4.7.2 Organisation of an ecosystem (will come up) P2 2 Flashcards
Describe how materials cycle through the living and non living components of an ecosystem
Organisms take in elements from their surroundings eg soil, air
Elements converted to complex molecules which become biomass
Elements transferred along food chains
Elements returned to environment during excretion and decomposition of dead organisms
3 molecules which are cycled through ecosystems
Oxygen
Carbon dioxide
Water
Describe the carbon cycle
Plants fix carbon dioxide into organic molecules during photosynthesis
The organic carbon containing molecules are passed onto organisms that eat the plants
Carbon dioxide is released back into the atmosphere by respiration from animals and plants
Burning fossil fuels also releases carbon dioxide into the atmosphere
Why is the carbon cycle important
Carbon containing molecules such as glucose are important for living organisms to grow and provide energy for vital functions within cells
Describe the water cycle
Water from lakes and oceans evaporates
The evaporated water condenses into clouds returns to earth as precipitation
The water from precipitation is useful for life on land
The water then returns to rivers and oceans through surface runoff
Why is the water cycle important
Living organisms require water and the water cycle provides organisms on land with a continuous supply of water
Why are microorganisms important for the cycling of materials through an ecosystem
Microorganisms return carbon to the environment by releasing carbon dioxide through respiration while they decompose dead matter
The decomposition of dead matter in soil returns mineral ions to the environment for other organisms to use
What is meant by decomposition
The breakdown of dead materials into simpler organic materials
How do decomposers break down dead matter
Decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules
What are the 2 types of decomposition
Aerobic decomposition
Anaerobic decomposition
What factors affect the rate of decomposition
Oxygen availability
Temperature
Water content
Why is oxygen required for decomposition
Most decomposers require oxygen for aerobic respiration
How does the availability of oxygen affect the rate of decomposition
As oxygen levels increase the rate of decomposition increases
Why can decomposition still occur in the absence of oxygen
Some decomposers respire anaerobically, however the rate is slower as anaerobic respiration produces less energy
How does soil water content affect the rate of decomposition
Decomposers require water to survive
In moist conditions the rate of decomposition is high
In waterlogged soils there is little oxygen for respiration so the rate of decomposition decreases
