Option G3Impact of Humans on

Ecosystems

Alien SpeciesAn alien species is one which

arrives in a non-native habitat.

Introduction of an alien species may be intentional or accidental

Often they are not well adapted to the new habitat so it will not survive

Some can adapt well and become very invasive causing ecological and economic damage.

Examples:Zebra Mussel – accidental releaseJapanese Knotweed – deliberateintroductionCane Toad – biological control

Zebra mussels – an invasive speciesDressenia polymorpha is native to the Black and

Caspian SeasAccidental release into the Great Lakes through the

ballast water of ships in the mid 1980’sFirst found in Lake St. Clair and quickly spread to L.

OntarioHas spread throughout all the great lakes and most

waterways in eastern North America

Impacts of the Zebra MusselFew natural predators. Takes over niche of native

musselsWill grow on any hard surface –

pipes, boats, rocks, other organisms

Clogs water intake pipesFilters water and removes water

contaminants. These contaminants passed

through the food chain Biomagnification!

Cleared up Lake Erie water

Round Goby – an invasive species- Round Goby- Survives well in degraded environmental conditions -Competitive advantage compared to native species. -Heavy feeding on invasive mussels(zebra and quagga) results in greater biomagnification- No predators due to defensive mechanism

Japanese Knotweed -deliberately introducedFallopia japonica is an aggressive

semi-woody perennial plant that is native to eastern Asia.

Was introduced in the 1800′s it was introduced to North America as an ornamental species and also planted for erosion control

Has a vigorous root system that can spread up to 10m from the parent stem. Very difficult to control.

Reduces plant biodiversity by competing with other native vegetation.

Roots are known to break through asphalt and concrete.

Define biomagnification – At each trophic level, toxic substances (Hg, pesticides, TCDD, etc.) become more concentrated

The Ozone LayerThe stratosphere is located 15-40 km above the

Earth’s surfaceThe ozone layer is the “Earth’s sunscreen” and

absorbs 93% of UV radiation from the sunOzone is continually being broken down and

reformed by UV radiationO2 + O O3

The presence of CFC’s causes thinning of the ozone layer

http://www.youtube.com/watch?v=qUfVMogIdr8

Montreal ProtocolAn international agreement to reduce the

use of substances that deplete ozone by 2000such as those used in:refrigerator coolantspropellants in aerosolsmanufacturing of foam packaging

The treaty was originally signed in 1987 with amendments in 1990 and 1992

Size of the ozone hole peaked in 2001 and has now started to shrink

Estimated by 2070 it will have disappeared

Effects of Ultraviolet RadiationNon-lethal skin cancer (carcinoma)Lethal skin cancer (malignant melanoma)

DNA mutations (Thymine dimers)Sunburn – leads to skin cancer

Cataracts – clouding of the lens of the eye leading to loss of vision

Suppression of the immune system

Reduction in growth of phytoplankton in Ocean’s

UV damage kills plant cells and reduces photosynthesis