02 July 2016

#152 Controlling alien species

Alien or invasive species are those that have moved from one ecosystem to another where they were previously unknown.


  • humans trading animals and plants
  • introduced as biological control agents to control pests
  • escapees
  • animals introduced for sport

  • become successful predators
  • compete effectively with native organisms of the same niche, pushing them to extinction
  • introduce diseases --> spread to organisms that have been exposed to that pathogen


Water hyacinth: 
  • grow successfully --> covers huge areas of land and water
         ---> blocks sunlight from reaching native aquatic plants
         ---> reduce concentration of oxygen in the water
         ---> kills fish
  • habitat for mosquito larvae

Japanese knotweed:

  • vigorous root systems --> forces its way through concrete and damaged buildings, roads, walls
  • outcompetes native species by reducing space where they grow

Cane toad:
  • introduced to Queensland, Australia from Hawaii in 1935
  • aim: control insect pest of cane sugar
  • the cane toad bred rapidly, spreading across the country
  • has few predators in Australia as the toad produces a toxing that kills animals that eat it

Red lionfish:
  • native to seas of South-East Asia
  • escapee from the Caribbean
  • becomes a predator in its new environment; eats local species of coral reefs

Indian mongoose:
  • introduced to Jamaica in 1872
  • aim: control rats in cane fields
  • the mongoose did so well it became a predator to other animal

  Syllabus 2016-2018

18.3 Conservation

Maintaining biodiversity is important for many reasons. Actions to maintain biodiversity must be taken at local, national and global levels. 

 It is important to conserve ecosystems as well as individual species.

a) discuss the threats to the biodiversity of aquatic and terrestrial ecosystems (see 18.1b) 

b) discuss the reasons for the need to maintain biodiversity 

c) discuss methods of protecting endangered species, including the roles of zoos, botanic gardens, conserved areas (national parks and marine parks), ‘frozen zoos’ and seed banks 

d) discuss methods of assisted reproduction, including IVF, embryo transfer and surrogacy, used in the conservation of endangered mammals 

e) discuss the use of culling and contraceptive methods to prevent overpopulation of protected and non-protected species 

f) use examples to explain the reasons for controlling alien species 

g) discuss the roles of non-governmental organisations, such as the World Wide Fund for Nature (WWF) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), in local and global conservation 

h) outline how degraded habitats may be restored with reference to local or regional examples

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