CLOSED LOOP SYSTEMS
WHAT IS A CLOSED LOOP SYSTEM? An ecosystem replies on inputs to ensure that growth can continue. If all of the inputs are met by most of the outputs, from the ecosystem (i.e no new inputs are needed) then it is a closed loop system
This means that the waste form one part of the system is used by another part of the system. This is very efficient and means that, undisturbed, an ecosystem can remain that way for an indefinite period.
WHAT IS A PERFECT CLOSED LOOP SYSTEM?
A perfect cosed loop system would mean that no waste was ever lost and the system could last infinitely
CAN AN ECOSYSTEM BE A CLOSED LOOP SYSTEM?
No, it is impossible because organisms migrate out of the area and nutrients can be lost because they are transferred to another ecosystem by wind or water. However, to be a stable ecosystem the outputs must be balanced by gains - a rainforest, such as the Amazon, is an example of this.
WHAT ARE THE WASTE PRODUCTS IN AN ECOSYSTEM?
- OXYGEN - from photosynthesis
- CARBON DIOXIDE - from respiration
- DEAD ORGANICE MATTER - fallen leaves, petals, fruit, faeces, remains of dead animals
IS IT REALLY WASTE?
Although classed as being 'waste', it is only so for the organism that produced it. Other organisms may find the waste useful.
Humans need oxygen (waste products of photosynthesis) and many drink alcohol (waste product from yeast)
WHAT CAN WE USE WASTE AS?
The chemicals that make up 'waste' materials can be used either as food or as reactants for different chemical reactions in the organism (i.e plants, animals or micro organisms)
WHAT ARE DIGESTIVE ENZYMES AND WHAT DO THEY DO?
To break down food products, organisms oftern have to use digestive enzymes.
Digestive enzymes break down large molecules into size that are small enough to pass through the intestine. So that they can be used to make new larger molecules.
USING 'WASTE' CONT.
If it were not for micro organisms, waste in the environment would build up to intolerable levels. Micro organisms use enzymes to break down the different food groups;
Breakdown of protein;
proteins are broken down to amino acids by proteases
Breakdown of lipids;
lipids (oils+fats) are broken down into fatty acids and glycerol by lipases
Breakdown of carbohydrates;
carbohydrates are broken down into sugars by carbohydrases (e.g amylase)
- As micro organisms can grow very rapidly, waste can be broken down very quickly
REPRODUCTION - ANIMALS
HOW CAN YOU MAXIMISE THE CHANCES OF REPRODUCING SUCCESSFULLY?
To reproduce successfully, organisms need to use a strategy that maximises the chances of the offspring reaching adulthood and reproducing themselves.
In most ecosystems there is competition between species. This means that organisms have to invest energy and resources in achieving their goal of reproducing.
Females usually produce large numbers of eggs, while males produce large quantities of sperm. This ensures a high chance that at least one successfull fertilisation will occur. Growing offspring are a good food source, so there is always a high chance that some of the offspring will be eaten by predators. Producing large numbers of offspring helps to mitigate against this loss.
REPRODUCTION - PLANTS
Plants, which cannot move around, also have to employ strategies to ensure the success of the species:
FLOWERS - to attract insects in sufficient numbers to ensure that reproduction occurs, large numbers of attractive looking and nice smelly flowers have to be produced. Not all fowers will be successfully fertilised.
POLLEN - large quantities of pollen have to be produced. This is take either by the wind (wind-polliated plants) or carried by insects (insect-pollinated plants) to the destination plant. There is no guarantee that the pollen will land where it is supposed to.
FRUIT - having been fertilised, the next stage in a flower's life cycle is to produce fruit. A fruit contains the see and is grown to encourage animals to take the fruit and eat. Seeds, which are quite resiliant, pass through the digestive system unharmed and are deposited in faeces. Faeces is a good source of nutrients (fertiliser) which will help the seed to grow. Not all seeds will be successfull, they may be deposited in the wrong area, or chewed up and damaged.
PLANTS AND SOIL
PROTECTING THE SOIL
ROOTS? As well as contributing to the inputs and outputs of an ecosystem, organisms (particularly plants) have a big physical effect on the ecosystem itself. Plants have roots, which effectively bind the soil together. The larger the plants, the most extensive its root systems. This means that the soil is bound together more effectively and is unlikely to be washed away.
FOLIAGE? The foliage of plants also reduces the effect of heavy rainfall washing away the surface soil. Most of the rainfaill hits leaves, so water only gets to the surface gently and indirectly.
VEGETATION? Vegetation can also alter the climate. It can prevent extremes of temperature by reducing the amount of carbon dioxide ( a greenhouse gas) in the atmoshpehere. Rainforests transport a high quantity of water via transpiration. This means water is cycled form the ground to the air and this can stimulate cloud formation.
HUMANS AND ECOSYSTEMS
Humans benefirt from and depend on ecosystems to provide a huge range of resources and processes. These are known as ecosystem services.
HUMAN ACTIVITY EFFECTS ON ECOSYSTEMS, GOOD OR BAD?
- Systems involving humans are not closed loops systems. Human waste from households, argriculture and industry leaves the system as non-recycled waste, as well as through pollution from burning fossil fules. This means the system is losing resources. Sometimes the waste can build up to harmful levels, which then affects other organisms.
- Human activities can unbalance an ecosystem, changing the inputs and outputs so much that the ecosystem can no longer adapt. This means that the system is no longer a closed loop. Households produce waste (unconsumed food, etc) which is an additional input to the ecosystem, changing its balance
- Industry produces large amounts of waste and pollution, which alter the environment. Carbon dioxied although needed for photosynthesis, causes climate change through the process of enhanced global warming. Pollution by chemical waste can kill parts of food webs
WHAT IS BIOACCUMULATION?
It is where a chemical that is deliberately or accidently introduced into the environment starts to build up in concentraion at each level in the food chain.
This causes serious problems for that particular food chain, resulting in death and reduced species amount
HUMAN ACTIVITY - REMOVING RESOURCES
HOW CAN HUMAN ACITIVITY AFFECT AN ECOSYSTEM?
- When humas take away too many resources as biomass, it reduces the amount available to be recycled within the ecosytem
- For example, cutting down a rainforest for wood removes a large number of trees. The problem is that, the tree canopies would have protected the soil from rainfall and the roots would have bound the soil together, the trees would also have provided habitats for other organisms.
- Removing too many trees caused the closed ecosystem to become open. The soil dries out and is blown away, and the organisms that relied on the trees for survival die. The entire ecosystem is damaged to the point of destruction.
DESERTIFICATION - CAUSES AND EFFECTS
- An increasing population requires more food, so farming has replaced the natural vegetation with agricultural crops and live stock.
- The consequences of this land use change, inludes a loss of biodiversity (especially if the farming is a crop monoculture). The removal of trees and shrubs to make way for livestock or crop plants can reduce the soil quality as it is more likely to be washed away by rain.
- Overgrazing by farm animals also removes the remaining plants and their roots, which binds the soil together. When washed away, the soil ends up in nearyby rivers and streams, silting them up and altering the flow of the water.
- If the farming is not managed properly (with crop rotation) then ultimately what used to be forest can end up as desert this process is called desertification
WHAT IS EUTROPHICATION?
Eutrophication is where an excess of nutrients is put into a system causing the productivity of the system to increase. Unfortunately, this causes the balance of organisms to change, often drastically and irreversibly
FOR EXAMPLE; A farmer who has applied too much fertiliser (organic or chemical) to a crop.
- The excess fertiliser is washed away into nearby rivers and streams.
- The fertiliser, which is high in nutrients, causes a large increase in algae. These rapidly choke the water course.
- The algae then die. Bacteria, which decompose to algae, reproduce in very large numbers using up the available oxygen in the water. This then causes animals, such as fish, to die.
- Eventually the watercourse is unable to support life, other than that which can survive on putrefying plant and animal material.
WHAT IS IT AND HOW IS IT FORMED?
- Crude oil is formed from the remains of plants and animals that died millions of years ago.
- The biomass is covered by silt and rock, and subjected to immense pressure and heat.
- Over millions of years this causes the biomass to be converted into oil.
- The sun originally supplied the energy for the plants and animals to grow. In effect, all the energy that was stored in each plant and animal is now compressed in a much smaller space, in oil. When we burn oil, we are effectively using fossil sunlight energy.
- Due to the immense length of time needed to create it, crude oil is regarded as being non-renewable and is not part of a closed loop system.
COULD WE, SHOULD WE?
ARGUMENTS ABOUT ENERGY
Sunlight is a sustainable source of energy - it will not run out for billions of years - and it allows sustainable agriculture and the growth of natural ecosystems.
Nowadays, when we understand more about how ecosystems work and how they can fail, we need to balance the need to conserve natural ecosystems with the needs of the human population - (sustainability)
PROBLEMS AND ISSUES THAT COME WITH THIS
Would it be right to let a community starve just to protect an ecosystem?
Should a river be damaged to provide water and energy for an increasing population, even though it would mean the destruction of habitats?