Extinction Loss of a species or group of taxa Primary cause: Failure of species to adapt to changes in environment Extinction happens

Example: Species Lifespan Mammals ~ 1 million year lifespan 5000 currently alive Background rate ~ 1 species / 200 years 89 species extinct in last 400 years www.pbs.org/wgbh/evolution/library/03/2/l_032_04.html

Extinction Mass extinctions account for 4% of all extinctions The big 5 of the phanerozoic.

Ordovician/Silurian Extinction 490 – 443 mya Diversification of phyla, including 21 classes of echinoderms Formation of coral reefs Evolution of agnathans and trilobites Plants invade land Gondwana centered in southern hemisphere

Ordovician/Silurian Extinction 57% of marine genera wiped out Probable cause: Global cooling Glaciation over Gondwana led to cooling and drop in sea levels Time span: 2 my (rapid) Created opportunity for surviving species: ostracoderms

Permian/Triassic Extinction Largest of mass extinctions Lost 96% of marine species Trilobites gone Lost 75% of all land vertebrate families Estimated that 84% of all genera on Earth became extinct Time span: 1 million years Prelude to the age of dinosaurs

Permian/Triassic Extinction Plate Tectonics – Pangea formation Supernova – destroyed ozone layer Asteroid impact – trigger volcanoes Siberian traps – 200,000 cubic kilometers covered with lava Global warming caused methane hydrate release from oceans Oxygen depleted from oceans

Cretaceous/Tertiary Extinction Extinction of Dinosaurs 50% of all genera Pterosaurs, dinosaurs, sea reptiles Cause: Asteroid impact Prelude to the age of mammals

Iridium concentration in clay layer at KT Boundary Other evidence: Chicxulub crater Microtektites Soot deposits Evidence of tsunami

Evidence of the Impact Normal Quartz Shocked Quartz Abundant shocked quartz and microtektites in the KT clay layer in Caribbean

Microtektites from the crater wall date to 65 mya

Direct Effects: Tsunami, dust induced global cooling, fires, acid rain, earthquakes, volcanism Indirect Effects: Disruption of ecological processes and biogeochemical nutrient cycles.

Broadly distributed species are more likely to survive extinction events Bivalve Genera Number of Geographical Provinces Jablonski and Raup, 1995

Habitat Destruction Human Population by 2050 = 13 billion Current extinctions are occurring at 100 - 1000 times the normal or background rate. May et al. 1995, Pimm et al., 1995 Human Population by 2050 = 13 billion

Vertebrates Hair Mammary Glands Amniotic Egg Endothermy Four Limbs Cartilagenous Fish Hagfish, Lampreys Bony Fish Amphibians Mammals Birds Reptiles Hair Mammary Glands Amniotic Egg Endothermy Four Limbs Terrestrial Phase Bony Skeleton Swim Bladder Skull Backbone Paired Fins Jaws

Mammals Hair, mammary glands Most advanced nervous system Learning important to survival Warm blooded Humans are mammals

Humans are primate mammals Class Mammalia Order Primates Prosimians (e.g. lemurs) Tarsiers Anthropoids (e.g. monkeys, hominoids)

Lemur Tarsier Macaque

Primates : Humble Beginning Rabbit Shrew Shrew-like Ancestor

Homininae : African Great Apes Major Primate Groups Family Hominidae Old World Monkeys Orangutan Chimp Human Tarsiiformes Gibbons Gorilla Lemurs New World Monkeys Homininae : African Great Apes and Humans Hominidea : Great Apes and Humans Hominoidea : Apes and Humans

What Features Are Associated With Primate Evolution? I. Sensory Adaptations Protected, forward looking eyes with stereoscopic vision Improved sight : more detail even in low light Reduction of olfactory structures

What Features Are Associated With Primate Evolution? II. Adaptations for tree-climbing and insectivory Freely moving limbs and digits Long mobile digits capable of grasping Retention of tail as organ of balance Evolution of upright body posture and extensive head rotation Increased body size Evolution of nervous system to give precise and rapid control of movement