6.6 - Ecosystems Flashcards
Define Habitat
The place where an organism lives
Define population
All the organisms of 1 species in a habitat
Define Producer
An organism that produces organic molecules using sunlight energy
Define Consumer
An organism that eats other organisms
Define decomposer
An organism that breaks down dead or undigested organic material.
Define Trophic level
A stage in the food chain occupied by a particular group of organisms.
What is a biotic factor?
The living features of an ecosystem (Predators or food)
What is an abiotic factor?
Non - living features of an ecosystem (Temperature, rainfall, topology and soil nutrient availability)
What is Net productivity?
The amount of energy that available to the next tropic level.
What is the net productivity equation?
Net productivity =
Gross productivity - respiratory loss
What is the Energy Efficiency equation?
(Energy transferred / Energy intake) x 100
How do we measure energy change through tropic levels?
Calculate the energy difference between each level.
This energy can be calculated by working out the biomass of the organism.
How can humans increase the transfer of energy?
- Herbicides to kill weeds which compete with crops.
- Fungicides so crops use more energy for growth, not fighting infection.
- Insecticides or natural predators so less biomass is lost from pests eating crops.
- Intensive livestock rearing:
- Animals kept in warm indoor pens, with restricted movement, so less energy is wasted keeping warm and moving.
- Animals given feed which is higher in energy, so more energy for growth.
What is nitrogen fixation, and what are the reactions and bacteria required?
Where Nitrogen gas is converted to Ammonia
Rhizobium - found in mutualistic plants
Azotobacter - found in living soil
What is Ammonification?
Nitrogen in dead organisms are turned into ammonia by decomposers.
What is Nitrification?
Ammonium ions in soil are changed into nitrites and nitrates.
Ammonia -> nitrites - Nitrosomonas
Nitrites -> Nitrates - Nitrobacter
What is denitrification?
Nitrates in soil are converted into nitrogen gas by denitrifying bacteria
Only done in anaerobic conditions.
What is primary succession?
Happens on land which has been newly formed or exposed. There is no soil or organic matter.
What is secondary succession?
Happens on land that has been cleared of all the plants, but soil still remains.
How does primary succession occur?
- Abiotic conditions are very harsh, so only pioneer species grow, and these change the abiotic conditions, and eventually die and decompose
- This makes conditions less hostile and other organisms grow. This process repeats until soil is more fertile and multiple habitats form.
How can succession be prevented or Deflected?
Human activities can prevent succession. When it’s stopped artificially the climax community is called the phlagioclimax.
When succession is deflected the climax community is one that’s different to any natural stages of the ecosystem.
