Historical Biogeography

CH 7

Current Distribution

• Result of the interaction of:– Early history and place of origin– Fragmentation of continents– Climactic changes during Cenozoic– Cooling and eventual ice age in Pleistocene– Mass extinctions and adaptive radiations– Land Bridges

• Bering• Greenland

I. Deep Time PerspectiveA. 4 Zoic Eras B. Overview of Major EventsC. Historic Biogeography

Table 25-1b

The rise and fall of dominant groups reflect continental drift, mass extinctions, and adaptive radiations

SouthAmerica

Pangaea

Mill

ions

of y

ears

ago

65.5

135

Mes

ozoi

c

251

Pale

ozoi

c

Gondwana

Laurasia

Eurasia

IndiaAfrica

AntarcticaAustralia

North America

Madagascar

Ceno

zoic

Present

Continental Drift

• At three points in time, the land masses of Earth have formed a supercontinent: 1.1 billion, 600 million, and 250 million years ago

• Earth’s continents move slowly over the underlying hot mantle through the process of continental drift

• Oceanic and continental plates can collide, separate, or slide past each other

• Interactions between plates cause the formation of mountains and islands, and earthquakes

Mass Extinctions

• The fossil record shows that most species that have ever lived are now extinct

• At times, the rate of extinction has increased dramatically and caused a mass extinction

• In each of the five mass extinction events, more than 50% of Earth’s species became extinct

Dimetrodon Hallucigenia

Fig. 25-14

Tota

l exti

nctio

n ra

te(f

amili

es p

er m

illio

n ye

ars)

:

Time (millions of years ago)

Num

ber o

f fam

ilies

:

CenozoicMesozoicPaleozoicE O S D C P Tr J

542

0

488 444 416 359 299 251 200 145

EraPeriod

5

C P N

65.5

0

0

200

100

300

400

500

600

700

800

15

10

20

Adaptive Radiations

• Adaptive radiation is the evolution of many new species adapted from a common ancestor upon introduction to new environmental opportunities (new niches)

• Occurs via:– Evolution of novelty (i.e., seeds)– After a mass extinction (i.e., mammals) – Formation of new land (i.g. islands)– Piggyback on other organisms (insect radiations follow flowering

plants)

BASICALLY, any time many new niches (ecological livelihoods) are available, there is opportunity for adaptive radiation.

Table 25-1a

Table 25-1aIII. Multicellular Life - Neoproterozoic

Table 25-1a

V. First Life on LandVI. Conquest of Land

Challenges:structural supportdehydrationreproduction

Solutions:exoskeleton, lungs in animalswhat about plants?

cuticle, stomata, vascular tissue,pollen – not all at once

Table 25-1a

Massive extinction – 250myafollowed by adaptive radiation

Table 25-1b

SouthAmerica

Pangaea

Mill

ions

of y

ears

ago

65.5

135

Mes

ozoi

c

251

Pale

ozoi

c

Gondwana

Laurasia

Eurasia

IndiaAfrica

AntarcticaAustralia

North America

Madagascar

Ceno

zoic

Present

VIII. Emerging Modern LineagesTriassic/Jurassic:

global warming, arid Pangaea interior, mountain formation

Reptiles loved it!

Table 25-1b

SouthAmerica

Pangaea

Mill

ions

of y

ears

ago

65.5

135

Mes

ozoi

c

251

Pale

ozoi

c

Gondwana

Laurasia

Eurasia

IndiaAfrica

AntarcticaAustralia

North America

Madagascar

Ceno

zoic

Present

Extinction

Fig. 25-17

Millions of years ago

Monotremes(5 species)

250 150 100200 50

ANCESTRALCYNODONT

0

Marsupials(324 species)

Eutherians(placentalmammals;5,010 species)

Ancestralmammal

SouthAmerica

Pangaea

Mil

lio

ns

of

year

s ag

o

65.5

135

Mes

ozo

ic

251

Pal

eozo

ic

Gondwana

Laurasia

Eurasia

IndiaAfrica

AntarcticaAustralia

North Americ

a

Madagascar

Cen

ozo

ic

Present

Mountain ranges: Himalayans , Rockies (Eocene), Sierra Nevada (Miocene), Cascades, Coast ranges (late Miocene)

Great American Interchange

Panama Isthmus formed 3 mya

Panama bridge26 genera S12 went NTapirs/llamas went extinct in N Am, so disjunct w/Asian