C.3 Impacts of humans on ecosystems Flashcards
What are alien species?
A species whose introduction outside their present distribution threatens biodiversity
How have humans introduced alien species into ecosystems?
Through:
- Human migration
- Biological control
- Accidental transport
What are consequences of alien species?
They often tend to not have natural predators, more resistance to disease and may be voracious feeders. Consequences are therefore:
- Reduced biodiversity
- Exclusion of species into extinction through competitive exclusion
Explain the case study of the cane toad.
Cane toads were brought in to Australia from South America in attempt to curb the population of the french and grey cane beetle. It was to improve crops and agricultural economy. Cane toads did however not eat the cane beetles and instead spread everywhere else and bad impact on the environment and species living there. Many species existence were threatened by the cane toad as it is poisonous when ingested and it feeds on nearly anything. A female toad can lay up to 35,000 eggs twice a year. Because of their poison they lack natural predators, meaning they can easily thrive.
Explain the three methods of removal of alien species
Biological control - involves using enemies of invasive species against them. Such as when rabbit viruses were used to control rabbit populations in Australia
Physical control - involves using physical removal of alien species. Removal of garlic mustard from forest floor.
Chemical control - involves using chemical as a way to remove alien species. Is often used against plants as herbicides.
Define bioaccumulation
Refers to when an organism accumulate toxins from the food they consume
Define biomagnification
As organisms feed on more and more organisms in the trophic level below they accumulate certain toxins to a concentration that is greater than the trophic level below.
Explain case study of DDT
- DDT was used in world war II in order to protect soldiers and control spread of malaria and typhus
- Rachel Carson wrote a book called silent springs
- She claimed it caused leukaemia through bioaccumulation and magnification
- She claimed is was responsible for decline in bird species such as osprey
Explain evidence against Rachel Carson claims.
- A national cancer institute report concluded that DDT was not carcinogenic.
- A report from Great Britain stated that thrush egg shells had been thinning 47 years before DDT was used.
- In Canada peregrines were observed to be reproducing normally despite the fact their tissue contained 30 times more DDT than controls.
What are plastics and who mass produced them first?
Plastics are synthetic materials made from organic polymers and they were first mass synthesised by Leo Baekeland.
What are macro-plastics?
They represent the big plastic products that are seen and litters the streets, lakes and oceans.
What are micro-plastics?
They are plastics that have been shred into tiny plastics from gyros which are ocean currents.
