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

The big 5 of the phanerozoic.

Extinction

Mass extinctions account for4% of all extinctions

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

• 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

Ordovician/Silurian Extinction

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

• 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

Permian/Triassic Extinction

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

Shocked QuartzNormal Quartz

Abundant shockedquartz and

microtektitesin 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 andbiogeochemical nutrient cycles.

Broadly distributed species are morelikely to survive extinction events

Bivalve Genera

Jablonski and Raup, 1995

Habitat Destruction

Current extinctions are occurring at 100 - 1000 timesthe normal or background rate.

May et al. 1995, Pimm et al., 1995

Human Population by 2050 = 13 billion

Vertebrates

Hagfish,Lampreys

CartilagenousFish Bony

Fish Amphibians MammalsBirdsReptiles

SkullBackbone Paired Fins

Jaws

Bony SkeletonSwim Bladder

Four LimbsTerrestrial Phase

Amniotic EggEndothermy

HairMammary Glands

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)

Tarsier

Macaque

Lemur

Primates : Humble Beginning

Primates

ShrewRabbit

Shrew-likeAncestor

Major Primate Groups

Lemurs

Tarsiiformes

New WorldMonkeys

Old WorldMonkeys

Gibbons

Orangutan

Gorilla

Chimp Human

Family Hominidae

Hominoidea : Apes and Humans

Hominidea : Great Apes and Humans

Homininae : African Great Apesand 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

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

What Features Are Associated With Primate Evolution?