extinction loss of a species or group of taxa primary cause: failure of species to adapt to changes...
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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 AmphibiansMammalsBirdsReptiles
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?