1. Get a computer or use a phone to take a “Poll Everywhere” survey

2. Descent with Modification: A Darwinian View of Life
Chapter 22
Descent with Modification: A Darwinian View of Life

3. How are all of these beetles adapted for their environments?
Why are there so many variations to the “beetle theme”?

4. Overview: Endless Forms Most Beautiful
A new era of biology began in 1859 when Charles Darwin published The Origin of Species
The Origin of Species focused biologists’ attention on the great diversity of organisms
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5. Darwin noted that current species are descendants of ancestral species
Evolution can be defined by Darwin’s phrase descent with modification
Evolution can be viewed as both a pattern and a process
Pattern- present in a range of science disciplines (geology, biology, chemistry)
Process- mechanisms that produce the pattern of change
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

6. How Darwin’s Views Were Shaped
Fig. 22-2
How Darwin’s Views Were Shaped
Linnaeus (classification)
Hutton (gradual geologic change)
Lamarck (species can change)
Malthus (population limits)
Cuvier (fossils, extinction)
Lyell (modern geology)
Darwin (evolution, natural selection)
Wallace (evolution, natural selection)
American Revolution
French Revolution
U.S. Civil War
1750
1800
1850
1900
1795
Hutton proposes his theory of gradualism.
1798
Malthus publishes “Essay on the Principle of Population.”
1809
Lamarck publishes his hypothesis of evolution.
1830
Lyell publishes Principles of Geology.
Figure 22.2 The historical context of Darwin’s life and ideas
1831–1836
Darwin travels around the world on HMS Beagle.
1837
1837
Darwin begins his notebooks.
1844
Darwin writes essay on descent with modification.
1858
Wallace sends his hypothesis to Darwin.
1859
The Origin of Species is published.

7. Ideas About Change over Time
The study of fossils helped to lay the groundwork for Darwin’s ideas
Fossils are remains or traces of organisms from the past, usually found in sedimentary rock, which appears in layers or strata
Video: Grand Canyon
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8. Layers of deposited sediment Younger stratum with more recent fossils
Fig. 22-3
Layers of deposited
sediment
Younger stratum
with more recent
fossils
Figure 22.3 Formation of sedimentary strata with fossils
Older stratum
with older fossils

9. Paleontology, the study of fossils, was largely developed by French scientist Georges Cuvier
Cuvier advocated catastrophism, speculating that each boundary between strata represents a catastrophe
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

10. This view strongly influenced Darwin’s thinking
Geologists James Hutton and Charles Lyell perceived that changes in Earth’s surface can result from slow continuous actions still operating today
Lyell’s principle of uniformitarianism states that the mechanisms of change are constant over time
This view strongly influenced Darwin’s thinking
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

11. Lamarck’s Hypothesis of Evolution
Lamarck hypothesized that species evolve through use and disuse of body parts and the inheritance of acquired characteristics
Lamarck is the first to propose the idea of gradual change to evolution, not Darwin!
The mechanisms he proposed are unsupported by evidence (use and disuse principle)
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

12. What are some examples of things in the human body that may “fit” this principle?
Lamarck believed the giraffe neck to be a perfect example
But he also thought these acquired characteristics could be passed on to offpsring

13. Are bonsai trees like the one seen here naturally this size and shape?
Fig. 22-4
Are bonsai trees like the one seen here naturally this size and shape?
No, they are pruned to be this way, it is not an inherited acquired trait. They would produce normal size seeds for offspring.
Without Pruning
Figure 22.4 Acquired traits cannot be inherited

14. The Voyage of the Beagle (Darwin’s Research)
During his travels on the Beagle, Darwin collected specimens of South American plants and animals
He observed adaptations of plants and animals that inhabited many diverse environments
Darwin was influenced by Lyell’s Principles of Geology and thought that the earth was more than 6000 years old (after earthquake found ocean fossils high in the Andes)
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15. Fig. 22-5 Figure 22.5 The voyage of HMS Beagle
GREAT
BRITAIN
EUROPE
NORTH
AMERICA
ATLANTIC
OCEAN
The
Galápagos
Islands
AFRICA
Pinta
Genovesa
Marchena
Equator
SOUTH
AMERICA
Santiago
Daphne
Islands
Pinzón
AUSTRALIA
Fernandina
PACIFIC
OCEAN
Isabela
Figure 22.5 The voyage of HMS Beagle
For the Discovery Video Charles Darwin, go to Animation and Video Files.
Santa
Cruz
Andes
Cape of
Good Hope
Santa Fe
San
Cristobal
Tasmania
Florenza
Española
Cape Horn
New
Zealand
Tierra del Fuego

16. Darwin’s Focus on Adaptation
His interest in geographic distribution of species was kindled by a stop at the Galápagos Islands near the equator west of South America
In reassessing his observations, Darwin perceived adaptation to the environment and the origin of new species as closely related processes
From studies made years after Darwin’s voyage, biologists have concluded that this is indeed what happened to the Galápagos finches
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

17. (a) Cactus-eater (c) Seed-eater (b) Insect-eater Fig. 22-6
Figure 22.6 Beak variation in Galápagos finches
(b) Insect-eater

18. 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 Russell 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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

19. Darwin developed two main ideas:
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 (individuals with certain inherited traits leave more offspring than others)
Do you get why Lamarck was wrong?! Longer necked giraffes survived better and passed those genes on to their young. They didn’t stretch their necks out over one lifetime.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

20. Daily Science
A theory is just as valid as a law, justify why using examples we discussed last week.
Answer: both are reviewed by scientific experts, both use experimentation, both take years to become validated
Who were the 2 geologists from England that helped shape Darwin’s ideas of evolution? Why did he prefer their ideas?
Answer: Hutton and Lyell (uniformitarianism), believed that Earth was older than 6,000 years and changes in organisms are a longer process rather than shorter
Although Lamarck first proposed evolution, why were his ideas widely wrong? Use the giraffe as an example.
Answer: He believed in acquired inheritance not genetic (use/disuse theory), he thought a giraffe could stretch out its’ neck and pass that stretched neck to offspring. But, it was giraffes with the longest necks survived better because they could feed from tall trees and passed those genes on.

22. Descent with Modification
Darwin never used the word evolution in the first edition of The Origin of Species
The phrase descent with modification summarized Darwin’s perception of the unity of life
The phrase refers to the view that all organisms are related through descent from an ancestor that lived in the remote past
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

23. Darwin’s theory meshed well with the hierarchy of Linnaeus
Fig. 22-7
In the Darwinian view, the history of life is like a tree with branches representing life’s diversity.
Darwin’s theory meshed well with the hierarchy of Linnaeus
Figure 22.7 “I think . . .”

24. Fig. 22-8 Figure 22.8 Descent with modification Millions of years ago
Hyracoidea
(Hyraxes)
Sirenia
(Manatees
and relatives)
Moeritherium
Barytherium
Deinotherium
Mammut
Platybelodon
Stegodon
Mammuthus
Figure 22.8 Descent with modification
Elephas maximus
(Asia)
Loxodonta
africana
(Africa)
Loxodonta cyclotis
(Africa) 34 24
5.5 2
104
Millions of years ago
Years ago

25. Anatomical and Molecular Homologies
Evidence Supporting Evolution
Anatomical and Molecular Homologies
Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor
Homology is similarity resulting from common ancestry
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

26. Fig
Very different functions, but all developed from the same structural theme.
Humerus
Radius
Ulna
Carpals
Metacarpals
Figure Mammalian forelimbs: homologous structures
Phalanges
Human
Cat
Whale
Bat

27. Pharyngeal pouches Post-anal tail Chick embryo (LM) Human embryo
Fig
Pharyngeal
pouches
Post-anal
tail
Figure Anatomical similarities in vertebrate embryos
Chick embryo (LM)
Human embryo