Broad Patterns of Evolution

Broad Patterns of Evolution
23 Broad Patterns of Evolution

Overview: Lost Worlds Past organisms were very different from those now alive The fossil record shows evidence of macroevolution, broad changes above the species level; for example The emergence of terrestrial vertebrates The impact of mass extinctions The origin of flight in birds 2

Figure 23.1 Figure 23.1 On what continent did these dinosaurs roam? 3

Cryolophosaurus skull
Figure 23.UN01 Figure 23.UN01 In-text figure, Cryolophosaurus skull, p. 436 Cryolophosaurus skull 4

Concept 23.1: The fossil record documents life’s history
The fossil record reveals changes in the history of life on Earth Video: Grand Canyon 5

Coccosteus cuspidatus 375 400 Hallucigenia
Figure 23.2 1 m 100 mya Rhomaleosaurus victor 175 0.5 m 200 Dimetrodon 270 Tiktaalik 300 4.5 cm Coccosteus cuspidatus 375 400 1 cm Hallucigenia Figure 23.2 Documenting the history of life 500 510 2.5 cm Dickinsonia costata 560 Stromatolites 600 1,500 3,500 Tappania 6

Stromatolite cross section Figure 23.2a
Figure 23.2a Documenting the history of life (part 1: stromatolite cross section) Stromatolite cross section 7

Stromatolites Figure 23.2b
Figure 23.2b Documenting the history of life (part 2: stromatolite rocks) Stromatolites 8

Figure 23.2c Figure 23.2c Documenting the history of life (part 3: Tappania) Tappania 9

2.5 cm Dickinsonia costata Figure 23.2d
Figure 23.2d Documenting the history of life (part 4: Dickinsonia costata) Dickinsonia costata 10

1 cm Hallucigenia Figure 23.2e
Figure 23.2e Documenting the history of life (part 5: Hallucigenia) Hallucigenia 11

Coccosteus cuspidatus
Figure 23.2f Figure 23.2f Documenting the history of life (part 6: Coccosteus cuspidatus) 4.5 cm Coccosteus cuspidatus 12

Figure 23.2g Figure 23.2g Documenting the history of life (part 7: Tiktaalik) Tiktaalik 13

Figure 23.2h 0.5 m Figure 23.2h Documenting the history of life (part 8: Dimetrodon) Dimetrodon 14

Rhomaleosaurus victor
Figure 23.2i Figure 23.2i Documenting the history of life (part 9: Rhomaleosaurus victor) 1 m Rhomaleosaurus victor 15

The Fossil Record Sedimentary rocks are deposited into layers called strata and are the richest source of fossils The fossil record indicates that there have been great changes in the kinds of organisms on Earth at different points in time 16

Few individuals have fossilized, and even fewer have been discovered
The fossil record is biased in favor of species that Existed for a long time Were abundant and widespread Had hard parts 17

How Rocks and Fossils Are Dated
Sedimentary strata reveal the relative ages of fossils The absolute ages of fossils can be determined by radiometric dating A “parent” isotope decays to a “daughter” isotope at a constant rate Each isotope has a known half-life, the time required for half the parent isotope to decay 18

½ ¼ ⅛ Accumulating “daughter” isotope Fraction of parent
Figure 23.3 Accumulating “daughter” isotope Fraction of parent isotope remaining Figure 23.3 Radiometric dating Remaining “parent” isotope ⅛ 1 16 1 2 3 4 Time (half-lives) 19

Radiocarbon dating can be used to date fossils up to 75,000 years old
For older fossils, some isotopes can be used to date volcanic rock layers above and below the fossil 20

The Geologic Record The geologic record is a standard time scale dividing Earth’s history into the Hadean, Archaean, Proterozoic, and Phanerozoic eons The Phanerozoic encompasses most of the time that animals have existed on Earth The Phanerozoic is divided into three eras: the Paleozoic, Mesozoic, and Cenozoic Major boundaries between geological divisions correspond to extinction events in the fossil record Animation: The Geologic Record 21

Table 23.1 Table 23.1 The geologic record 22

Table 23.1a Table 23.1a The geologic record (part 1: Hadean eon through Paleozoic era) 23

Table 23.1b Table 23.1b The geologic record (part 2: Mesozoic era and Cenozoic era) 24

Stromatolites date back 3.5 billion years ago
The oldest known fossils are stromatolites, rocks formed by the accumulation of sedimentary layers on bacterial mats Stromatolites date back 3.5 billion years ago Prokaryotes were Earth’s sole inhabitants for more than 1.5 billion years 25

Early prokaryotes released oxygen into the atmosphere through the process of photosynthesis
The increase in atmospheric oxygen that began 2.4 billion years ago led to the extinction of many organisms The eukaryotes flourished in the oxygen-rich atmosphere and gave rise to multicellular organisms 26

The Origin of New Groups of Organisms
Mammals belong to the group of animals called tetrapods The evolution of unique mammalian features can be traced through gradual changes over time 27

†Very late (non- mammalian) cynodonts
Figure 23.4 Reptiles (including dinosaurs and birds) Key to skull bones Articular Dentary OTHER TETRA- PODS Quadrate Squamosal †Dimetrodon Early cynodont (260 mya) Synapsids †Very late (non- mammalian) cynodonts Temporal fenestra (partial view) Therapsids Cynodonts Mammals Hinge Synapsid (300 mya) Later cynodont (220 mya) Temporal fenestra Hinge Figure 23.4 Exploring the origin of mammals Original hinge New hinge Therapsid (280 mya) Very late cynodont (195 mya) Temporal fenestra Hinge Hinge 28

†Very late (non- mammalian) cynodonts
Figure 23.4a Reptiles (including dinosaurs and birds) OTHER TETRAPODS †Dimetrodon Synapsids †Very late (non- mammalian) cynodonts Figure 23.4a Exploring the origin of mammals (part 1: tetrapod tree) Therapsids Cynodonts Mammals 29

Synapsids (300 mya) had single-pointed teeth, large temporal fenestra, and a jaw hinge between the articular and quadrate bones 30

Therapsids (280 mya) had large dentary bones, long faces, and specialized teeth, including large canines 31

Synapsid (300 mya) Therapsid (280 mya) Key to skull bones Articular
Figure 23.4b Synapsid (300 mya) Key to skull bones Articular Quadrate Dentary Temporal fenestra Squamosal Hinge Therapsid (280 mya) Figure 23.4b Exploring the origin of mammals (part 2: synapsids and therapsids) Temporal fenestra Hinge 32

Early cynodonts (260 mya) had large dentary bones in the lower jaw, large temporal fenestra in front of the jaw hinge, and teeth with several cusps 33

Later cynodonts (220 mya) had teeth with complex cusp patterns and an additional jaw hinge between the dentary and squamosal bones 34

Very late cynodonts (195 mya) lost the original articular-quadrate jaw hinge
The articular and quadrate bones formed inner ear bones that functioned in transmitting sound In mammals, these bones became the hammer (malleus) and anvil (incus) bones of the ear 35

Very late cynodont (195 mya)
Figure 23.4c Early cynodont (260 mya) Key to skull bones Articular Temporal fenestra (partial view) Quadrate Dentary Squamosal Hinge Later cynodont (220 mya) Original hinge Figure 23.4c Exploring the origin of mammals (part 3: cynodonts) New hinge Very late cynodont (195 mya) Hinge 36

Concept 23.2: The rise and fall of groups of organisms reflect differences in speciation and extinction rates The history of life on Earth has seen the rise and fall of many groups of organisms The rise and fall of groups depend on speciation and extinction rates within the group 37

† † Lineage A † † † Common ancestor of lineages A and B Lineage B † 4
Figure 23.5 † † Lineage A † † † Common ancestor of lineages A and B Lineage B † Figure 23.5 How speciation and extinction affect diversity 4 3 2 1 Millions of years ago 38

Plate Tectonics At three points in time, the landmasses of Earth have formed a supercontinent: 1.1 billion, 600 million, and 250 million years ago According to the theory of plate tectonics, Earth’s crust is composed of plates floating on Earth’s mantle 39

Crust Mantle Outer core Inner core Figure 23.6
Figure 23.6 Cutaway view of Earth Inner core 40

Tectonic plates move slowly through the process of continental drift
Oceanic and continental plates can separate, slide past each other, or collide Interactions between plates cause the formation of mountains and islands and earthquakes Video: Lava Flow Video: Volcanic Eruption 41

North American Plate Eurasian Plate Juan de Fuca Plate Caribbean Plate
Figure 23.7 North American Plate Eurasian Plate Juan de Fuca Plate Caribbean Plate Philippine Plate Arabian Plate Indian Plate Cocos Plate South American Plate Pacific Plate Nazca Plate African Plate Australian Plate Figure 23.7 Earth’s major tectonic plates Scotia Plate Antarctic Plate 42

Consequences of Continental Drift
Formation of the supercontinent Pangaea about 250 million years ago had many effects A deepening of ocean basins A reduction in shallow water habitat A colder and drier climate inland 43

Present Collision of India with Eurasia 45 mya Cenozoic Present-day
Figure 23.8 Present Collision of India with Eurasia 45 mya Cenozoic North America Eurasia Present-day continents 65.5 mya Africa South America India Madagascar Australia Antarctica Laurasia Laurasia and Gondwana landmasses 135 mya Mesozoic Gondwana Figure 23.8 The history of continental drift during the Phanerozoic eon The supercontinent Pangaea 251 mya Pangaea Paleozoic 44

Laurasia and Gondwana 135 mya landmasses Mesozoic The supercontinent
Figure 23.8a Laurasia Laurasia and Gondwana landmasses 135 mya Gondwana Mesozoic Figure 23.8a The history of continental drift during the Phanerozoic eon (part 1: Paleozoic and Mesozoic eras) The supercontinent Pangaea 251 mya Pangaea Paleozoic 45

Present Collision of India with 45 mya Eurasia Cenozoic Present-day
Figure 23.8b Present Collision of India with Eurasia 45 mya Cenozoic North America Eurasia Present-day continents Africa 65.5 mya South America India Figure 23.8b The history of continental drift during the Phanerozoic eon (part 2: Mesozoic and Cenozoic eras) Madagascar Australia Antarctica 46

Separation of landmasses can lead to allopatric speciation
Continental drift can cause a continent’s climate to change as it moves north or south Separation of landmasses can lead to allopatric speciation For example, frog species in the subfamilies Mantellinae and Rhacophorinae began to diverge when Madagascar separated from India 47

Millions of years ago (mya)
Figure 23.9 Mantellinae (Madagascar only): 100 species Rhacophorinae (India/southeast Asia): 310 species 80 60 40 20 1 2 Millions of years ago (mya) 1 2 Figure 23.9 Speciation in frogs as a result of continental drift India Madagascar 88 mya 56 mya 48

The distribution of fossils and living groups reflects the historic movement of continents
For example, the similarity of fossils in parts of South America and Africa is consistent with the idea that these continents were formerly attached 49

Mass Extinctions The fossil record shows that most species that have ever lived are now extinct Extinction can be caused by changes to a species’ environment At times, the rate of extinction has increased dramatically and caused a mass extinction Mass extinction is the result of disruptive global environmental changes 50

The “Big Five” Mass Extinction Events
In each of the five mass extinction events, more than 50% of Earth’s species became extinct 51

(families per million years):
Figure 23.10 1,100 25 1,000 900 20 800 700 15 600 (families per million years): Total extinction rate Number of families: 500 10 400 300 5 200 Figure Mass extinction and the diversity of life 100 Era Period Paleozoic Mesozoic Cenozoic Q E O S D C P Tr J C P N 542 488 444 416 359 299 251 200 145 65.5 Time (mya) 52

The Permian extinction defines the boundary between the Paleozoic and Mesozoic eras 251 million years ago This mass extinction occurred in less than 500,000 years and caused the extinction of about 96% of marine animal species 53

A number of factors might have contributed to these extinctions
Intense volcanism in what is now Siberia Global warming resulting from the emission of large amounts of CO2 from the volcanoes Reduced temperature gradient from equator to poles Oceanic anoxia from reduced mixing of ocean waters 54

The Cretaceous mass extinction 65
The Cretaceous mass extinction 65.5 million years ago separates the Mesozoic from the Cenozoic Organisms that went extinct include about half of all marine species and many terrestrial plants and animals, including most dinosaurs 55

The presence of iridium in sedimentary rocks suggests a meteorite impact about 65 million years ago
Dust clouds caused by the impact would have blocked sunlight and disturbed global climate The Chicxulub crater off the coast of Mexico is evidence of a meteorite collision that dates to the same time 56

Figure 23.11 NORTH AMERICA Chicxulub crater Yucatán Peninsula Figure Trauma for Earth and its Cretaceous life 57

Is a Sixth Mass Extinction Under Way?
Scientists estimate that the current rate of extinction is 100 to 1,000 times the typical background rate Extinction rates tend to increase when global temperatures increase Data suggest that a sixth, human-caused mass extinction is likely to occur unless dramatic action is taken 58

Relative extinction rate of
Figure 23.12 3 Mass extinctions 2 1 Relative extinction rate of marine animal genera −1 Figure Fossil extinctions and temperature −2 −3 −2 −1 1 2 3 4 Cooler Warmer Relative temperature 59

Consequences of Mass Extinctions
Mass extinction can alter ecological communities and the niches available to organisms It can take 5–100 million years for diversity to recover following a mass extinction The type of organisms residing in a community can change with mass extinction For example, the percentage of marine predators increased after the Permian and Cretaceous mass extinctions Mass extinction can pave the way for adaptive radiations 60

Predator genera (%) E O S D C P Tr J C P N Q
Figure 23.13 50 Cretaceous mass extinction Permian mass extinction 40 30 Predator genera (%) 20 10 Era Period Paleozoic Mesozoic Cenozoic Figure Mass extinctions and ecology E O S D C P Tr J C P N 542 488 444 416 359 299 251 200 145 65.5 Q Time (mya) 61

Adaptive Radiations Adaptive radiation is the evolution of many diversely adapted species from a common ancestor Adaptive radiations may follow Mass extinctions The evolution of novel characteristics The colonization of new regions 62

Worldwide Adaptive Radiations
Mammals underwent an adaptive radiation after the extinction of terrestrial dinosaurs The disappearance of dinosaurs (except birds) allowed for the expansion of mammals in diversity and size Other notable radiations include photosynthetic prokaryotes, large predators in the Cambrian, land plants, insects, and tetrapods 63

Time (millions of years ago)
Figure 23.14 Ancestral mammal Monotremes (5 species) ANCESTRAL CYNODONT Marsupials (324 species) Eutherians (5,010 species) Figure Adaptive radiation of mammals 250 200 150 100 50 Time (millions of years ago) 64

Regional Adaptive Radiations
Adaptive radiations can occur when organisms colonize new environments with little competition The Hawaiian Islands are one of the world’s great showcases of adaptive radiation Animation: Allometric Growth 65

Close North American relative, the tarweed Carlquistia muirii
Figure 23.15 Close North American relative, the tarweed Carlquistia muirii KAUAI 5.1 million years Dubautia laxa MOLOKAI 1.3 million years MAUI Argyroxiphium sandwicense OAHU 3.7 million years LANAI HAWAII 0.4 million years N Figure Adaptive radiation on the Hawaiian Islands Dubautia waialealae Dubautia scabra Dubautia linearis 66

KAUAI 5.1 million years MOLOKAI 1.3 million OAHU years 3.7 MAUI
Figure 23.15a KAUAI 5.1 million years MOLOKAI 1.3 million years MAUI OAHU 3.7 million years LANAI HAWAII 0.4 million years Figure 23.15a Adaptive radiation on the Hawaiian Islands (part 1: map) N 67

Close North American relative, the tarweed Carlquistia muirii
Figure 23.15b Close North American relative, the tarweed Carlquistia muirii Figure 23.15b Adaptive radiation on the Hawaiian Islands (part 2: Carlquistia muirii) 68

Dubautia waialealae Figure 23.15c
Figure 23.15c Adaptive radiation on the Hawaiian Islands (part 3: Dubautia waialealae) Dubautia waialealae 69

Figure 23.15d Figure 23.15d Adaptive radiation on the Hawaiian Islands (part 4: Dubautia laxa) Dubautia laxa 70

Dubautia scabra Figure 23.15e
Figure 23.15e Adaptive radiation on the Hawaiian Islands (part 5: Dubautia scabra) Dubautia scabra 71

Argyroxiphium sandwicense Figure 23.15f
Figure 23.15f Adaptive radiation on the Hawaiian Islands (part 6: Argyroxiphium sandwicense) Argyroxiphium sandwicense 72

Dubautia linearis Figure 23.15g
Figure 23.15g Adaptive radiation on the Hawaiian Islands (part 7: Dubautia linearis) Dubautia linearis 73

Concept 23.3: Major changes in body form can result from changes in the sequences and regulation of developmental genes Studying genetic mechanisms of change can provide insight into large-scale evolutionary change 74

Effects of Development Genes
Genes that program development influence the rate, timing, and spatial pattern of changes in an organism’s form as it develops into an adult 75

Changes in Rate and Timing
Heterochrony is an evolutionary change in the rate or timing of developmental events It can have a significant impact on body shape The contrasting shapes of human and chimpanzee skulls are the result of small changes in relative growth rates 76

Chimpanzee infant Chimpanzee adult Chimpanzee fetus Chimpanzee adult
Figure 23.16 Chimpanzee infant Chimpanzee adult Figure Relative skull growth rates Chimpanzee fetus Chimpanzee adult Human fetus Human adult 77

Chimpanzee infant Chimpanzee adult Figure 23.16a
Figure 23.16a Relative skull growth rates (photo) Chimpanzee infant Chimpanzee adult 78

Another example of heterochrony can be seen in the skeletal structure of bat wings, which resulted from increased growth rates of the finger bones 79

Hand and finger bones Figure 23.17
Figure Elongated hand and finger bones in a bat wing Hand and finger bones 80

Heterochrony can alter the timing of reproductive development relative to the development of nonreproductive organs In paedomorphosis, the rate of reproductive development accelerates compared with somatic development The sexually mature species may retain body features that were juvenile structures in an ancestral species 81

Figure 23.18 Gills Figure Paedomorphosis 82

Changes in Spatial Pattern
Substantial evolutionary change can also result from alterations in genes that control the placement and organization of body parts Homeotic genes determine such basic features as where wings and legs will develop on a bird or how a flower’s parts are arranged 83

Hox genes are a class of homeotic genes that provide positional information during animal development If Hox genes are expressed in the wrong location, body parts can be produced in the wrong location For example, in crustaceans, a swimming appendage can be produced instead of a feeding appendage 84

The Evolution of Development
Adaptive evolution of both new and existing genes may have played a key role in shaping the diversity of life Developmental genes may have been particularly important in this process 85

Changes in Gene Sequence
New morphological forms likely come from gene duplication events that produce new developmental genes A possible mechanism for the evolution of six-legged insects from a many-legged crustacean ancestor has been demonstrated in lab experiments Specific changes in the Ubx gene have been identified that can “turn off” leg development 86

Hox gene 6 Hox gene 7 Hox gene 8 Ubx About 400 mya Drosophila Artemia
Figure 23.19 Hox gene 6 Hox gene 7 Hox gene 8 Ubx About 400 mya Figure Origin of the insect body plan Drosophila Artemia 87

Changes in Gene Regulation
Changes in morphology likely result from changes in the regulation of developmental genes rather than changes in the sequence of developmental genes For example, threespine sticklebacks in lakes have fewer spines than their marine relatives The gene sequence remains the same, but the regulation of gene expression is different in the two groups of fish 88

Threespine stickleback (Gasterosteus aculeatus)
Figure 23.UN03 Ventral spines Figure 23.UN03 In-text figure, threespine stickleback, p. 451 Threespine stickleback (Gasterosteus aculeatus) 89

Hypothesis A: Differences in sequence Result: No
Figure 23.20 Results Hypothesis A: Differences in sequence Result: No The 283 amino acids of the Pitx1 protein are identical. Hypothesis B: Differences in expression Result: Yes Marine stickleback embryo: expression in ventral spine and mouth regions Lake stickleback embryo: expression only in mouth regions Figure Inquiry: What caused the loss of spines in lake stickleback fish? Red arrows indicate regions of Pitx1 expression. 90

Marine stickleback embryo: expression in ventral spine and
Figure 23.20a Marine stickleback embryo: expression in ventral spine and mouth regions Figure 23.20a Inquiry: What caused the loss of spines in lake stickleback fish? (part 1: marine stickleback embryo) Red arrows indicate regions of Pitx1 expression. 91

Lake stickleback embryo: expression only in mouth regions
Figure 23.20b Lake stickleback embryo: expression only in mouth regions Figure 23.20b Inquiry: What caused the loss of spines in lake stickleback fish? (part 2: lake stickleback embryo) Red arrows indicate regions of Pitx1 expression. 92

Concept 23.4: Evolution is not goal oriented
Evolution is like tinkering—it is a process in which new forms arise by the slight modification of existing forms 93

Evolutionary Novelties
Most novel biological structures evolve in many stages from previously existing structures Complex eyes have evolved from simple photosensitive cells independently many times Exaptations are structures that evolve in one context but become co-opted for a different function Natural selection can only improve a structure in the context of its current utility 94

(a) Patch of pigmented cells (b) Eyecup
Figure 23.21 (a) Patch of pigmented cells (b) Eyecup Pigmented cells (photoreceptors) Pigmented cells Epithelium Nerve fibers Nerve fibers Example: Pleurotomaria, a slit shell mollusc Example: Patella, a limpet (c) Pinhole camera-type eye (d) Eye with primitive lens (e) Complex camera lens- type eye Epithelium Cellular mass (lens) Cornea Fluid-filled cavity Cornea Figure A range of eye complexity in molluscs Lens Retina Optic nerve Optic nerve Optic nerve Pigmented layer (retina) Example: Murex, a marine snail Example: Nautilus Example: Loligo, a squid 95

(a) Patch of pigmented cells
Figure 23.21a (a) Patch of pigmented cells Pigmented cells (photoreceptors) Epithelium Nerve fibers Figure 23.21a A range of eye complexity in molluscs (part 1: patch of cells) Example: Patella, a limpet 96

Example: Pleurotomaria, a slit shell mollusc
Figure 23.21b (b) Eyecup Pigmented cells Nerve fibers Example: Pleurotomaria, a slit shell mollusc Figure 23.21b A range of eye complexity in molluscs (part 2: eyecup) 97

(c) Pinhole camera-type eye
Figure 23.21c (c) Pinhole camera-type eye Epithelium Fluid-filled cavity Optic nerve Pigmented layer (retina) Figure 23.21c A range of eye complexity in molluscs (part 3: pinhole) Example: Nautilus 98

(d) Eye with primitive lens
Figure 23.21d (d) Eye with primitive lens Cellular mass (lens) Cornea Optic nerve Figure 23.21d A range of eye complexity in molluscs (part 4: primitive lens) Example: Murex, a marine snail 99

(e) Complex camera lens- type eye
Figure 23.21e (e) Complex camera lens- type eye Cornea Lens Retina Optic nerve Figure 23.21e A range of eye complexity in molluscs (part 5: camera lens) Example: Loligo, a squid 100

Evolutionary Trends Extracting a single evolutionary progression from the fossil record can be misleading Apparent trends should be examined in a broader context The species selection model suggests that differential speciation success may determine evolutionary trends Evolutionary trends do not imply an intrinsic drive toward a particular phenotype 101

Figure 23.22 Holocene Pleistocene Equus Pliocene Hippidion and close relatives 5 Nannippus Pliohippus Neohipparion 10 Sinohippus Callippus Hipparion Miocene Megahippus Archaeohippus Hypohippus 15 Anchitherium Parahippus 20 Merychippus 25 Millions of years ago Oligocene Miohippus 30 35 Figure The evolution of horses Haplohippus Mesohippus Key Palaeotherium Grazers Pachynolophus Browsers 40 Propalaeotherium Epihippus Eocene 45 Orohippus 50 Hyracotherium relatives 55 Hyracotherium 102

25 Grazers Browsers Oligocene Miohippus 30 Haplohippus 35
Figure 23.22a 25 Grazers Browsers Oligocene 30 Miohippus 35 Haplohippus Mesohippus Palaeotherium Millions of years ago Pachynolophus 40 Propalaeotherium Epihippus Eocene 45 Figure 23.22a The evolution of horses (part 1: 55 mya to 25 mya) Orohippus 50 Hyracotherium relatives 55 Hyracotherium 103

Grazers Browsers Holocene Equus Pleistocene Pliocene 5 Neohipparion
Figure 23.22b Grazers Browsers Holocene Pleistocene Equus Pliocene 5 Pliohippus Neohipparion 10 Sinohippus Hipparion Miocene Megahippus Archaeohippus Millions of years ago Hypohippus 15 Anchitherium Figure 23.22b The evolution of horses (part 2: 25 mya to present) 20 Parahippus Merychippus hippus Mio- 104

Millions of years ago (mya)
Figure 23.UN02 Species with planktonic larvae Species with nonplanktonic larvae Figure 23.UN02 Skills exercise: estimating quantitative data from a graph and developing hypotheses Paleocene Eocene 65 60 55 50 45 40 35 Millions of years ago (mya) 105

Flies and fleas Caddisflies Moths and butterflies Herbivory
Figure 23.UN04 Flies and fleas Caddisflies Moths and butterflies Figure 23.UN04 Test your understanding, question 7 (herbivory) Herbivory 106

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