19 Descent with Modification.

19 Descent with Modification

Endless Forms Most Beautiful
Lepidopteran insects (moths and butterflies) have many features in common including a juvenile feeding stage called a caterpillar Lepidopteran species also have many features that are distinct from each other in both the caterpillar and adult forms © 2017 Pearson Education, Ltd. 2

Lepidopterans illustrate three key observations about life
The fit between organisms and their environment The shared characteristics (unity) of life The diversity of life © 2017 Pearson Education, Ltd. 3

A new era of biology began in 1859 when Charles Darwin published On the Origin of Species
On the Origin of Species focused biologists’ attention on the great diversity of organisms © 2017 Pearson Education, Ltd. 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 © 2017 Pearson Education, Ltd. 6

Concept 19.1: The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species Darwin’s revolutionary ideas had deep historical roots © 2017 Pearson Education, Ltd. 7

Figure 19.2 Unusual species inspired novel ideas.
© 2017 Pearson Education, Ltd.

Scala Naturae and Classification of Species
The Greek philosopher Aristotle viewed species as fixed and arranged them on a scala naturae This view was consistent with the Old Testament, which holds that species were individually designed by God and therefore perfect 自然阶梯（scala naturae）(The great chain of Being) © 2017 Pearson Education, Ltd. 9

Carolus Linnaeus was the founder of taxonomy, the branch of biology that organizes species into a nested classification system of increasingly general categories He also developed the binomial format for naming species (for example, Homo sapiens) Linnaeus ascribed the resemblance among species to the pattern of creation rather than evolution © 2017 Pearson Education, Ltd. 10

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 © 2017 Pearson Education, Ltd. 11

Younger stratum with more recent fossils Older stratum
Figure 19.3 Figure 19.3 Formation of sedimentary strata with fossils Younger stratum with more recent fossils Older stratum with older fossils © 2017 Pearson Education, Ltd.

Paleontology, the study of fossils, was largely developed by French scientist Georges Cuvier
Cuvier speculated that each boundary between strata represents a catastrophe that destroyed many species © 2017 Pearson Education, Ltd. 14

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 further proposed that the mechanisms of change are constant over time This view strongly influenced Darwin’s thinking © 2017 Pearson Education, Ltd. 15

Lamarck’s Hypothesis of Evolution
Lamarck hypothesized that species evolve through use and disuse of body parts and the inheritance of acquired characteristics The mechanisms he proposed are unsupported by evidence © 2017 Pearson Education, Ltd. 16

Figure 19.4 Acquired traits cannot be inherited.

Concept 19.2: Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life Some doubt about the permanence of species preceded Darwin’s ideas © 2017 Pearson Education, Ltd. 18

Darwin’s Research As a boy and into adulthood, Charles Darwin had a consuming interest in nature Darwin first studied medicine (unsuccessfully) and then theology at Cambridge University After graduating, he took an unpaid position as naturalist and companion to Captain Robert FitzRoy for a five-year around-the-world voyage on the Beagle © 2017 Pearson Education, Ltd. 19

The Voyage of the Beagle
During his travels on the Beagle, Darwin collected specimens of South American plants and animals He observed that fossils resembled living species from the same region, and living species resembled other species from nearby regions © 2017 Pearson Education, Ltd. 20

Darwin was influenced by Lyell’s Principles of Geology and thought that Earth was more than 6,000 years old He observed the uplift of rocks on the coast of Chile following an earthquake and inferred that similar processes could explain the fossils of ocean organisms he found in the Andes © 2017 Pearson Education, Ltd. 21

His interest in geographic distribution of species was kindled by a stop at the Galápagos Islands west of South America He hypothesized that species from South America had colonized the Galápagos and speciated on the islands © 2017 Pearson Education, Ltd. 22

Darwin in HMS Beagle in port 1840, after his return from the voyage
Figure 19.5 Darwin in 1840, after his return from the voyage HMS Beagle in port Great Britain EUROPE NORTH AMERICA ATLANTIC OCEAN The Galápagos Islands AFRICA PACIFIC OCEAN PACIFIC OCEAN Pinta Genovesa Equator SOUTH AMERICA Equator Malay Archipelago Marchena Santiago Mtns. Chile Brazil AUSTRALIA Fernandina Figure 19.5 The voyage of HMS Beagle (December 1831–October 1836) PACIFIC OCEAN Andes Cape of Good Hope Isabela Santa Cruz Santa Fe San Cristobal Argentina Tasmania Floreana Kilometers Española Cape Horn New Zealand © 2017 Pearson Education, Ltd.

Great Britain EUROPE NORTH AMERICA ATLANTIC OCEAN AFRICA PACIFIC OCEAN
Figure Great Britain EUROPE NORTH AMERICA ATLANTIC OCEAN AFRICA PACIFIC OCEAN SOUTH AMERICA Equator Malay Archipelago Mtns. Brazil Chile AUSTRALIA Figure The voyage of HMS Beagle (December 1831–October 1836) (part 1: full map) PACIFIC OCEAN Andes Cape of Good Hope Argentina Tasmania New Zealand Cape Horn © 2017 Pearson Education, Ltd.

Darwin in 1840, after his return from the voyage Figure 19.5-2
Figure The voyage of HMS Beagle (December 1831–October 1836) (part 2: Darwin portrait) Darwin in 1840, after his return from the voyage © 2017 Pearson Education, Ltd.

The Galápagos Islands PACIFIC OCEAN Pinta Genovesa Marchena Equator
Figure The Galápagos Islands PACIFIC OCEAN Pinta Genovesa Marchena Equator Santiago Fernandina Isabela Santa Cruz Figure The voyage of HMS Beagle (December 1831–October 1836) (part 3: Galápagos map) Santa Fe San Cristobal 20 40 Floreana Española Kilometers © 2017 Pearson Education, Ltd.

HMS Beagle in port Figure 19.5-4
Figure The voyage of HMS Beagle (December 1831–October 1836) (part 4: HMS Beagle at sea) HMS Beagle in port © 2017 Pearson Education, Ltd.

Darwin’s Focus on Adaptation
Darwin perceived adaptation to the environment and the origin of new species as closely related processes Biologists have since concluded that the diverse group of Galápagos finches arose from an ancestral form by the gradual accumulation of adaptations to different environments © 2017 Pearson Education, Ltd. 28

(a) Cactus-eater (c) Insect-eater (b) Seed-eater Figure 19.6
Figure 19.6 Three examples of beak variation in Galápagos finches (b) Seed-eater © 2017 Pearson Education, Ltd.

(a) Cactus-eater Figure 19.6-1
Figure Three examples of beak variation in Galápagos finches (part 1: cactus-eater) (a) Cactus-eater © 2017 Pearson Education, Ltd.

(b) Seed-eater Figure 19.6-2
Figure Three examples of beak variation in Galápagos finches (part 2: seed-eater) (b) Seed-eater © 2017 Pearson Education, Ltd.

(c) Insect-eater Figure 19.6-3
Figure Three examples of beak variation in Galápagos finches (part 3: insect-eater) (c) Insect-eater © 2017 Pearson Education, Ltd.

In 1844, Darwin wrote an essay on natural selection as the mechanism of descent with modification but did not introduce his theory publicly Natural selection is a process in which individuals with favorable inherited traits are more likely to survive and reproduce © 2017 Pearson Education, Ltd. 33

In June 1858, Darwin received a manuscript from Alfred Russell Wallace, who had developed a theory of natural selection similar to Darwin’s In July 1958, Lyell presented Wallace and Darwin’s work together to the Linnean Society of London Darwin quickly finished On the Origin of Species and published it the next year © 2017 Pearson Education, Ltd. 34

Figure 19.7 Alfred Russel Wallace

Figure 19.7-1 Alfred Russel Wallace (part 1: frog painting)

Figure 19.7-2 Alfred Russel Wallace (part 2: Wallace portrait)

Ideas from On the Origin of Species
Darwin explained three broad observations about life The unity of life The diversity of life The match between organisms and their environment © 2017 Pearson Education, Ltd. 38

Descent with Modification
Darwin never used the word evolution in the first edition of On 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 © 2017 Pearson Education, Ltd. 39

In the Darwinian view, the history of life is like a tree with branches representing life’s diversity Fossils of extinct species help to “fill in” the morphological gaps between present-day groups © 2017 Pearson Education, Ltd. 40

Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) †Moeritherium
Figure 19.9 Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) †Moeritherium †Barytherium †Deinotherium †Mammut †Platybelodon †Stegodon †Mammuthus Figure 19.9 Descent with modification Elephas maximus (Asia) Loxodonta africana (Africa) Loxodonta cyclotis (Africa) 60 34 24 Millions of years ago Years ago © 2017 Pearson Education, Ltd.

Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) †Moeritherium
Figure Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) †Moeritherium †Barytherium †Deinotherium Figure Descent with modification (part 1) †Mammut 60 34 24 Millions of years ago Years ago © 2017 Pearson Education, Ltd.

†Platybelodon †Stegodon †Mammuthus Elephas maximus (Asia)
Figure †Platybelodon †Stegodon †Mammuthus Elephas maximus (Asia) Loxodonta africana (Africa) Figure Descent with modification (part 2) Loxodonta cyclotis (Africa) 60 34 24 Millions of years ago Years ago © 2017 Pearson Education, Ltd.

Artificial Selection, Natural Selection, and Adaptation
Darwin noted that humans have modified other species by selecting and breeding individuals with desired traits, a process called artificial selection Darwin argued that a similar process occurs in nature © 2017 Pearson Education, Ltd. 45

Cabbage Selection for apical (tip) bud Brussels sprouts Selection for
Figure 19.10 Cabbage Selection for apical (tip) bud Brussels sprouts Selection for axillary (side) buds Broccoli Selection for flowers and stems Figure Artificial selection Selection for stems Selection for leaves Kale Wild mustard Kohlrabi © 2017 Pearson Education, Ltd.

Kale Figure 19.10-2 Figure 19.10-2 Artificial selection (part 2: kale)

Brussels sprouts Figure 19.10-3
Figure Artificial selection (part 3: brussels sprouts) Brussels sprouts © 2017 Pearson Education, Ltd.

Darwin drew two inferences from two observations
Observation #1: Members of a population often vary in their inherited traits © 2017 Pearson Education, Ltd. 53

Figure 19.11 Variation in a population

Spore cloud Figure 19.12 Figure 19.12 Overproduction of offspring

Inference #1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals © 2017 Pearson Education, Ltd. 58

Darwin was influenced by Thomas Malthus, who noted the potential for human population to increase faster than food supplies and other resources If some heritable traits are advantageous, these will accumulate in a population over time, and this will increase the frequency of individuals with these traits This process explains the match between organisms and their environment © 2017 Pearson Education, Ltd. 60

Key Features of Natural Selection
Individuals with certain heritable traits survive and reproduce at a higher rate than other individuals Over time, natural selection increases the frequency of adaptations that are favorable in a given environment If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species © 2017 Pearson Education, Ltd. 61

Figure 19.13 Camouflage as an example of evolutionary adaptation

Note that individuals do not evolve; populations evolve over time
Natural selection can only increase or decrease heritable traits that vary in a population The traits that are adaptive will vary with different environments © 2017 Pearson Education, Ltd. 65

Concept 19.3: Evolution is supported by an overwhelming amount of scientific evidence
New discoveries continue to fill the gaps identified by Darwin in On the Origin of Species There are four types of data that document the pattern of evolution Direct observations Homology The fossil record Biogeography © 2017 Pearson Education, Ltd. 66

Direct Observations of Evolutionary Change
Two examples provide evidence for natural selection: natural selection in response to introduced species and the evolution of drug-resistant bacteria © 2017 Pearson Education, Ltd. 67

Natural Selection in Response to Introduced Species
Soapberry bugs use their “beak” to feed on seeds within fruits Soapberry bugs feed most effectively when their beak length is similar to the depth of the seeds within the fruit In southern Florida, soapberry bugs feed on the larger fruit of balloon vines; they have longer beaks In central Florida, they feed on the smaller fruit of introduced goldenrain trees; they have shorter beaks © 2017 Pearson Education, Ltd. 68

Soapberry bug with beak inserted in balloon vine fruit 2
Figure 19.14 Field Study Results 10 On native species, balloon vine (southern Florida) 8 6 Number of individuals 4 2 10 On introduced species, goldenrain tree (central Florida) 8 6 Figure Inquiry: Can a change in a population’s food source result in evolution by natural selection? Averages in museum specimens 4 Soapberry bug with beak inserted in balloon vine fruit 2 6 7 8 9 10 11 Beak length (mm) © 2017 Pearson Education, Ltd.

Soapberry bug with beak inserted in balloon vine fruit
Figure Figure Inquiry: Can a change in a population’s food source result in evolution by natural selection? (part 1: photo) Soapberry bug with beak inserted in balloon vine fruit © 2017 Pearson Education, Ltd.

These cases are examples of evolution by natural selection
Correlation between fruit size and beak size has also been observed in other locations In all cases, beak size has evolved in populations that feed on introduced plants with fruits that are smaller or larger than the native fruits These cases are examples of evolution by natural selection In Florida, this evolution in beak size occurred in less than 35 years © 2017 Pearson Education, Ltd. 71

The Evolution of Drug-Resistant Bacteria
The bacterium Staphylococcus aureus is commonly found on people’s skin or in their nasal passages Methicillin-resistant S. aureus (MRSA) strains are dangerous pathogens S. aureus became resistant to penicillin in 1945, two years after it was first widely used S. aureus became resistant to methicillin in 1961, two years after it was first widely used © 2017 Pearson Education, Ltd. 72

MRSA bacteria use a different protein in their cell walls
Methicillin works by inhibiting a protein used by bacteria in their cell walls MRSA bacteria use a different protein in their cell walls When exposed to methicillin, MRSA strains are more likely to survive and reproduce than nonresistant S. aureus strains MRSA strains are now resistant to many antibiotics © 2017 Pearson Education, Ltd. 73

Annual hospital admissions
Figure 19.15 2,750,000 1 250,000 base pairs 2,500,000 400 Annual hospital admissions with MRSA (thousands) Chromosome map of S. aureus clone USA300 500,000 350 300 Key to adaptations 2,250,000 250 Methicillin resistance Ability to colonize hosts 200 750,000 Increased disease severity 150 2,000,000 Increased gene exchange (within species) and toxin production 100 50 1,000,000 Figure The rise of methicillin-resistant Staphylococcus aureus (MRSA) ’93 ’94 ’95 ’96 ’97 ’98 ’99 ’00 ’01 ’02 ’03 ’04 ’05 1,750,000 Year 1,250,000 1,500,000 © 2017 Pearson Education, Ltd.

Chromosome map of S. aureus clone USA300
Figure 1 2,750,000 250,000 base pairs 2,500,000 Chromosome map of S. aureus clone USA300 500,000 Key to adaptations 2,250,000 Methicillin resistance Ability to colonize hosts 750,000 Increased disease severity Increased gene exchange (within species) and toxin production 2,000,000 Figure The rise of methicillin-resistant Staphylococcus aureus (MRSA) (part 1: chromosome map) 1,000,000 1,750,000 1,250,000 1,500,000 © 2017 Pearson Education, Ltd.

Annual hospital admissions
Figure 400 Annual hospital admissions with MRSA (thousands) 350 300 250 200 150 100 Figure The rise of methicillin-resistant Staphylococcus aureus (MRSA) (part 2: hospital admissions) 50 ’93 ’94 ’95 ’96 ’97 ’98 ’99 ’00 ’01 ’02 ’03 ’04 ’05 Year © 2017 Pearson Education, Ltd.

Natural selection does not create new traits, but edits or selects for traits already present in the population The local environment determines which traits will be selected for or selected against in any specific population © 2017 Pearson Education, Ltd. 77

Homology Evolution is a process of descent with modification
Related species can have characteristics with underlying similarity that function differently Homology is similarity resulting from common ancestry © 2017 Pearson Education, Ltd. 78

Anatomical and Molecular Homologies
Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor © 2017 Pearson Education, Ltd. 79

Humerus Radius Ulna Carpals Metacarpals Phalanges Human Cat Whale Bat
Figure 19.16 Humerus Radius Ulna Carpals Metacarpals Figure Mammalian forelimbs: homologous structures Phalanges Human Cat Whale Bat © 2017 Pearson Education, Ltd.

Comparative embryology reveals anatomical homologies not visible in adult organisms
© 2017 Pearson Education, Ltd. 81

Pharyngeal arches Post-anal tail Chick embryo (LM) Human embryo
Figure 19.17 Pharyngeal arches Post-anal tail Figure Anatomical similarities in vertebrate embryos Chick embryo (LM) Human embryo © 2017 Pearson Education, Ltd.

Pharyngeal arches Post-anal tail Chick embryo (LM) Figure 19.17-1
Figure Anatomical similarities in vertebrate embryos (part 1: chick embryo) Chick embryo (LM) © 2017 Pearson Education, Ltd.

Pharyngeal arches Post-anal tail Human embryo Figure 19.17-2
Figure Anatomical similarities in vertebrate embryos (part 2: human embryo) Human embryo © 2017 Pearson Education, Ltd.

Examples of homologies at the molecular level are genes shared among organisms inherited from a common ancestor Homologous genes can be found in organisms as dissimilar as humans and bacteria Many organisms have retained genes that, like vestigial structures, have lost their function © 2017 Pearson Education, Ltd. 86

A Different Cause of Resemblance: Convergent Evolution
Convergent evolution is the evolution of similar, or analogous, features in distantly related groups Analogous traits arise when groups independently adapt to similar environments in similar ways Convergent evolution does not provide information about ancestry © 2017 Pearson Education, Ltd. 87

Sugar glider NORTH AMERICA AUSTRALIA Flying squirrel Figure 19.18
Figure Convergent evolution Flying squirrel © 2017 Pearson Education, Ltd.

Flying squirrel Figure 19.18-2
Figure Convergent evolution (part 2: flying squirrel) Flying squirrel © 2017 Pearson Education, Ltd.

The Fossil Record The fossil record provides evidence of
The extinction of species The origin of new groups Changes within groups over time © 2017 Pearson Education, Ltd. 91

Cetaceans and even-toed ungulates
Figure 19.19 Most mammals Cetaceans and even-toed ungulates Figure Ankle bones: one piece of the puzzle (a) Canis (dog) (b) Pakicetus (c) Sus (pig) (d) Odocoileus (deer) © 2017 Pearson Education, Ltd.

(a) Canis (dog) Figure 19.19-1
Figure Ankle bones: one piece of the puzzle (part 1: Canis, dog) (a) Canis (dog) © 2017 Pearson Education, Ltd.

(d) Odocoileus (deer) Figure 19.19-4
Figure Ankle bones: one piece of the puzzle (part 4: Odocoileus, deer) (d) Odocoileus (deer) © 2017 Pearson Education, Ltd.

Fossils can document important transitions
For example, the transition from land to sea in the ancestors of cetaceans © 2017 Pearson Education, Ltd. 97

Pelvis and hind limb bones Other even-toed ungulates Hippopotamuses
Figure 19.20 Pelvis and hind limb bones Other even-toed ungulates Hippopotamuses †Pakicetus †Rodhocetus Common ancestor of cetaceans †Dorudon Figure The transition to life in the sea Living cetaceans 70 60 50 40 30 20 10 Key Pelvis Femur Tibia Foot Millions of years ago © 2017 Pearson Education, Ltd.

Common ancestor of cetaceans Living cetaceans 50 40 30 20 10 Key
Figure Common ancestor of cetaceans †Pakicetus †Rodhocetus †Dorudon Figure The transition to life in the sea (part 1: detail) Living cetaceans 50 40 30 20 10 Key Pelvis Femur Tibia Foot Millions of years ago © 2017 Pearson Education, Ltd.

Fossil evidence shows that living cetaceans and their close relatives, the even-toed ungulates, are more different from each other today than were early cetaceans and even-toed ungulates © 2017 Pearson Education, Ltd. 100

20 cm Figure 19.21 Figure 19.21 Diacodexis

Biogeography Biogeography, the scientific study of the geographic distribution of species, provides evidence of evolution Earth’s continents were formerly united in a single large continent called Pangaea, but have since separated by continental drift An understanding of continent movement and modern distribution of species allows us to predict when and where different groups evolved © 2017 Pearson Education, Ltd. 102

Endemic species are species that are not found anywhere else in the world
Islands have many endemic species that are often closely related to species on the nearest mainland or island Darwin explained that species on islands gave rise to new species as they adapted to new environments © 2017 Pearson Education, Ltd. 103

What Is Theoretical About Darwin’s View of Life?
In science, a theory accounts for many observations and explains and integrates a great variety of phenomena The predictions of a scientific theory must stand up to continual testing by experimentation and observation Darwin’s theory of evolution by natural selection integrates diverse areas of biological study and stimulates many new research questions Ongoing research adds to our understanding of evolution © 2017 Pearson Education, Ltd. 104

Guppies transplanted Pools with pike-cichlids and guppies
Figure 19.UN01-1 Guppies transplanted Pools with pike-cichlids and guppies Figure 19.UN01-1 Skills exercise: making and testing predictions (part 1) Pools with killifish, but no guppies prior to transplant © 2017 Pearson Education, Ltd.

Area of colored spots (mm2) colored spots Number of
Figure 19.UN01-2 12 12 10 Area of colored spots (mm2) 10 colored spots Number of 8 8 6 6 4 4 2 2 Source population Transplanted population Source population Transplanted population Figure 19.UN01-2 Skills exercise: making and testing predictions (part 2) Data from J. A. Endler, Natural selection on color patterns in Poecilia reticulata, Evolution 34:76–91 (1980). © 2017 Pearson Education, Ltd.

Individuals in a population vary in their heritable characteristics.
Figure 19.UN02 Observations Individuals in a population vary in their heritable characteristics. Organisms produce more offspring than the environment can support. Inferences Individuals that are well suited to their environment tend to leave more offspring than other individuals. Figure 19.UN02 Summary of key concepts: natural selection and Over time, favorable traits accumulate in the population. © 2017 Pearson Education, Ltd.

Figure 19.UN03 Test your understanding, question 6 (DDT resistance)

Figure 19.UN04 Test your understanding, question 9 (honeypot ant)

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