds 3500 gCm^-2yr^-1
Tundra rainforest- low productivity.
NPP is 100-200 gCm^-2yr^-1
gCm^-2yr^-1 = grams of carbon per metre sq/yr
Define secondary productivity
Rate of production of new biomass by heterotrophic organisms.
Energy flow through a food chain.
Most of the energy passes to the decomposer community. Energy is lost as it passes through the food chain.
Food chain trends
Higher trophic levels tend to support fewer species and smaller populations. Other trends include:
* Larger bodysize
* Longer lifespan
* Lower reproductive rates
* Higher metabolic costs
* Food with a high calorific value
* Greater assimilation efficiency.
Pyramids of energy and biomass
Illustrates rapid loss of energy as one moves from plants to herbivores to carnivores.
Role of decomposers in food chain and food webs?
Detritivores and decomposers release the energy locked in a range of dead, decaying and waste materials.
Reducer communities are important in returning nutrients and energy to the rest of the ecosystem. These organisms are essential for maintaining energy and nutrient flows and many ecosystem services.
Production efficiencies of endotherms vs ectotherms
Ectothermic animals - 9.8% - 55.6%
Endothermic animals - 0.9 - 3.1%
Endotherms use more energy to regulate body temp, i.e less efficient than ectotherms.
Growth involves 2 flows of energy?
Chemical energy used to make tissues (proteins, nucleic acids etc.) (measured from energy content of tissues)
Metabolic energy used to build those tissues (estimated via O2 consumption)`
Importance of energetics information
- Energetics can tell us how animals survive in unusual environments or with unusual life histories.
- Measurements of metabolic rate have shown energetic costs of capturing prey are linked to hunting success. This is imporant for determining population viability when endangered populations are small, e.g. cheetahs and pumas.
- Measurements of polar bears show unusually high energy requirements associated with carnivory, and how increased search costs fpr prey due to sea ice loss as a result of climate warming threatens their survival
Regulatory variables of decomposition?
organisms (O), resource quality (Q), physical environment (P). Combination of these dictates rate of decay.
Decomposition = sum of component losses attributable to:
Catabolism (k)
Comminution (C)
Leaching (L)
D= KCL
Define catabolism
Catabolism is the enzymatic degradation of a compound from a polymer to a monomer. (e.g. cellulose to glucose) or to its mineral constituents ( glucose to CO2 and H2O)
Define comminution
Comminution is the physical reduction of particle size by animal feeding and abiotic factors.
Define leaching
Leaching is the physical removal fo soluble materials by water. Leaching is influenced by catabolism and comminution.
