ecosystems Flashcards
ecosystems and biomass
Ecosystems are dynamic (constantly changing) and vary in size, and this is determined by biotic and abiotic factors. For example, a rock pool, a playing field and a large tree are all very different-sized ecosystems.
Biomass Transfers through Ecosystems
In any ecosystem, plants are the producers of a food web as they are able to produce their own carbohydrates using carbon dioxide in the atmosphere or water.
Between each trophic level in a food web, the majority of the energy is lost due to respiration and excretion. The remaining energy is used to form biomass.
calculating biomass
The amount of biomass remaining in an organism can be measured in terms of the mass of carbon or dry mass of tissue per given area. How productive an ecosystem is depends on abiotic and biotic factors. Plenty of water, light, warmth and plants Plants will maximise the rates of photosynthesis and therefore result in more carbohydrates being produced in the
The efficiency of biomass transfers between trophic levels can be calculated using the following formula:
Efficiency = biomass transferred/biomass intake x 100
• Humans can manipulate the transfer of biomass through ecosystems by reducing the energy lost at each trophic level.
1. Restricting the movement (and therefore respiration) of animals
2. Providing animals with higher energy food (increasing the energy input)
3. Keeping animals indoors to reduce the energy transferred as heat
4. Removing competition and predators (growing indoors and providing animals and plants with all they need)
The importance of the nitrogen cycle
• The air is 78% nitrogen, however plants and animals cannot obtain nitrogen through gas exchange.
• Nitrogen gas (N2) contains a triple bond.
• Microorganisms are needed to convert nitrogen gas into nitrogen containing substances that plants and animals can absorb.
• Which biological molecules contain nitrogen?
• Proteins, ATP and nucleic acids
The nitrogen cycle
- Saprobiotic nutrition and microbes
- Ammonification
- Nitrification
- Nitrogen fixation
- Denitrification
Let’s start with nitrogen gas can be converted into nitrogen containing compounds such as ammonium through bacteria which can break the triple bond and that is nitrogen fixing bacteria which is naturally found in the soil or nitrogen fixing bacteria that naturally occurs in the root nodules of leguminous plants, nitrogen fixing soil bacteria are able to convert nitrogen gases in the air in the soil into ammonium-which is oxidised by nitrifying bacteria into nitrites-this process is nitrification. The nitrites are oxidised further into nitrates, again by nitrifying bacteria- the nitrates can be absorbed into the plants by active transport, the plants use nitrates to make proteins, DNA and ATP. Plants will be eaten by animals, proteins in the food will be digested to release the nitrogen containing compounds which can be assimilated into the proteins and DNA, RNA and ATP for animals
When plants/animals die, saprobiotic microbes release enzymes that digest proteins in the dead plant/animals matter, or digest and break down the urea in excretion into ammonium, this then loops back round.
Nitrates could be converted back into nitrogen gas by denitrifying bacteria, only happens in anaerobic conditions, eg soil is waterlogged. Denitrifying bacteria thrive in anaerobic conditions.
The carbon cycle
The carbon cycle is also dependent on organisms.
Plants photosynthesise to fix carbon from the atmosphere (carbon dioxide) into carbohydrates which can be ingested by animals. All organisms respire, and this converts the carbon in carbohydrates back into carbon dioxide in the atmosphere or oceans. When organisms die or excrete, the carbon is broken down to carbon dioxide by decomposers that respire using the carbohydrates within the dead or waste matter.
An imbalance in this cycle is leading to ocean acidification and global warming. This imbalance is caused by deforestation and burning too many fossil fuels, therefore less carbon dioxide is being used in photosynthesis and more is being produced by combustion.
what is succession
The change in an ecological community over time
primary succession
A primary succession starts with a pioneer species colonising bare rock or sand.
Pioneer species, such as lichen, are adapted to survive in harsh abiotic factors and through their death and decomposition change the abiotic factors to become less harsh and form a thin layer of soil, humus.
Mosses and smaller pants can now survive, and they further increase the depth and nutrient content of soil. This pattern continues, and as the abiotic factors continue to be less harsh larger plants can survive and change the environment further.
Each new species may change the environment in such a way that it becomes less suitable for the previous species. Therefore each existing species is outcompeted by a new species colonising.
Increases biodiversity.
The final stage in a succession is known as the climax community, and this is dominated by trees.
secondary colonisers, tertiary colonisers
secondary succession
The succession is disrupted and plants are destroyed
Succession starts again, but the soil is already created, so it does not start from the bare rock seral stage.
succession summary
The species richness and number of organisms increases (biodiversity increases).
As succession occurs, larger plant species and animals start to colonise the area.
deflected succession
Human activities can prevent the progress of succession. A climax community won’t be reached if there are animals grazing or trampling an area by humans.
Controlled burning and removal of vegetation will also prevent the formation of a climax community.
This is known as deflected succession.
By maintaining earlier stages in succession, and preventing a climax community, a greater variety of habitats are conserved and therefore a greater range of species survive.
This can lead to conflict between human needs and conservation in order to maintain the sustainability of natural resources.
To try and manage this conflict compromises are needed, for example, forests can be coppiced to provide timber for fuel and furniture, whilst still allowing the tree to survive.
estimating population size
To measure the impact of changing environments
need to be able to measure the size of a
population.
It would be too time-consuming and inaccurate to count every individual within a population, and therefore samples are taken instead to provide an estimate. Population sizes can be estimated via various techniques, but a few aspects are in common.
For the sampling to provide an accurate estimate that is representative of the population size, many samples (30+ ideally) should be taken, and sampling should be random to avoid bias.
measuring distribution- line/belt transect.
Line transect involves laying a line or surveyors tape along the ground and taking samples at regular intervals. Belt transect provides more information, two parallel lines are marked, and samples are taken of the area between these specified points. Both forms of systematic sampling-non-random
systematic sampling has advantages over random sampling as it allows scientists to study how the differing abiotic factors in different areas of the habitat affect the distribution of a species. Eg how plant species change moving inland from sea.
plant abundance-quadrats placed randomly in area
estimated number in population= number of individuals in sample/area of sample (m*2)
animal abundance-capture individuals in sample area-tag them-release- recapture individuals in sample area again, record number of marked and unmarked
estimated population size= (individuals in first sample x number of individuals in second sample)/ number of recaptured marked individuals
