C.2 Communities and Ecosystems Flashcards
Use of owl pellet to identify trophic levels
An owl pellet is a mass of undigested parts of the owl’s diet which it regurgitates.
The content of the pellet can be analyzed to identify on which species the owl feeds, and the respective trophic levels by examining the adaptations (e.g. arrangment of teeth–dentition).
Pros:
Shows that owl feed on organsims from different trophic levels;
Without harming/disturbing the bird
Food convertion ratios
= quantity of dietary input (g) / increase in desired output (g) per specific time period
The lower the food convertion ratio, the more efficient the method of feeding.
Can be lowered by minimizing respiratory losses by:
Restricting movements;
Slaughting animals at young age (as growth slows down at older ages – lower gross production)
Optimizing feed so it is efficiently digested
Net primary productivity
Photosynthetic/chemosynthetic rate - respiratory rate
It is the rate at which an ecosystem accumulates biomass, excluding the energy lost through respiration.
Primary production
The synthesis of organic materials from inorganic compounds by producers.
The lengths of food chains are determined by…
Net primary productivity
Efficiency of energy transfer between trophic levels
Net production at each level
Net production
Gross production (the total amount of organic matter produced per unit area per unit time by a trophic level in an ecosystem) - respiratory losses
Gersmehl nutrient cycle diagrams
Temperate forests
Rain forests
Deserts
Pools in Gersmehl nutrient cycles
Biomass
Litter
Soil
Fluxes in Gersmehl nutrient cycles
Biomass: + plant uptake, - littering
Litter: + littering, rainfall, - surface runoff
Soil: + decomposition, weathering, - leaching
Ecological successions
Changes that transform ecosystems over time, involving both the species and the abiotic environment.
Primary + secondary
Primary succession
Development of ecosystems in an environment where living organisms have not previously existed.
Steps of primary succession
- Lichens colonizes on rock surfaces
- Soil builds up (by weathering and erosion, and death of small lichens)
- Grasses and other herbaceous plants grow;
- Soil is deepened by detritivores following death of plants and animals
- Small shrubs take root in the area, followed and substituted by larger plants
- As plant grows, their roots grow deeper and break rock into smaller particles, helping soil formation. Death of plants also enrich soil as they decompose
- More soil allows for burrowers, worms and detritivores, allowing nutrient cycling
- Biodiversity increases, more plant and animal species providing new niches
- Productivity plateaus as soil’s carry capacity is reached
During succession, plant roots retain water and slows down drainage –> prevent floods and draughts. The roots also hold soil particles together, retaining nutrients and preventing soil erosion.
Secondary succession
The replacement of one ecosystem by another following an environmental change.
Example of secondary succession
- A stable decidous (每年落叶的) forest community
- Wild fire destroys the forest, leaving 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, shade intolerant ever-green trees die as the larger deciduous trees overlap them –> back to the initial stage
How human interfere wiht nutrient cycling
Injections to the agricultural ecosystem:
Use of phosphate fertilizers: mining phosphates and convert them into fertilizers
Use of nitrate fertilizer produced from atmospheric nitrogen (by the Haber process)
Leakages out of the agricultural ecosystem:
Harvesting of crops and transporting them elsewhere
Water run-off from agricultural fields results in build-up of phosphates and nitrates in waterways leading to euthrophication –> nutrients removed and added to adjacent aquatic ecosystems.
