Human influences on the environment Flashcards
List the gases responsible for the greenhouse effect
Water vapour, carbon dioxide, methane, nitrous oxides and CFCs
What is the biological consequence of sulphur dioxide?
Dissolves in rainwater, causing acid rain which can harm marine life in ponds.
What is the biological consequence of carbon monoxide?
Carbon monoxide is a harmful gas when inhaled as it binds irreversibly to haemoglobin, reducing the oxygen-carrying capacity of the blood and reducing respiration.
Describe the greenhouse effect
the Sun emits rays that enter the Earth’s atmosphere
heat bounces back from the Earth’s surface
some heat is reflected back out into space
some heat is absorbed by greenhouse gases and is trapped within the Earth’s atmosphere – this is normal
Describe the enhanced greenhouse effect
when increasing levels of greenhouse gases from human activities cause the Earth’s average temperature to rise above normal, leading to global warming
How is carbon dioxide produced by human activity?
Burning fossil fuels
Slash and burn forest clearance
How are nitrous oxides produced by human activity?
Burning fossil fuels
How is methane produced by human activity?
Produced by bacteria in cows’ guts
Bacteria in waterlogged rice paddy fields
How are CFCs produced by human activity?
Used as a solvent for aerosols and in fridges and freezers.
Consequences of global warming
Destruction of habitats
Decreases in biodiversity
Spread of disease
Change in crops
Ocean temperatures rise leading to ice caps melting
Explain how deforestation leads to leaching
Water is no longer taken up by plants and so begins to ‘run off’ from the soil into rivers and lakes. This water contains dissolved mineral ions (otherwise absorbed by the plant). Mineral ions are removed from the soil (loss of nutrients) and some cause eutrophication
Explain how deforestation leads to soil erosion
Water running off deforested areas may carry away topsoil leading to erosion. Due to deforestation, less roots in soil so topsoil is not held in place. Topsoil is most fertile, mineral ion rich so when it is lost, land is difficult to use for crop growth and reduces chances of plants re-growing.
Explain how deforestation can lead to droughts
Plants carry out transpiration. The evaporated water from transpiration moves into atmosphere and eventually makes rain. Deforestation breaks this cycle so water doesn’t end up in the atmosphere so rain doesn’t occur. Leads to droughts.
Explain eutrophication
Nitrates are absorbed by the green algae in the water.
They multiply rapidly and may cover surface of water. This is called algal bloom.
This blocks out the sunlight for other plants in the lake/river.
The plants can’t photosynthesise so they die.
The algae on top eventually die.
The dead remains provide food for bacteria. The bacteria multiply rapidly.
Large population of bacteria respire increasing biological oxygen demand (B.O.M), using up oxygen in the water.
Decreases level of oxygen in the water and results in the death of other organisms in the water as they cannot respire aerobically.
Explain how sewage pollutes water
Sewage provides a good source of food for the bacteria. The bacteria multiply rapidly. Large population of sewage respire increasing B.O.D, using up oxygen in the water. This decreases the level of oxygen and results in the death of other organisms in the water, as they cannot respire aerobically.
Explain how deforestation affects the carbon cycle and the balance of atmospheric gases
During photosynthesis, carbon dioxide is taken into plants. Plant acts as a ‘carbon sink’. If deforestation occurs, there are less plants to store carbon and carbon dioxide levels increase in the atmosphere. Oxygen levels decrease as there is less photosynthesis
What are the 5 main effects of deforestation
Leaching
Soil erosion
Disturbance of evapotranspiration
Affects carbon cycle
Affects balance of atmospheric gases
