nutrient cycles
1) Describe the Carbon Cycle
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Carbon is an essential element that makes up the majority of molecules in living organisms. The carbon cycle shows how carbon atoms move between the atmosphere and living organisms.
Processes involved in the carbon cycle are:
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source: UCAR
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- Respiration: when living organisms (plants, animals and decomposers) respire they release carbon dioxide into the atmosphere (a form of excretion).
- Fossilisation: if conditions are not favourable for the process of decomposition, dead organisms decay slowly or not at all. These organisms build up and, if compressed over millions of years, can form fossil fuels (coal, oil or gas).
- Combustion: the burning of fossil fuels releases carbon dioxide into the atmosphere.
- Decomposition: when complex, carbon compounds in dead organisms, urine and faeces are broken down into simpler carbon compounds by bacteria or fungi
2) Effects of Combustion of Fossil Fuels and Deforestation on Carbon Dioxide Concentrations in the Atmosphere
- Combustion of fossil fuel produces CO2. This and other ‘greenhouse gases’ causes the Earth’s temperature to rise, ie. global warming.
- Deforestation reduces the number of trees. Trees are responsible for removing gaseous CO2 and trapping the carbon in organic molecules (carbohydrates, proteins and fats). When they are cut down the amount of photosynthesis globally is reduced. Often deforestation is achieved by a process called ‘slash and burn’, where the felled trees are burned to provide land for agriculture and this releases even more atmospheric CO2.
population size
3) Define Key words:
- Ecosystem: a unit containing the community of organisms and their environment, interacting together, e.g. decomposing log or a lake.
- Population: a group of organisms of one species, living in the same area, at the same time.
- Community: all of the populations of different species in an ecosystem.
4) Factors affecting Rate of Population Growth
- Food supply: if there is a large amount of food, more organisms can breed successfully. If there is a food shortage, there is a higher death rate which results in a slow or negative population growth.
- Predation: organisms which have lots of predators will have a slower rate of population growth as more will be killed by predators.
- Disease: disease can reduce the population by killing organisms. In densely populated areas, disease can spread quickly, thus a large proportion of the population may be wiped out.
* food supply
5) State how Modern Technology has resulted in Increased Food Production
- Agricultural machinery are used in larger areas of land to improve efficiency
- Use of chemical fertilisers to improve yields
- Use of insecticides to improve quality and yield.
- Use of herbicides to kill plants that compete with crop plant for space, minerals and sunlight.
- Selective breeding to improve production by crop plants and livestock, e.g. cattle, fish and poultry.
6) Discuss Negative Impacts of Large-Scale Monocultures
- Crop farming is to remove a mixed population of trees, shrubs, wildflowers and grasses and replace it with a dense population of only one species of crop.
- Monoculture is when a crop of a single species is grown on the same land, year after year.
- In a monoculture, every attempt is made to destroy organisms that feed on, compete with or infect the crop plant.
- There will be a loss of biodiversity as only one species is grown. This can harm food chains and reduce the population of some species.
7) Describe Negative Impacts of Intensive Livestock Production
- Intensive farming of crops means farming in a monoculture using high amounts of pesticides, herbicides and fertilisers to maximise production.
- Intensive livestock production means animals are kept in high densities and energy loss is limited by restricting movement and keeping a constant optimum temperature so that the organisms do not waste energy. High amounts of antibiotics are also used to prevent diseases.
- Intensive farming is however not sustainable as livestock produce large amounts of methane gas, which is a main contributor to global warming. Crops take up huge amounts of space, meaning that forests and other habitats must be destroyed to make space for farming.
8) Discuss Problems contribute to Famine
- Unequal distribution of food
- Drought and flooding
- Increasing population
- Poverty
9) Discuss Implications of Providing Sufficient Food for Increasing Human Population
- When people do not receive enough food, famine occurs.
- As the world human population increases, food production must also be increased to sustain the population.
- Social implications: shortage of water caused by diverting supply to farming purposes. Urbanisation means less land for farming. Use of farmland to grow cash crops.
- Economic implications: lack of money to buy fertilisers or machinery
- Environmental implications: need for faster deforestation, and increasing amount of greenhouse gases emitted from animal production. Greenhouse gases cause global warming, which is a worldwide issue that leads to increased natural disasters, such as tropical storms and drought, as well as rising sea levels, which floods homes and decreases the amount of habitable land.
habitat destruction
- Many habitats are destroyed by humans to make space for other economic activities.
- This interrupts food chains and food webs.
Main causes of habitat destruction:
- Clearing land for farming and housing: crops, livestock and homes all take up a large amount of space. As there is an increasing population and demand for food, the amount of land available for these things must be increased by clearing habitats such as forests (deforestation).
- Natural resource extraction: natural resources such as wood and stone must be gathered to make different products. Therefore many trees are cut down, destroying forest habitats. In addition, some resource extraction takes up a large amount of space, for example mining, which means that the land must be cleared first.
- Marine pollution - human activities lead to the pollution of marine habitats. In many places, oil spills and other waste pollutes the oceans, killing sea life. In addition, eutrophication can occur when fertilisers from intensively farmed fields enters waterways. This causes a huge decrease in biodiversity as most species die.
10) List the undesirable effects of Deforestation
Deforestation involves cutting down large amounts of trees to gather as resources for manufacturing or to clear space for other economic activities. This is an example of habitat destruction. Undesirable effects include:
- Extinction: habitat destruction can lead to the extinction of species that lived there.
- Soil erosion: without roots to anchor the soil, it is carried away by the wind and heavy rains. This decreases the fertility of these areas.
- Flooding: forests prevent flooding by slowing the time that water takes to reach the ground. They also allow the water to be absorbed into the soil.
- Increased carbon dioxide in the atmosphere: trees absorb carbon dioxide from the atmosphere during photosynthesis. If there are fewer trees, less carbon dioxide is absorbed, thus there is more in the atmosphere. This increases global warming.
pollution
11) State the sources and effects of Pollution of Water (rivers, lakes and the sea)
- Human activities have led to the pollution of land, water and air.
- This has a variety of negative outcomes, including global warming and habitat destruction.
- Pollution comes from a variety of sources, including chemical waste, discarded rubbish, industry and fertilisers.
- Chemical waste and sewage: in rivers results in water not being drinkable
- Non-biodegradable plastics: choke birds, fish and other animals. Fill up the animals’ stomachs so that they can’t eat food. Collect in rivers, and get in the way of fish.
- Acid rain: caused by sulphur dioxide (burning fossil fuels) and nitrogen oxides (nitrogen reacting hot engines), as they dissolve and cause acid rain. Damages trees and plants, and kills fish and other river life.
Prevention:
- Catalytic converters, in factories slaked lime neutralizes these acidic oxides and use of flue-gas desulfurization.
12) Explain Eutrophication and Water Pollution
Eutrophication is excessive richness of nutrients in a lake or other body of water, frequently due to run-off from the land, which causes a dense growth of plant life.
One of the major pollutants to lakes and rivers is chemicals from fertilisers. When fertilisers are washed off the fields into waterways by rain, eutrophication occurs:
One of the major pollutants to lakes and rivers is chemicals from fertilisers. When fertilisers are washed off the fields into waterways by rain, eutrophication occurs:
- Fertilisers put in soil by farmers.
- Fertilisers are washed from fields into the waterways by rain.
- Fertilisers encourage more algae to grow on surface of water.
- Algae block sunlight and kill plants underneath as they cannot photosynthesize.
- As there are less plants to photosynthesize, less oxygen is released into the water.
- The dead plants are broken down by decomposers, which use up the remaining oxygen from the water.
- The lack of oxygen causes organisms such as fish to die.
* 13) State Sources and Effects of Air Pollution
- Methane and carbon dioxide are greenhouse gases.
- Carbon dioxide is produced by burning of fossil fuels. Methane is produced from the decay of organic matter and as a waste gas from digestive processes in cattle.
- These gases leads to global warming and climate change.
- Global warming occurs when greenhouse gases rise into the atmosphere and form a layer around the Earth, preventing heat from the Sun escaping the atmosphere. This is called enhanced greenhouse effect. This causes global warming, the Earth becomes hotter.
* 14) Discuss the Causes and Effects of Acid Rain
- Air pollution can also cause acid rain.
- Acid rain is caused by carbon dioxide dissolving in rain water to form carbonic acid, and sulphur dioxide dissolving to make sulphuric acid.
- Acid rain then falls and accumulates in bodies of water and soils, causing a change in pH which may harm organisms living there.
- The acid also corrodes infrastructure and damages tree bark and leaves.
- To reduce acid rain, sulphur dioxide is removed from gases before they are released into the atmosphere.
- Sulphur can also be removed from fossil fuels before burning, although this process is expensive.
- Soils and water can be made less acidic by adding powdered limestone or slaked lime.
* 15) Describe the negative impacts of Female Contraceptive Hormones in Water Courses
- When women use the contraceptive pill, the hormones in it (oestrogen or progesterone) are excreted in urine and become present in sewage.
- The process of sewage treatment does not extract the hormones, so they end up in water systems such as rivers, lakes and the sea.
- Their presence in this water affects aquatic organisms as they enter food chain.
- Male frogs and fish can become ‘feminised’ (they can start producing eggs in their testes instead of sperm).
- This causes an imbalance between numbers of male and female animals.
- Drinking water, extracted from rivers where water from treated sewage has been recycled, can also contain the hormones.
- This has been shown to reduce the sperm count in men, causing a reduction in fertility.
* conservation
16) State how some Resources can be Maintained
- Sustainable resources are those which can be taken from the environment without the risk of them running out, i.e. they can be produced naturally as quickly as they are harvested.
- Resources such as coal and oil are not sustainable as fossil fuels are non-renewable.
- Others, such as wood and fish, can be harvested sustainably with the help of quotas, education and re-stocking.
17) What Sustainable Development Requires
- Sustainable development is defined as development providing for the needs of an increasing human population without harming the environment.
- This requires management of conflicting demands eg. companies wanting to harvest resources for profit, while people disagree as it could damage habitats.
- So it requires planning and co-operation from local councils and companies, local government and even between governments of different countries.
18) Recycling Products
- Unsustainable practices can lead to large amounts of waste.
- This waste can be reduced by introducing recycling programmes.
- Paper, glass, plastic and metals can all be reused and recycled, which greatly reduces the amount of these materials polluting the environment or in landfills.
- It also reduces the demand on sourcing raw materials, which in turn reduces the amount of habitat destruction.
19) Outline how Sewage is treated to make Water safe for use
- Water treatment happens in three stages: sedimentation, filtration and chlorination.
- In sedimentation, larger solids separate out from the water to form sludge, whilst water and lighter particles which float on top are drained into another tank.
- This liquid is then passed through gravel and sand filters in filtration to remove any particles still left in the water.
- Finally, chlorine is added to the water to kill microorganisms such as bacteria which makes the water safe to consume.
20) Explain why Organisms become Endangered or Extinct
- Conservation of endangered species:
- When the number of surviving organisms in a species becomes very low, the species is classed as endangered.
- This is harmful to a species as it greatly reduces the gene pool by decreasing the number of alleles available. This makes the species more susceptible to disease and less able to adapt to changes.
- Species can become endangered for a variety of reasons, such as habitat destruction, climate change, hunting, pollution, and competition from introduced species.
- If an endangered species is not protected, it can become extinct.
21) Describe how Endangered Species can be Conserved
- Measures to protect a species from extinction:
- Monitoring: endangered animals can be monitored. This allows the number of organisms left to be tracked over time and can also highlight their preferred habitats and migration patterns, allowing important habitats to be protected.
- Education: this allows people to understand why a species is becoming extinct so that protective measures can be implemented.
- Captive breeding programmes: endangered animals can be bred in captivity where their chance of survival is greater. They can later be reintroduced to habitats in the wild.
- Seed banks: seeds from endangered plant species can be preserved so that the plants may be grown in the future.
22) Explain Importance of Conservation Programmes
- To prevent the extinction of species.
- To protect vulnerable environment.
- Maintaining ecosystem functions, such as nutrient cycling and resource provision, e.g. food, drugs, fuel and genes.
