extinctions 99.9% of all species that ever existed are now extinct Does this statement surprise you? Why or why not? Do you disagree?

Objectives Review the Earth’s extinction history Discuss the current mass extinction problem

Biodiversity at Risk Life on Earth has a long history of mass extinctions, AND is currently experiencing a mass extinction event. Reasons: –Competition –Global/Environmental change –Catastrophe Meteor strikes volcanism

Time P-T Crisis K-T Crisis Pleistocene

Permo-Triassic Extinction Within a 5 million year time span.. –The Earth lost… 52% of families 60% of genera And 95% of species

Causes? Asteroid impact off of Australia Ocean Currents slowing Toxic gases

"Toward the end of the Permian, we had a warming climate with much more carbon dioxide than today, ocean circulation was extremely sluggish, and the oceans became anoxic— essentially deprived of oxygen,"

Salinity in sea dropped Atmosphere went from high oxygen to low during permian Warming Extreme erosion of land Dead organic matter flooded the seas; reducing oxygen levels, devastating marine life Geomagnetic reversal Massive volcanism in present day Siberia Permo-Triassic Extinction

Floating species (plankton) and swimming species (nekton) suffered more extinctions than bottom- dwelling species (benthos). Permo-Triassic Extinction

insects had severe losses. A great peak in fungus spores marks the P-Tr boundary, a sign of massive plant and animal death and decomposition. Higher animals and land plants underwent significant extinctions, though not as devastating as in the marine setting. Among the four-legged animals (tetrapods), the ancestors of the dinosaurs came through on top. Permo-Triassic Extinction

Slow to recover Early successional plants Fungus spores No reefs or coal deposits Many marine species disappeared and then reappeared millions of years later –Lazarus species. Permo-Triassic Extinction

Time P-T Crisis K-T Crisis Pleistocene

Cretaceous-Tertiary Extinction Extinction of the non-avian dinosaurs Plankton in the seas hit hard. Marine life Vegetation Lost… –14% of families –38% of genera –65-75% of species

Impact of meteor in Gulf of Mexico Volcanism Cretaceous-Tertiary Extinction

Time P-T Crisis K-T Crisis Pleistocene

Modern Ice age

The Current Mass Extinction

“Anthropocene” extinction No meteors or volcanism Human-induced mass extinction extinction rates today are comparable to those of the great past extinctions. For example, for birds, of about 10,000 species worldwide, at least 128 have disappeared in the last 500 years, about 1,200 are currently seriously threatened with extinction (all but three from human activities); there is a real prospect of the loss of 500 bird species within this century.

Endangered and threatened species What makes a species prone to extinction? small population sizes Limited ranges Migratory Specialists Exploited by humans

Endangered and threatened species What are the leading causes of extinctions today? Habitat destruction Invasive species Harvesting, Hunting, Poaching Pollution

Endemic species Species that only occur in very limited areas –High endemism on Tropical rainforests Islands Reefs