Descent with Modification 19 Descent with Modification

Overview: 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 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 3

Figure 19.1 Figure 19.1 How is this caterpillar protecting itself from predators? 4

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 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 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 7

Figure 19.2 Figure 19.2 Unusual species inspired novel ideas. 8

Scala Naturae and Classification of Species The Greek philosopher Aristotle viewed species as fixed and arranged them on a scala naturae The Old Testament holds that species were individually designed by God and therefore perfect 9

Carolus Linnaeus interpreted organismal adaptations as evidence that the Creator had designed each species for a particular purpose Linnaeus was the founder of taxonomy, the branch of biology concerned with classifying organisms He developed the binomial format for naming species (for example, Homo sapiens) 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 Video: Grand Canyon 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 12

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 13

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 14

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 15

Figure 19.4 Figure 19.4 Acquired traits cannot be inherited. 16

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 17

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 18

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 He experienced an earthquake in Chile and observed the uplift of rocks 19

Darwin was influenced by Lyell’s Principles of Geology and thought that Earth was more than 6,000 years old 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 20

Video: Albatross Courtship Video: Boobies Courtship Video: Galápagos Islands Video: Marine Iguana Video: Sea Lion Video: Soaring Hawk Video: Tortoise 21

Darwin in 1840, after his return HMS Beagle at sea from the voyage Figure 19.5 Darwin in 1840, after his return from the voyage HMS Beagle at sea Great Britain EUROPE NORTH AMERICA ATLANTIC OCEAN The Galápagos Islands PACIFIC OCEAN AFRICA Pinta Genovesa Equator Marchena SOUTH AMERICA Malay Archipelago Equator PACIFIC OCEAN Santiago Daphne Islands Chile Brazil AUSTRALIA Fernandina Pinzón PACIFIC OCEAN Andes Mtns. Figure 19.5 The voyage of HMS Beagle Isabela Santa Cruz Santa Fe San Cristobal Argentina Cape of Good Hope Tasmania 20 40 Florenza Española Cape Horn New Zealand Kilometers 22

Great Britain EUROPE NORTH AMERICA ATLANTIC OCEAN AFRICA SOUTH Equator Figure 19.5a Great Britain EUROPE NORTH AMERICA ATLANTIC OCEAN AFRICA SOUTH AMERICA Equator Malay Archipelago PACIFIC OCEAN Chile Brazil AUSTRALIA PACIFIC OCEAN Andes Mtns. Figure 19.5a The voyage of HMS Beagle (part 1: full map) Argentina Cape of Good Hope Tasmania Cape Horn New Zealand 23

Darwin in 1840, after his return from the voyage Figure 19.5b Figure 19.5b The voyage of HMS Beagle (part 2: Darwin portrait) Darwin in 1840, after his return from the voyage 24

The Galápagos Islands PACIFIC OCEAN Pinta Genovesa Marchena Equator Figure 19.5c The Galápagos Islands PACIFIC OCEAN Pinta Genovesa Marchena Equator Santiago Daphne Islands Pinzón Fernandina Isabela Santa Cruz Santa Fe Figure 19.5c The voyage of HMS Beagle (part 3: Galápagos map) San Cristobal 20 40 Florenza Española Kilometers 25

HMS Beagle at sea Figure 19.5d Figure 19.5d The voyage of HMS Beagle (part 4: Beagle at sea) HMS Beagle at sea 26

Darwin’s Focus on Adaptation 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 what happened to the Galápagos finches 27

(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 28

(a) Cactus-eater Figure 19.6a Figure 19.6a Three examples of beak variation in Galápagos finches (part 1: cactus-eater) (a) Cactus-eater 29

(b) Seed-eater Figure 19.6b Figure 19.6b Three examples of beak variation in Galápagos finches (part 2: seed-eater) (b) Seed-eater 30

(c) Insect-eater Figure 19.6c Figure 19.6c Three examples of beak variation in Galápagos finches (part 3: insect-eater) (c) Insect-eater 31

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 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 32

Figure 19.7 Figure 19.7 Alfred Russel Wallace 33

Figure 19.7a Figure 19.7a Alfred Russel Wallace (part 1: frog painting) 34

Figure 19.7b Figure 19.7b Alfred Russel Wallace (part 2: Wallace portrait) 35

Ideas from 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 36

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 37

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 38

Figure 19.8 Figure 19.8 “I think . . .” 39

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 5.5 2 104 Millions of years ago Years ago 40

Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) † Moeritherium † Figure 19.9a Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) Moeritherium † † Barytherium † Deinotherium Figure 19.9a Descent with modification (part 1) † Mammut 41

† Platybelodon † Stegodon Mammuthus † Elephas maximus (Asia) Figure 19.9b † Platybelodon † Stegodon Mammuthus † Elephas maximus (Asia) Loxodonta africana (Africa) Figure 19.9b Descent with modification (part 2) Loxodonta cyclotis (Africa) 60 34 24 5.5 2 104 Millions of years ago Years ago 42

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 43

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 19.10 Artificial selection Selection for stems Selection for leaves Kale Wild mustard Kohlrabi 44

Figure 19.10a Figure 19.10a Artificial selection (part 1: wild mustard) Wild mustard 45

Kale Figure 19.10b Figure 19.10b Artificial selection (part 2: kale) 46

Brussels sprouts Figure 19.10c Figure 19.10c Artificial selection (part 3: brussels sprouts) 47

Figure 19.10d Cabbage Figure 19.10d Artificial selection (part 4: cabbage) 48

Figure 19.10e Broccoli Figure 19.10e Artificial selection (part 5: broccoli) 49

Figure 19.10f Figure 19.10f Artificial selection (part 6: kohlrabi) Kohlrabi 50

Darwin drew two inferences from two observations Observation #1: Members of a population often vary in their inherited traits 51

Figure 19.11 Figure 19.11 Variation in a population 52

Observation #2: All species can produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce Video: Sea Horses 53

Figure 19.12 Spore cloud Figure 19.12 Overproduction of offspring 54

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 55

Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations 56

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 57

Natural Selection: A Summary Individuals with certain heritable traits survive and reproduce at a higher rate than other individuals Over time, natural selection increases the match between organisms and their environment If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species 58

(a) A flower mantid in Malaysia (b) A leaf mantid in Borneo Figure 19.13 Figure 19.13 Camouflage as an example of evolutionary adaptation (a) A flower mantid in Malaysia (b) A leaf mantid in Borneo 59

(a) A flower mantid in Malaysia Figure 19.13a Figure 19.13a Camouflage as an example of evolutionary adaptation (part 1: flower mantid) (a) A flower mantid in Malaysia 60

(b) A leaf mantid in Borneo Figure 19.13b Figure 19.13b Camouflage as an example of evolutionary adaptation (part 2: leaf mantid) (b) A leaf mantid in Borneo 61

Note that individuals do not evolve; populations evolve over time Natural selection can only increase or decrease heritable traits that vary in a population Adaptations vary with different environments 62

Concept 19.3: Evolution is supported by an overwhelming amount of scientific evidence New discoveries continue to fill the gaps identified by Darwin in The Origin of Species There are four types of data that document the pattern of evolution Direct observations Homology The fossil record Biogeography 63

Direct Observations of Evolutionary Change Two examples provide evidence for natural selection: natural selection in response to introduced plant species and the evolution of drug-resistant bacteria 64

Natural Selection in Response to Introduced Plant Species Soapberry bugs use their “beak” to feed on seeds within fruits In southern Florida soapberry bugs feed on balloon vine with larger fruit; they have longer beaks In central Florida they feed on goldenrain tree with smaller fruit; they have shorter beaks Correlation between fruit size and beak size has also been observed in Louisiana, Oklahoma, and Australia 65

These cases are examples of evolution by natural selection 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 66

Museum-specimen average Figure 19.14 Field Study Results 10 On native species, balloon vine (southern Florida) Beak 8 6 4 2 Number of individuals Museum-specimen average 10 On introduced species, goldenrain tree (central Florida) 8 Soapberry bug with beak inserted in balloon vine fruit Figure 19.14 Inquiry: Can a change in a population’s food source result in evolution by natural selection? 6 4 2 6 7 8 9 10 11 Beak length (mm) 67

Soapberry bug with beak inserted in balloon vine fruit Figure 19.14a Field Study Figure 19.14a Inquiry: Can a change in a population’s food source result in evolution by natural selection? (part 1: field study) Soapberry bug with beak inserted in balloon vine fruit 68

Museum-specimen average Figure 19.14b Results 10 On native species, balloon vine (southern Florida) Beak 8 6 4 2 Number of individuals Museum-specimen average 10 On introduced species, goldenrain tree (central Florida) Figure 19.14b Inquiry: Can a change in a population’s food source result in evolution by natural selection? (part 2: results) 8 6 4 2 6 7 8 9 10 11 Beak length (mm) 69

Museum-specimen average Figure 19.14c Results 10 On native species, balloon vine (southern Florida) 8 6 4 2 Number of individuals Museum-specimen average 10 On introduced species, goldenrain tree (central Florida) 8 Figure 19.14c Inquiry: Can a change in a population’s food source result in evolution by natural selection? (part 3: results, detail) 6 4 2 6 7 8 9 10 11 Beak length (mm) 70

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 71

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 72

Annual hospital admissions Figure 19.15 2,750,000 1 250,000 base pairs 400 2,500,000 350 Chromosome map of S. aureus clone USA300 500,000 300 Key to adaptations 250 2,250,000 Annual hospital admissions with MRSA (thousands) Methicillin resistance 200 Ability to colonize hosts 750,000 150 Increased disease severity 100 Increased gene exchange (within species) and toxin production 2,000,000 50 1,000,000 ’93 ’94 ’95 ’96 ’97 ’98 ’99 ’00 ’01 ’02 ’03 ’04 ’05 Figure 19.15 The rise of methicillin-resistant Staphylococcus aureus (MRSA) Year 1,750,000 1,250,000 1,500,000 73

Chromosome map of S. aureus clone USA300 Figure 19.15a 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 19.15a The rise of methicillin-resistant Staphylococcus aureus (MRSA) (part 1: chromosome map) 1,000,000 1,750,000 1,250,000 1,500,000 74

Annual hospital admissions Figure 19.15b 400 350 300 250 Annual hospital admissions with MRSA (thousands) 200 150 100 Figure 19.15b The rise of methicillin-resistant Staphylococcus aureus (MRSA) (part 2: hospitalization increases) 50 ’93 ’94 ’95 ’96 ’97 ’98 ’99 ’00 ’01 ’02 ’03 ’04 ’05 Year 75

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 76

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 77

Anatomical and Molecular Homologies Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor 78

Humerus Radius Ulna Carpals Metacarpals Phalanges Human Cat Whale Bat Figure 19.16 Humerus Radius Ulna Carpals Figure 19.16 Mammalian forelimbs: homologous structures Metacarpals Phalanges Human Cat Whale Bat 79

Comparative embryology reveals anatomical homologies not visible in adult organisms Vestigial structures are remnants of features that served important functions in the organism’s ancestors 80

Pharyngeal arches Post-anal tail Chick embryo (LM) Human embryo Figure 19.17 Pharyngeal arches Post-anal tail Figure 19.17 Anatomical similarities in vertebrate embryos Chick embryo (LM) Human embryo 81

Pharyngeal arches Post-anal tail Chick embryo (LM) Figure 19.17a Figure 19.17a Anatomical similarities in vertebrate embryos (part 1: chick embryo, LM) Chick embryo (LM) 82

Pharyngeal arches Post-anal tail Human embryo Figure 19.17b Figure 19.17b Anatomical similarities in vertebrate embryos (part 2: human embryo) Human embryo 83

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 84

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 85

NORTH AMERICA Sugar glider AUSTRALIA Flying squirrel Figure 19.18 Figure 19.18 Convergent evolution AUSTRALIA Flying squirrel 86

The Fossil Record The fossil record provides evidence of The extinction of species The origin of new groups Changes within groups over time 87

Cetaceans and even-toes ungulates Figure 19.19 Most mammals Cetaceans and even-toes ungulates Figure 19.19 Ankle bones: one piece of the puzzle (a) Canis (dog) (b) Pakicetus (c) Sus (pig) (d) Odocoileus (deer) 88

(a) Canis (dog) Figure 19.19a Figure 19.19a Ankle bones: one piece of the puzzle (part 1: Canis, dog) (a) Canis (dog) 89

Figure 19.19b Figure 19.19b Ankle bones: one piece of the puzzle (part 2: Pakicetus) (b) Pakicetus 90

Figure 19.19c Figure 19.19c Ankle bones: one piece of the puzzle (part 3: Sus, pig) (c) Sus (pig) 91

(d) Odocoileus (deer) Figure 19.19d Figure 19.19d Ankle bones: one piece of the puzzle (part 4: Odocoileus, deer) (d) Odocoileus (deer) 92

Fossils can document important transitions For example, the transition from land to sea in the ancestors of cetaceans 93

Other even-toed ungulates Hippopotamuses Pakicetus † Rodhocetus † Figure 19.20 Other even-toed ungulates Hippopotamuses Pakicetus † Rodhocetus † Common ancestor of cetaceans Dorudon † Figure 19.20 The transition to life in the sea Living cetaceans 70 60 50 40 30 20 10 Key Pelvis Tibia Millions of years ago Femur Foot 94

Pakicetus † Common ancestor of cetaceans Rodhocetus † Dorudon † Living Figure 19.20a Pakicetus † Common ancestor of cetaceans Rodhocetus † Dorudon † Living cetaceans Figure 19.20a The transition to life in the sea (detail) 50 40 30 20 10 Key Pelvis Tibia Millions of years ago Femur Foot 95

20 cm Diacodexis, an early even-toed ungulate Figure 19.UN01 Figure 19.UN01 In-text figure, Diacodexis, p. 377 Diacodexis, an early even-toed ungulate 96

Biogeography Biogeography, 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 97

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 98

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 99

Guppies transplanted Pools with pike-cichlids and guppies Figure 19.UN02a Guppies transplanted Pools with pike-cichlids and guppies Figure 19.UN02a Skills exercise: making and testing predictions (part 1) Pools with killifish, but no guppies prior to transplant 100

colored spots Number of Area of colored spots (mm2) Figure 19.UN02b 12 12 10 10 8 8 colored spots Number of Area of colored spots (mm2) 6 6 4 4 2 2 Figure 19.UN02b Skills exercise: making and testing predictions (part 2) Source population Transplanted population Source population Transplanted population 101

Individuals in a population vary in their heritable characteristics. Figure 19.UN03 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.UN03 Summary of key concepts: natural selection and Over time, favorable traits accumulate in the population. 102

Figure 19.UN04 Figure 19.UN04 Test your understanding, question 6 (DDT resistance data) 103