Biology - 18 Biodiversity and Ecosystems - 18.1 The Human Population Explosion & 18.2 Land and Water Pollution & 18.3 Air Pollution & 18.4 Deforestation and Peat Destruction

Biodiversity

variety of life in the world or in a particular habitat or ecosystem.

How does biodiversity make ecosystems stable? [3]

- organisms have less dependence on one another

- if one population changes, it has less impact on the ecosystem

- because other species take its place

Factors that have caused human population growth [3]:

- agricultural development

- medical development

- lack of natural predators

How do humans affect biodiversity by use of land and resources? [4]

- land used for building

- land used for farming

- land used for mining

- industrial, agricultural and organic waste pollutes

Main finite resources humans use [2]:

- fossil fuels (gas, coal, oil)

- metal ore

How is water polluted? [5]

- sewage

- fertilisers

- toxic industrial chemicals

- landfill leachate

- acid rain

How is air polluted? [3]

- smoke

- poisonous gases

- soot

How is land/soil polluted? [3]

- agricultural waste (pesticides and herbicides)

- industrial waste (heavy metals)

- toxic landfill leachate

Disadvantages of landfill [3]:

- occupy land and destroy habitats, reducing biodiversity

- pollute surrounding land and water with leachate

- release of greenhouse gases like methane

Disadvantages of agricultural waste [3]:

- pesticides and herbicides kill organisms and reduce biodiversity

- bioaccumulation

- fertilisers cause eutrophication

Bioaccumulation

increased concentration of a chemical within an organism over time

Biomagnification

accumulation of pollutants at successive levels of the food chain

What types of pollution cause eutrophication? [2]

- sewage

- fertilisers

Why do sewage and fertilisers cause eutrophication?

they contain nitrates

Eutrophication

excessive nutrients cause uncontrolled algal bloom, affecting the biodiversity of a water system

Eutrophication process [6]:

1. nitrate-rich pollutants enter water systems

2. nitrates stimulate algal bloom and rapid plant growth

3. algae and plants die due to lack of photosynthesis; algae blocks out sunlight

4. decomposers respire aerobically and decrease oxygen content in water

5. aerobic organisms (e.g. fish) die and decompose, as well as aerobic decomposers, due to lack of oxygen

6. anaerobic decomposers produce toxic waste chemicals

Algal bloom

rapid growth of a population of algae

Bioindicator

species that serves as an indicator of environmental conditions

Acidic gases [2]

- sulfur dioxide

- nitrogen oxides

What do acidic gases form and how?

acid rain, by dissolving in rainwater and reacting with oxygen from the air

Effects of smoke as a pollutant [2]

- particulates may cause respiratory issues (bronchitis, asthma)

- dimming effect may slow photosynthesis and disrupt food chains

Effects of acid rain [4]

- erodes buildings

- damages and kills plants, weakening an ecosystem

- changes pH of soil

- changes pH of water systems, killing aquatic organisms

Deforestation

action of clearing a wide area of trees

Reasons for deforestation [4]

- growing staple crops and cheap food sources

- rearing cattle

- growing crops to make biofuels

- timber production

'Slash-and-burn' clearance

farming method involving the cutting of trees, then burning them to provide ash-enriched soil for the planting of crops

Effects of deforestation [5]

- burning and decaying vegetation releases 'locked-in' carbon

- less carbon removed from atmosphere by carbon sink

- reduces biodiversity by removing habitats and food sources

- causes leaching and soil erosion

- disrupts the water cycle

Leaching

removal of dissolved materials from soil by water moving downwards

Soil erosion

wearing away of surface soil by water and wind

Peat

partially decayed plant matter found in bogs containing locked-in carbon

Peat bog

acidic wetland area with an accumulation of partially-decomposed plants

Peatland

generic term of any wetland that accumulates peat

Uses of peat [3]:

- used as fertiliser/compost in farming

- dried and burned as fuel

- drained to make space for farming

Effects of peat destruction [3]:

- non-renewable so cannot return; used unsustainably

- releases locked-in carbon; contributes to greenhouse effect and global warming

- reduces habitat for unique organisms