Extinction Extinction occurs when all individuals of a species are gone and have left no descendants. If all the species within a genus are extinct then the genus is extinct. If all genera in a family are extinct then the family is extinct. Extinction removes a potential branch on the evolutionary tree. Extinction is Forever
We can conclude a species has gone extinct when the last member of that species has died. d Tecopa pupfish - 1977
Dodo - 1581
Elephant Bird (Madagascar) ~ 1500 Moa (New Zealand) 4 species ~ 1400
Quagga - 1883
Passenger Pigeon 1914 Once the most common bird in North America.
Tasmanian Tiger or Thylacine - 1936
Caribbean Monk Seal - 1952
Golden Toad - 1989
Pyrenean Ibex - 2000
Baiji River Dolphin - 2006
It is often difficult to prove that no individuals of a species remain in the wild. It is easier to prove for large animals. Ivorybilled Woodpecker -?
What makes a species vulnerable to extinction? Vulnerability to introduced exotics Overexploitation Rarity Habitat loss / Fragmentation Small population size makes extinction more likely l
A small population p is prone to positive-feedback loops that draw it down an extinction vortex The key factor driving the extinction vortex is loss of the genetic variation necessary to enable evolutionary responses to environmental change
Small population Inbreeding Genetic drift Lower reproduction Reduction in individual fitness and population adaptability Higher mortality Loss of genetic variability Smaller population
Natural Extinctions Habitat Disruption Volcanic Eruptions Asteroid Impact Hbi Habitat Mdifi Modificationi Climate Change Mountain-Building Sea Level Change Exotic Species Natural Dispersal Continental Drift
Extinctions are most easily seen in species that have restricted distributions endemic species.
Hotspots of biodiversity are also hotspots of extinction
Human-Caused Extinction Overexploitation (Food, fur, collecting, pest eradication, etc.) Habitat Degradation/Destruction Destruction of keystone species Introduction of Exotic Species Competitors Predators Diseases Pollution, Contamination, Climate Change
Overexploitation Human harvesting of wild plants or animals at rates exceeding ability of populations of those species to rebound Large organisms with low reproductive rates are Large organisms with low reproductive rates are especially vulnerable
Overexploitation by the fishing industry has greatly reduced populations of some game fish, such as blue-fin tuna World s fish stocks have been reduced by 90% World s fish stocks have been reduced by 90% since the start of industrial fishing
Human exploitation of other species increases with our population size.
Humans Arrivals are Linked to Large Mammal Extinctions Australia 40,000 years ago Americas 15,000 years ago Madagascar 1000 years ago New Zealand 1000 years ago
Destruction of Habitat Habitat Degradation Save the Rainforests! Elimination i i of living i space Change in habitat Rif Rainforest to pasture lands Leads to diminishing resources Increases competition Can also be caused by natural processes Volcanoes, floods, drought, etc
Satellite Images of Amazon Deforestation Satellite Images of Amazon Deforestation between 1975 and 2001
Climate Change alters habitats over the entire Earth.
Habitat Fragmentation Smaller fragments have: fewer habitat types fewer species smaller populations higher extinction rates
Predation Introduction of predators can impact natives Invasive alien species Can eat other species Compete for food sources Introduce diseases
Predators reduce the population size of prey species. Predators that are very effective can reduce the size of prey populations to the point of extinction. The introduction of cats to areas that formerly lacked mammalian predators has caused the extinction of many species of birds, reptiles, and mammals. Introduced rats have caused the extinction of many birds and egg-laying reptiles.
Lake Victoria had over 150 endemic species of fish belonging to one family. Each had specialized feeding adaptations. The introduction of a large predator, the Nile perch, has caused the extinction of about half the species.
Coextinction Everything is Connected to Everything - ECE The loss of one species leads to the loss of another loss of a prey species impacts predators Chain of extinction Can be caused by small impacts in the beginning