Ecosystems Flashcards
What is an ecosyatem?
An ecosystem is made up of all of the living organisms that interact with each other in a given area.
What are the names of the categories of factors that affect ecosystems?
Biotic and Abiotic
What are biotic factors?
The living factors e.g. in a forest ecosystem, shrews and hedgehogs would be biotic
What are abiotic factors?
Non living factors e.g. in a forest ecosystem the amout of rainfall is an abiotic factor.
Why do we refer to ecosystems as dynamic?
Because they are constantly changing.
What is a trophic level?
Each stage in the food chain is referred to as a trophic level.
What are the different trophic levels called?
The first one is a producer
The second is primary consumer
The third is secondary consumer
The fourth is tertiary consumer
What are decomposers?
Decomposers are organisms which break down dead organisms releasing nutrients back into ecosystems
What is biomass?
The mass of living material present in a particular place or in particular organisms
How do you measure biomass?
Multiply the biomass present in each organism by the number of organisms in that trophic level.
How is biomass affected as you go up the food chain?
Biomass can equal energy content so when animals eat, only a small proportion of the food they ingest is converted to new tissue so it is only this part of the biomass which gets transferred therefore biomass in each level is always less than the level below.
How do you calculate efficiency of biomass?
efficiency = biomass transferred/ biomass intake x 100
How much energy originally present in sunlight becomes finally embodied as biomass in a tertiary consumer?
0.001%
How can human activities influence biomass.
Agriculture allows plants and animals to have the optimum biotic and abiotic conditions to thrive e.g. adequate watering and warmth. It also reduces competition for survival. In doing this, agriculture is creating very small food chains so as much biomass as possible can be transferred to each level and eventually to humans
What is meant by a decomposer?
An organism that feeds on or breaks down dead plant or animal matter. Usually microscopic fungi and bacteria but can also be larger fungi e.g. toadstools
Whst is a detritivore?
An organism e.g. woodlice which helps speed up the decay process by feeding on dead and decaying material to break it down into smaller organic pieces which can increase surface area for decomposers to work on.
Describe the carbon cycle.
- Carbon dioxide in the air is used for photosynthesis for plants, the plants respire giving some of the CO2 back. If the plant dies whilst no decomposers are around then over millions of years it will become a fossil if there is enough heat and pressure. If the plant gets eaten by an animal then the carbon passes to the animal.
The animal respires releasing some CO2 and if the animal dies (same as with plants) the CO2 will be transferred to the decomposers and if there are no decomposers around then it can also end up as a fossil and used as fossil fuels. These fossil fuels are combusted releasing carbon back to the atmosphere. The carbon in animals and plants can be turned into rocks such as limestone which can then be released from volcanoes or weathered to dissolve the carbon in oceans which can then release it back into the atmosphere. The ocean also absorbs carbon from the atmosphere.
What are the 4 stages of the nitrogen cycle?
Nitrogen fixation, ammonification, nitrification and denitrification.
What happens during nitrogen fixation?
Nitrogen gas in the air can be combined with hydrogen to form ammonia, this is done by bacteria e.g. rhizobium and aotobacter). This allows the nitrogen to be absorbed by plants. Rhizobium live within the root nodules of leguminous plants e.g. peas beans and clovers where they have a mutualistic symbiotic relationship with plants which means they both benefit:
- the plant gains amino acids from rhizobium
- the bacteria gain carbohydrates produced by the plant in photosynthesis
What happens during Nitrification?
Nitrification is the process by which ammonium compounds in the soil are converted into nitrogen containing molecules that can be used by plants. Nitrifying bacteria such as Nitrosomonas oxidise ammonium compounds into nitrites (NO2-). Nitrobacter (another genus of nitrifying bacteria ocidise nitrites into nitrates (NO3-). This process only occurs in aerobic conditions.
What happens during denitrification?
If there is an absence of oxygen in the soil then denitrifying bacteria convert nitrates back into to nitrogen gas. This is denitrification. It only happens under anaerobic conditions and the bacteria use nitrates as a source of energy for respiration and nitrogen gas is released
What happens during ammonification?
Ammonification is the name given to the process by which decomposers convert nitrogen containing molecules in dead organisms faeces and urine into ammonium compounds.
What is meant by succession?
Succession is when a plant or animal species changes as a result of changes to the environment.
What is primary succession?
Succession that occurs on an area of land that has been newly formed or exposed e.g. bare rock.
