Ecosystems (6) Flashcards
What is a habitat?
The place where an organism lives
What is a population?
All the organisms of one species in a habitat
What is a decomposer?
An organism that breaks down dead or undigested organic material
What is a producer?
An organism that produces organic molecules using sunlight energy
What is a consumer?
An organism that eats other organisms
What is a trophic level?
A stage in a food chain occupited by a particular group of organisms
What is an ecosystem?
It is all the organisms living in a certain area and all the non living conditions found there. It is a dynamic system, which means that it is changing all the time.
What are biotic factors?
They are the living features of an ecosystem.
- predators
- prey
What are abiotic factors?
They are the nonliving features of an ecosystem
- temperature
- rainfall
- topology
- soil nutrient availability
- pH
- Salinity
How are rock pools affected by abiotic factors?
Rock pools are heavily influenced by the tides. At high tide they are completely submerged by the ocean so experience similar abiotic factors to the ocean ecosystem. However at low tide they experience more extreme abiotic conditions, only some organisms can tolerate these conditions.
How are rock pools affected by biotic factors?
Seaweed can be a food source for consumers such as limpets that graze on this produce. Intense competition for food can limit the number of organisms that are present in a small rock pool ecosystem.
How are playing fields affected by abiotic factors?
Rainfall and sunlight affect the growth of the producers in the ecosystem. In a very wet year, the soil may become waterlogged, making it difficult for plants to frow. Poor plant growth may decrease the number of consumers the ecosystem can support.
How are Playing fields affected by biotic factors?
Producers include grass and other plants such as daisies, clover, and dandelions. The large amount of these plants might attract a large number of organisms that use them as a food source.
How are large trees affected by biotic factors?
Insects such as caterpillars can use the leaves of a tree as a source of food. However, if they consume all the leaves on a tree, they can slow tree growth and even lead to its death.
How are large trees affected by abiotic factors?
Drought conditions can negatively impact the growth of a tree. In severe cases it can result in the whole tree dying.
How does energy enter an ecosystem?
The main route which energy enters an ecosystem is through photosynthesis. Plants convert light energy into a form that can be used by other organisms, they store it as biomass.
How is energy transferred throuh an ecosystem?
Energy is transferred though the living organims of an ecosystem when organisms eat other organisms.
What is biomass?
Biomass is the mass of living material.
What do food chains and food webs show?
They show how energy is transferred through an ecosysem.
What is the difference between a food chain and food webs?
Food chains show simple lines of energy transfer. Food webs show lots of food chains in an ecosystem and how they overlap.
How much of the energy is transferred between trophic levels?
around 10% of the total avaliable energy is transferred between trophic levels.
What is the gross productivity?
The rest of the available energy 40% is taken in.
What percentage of energy do organisms waste and how?
Around 60% is never taken in by the organisms
- plants don’t use all the light energy in photosynthesis
- some sunlight isn’t used as it hits part of the plant that cannot photosynthesise
- some parts of food are not eaten by organisms, so the energy isn’t taken in, they pass to the decomposers
- some parts of food are indigestible, so they pass through the organism and come out as waste.
How much is lost to the environment as respiratory loss?
30% of the total energy available is lost to the environment when organisms use energy produced from respiration for movement or body heat.
What is the net productivity?
10% of the total energy available becomes biomass, this is called the net productivity. Net productivity is the amount of energy that is available to the next trophic level. The flow of energy transfer continues at the next trophic level, the process starts again from the beginning.
How do you calculate how efficient the energy transfer between trophic levels is?
(energy transferred/energy intake) x100
How do you calculate the net productivity?
Net productivity = gross productivity - respiratory loss
What are problems with the method of energy transfer between trophic levels?
There are problems with this method. For example, the consumer might have taken in energy from sources other than the producer measured. This means the difference between the two figures wouldn’t be an accurate estimate of the energy transferred between only those two organisms. For an accurate estimate you’d need to include all the individual organisms at each trophic level.
How can you measure the energy transfer between trophic levels?
1) To measure the energy transfer between two trophic levels, you need to calculate the difference between the amount of energy in each level
2) You can calculate the amount of energy in a trohpic level b y measuring the dry mass of the organisms.
3) Calculate the amount of biomass in a sample of the organism
4) THen you multiply the results from the sample by the size of the total population to give the total amount of enery in hte organims at that trophic level.
5) The difference in energy between trophic levels is the amount of energy transferred.
How do herbicides increase the transfer of energy?
Herbicides kill weeds that compete with agricultural crops for energy. Reducing competition means crops receive more energy, so they grow fast and become larger, increasing productivity.
How do fungicides increase the transfer of energy?
Fungicides kill fungal infections that damage agricultural crops. The crops use more energy for growth and less for fighting infection, so they grow fast and become larger, increasing productivity
How do insecticides increase the transfer of energy?
Insecticides kill insect pests that eat and damage crops. Killing insect pests means less biomass is lost from crops, so they grow to be larger which means productivity is greater.
How do natural predators increase the transfer of energy?
Natural predators introduced to the ecosystem eat the pest species. This means the crops lose energy and biomass, increasing productivity.
How do fertilisers increase the transfer of energy?
Fertilisers are chemicals that provide crops with minerals needed for growth. Crops use up minerals in the soil as they grow, so their growth is limited when there aren’t enough minerals. Adding fertiliser replaces the lost minerals, so more energy from the ecosystem can be used to grow, increasing the efficiency of energy conversion.
How does rearing livestock intensively increase the transfer of energy?
Rearing livestock intensively involves controlling the conditions they live in, so more of their energy is used for growth and less is used for other activities, the efficiency of energy conversion is increased so more nutrients are produced and productivity is increased.
What are the benefits and negatives of rearing livestock intensively to increase the transfer of energy?
The benefits are that more food can be produced in a shorter space of time, often at lower cost. However, enhancing productivity by intensive rearing raises ethical issues.
What are some examples of rearing livestock intensively?
- Animals may be kept in warm, indoor pens where their movement is restricted. Less energy is wasted keeping warm and moving around
- Animals may be given feed that is higher in energy than their natural food. This increases the energy input, so more energy is available for growth.
What processes are used in the carbon cycle?
Photosynthesis, respiration, decomposition, combustion and weathering.
How is carbon absorbed by plants?
Carbon is absorbed by plants when they carry out photosynthesis, it becomes carbon compounds in plant tissues.
How is carbon passed through organisms in the carbon cycle?
Carbon is passed on to primary consumers when they eat the plants. It is passed on to secondary and tertiary consumers when they eat other consumers.
What are saprobiotic conditions?
All living organisms die and the carbon compounds in the dead organisms are digested by microorganisms called decomposers. Feeding on dead organic matter is called saprobiontic nutrition.
How are fossil fuels/crude oil formed?
If dead organic matter ends up in a place where there aren’t any decomposers, their carbon compounds can be turned into fossil fuels over millions of years.
How do most organisms return carbon back to the atmosphere?
Carbon is returned to the air and water as all living organisms carry out respiration which produces CO2.
How is carbon released from fossil fuels?
The carbon in fossil fuels is released when they’re burnt in a process called combustion.
How can volcanoes return carbon to the atmosphere?
Carbon can be drawn down deep into the Earth’s crust by the movement of tectonic plates. They undergo chemical changes and release carbon dioxide, which is returned to the atmosphere by volcanoes.
How is carbon stored in aquatic environments?
As well as coal, other types of rock can be formed from dead organic matter deposited on the sea floor. For example, rocks such as limestone and chalk are mainly composed of calcium carbonate. This comes from marine organisms like crabs, mussels, sea urchins and coral that utilize this compound in their development.
How can chemical weathering occur?
Rainwater which is slightly acidic due tot he carbon dioxide dissolved in it can weather things. Chemical weathering causes mineral ions and bicarbonate ions to be released from the rock in to solution and enter groundwater from where they are transported into riversand the oceans. There they combine to form carbon containg compounds such as calcium carbonate.
How can physical weathering occur?
Things can be weathered by plant roos, animals etc.
What is weathering?
Weathering is the breaking down of something due to exposure to the atmosphere
How can CO2 be released back into the atmosphere using water?
Carbon dioxide can dissolve directly into the oceans form the atmosphere and be transported into the ocean by deep underwater currents. Carbon dioxide can remain in these slow moving currents for hundreds of years before returning to the surface and being released back into the atmosphere.
What percentage of the atmosphere is nitrogen?
78%
What are the main processes in the nitrogen cycle?
Nitrogen fixation, ammonifiction, nitrification and denitrification
What is denitrification?
Denitrification is when nitrates in the soil are converted into nitrogen gas by denitrifiying bacteria, they use nitrates in the soil to carry out respiration and produce nitrogen gas. This happens under anaerobic conditions.
What is nitrification?
Nitrification is when ammonium ions in the soil are changed into nitrogen compounds that can then be used by plants. First nitrifying bacteria called Nitrosomonas change ammonium ions into nitrites. Then other nitrifying bacteria called nitrobacter change nitrites into nitrates.
What is ammonification?
Ammonification is when nitrogen compounds from dead organisms are turned into ammonia by decomposers, which goes on to form ammonium ions. animal waste also contains nitrogen compounds. These are also turned into ammonia by decomposers and go on to form ammonium ions.
What is nitrogen fixation?
Nitrogen fixation is when nitrogen gas in the atmosphere is turned into ammonia by bacteria such as Rhizobium and Azotobacter. The ammonia can then be used by plants. Rhizobium are found inside root nodules of leguminous plants. They form a mutualistic relationship with the plants, they provide the plant with nitrogen compounds, and the plant provides them with carbohydrates. Azotobacter are found living in the soil. They don’t form mutualistic relationships with plants.
How does nitrogen enter an ecosystem?
Other ways that nitrogen gets into an ecosystem are by lightning or by artificial fertilisers.
What is secondary succession?
This happens on land that has been cleared of all the plants, but where the soil remains.
What is succession?
Succession is the process by which an ecosystem changes over time. The biotic conditions change as the abiotic conditions change as the abitoic conditions change.
What is primary succession?
This happens on land that has been newly formed or exposed. There is no soil or organic material to start with.
How does primary succession start?
Primary succession starts when species colonise a new land surface. Seeds and spores are blown in by the wind and begin to grow. The first species to colonise the area are called pioneer species.
How does primary succession develop?
- The abiotic conditions are hostile. Only pioneer species growt beacuae teyre specialised to cope with the harsh conditions.
- The pioneer species change the abiotic conditions, they die and microorganisms decompose the dead organic material. This forms a basic soil.
- This makes conditions less hostile, which means new organisms can move in and grow. These then die and are decomposed, adding more organic material, making the soil deeper and richer in minerals. This means larger plants like shrubs can start to grow in the deeper soil, which retains even more water. As more plants move in they create more habitats, so more animals move in.
What are the next stages in succession?
At each stage, different plants and animals that are better adapted for the improved conditions move in, out compete the plants and animals that are already there, and become the dominant species in the ecosystem.
How is the start of secondary succession different from primary succession?
Secondary succession happens in the sam way, but there is already a soil layer so succession starts at a later stage. The pioneer species in secondary successsion are larger plants.
What happens as succession goes on?
As succession goes on, the ecosystem becomes more complex. New species move in alongside existing species, which means the species diversity increases. The amount of biomass also increases because plants at later stages are larder and more dense.
What is the final stage in succession called?
The final stage is called the climax community, the ecosystem is supporting the largest and most complex community of plants and animals it can. It wont change much more, it is in a steady state.
What is an example of primary succession? (Bare rock to woodland)
1) Pioneer species colonise the rocks. E.g., lichens grown on and break down rocks, releasing minerals
2) The lichens die and are decomposed helping to form a thin soil, which thickens as more organic material is formed. This means other species sucha s mosses can grow.
3) Larger plants that need more water can move in as the soil deepens, e.g. grasses and small flowering plants. The soil continues to deepen as the larger plants die and are decomposed.
4) Shrubs, ferns, and small trees begin to grow, outcompeting the grasses and smaller plants to become the dominant species. diversity increases
5) Finally, the soil is deep and rich enough in nutrients to support large trees. These become the dominant species, and the climax community is formed.
What is a plagioclimax?
Human activities can prevent succession, stopping the normal climax community from developing. When succession is stopped artificially like this, the climax community is called a plagioclimax.
What is deflected succession?
Deflected succession is when succession is prevented by human activity, but the plagioclimax that develops is one that is different from any of the natural stages of the ecosystem.
What is an example of deflected succession?
- A regularly mown grassy field won’t develop woody plants, even if the climate of the ecosystem could support them
- The growing points of the woody plants are cut off by the lawnmower, so larger plant can’t establish themselves, only the grasses can survive being mowed, so the climax community is a grassy field
- a grassy field isn’t a natural stage, there should also be things like small flowering plants, so succession has been deflected.
What is the climactic climax?
Which species make up the climax community depends on what the climate’s like in an ecosystem. The climax community for a particular climate is called its climatic climax.
What is abundance?
It is the number of individuals of one species in a particular area. The abundance of mobile organisms and plants can be estimated by simply counting the number of individuals in samples taken.
What is percentage cover?
Percentage cover is how much of the area that you are investigating is covered by a species
What is distribution?
This is where a particular species is within the area you’re investigating
How do you take a random sample?
1) choose an area to be sampled, a small area within the area being investigate
2) Samples shoudl be random to avoid bias
3) Use an appropriate technique to take a sample of the population
4) Repeat the process, taking as many samples as possible. This gives a more precise estimate for the whole area.
5) The number of individuals for the whole area can then be estimated by taking an average of the data collected in each sample and multiplying it by the size of the whole area. The percentage cover for the whole area can be estimated by taking the average of all the samples.
How do you use a frame quadrat?
1) A frame quadrat is a square frame divided into a grid of 100 smaller squares by strings attached across the fame
2) They’re placed on the ground at random points within the area that you are investigating
3) The number of individuals of each species is recorded in each quadrat?
How would you calculate the percentage cover using a quadrat?
The percentage cover of a species can also be measured by counting how much of the quadrat is covered by the species, you can count a square if it more than half covered.
What are the benefits and downsides of frame quadrats?
- Frame quadrats are useful for quickly investigating areas with species that fit within a small quadrat
- Areas with larger plants and trees need very large quadrats. Large quadrats aren’t always in a frame, they can be marked out with a tape measure.
How do you use a point quadrat?
1) A point quadrat is a horizontal bar on two legs with a series of holes at set intervals along its length
2) Point quadrats are placed on the ground at random points within the area that you are investigating
3) Pins are dropped though the holes in the frame and every plant that each pin touches is recorded. If a pin touches several overlapping plants, then all of them are recorded
4) The number of individuals of each species is recorded in each quadrat.
5) The percentage cover of a species can also be measured by calculating the number of times a pin his touched a species as a percentage of the total number of pins dropped.
6) Point quadrats are especially useful in areas where there’s lots of dense vegetation close to the ground.
What is a line transect?
A tape measure is placed along the transect and the species that touch the tape measure are recorded.
What is a belt transect?
Data is collected along the transect using frame quadrats placed next placed next to each other.
What is an interrupted transect?
Instead of investigating the whole transect of either a line or a belt, you can take measurements at intervals.
