Human Influence on the Ecosystem
(Section B11 from the curriculum)
What you need to know (from the curriculum)
List the undesirable effects of deforestation (to include extinction, loss of soil, flooding, carbon dioxide build up).
Explain how increases in greenhouse gases (carbon dioxide and methane) are thought to cause global warming.
Describe the undesirable effects of overuse of fertilisers (to include eutrophication of lakes and rivers).
Describe the undesirable effects of pollution to include:
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water pollution by sewage and chemical waste,
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air pollution by greenhouse gases (carbon dioxide and methane) contributing to global warming.
Discuss the causes and effects on the environment of acid rain, and the measures that might be taken to reduce its incidence.
Describe the need for conservation of:
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species and their habitats,
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natural resources (limited to water and non-renewable materials including fossil fuels).
Deforestation
Real World Context
Today....
Some guiding questions for today
- What are the causes and reasons for so much deforestation?
- What are the undesirable consequences of deforestation?
- What is the greenhouse effect....
The causes
Example 1 - Indonesia
- the species' that live there?
- the soil
Example 2 - Amazon
Example 3 - Paraguay
The undesirable effects of deforestation
Loss of soil
North-West Madagascar
- the species' in the river?
- local people who depend on the river?
- the power of the river in times of flood?
Extinction
Burning the rainforest
- One method of clearing the rainforest is burning.
- This is how CO2 is added to the atmosphere
Biodiversity
Rainforests have a high biodiversity and this is an important reason to protect them.
What effect does deforestation have on biodiversity?
Deforestation and the carbon cycle
Summary
- Trees used for fuel
- Trees used to make paper and furniture products
- We need a huge amount of space to grow crops and raise animals for food (think of what the average person consumes!)
Undesirable consequences of deforestation
- Loss of fertile soil
- Increased flooding
- More CO2 in the atmosphere (when trees/vegetation are burned)
- Extinction of species
The greenhouse effect
What is the greenhouse effect and why is it described as 'greenhouse'?
The greenhouse effect is a process where certain compounds in the atmosphere retain heat from the sun, the main gases we need to know are carbon dioxide and methane
Key Words
- Visible light - light emitted from the sun (that we can see) that strikes the Earth
- Infra-red radiation - some visible light is converted to infra-red radiation when it strikes the Earth and this generates HEAT.
- Re-radiate - when the infra-red radiation is reflected from the ground but it is then re-reflected back towards the ground from greenhouse gases (CO2 and CH4) in the atmosphere.
- CO2 (carbon dioxide)
- CH4 (methane)
How the greenhouse effect works
Sunlight
Infra-red radiation
Infra-red radiation be reflected back towards Earth by certain compounds including H20, CO2 and CH4.
This infra-red radiation can be re-radiated many times increasing the amount of heat energy in the atmosphere.
Increase in greenhouse gases
This means that more heat energy will be retained by the atmosphere, and less heat energy lost into space.
Data
Greenhouse gas emissions
Temperature increase
Atmospheric CO2 and surface temperature trend
Eutrophication
What is it?
Fertilisers are highly soluble - they dissolve in water easily, rainfall washes fertilisers out of the soil.
It is caused when fertilisers (used to increase crop production) are washed into rivers, lakes and seas from farmland.
The overuse of fertiliser is responsible for eutrophication.
Lakes
- How does this affect the growth of plants underneath?
- How does this affect the herbivorous species in the lake that rely on the plants underneath?
On a larger scale....
- If the use of fertiliser is not regulated or controlled and the overuse continues over a period of time, huge bodies of water can be affected.
- Growth of bacteria in the lake provide food for aerobic bacteria, how will this affect the levels of oxygen in the water?
Death of populations
Why does it happen?
Nitrates - (NO3-) required to make protein
Phosphorus - (P) needed for healthy cell division and protein synthesis.
Potassium - (K) facilitates plant growth through a variety of life processes
Fertilisers containing these minerals are known as NPK fertilisers.
When there is too much fertiliser around the roots of the plant it can cause the plant to lose water by osmosis leading to wilting and then death of the plant.
Exam style question
Mark scheme
- Algae on the surface will undergo rapid growth
- They block sunlight to photosynthetic plants below
- Causing plants underneath to decrease in number/die
- Decomposers in the lake break down these dead plants (using up oxygen)
- Other organisms will decrease in number/die due to a lack of oxygen.
Pollution
Untreated sewage in UK waters
Raw Sewage entering rivers, seas
Sewage contains bacteria
This is because sewage contains high levels of nutrients such as phosphates, organic matter and bacteria. The phosphates act as fertilisers for algae, while the bacteria feed on the organic matter and reproduce rapidly, using up O2 in respiration.
If sewage is untreated before disposal it can lead to disease organisms such as cholera and typhoid being transmitted in the water.