3 - Ecocsystems Flashcards
(27 cards)
What is an ecosystem
A community of organisms and their physical environment, including flows and stocks of energy and nutrients
It involves interactions between organisms and the environment as an integrated system
What is ecosystem ecology
The study of ecosystems’ functioning in terms of energy and material inputs and outputs, focusing on large-scale units like grasslands, forests, and lakes
What are the three types of biodiversity defined at the 1992 Convention on Biological Diversity
Ecosystem diversity, species diversity, genetic diversity
List two reasons ecosystems have intrinsic value
- They’re biologically unique elements of biodiversity
- They help us understand biological patterns on large spatial scales.
List four ecosystem services with instrumental value to humans
Food, medicine, pollination, carbon storage
How are ecosystems involved in solving global environmental challenges
Disruptions to ecosystem processes contribute to climate change, food insecurity, eutrophication, habitat destruction, and pollution
Define Gross Primary Productivity (GPP)
Total energy fixed by autotrophs via photosynthesis per unit area and time
What is Net Primary Productivity (NPP)
NPP = GPP – R (respiration by autotrophs); energy available to heterotrophs
What is Net Ecosystem Production (NEP)
NEP = GPP – R_total or NPP – R_het;
Total ecosystem energy balance after all respiration
What is secondary productivity
Rate of biomass or energy production by heterotrophs per unit area and time
Name ecosystems with the highest NPP per unit area
Tropical rainforests, algal beds and reefs, wetlands
Name ecosystems with the lowest NPP per unit area
Deserts, open ocean, tundra
What percentage of unmodified global NPP is appropriated by humans
~25%, primarily via crops, fires, urbanisation, and soil degradation
What are the three main resources that limit productivity on land
Solar radiation, CO₂, water
What are the most common nutrient limitations for plants
Nitrogen (N) and phosphorus (P)
What differs in nutrient limitation between young and old soils
Young soils = N-limited (e.g. boreal forests); old tropical soils = P-limited
Key factors limiting productivity in aquatic systems
Light and nutrient availability, especially N and P
Redfield Ratio
Molar N:P = 15:1 in seawater; helps determine nutrient limitation
(P-limited if >15:1, N-limited if <15:1)
Define assimilation efficiency
(E ingested - E faeces) / E ingested x 100
Define gross growth efficiency
(E growth / E ingested) x 100
Define net growth efficiency
(E growth / E assimilated) x 100
What are typical percentages for fate of ingested energy in herbivores
~50% faeces, ~33% respiration, ~17% growth/reproduction
Describe the flow of energy through trophic levels
Sun → Primary producers → Herbivores → Primary carnivores → Secondary carnivores → Detritivores
With ~90% of energy lost as heat at each level
What is trophic transfer efficiency
Energy transferred between trophic levels, typically ~10%
