Themes in the Study of Life

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with varied

inherited traits.

Elimination

of individuals

with certain

traits.

Reproduction

of survivors.

Increasing

frequency

of traits that enhance survival and reproductive success.

4

3

2

1

Slide 84

Natural selection is often evident in adaptations of organisms to their way of life and environment

Bat wings are an example of adaptation

Video: Soaring Hawk

Slide 85

Fig. 1-21

Slide 86

The Tree of Life

“Unity in diversity” arises from “descent with modification”

For example, the forelimb of the bat, human, horse and the whale flipper all share a common skeletal architecture

Fossils provide additional evidence of anatomical unity from descent with modification

Slide 87

Darwin proposed that natural selection could cause an ancestral species to give rise to two or more descendent species

For example, the finch species of the Galápagos Islands

Evolutionary relationships are often illustrated with tree-like diagrams that show ancestors and their descendents

Slide 88

Fig. 1-22

COMMON

ANCESTOR

Warbler finches

Insect-eaters

Seed-eater

Bud-eater

Insect-eaters

Tree finches

Green warbler finch Certhidea olivacea

Gray warbler finch Certhidea fusca

Sharp-beaked

ground finch Geospiza difficilis

Vegetarian finch Platyspiza crassirostris

Mangrove finch Cactospiza heliobates

Woodpecker finch Cactospiza pallida

Medium tree finch Camarhynchus pauper

Large tree finch Camarhynchus psittacula

Small tree finch Camarhynchus parvulus

Large cactus

ground finch

Geospiza conirostris

Cactus ground finch

Geospiza scandens

Small ground finch

Geospiza fuliginosa

Medium ground finch

Geospiza fortis

Large ground finch

Geospiza magnirostris

Ground finches

Seed-eaters

Cactus-flower-eaters

Slide 89

Fig. 1-22a

Warbler finches

Insect-eaters

Seed-eater

Bud-eater

Green warbler finch Certhidea olivacea

Gray warbler finch Certhidea fusca

Sharp-beaked

ground finch Geospiza difficilis

Vegetarian finch Platyspiza crassirostris

Slide 90

Fig. 1-22b

Insect-eaters

Tree finches

Mangrove finch Cactospiza heliobates

Woodpecker finch Cactospiza pallida