Unit 4.5. Broad Patterns of Evolution CAMPBELL BIOLOGY IN FOCUS. Urry Cain Wasserman Minorsky Jackson Reece

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1 CAMPBELL BIOLOGY IN FOCUS Urry Cain Wasserman Minorsky Jackson Reece Unit 4.5 Broad Patterns of Evolution Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge

2 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

3 Figure 23.1

4 Figure 23.UN01 Cryolophosaurus skull

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

Figure 23.2 1m 100 mya 0.5 m Rhomaleosaurus victor 175 200 Dimetrodon 270 300 4.

6 Figure m 100 mya 0.5 m Rhomaleosaurus victor Dimetrodon cm Coccosteus cuspidatus Tiktaalik cm Hallucigenia 560 Stromatolites 2.5 cm Dickinsonia costata 600 1,500 3,500 Tappania

7 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

8 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

9 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

10 Fraction of parent isotope remaining Figure 23.3 ½ Remaining parent isotope 1 Accumulating daughter isotope ¼ ⅛ 2 3 Time (half-lives)

11 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

12 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

13 Table 23.1

14 Table 23.1a

15 Table 23.1b

16 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

17 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

18 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

19 Figure 23.4 Key to skull bones Articular Dentary Quadrate Squamosal Dimetrodon Early cynodont (260 mya) Cynodonts Therapsids Synapsids OTHER TETRAPODS Reptiles (including dinosaurs and birds) Synapsid (300 mya) Very late (nonmammalian) cynodonts Mammals Temporal fenestra (partial view) Hinge Later cynodont (220 mya) Temporal fenestra Hinge Therapsid (280 mya) Original hinge New hinge Very late cynodont (195 mya) Temporal fenestra Hinge Hinge

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

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

22 Figure 23.4b Synapsid (300 mya) Key to skull bones Temporal fenestra Articular Quadrate Dentary Squamosal Hinge Therapsid (280 mya) Temporal fenestra Hinge

23 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

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

25 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

26 Figure 23.4c Early cynodont (260 mya) Temporal fenestra (partial view) Hinge Later cynodont (220 mya) Original hinge New hinge Very late cynodont (195 mya) Hinge Key to skull bones Articular Quadrate Dentary Squamosal

27 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

28 Figure 23.5 Lineage A Lineage B Common ancestor of lineages A and B Millions of years ago 0

29 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 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

30 Figure 23.7 Juan de Fuca Plate North American Plate Caribbean Plate Cocos Plate Pacific Plate Nazca Plate South American Plate Scotia Plate Eurasian Plate Philippine Plate Arabian Plate Indian Plate African Plate Antarctic Plate Australian Plate

31 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

32 Figure 23.8 Present Collision of India with Eurasia Cenozoic 45 mya ica rth No 65.5 mya A r me Eurasia Africa India South Madagascar alia America str u A Antarctica 251 mya Paleozoic 135 mya Mesozoic Laurasia Gon d wan a a ae ng Pa Present-day continents Laurasia and Gondwana landmasses The supercontinent Pangaea

33 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

34 Figure 23.9 Mantellinae (Madagascar only): 100 species Rhacophorinae (India/southeast Asia): 310 species Millions of years ago (mya) 2 1 India Madagascar 88 mya 56 mya

35 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

36 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

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

38 Figure ,100 1, Era Period Mesozoic Paleozoic E 542 O S D C 359 P Tr J 200 Time (mya) Cenozoic C 145 P N Q 0 Number of families: Total extinction rate (families per million years): 25

39 The Permian mass 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

40 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

41 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

42 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

43 Figure NORTH AMERICA Yucatán Peninsula Chicxulub crater

44 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

45 Figure Mass extinctions Relative extinction rate of marine animal genera Cooler Warmer Relative temperature 2 3 4

46 Consequences of Mass Extinctions Mass extinction can alter ecological communities and the niches available to organisms It can take 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

47 Figure Cretaceous mass extinction Predator genera (%) 50 Permian mass extinction Era Period Paleozoic E 542 O S D Mesozoic C 359 P 299 Tr 251 Time (mya) J 200 Cenozoic C 145 P 65.5 N Q 0

48 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

49 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

50 Figure Ancestral mammal Monotreme s (5 species) Marsupials (324 species) ANCESTRAL CYNODONT Eutherians (5,010 species) Time (millions of years ago) 0

51 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

Figure 23.15 Close North American relative, the tarweed Carlquistia muirii Dubautia laxa KAUAI 5.1 million years MOLOKAI 1.

52 Figure Close North American relative, the tarweed Carlquistia muirii Dubautia laxa KAUAI 5.1 million years MOLOKAI 1.3 million OAHU years 3.7 MAUI million LANAI years N Argyroxiphium sandwicense HAWAII 0.4 million years Dubautia waialealae Dubautia scabra Dubautia linearis

53 Figure 23.15a KAUAI 5.1 million years N MOLOKAI 1.3 million OAHU years 3.7 MAUI million LANAI years HAWAI I 0.4 million years

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

55 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

56 Figure Chimpanzee infant Chimpanzee adult Chimpanzee fetus Chimpanzee adult Human fetus Human adult

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

58 Figure Hand and finger bones

59 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

60 Figure Gills

61 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

62 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

63 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

64 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

65 Figure Hox gene 6 Hox gene 7 Hox gene 8 Ubx About 400 mya Drosophila Artemia

66 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

67 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

68 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

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

70 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

100 mya Hallucigenia 1,500 3,500

100 mya Hallucigenia 1,500 3,500 1 1 m Dimetrodon 0.5 m 100 mya 175 200 Rhomaleosaurus victor 270 300 Tiktaalik 4.5 cm Coccosteus cuspidatus 375 400 Hallucigenia 1 cm Stromatolites 500 510 560 600 2.5 cm Dickinsonia costata 1,500 3,500