Descent with Modification A Darwinian View of Life

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AUSTRALIA

GREAT

BRITAIN

SOUTH

AMERICA

ATLANTIC

OCEAN

PACIFIC

OCEAN

Cape of

Good Hope

Tierra del Fuego

Cape Horn

Tasmania

New

Zealand

Andes

Equator

The

Galápagos

Islands

Pinta

Marchena

Genovesa

Santiago

Daphne

Islands

Pinzón

Fernandina

Isabela

San

Cristobal

Santa

Fe

Santa

Cruz

Florenza

Española

Slide 7

Darwin’s Focus on Adaptation

Darwin’s interest in geographic distribution of species was kindled by a stop at the Galápagos Islands near the equator west of South America.

Darwin perceived adaptation to the environment and the origin of new species as closely related processes.

Recent biologists have concluded that speciation is indeed what happened to the Galápagos finches.

Slide 8

Speciation of Galapagos Finches

(a) Cactus-eater

(c) Seed-eater

(b) Insect-eater

Slide 9

Fig. 22-6a

(a) Cactus-eater

Slide 10

Fig. 22-6b

(b) Insect-eater

Slide 11

Fig. 22-6c

(c) Seed-eater

Slide 12

In 1844, Darwin wrote an essay on the origin of species and natural selection but did not introduce his theory publicly, anticipating an uproar.

In June 1858, Darwin received a manuscript from Alfred Wallace, who had developed a theory of natural selection similar to Darwin’s.

Darwin quickly finished The Origin of Species and published it the next year.

Slide 13

The Origin of Species

Darwin developed two main ideas:

Descent with modification explains life’s unity and diversity.

Natural selection is a cause of adaptive evolution.

Slide 14

Descent With Modification

Hyracoidea

(Hyraxes)

Sirenia

(Manatees

and relatives)

Moeritherium

Barytherium

Deinotherium

Mammut

Elephas maximus

(Asia)

Stegodon

Mammuthus

Loxodonta

africana

(Africa)

Loxodonta cyclotis

(Africa)

0

104

2

5.5

24

34

Millions of years ago

Years ago

Platybelodon

Slide 15

Artificial Selection, Natural Selection, and Adaptation