Science 20 Unit C 2.1.Indd

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the process the process fossilization: by which any trace of the existence of ancient life is within rock preserved recovery Æ is much more discovery discovery Æ fossilization preservation preservation Æ n burial Æ death Æ life

The Changing Earth

The Cambrian Explosio Cambrian The Unit C: Trilobite fossils are from the Cambrian Period. from fossils are Trilobite 2.1 tree. If a mould is filled calcite or silica, a cast is formed. a mineral, such as in by 330 impression of the organic material left behind. Soft parts can sometimes be preservedimpression of the organic as a thin film of carbon. of sediment. But there buried in layers usually that it creates an impression of the are most often found in sedimentary rock because the remains were so quickly Fossils flows because lava lava been found in volcanic tree trunksare cases where have called an external mould. The impression of the inside of a shell results in an internal mould. These are sometimes so detailed The impression of the inside of a shell results in an internal mould. called an external mould. the muscles are attached to the shell can be preserved. that the places where with an material, of the organic the complete replacement and skin—can be fossilized by Soft tissue—such as leaves Hard parts—such as shells and teeth—can be found in the rock as unaltered remains. If the original material is replaced by a Hard parts—such as shells and teeth—can be found in the rock as unaltered remains. If the original material is replaced by the hardest be petrified. enough time, even mineral, such as silica, the resulting fossil would In the right conditions, and given The outside of a shell is the space left behind is called a mould. When the material dissolves, dissolve. shells and teeth may half of the impression, with only working found it challenging to identify an embedded object when have may Just as you missing pieces. with actual fossils often means trying a puzzle that has many to solve working complete decomposition. The first the burying step in the process of fossilization is before that organism’s of the organism complex and can be summarized as follows: complex Fossilization object by created a fossil impression of an everyday you Evidence,” In “Interpreting Fossil actual process of The into a mould. pouring plaster of Paris simply could allow What kind of evidence occurred these things if they such a long time ago? know possibly anyone could How to these questions are in the trilobite photograph. The answers someone to come to that kind of conclusion? the Cambrian Period, which took place in the firstAbout 50% of all Cambrian fossils are trilobites. which part Era. of the Paleozoic the Cambrian Period, the bottom of a near swam ago, the animal in this photograph million years suggests that more than 500 The evidence sediment. tropical sea, feeding on nutrients in the Figure C2.1: Figure fossils from index are excellent Trilobites called a trilobite. the remains of an organism C2.1 shows in Figure The photograph

Science 20 © 2006 Alberta Education (www.education.gov.ab.ca). Third-party copyright credits are listed on the attached copyright credit page. Science 20 © 2006 Alberta Education (www.education.gov.ab.ca). Third-party copyright credits are listed on the attached copyright credit page. 331 fossil.

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Canadia ? Canadia’s ? Canadia , shown in both , shown A Tropical Alberta Tropical A Canadia Canadia are found in a shale formation a predator, a herbivore that ate a herbivore a predator, Chapter 2: Chapter 2: specimen. What purpose would the Canadia Canadia Canadia Note the small stalks on the right-hand end of this of end right-hand the on stalks small the Note from mud and water near the sea bottom? from applying paleontologists are principle geological Which creatures? modern with fossils compare they when Compare the features of the modern the features bristle worm Compare with the stalks or small tentacles serve on Given that the modern shown in bristle worm C2.3 is found on the ocean bottom, what Figure can you make about the lifestyle (free inferences swimming, fixed to the bottom, bottom crawling) of named the fossil organism can you make about What inferences Was source? material organic algae, or a scavenger that filtered Practice 6. 6. 3. 4. 5. diverse group found in areas ranging from shallow water to water group areas ranging from shallow found in diverse Some regions. and from the tropics to the polar deep water some are free-swimming; along the bottom; crawl organisms The made in soft sediment. in burrows and others live as gills, as feathery structures in modern work bristle worms as for locomotion. well centimetres long size from a few range in Bristle worms consisting of nine jaws With to almost three metres in length. separate parts, some modern species are predators that drill filterholes in clam shells. Other species are feeders. Figure C2.4: Figure often need to compare and paleontologists Geologists because some information is not organisms fossils to living preserved in the fossil record. is a member of the group C2.4, of C2.2 and Figure Figure These animals first as bristle worms. known marine worms 500 million years appeared in the fossil record more than been ever or teeth, have ago; and no hard parts, such as jaws found. Specimens of Wapta. on Mount C2.3, form Moderna species, such as the one in Figure

, a marine worm. Canadia This is an artist’s drawing of This is an artist’s A modernA bottom. ocean the on lives worm bristle belongs to a group of worms that are the marine belongs to a group that are the of worms considered fossils even though they originate from they originate from fossils even though considered and animals. of ancient plants the remains Explain why the last four steps in the process of in the process the last four steps Explain why of life an incomplete record produce fossilization have existed on Earth. forms that not gas are coal, oil, and natural Explain why Practice 2. 1. Figure C2.2: C2.2: Figure Figure C2.3: Figure structures the body and the small tentacles or stalks along on the head. Canadia of common earthworms. Note the feather-like equivalent Comparing Fossils and Modern Comparing Fossils and Modern Organisms that you studied in Chapter 1 illustrate the importance studied in Chapter of that you from trace fossils. information that can be derived but there is evidence of their presence in the form of of trace but there is evidence fossils are very important determining when Trace fossils. The stromatolites of ancient plants and animals. the ecology of the rock, and the impression is on the other piece. This is This impression is on the other piece. of the rock, and the finger a much like its fingerprint. and organisms, There are sometimes no remains of actual Just as you discovered in “Try This Activity: InterpretingActivity: This in “Try discovered Just as you parts a geologist often result when two Evidence,” Fossil splits a rock to findThe actual fossil is on one part a fossil. Trace Fossils Trace . preting Hallucigenia om its back. Each because it looked like because it looked like yzing and Inter yzing and Anal � om China. He proposed that the om China. He proposed Hallucigenia resembles a caterpillar. resembles Science Skills Science This drawing is a representation of This drawing is a representation had a cylindrical body with seven pairs of had a cylindrical body with seven pairs Onychophora An Figure C2.6: Figure Hallucigenia Figure C2.8: Figure . was thought to walk on its rigid spikes, with its tentacles rising fr was thought to walk on its rigid spikes, fossil. Onychophora Hallucigenia Hallucigenia served a protective function and were actually placed along the back of the animal. If Ramskold’s actually placed along the back of the animal. If Ramskold’s function and were served a protective resembles resembles The Changing Earth fossils. Ramskold was given permission and, as soon as he removed a few chips of shale, he discovered a a few chips of shale, he discovered fossils. Ramskold was given permission and, as soon as he removed Hallucigenia

This is a photo of a Hallucigenia Unit C: Carefully examine the fossil evidence from 1977. Based upon this evidence, describe a possible ecosystem, feeding 1977. Based examine the fossil evidence from Carefully because it This is called a hypothetical interpretation the life of this creature. habits, and some description of a day in is so limited. given that the fossil evidence response and speculative a creative requires Investigation Hypothetical Interpretations of Fossil Evidence of Fossil Interpretations Hypothetical Figure C2.7: Figure Figure C2.5: Figure second row of seven tentacles lay under the first row. of seven tentacles lay under the first row. second row spikes of To legs, then they should be paired. legs. If they were hypothesis was true, this meant that the seven tentacles were a few chips of shale that encased one of the few samples of rare test his idea, Ramskold asked permission to remove Hallucigenia Fossil Evidence from 1992 Fossil Evidence from fossils fr In the late 1980s, Swedish paleontologist Lars Ramskold was studying similar 1. organisms that appear to have lived near the bottom in shallow, tropical ocean water. tropical in shallow, that appear to have lived near the bottom organisms 1977 of Evidence from Hypothetical Interpretation that C2.5 revealed A close examination of the fossil in Figure of tentacles is not a single row of seven tentacles along the other side. Since a slender spikes on one side and a row normal leg arrangement, found in a bed of fossils of aquatic to end with a tiny opening. This fossil, only about 25 mm long, was tentacle appeared Fossil Evidence from 1977 Fossil Evidence from was named at Mount Wapta the shale from recovered fossils ever One of the weirdest see in a hallucination. something you might You will look at fossil evidence and then apply it to create a hypothetical a hypothetical it to create and then apply will look at fossil evidence You of a fossilized organism. the possible lifestyle about interpretation Purpose 332

Hallucigenia fossils is so A Tropical Alberta Tropical A a Cambrian-age rock unit found found unit rock Cambrian-age a Hallucigenia be? Why is it essential for rare be? Why is it essential for rare . Unlike its ancient, aquatic . Unlike its . Concisely explain why the Chapter 2: Chapter 2: Burgess Shale: Burgess Canadian in the on the side of Mount Wapta fossils Rockies known for its well-preserved Hallucigenia Hallucigenia Onychophora . Again, the speculative nature of this question nature . Again, the speculative fossil containing the hidden row of legs discovered of legs discovered hidden row fossil containing the Hallucigenia Hallucigenia

This interpretation shows the Burgess Shale ecosystem inhabiting a shallow area. —note Figure C2.7—is now thought to be an animal that walked on be an animal that now thought to C2.7—is —note Figure in Figure C2.9. Describe the location of each of these organisms C2.9. Describe the location of each of these organisms in Figure

Figure C2.9: . . Hallucigenia Hallucigenia , and a Hallucigenia , and and , Canadia can be found in tropical rain forests in the Southern forests Hemisphere. rain can be found in tropical , and it’s considered considered it’s and , Canadia now shows some resemblance to caterpillar-like animals called animals called to caterpillar-like some resemblance now shows Onychophora Burgess Shale Burgess create a hypothetical interpretation by suggesting a possible habitat for a hypothetical interpretation create to be a hypothetical interpretation. C2.9 is also considered Shale in Figure illustration of the Burgess artist’s Identify a trilobite, a in the illustration. In “Hypothetical Interpretations of Fossil Evidence” you were asked to use fossil evidence to speculate about and of Fossil Evidence” you were In “Hypothetical Interpretations Practice You will have noticed that the science skills icon appears throughout this textbook to describe the process of scientific scientific of process the describe to textbook this throughout appears icon skills science the that noticed have will You and Interpreting, and Analyzing Recording, and Performing Planning, and Initiating are icon the on listed Skills investigation. the with Ramskold by out carried experiment the of parts the how Describe Teamwork. and Communication icon. the on noted skills the with categorized be each could fossil Why must the hypothetical interpretations generated by interpreting fossil evidence always be considered to be tentative always be considered fossil evidence generated by interpreting interpretations Why must the hypothetical state with 100% confidence? rather than facts that people best attempts at explanations fossils had taken the a bed of rare If some hiker visiting of understanding of the structure would people’s by Lars Ramskold, where care? with great fossil evidence to be treated Carefully examine the fossil evidence from 1992. Based upon this evidence, describe a possible ecosystem, 1992. Based upon this evidence, evidence from examine the fossil Carefully some description of a day in the life of feeding habits, and interpretation. a hypothetical makes your response 8. 7. a shallow area close to the shore of a tropical tropical a of shore the to close area shallow a this what of representation artist’s An sea. C2.9. Figure in shown is like been have might than more that evidence now have organisms the Geologists ago, years million 500 inhabiting were Shale Burgess the in fossilized as the the as important most the be to scientists many by Earth. on fossils Cambrian of source Samples of all three fossils have been found in in found been have fossils three all of Samples about Wapta, Mount of side the on shale the known is location This Banff. of west km 80 The Burgess Shale three to introduced been have you 2 Chapter In trilobite, a fossils: always the case. As you’ll soon see, there are some places where the number and variety of fossils provide a wealth of data. a wealth of fossils provide the number and variety soon see, there are some places where As you’ll the case. always ecosystems. glimpses into ancient The interpretation from these places can provide fossil evidence of the As you saw in “Hypothetical Interpretations of Fossil Evidence,” the fossil evidence left by the left by the fossil evidence Evidence,” in “Hypothetical Interpretations of Fossil saw As you this is not However, lifestyle. very difficult suggesting the organism’s interpret to attempt to by this evidence scant that it’s 5. 5. 3. 4. Analysis Hypothetical Interpretation of Evidence from 1992 of Evidence from Hypothetical Interpretation 2. seven pairs of flexible legs protected by seven pairs of spikes on its back. Although it is still a strange-looking organism, organism, it is still a strange-looking on its back. Although by seven pairs of spikes of flexible legs protected seven pairs Hallucigenia ancestor, hypothesis. confirmed Ramskold’s This . d io r e P

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i F eef top ged r submer Mud avalanches Figure C2.11: Figure fossils. preserved effectively e Befor . Evidence suggests that a series of underwater mud avalanches carried the mud avalanches . Evidence suggests that a series of underwater r reef sea floo The Changing Earth eef top Unit C: Identify the source of the fine silt and clay particles that formed the Burgess Shale. of the fine silt and clay particles that formed the Burgess Identify the source Shale fossils. of the Burgess particles in the preservation Describe the significance of these microscopic ged r Hypothesize why the fossils of the Burgess Shale are not arranged in an orderly way, such as lying on their sides. way, in an orderly not arranged Shale are Hypothesize why the fossils of the Burgess Particles in the Burgess Shale fossils are found in a variety of positions: some upside down, some vertical. found in a variety of Shale fossils are Particles in the Burgess Layers of microscopic silt and clay particles are often deposited as sediment at the mouths of rivers. If these silt and clay particles are Layers of microscopic is shale. Shale is the most for millions of years, the result acted upon by geological processes sediments are common type of sedimentary rock. Practice a. b. 10. 9. submer 334 the smallest sections of gills—became preserved as thin carbon films interspersed with particles of of fineThe extent mud. fine is so preservation system. that one fossil of a predator had its last meal preserved in its digestive added on top of the were C2.11, meant that additional mud layers the mud to be noted in Figure further sealed the carcasses, allowing of later mud avalanches, have The effect would above The pressure from the layers buried organisms. structures—such delicate as even body tissues. Eventually, react with the organism’s to chemically undisturbed as it began were immediately encased in mud and swept down into deep water, which likely had low concentrations of oxygen. The result concentrations of oxygen. had low likely which deep water, into down encased in mud and swept immediately were eliminated. were of scavengers limited and the effects was that decay was of these organisms were fossilized in much the same way as other Cambrian fossils. fossilized in much the same way were of these organisms This good also preserved. Shale unique is that the soft body parts the Burgess of these animals were makes what However, caught in the mud avalanche particles that the organisms comprised of such tiny due to the factfortune that the mud was was They represent a complete ecosystem. These animals are all found in what used to be soft mud on These animals are all found in what a complete ecosystem. represent They side of a the seaward The hard body parts of mud. then buried layers within were they edge, where cliff the over organisms A Muddy Grave organisms. creatures and deep-water Shale form shallow-water in the Burgess The animals found a collection of both warm to the ocean on Alberta’s shoreline. The fine particles of silt and clay that collected along Alberta’s Cambrian coastline were were Cambrian coastline Alberta’s The fine collected along that shoreline. particles of silt and clay Alberta’s to the ocean on form into the sandstones and shales that processes part Mountains, which geological transformed of the Rocky by eventually currentare found along the Columbia. border with British no Era, scientists suspect that of the Paleozoic Period During the Cambrian The confined on land—life was living bodies of water. to plants or animals were carried these rivers by were silt, and clay Particles of sand, rivers. being eroded by formed was Precambrian rock previously repeatedly submerged and then lifted above the ocean’s surface. After the surface. the ocean’s and then lifted above submerged repeatedly surface for millions the ocean’s above Alberta was of Era, most Paleozoic of years. outdoors between November and March. However, this was indeed the case indeed this was March. However, and November outdoors between Era, the Precambrian the time following much of For of years. for millions and was close to the equator positioned Alberta was that suggests evidence Alberta’s Tropical Coastline Tropical Alberta’s are you when hard to imagine climate is tropical a Alberta having of The idea

335 A Tropical Alberta Tropical A Cambrian Period trace fossil b. b. d. Chapter 2: Chapter 2: Questions 2.1 reasonable to assume that shallow-water ecosystems to assume that shallow-water reasonable to them available more oxygen also have would part of the Cambrian Period. during the early concentrations lower ecosystems have Deep-water be this would Explain why oxygen. of dissolved did this fact aid in the excellent the case. How Shale fossils? the Burgess of preservation List the steps in the fossilization process. The process of fossilization occurred in a unique Shale. found in the Burgess for the organisms way unique features that Describe the steps involving at this site. fossil preservation led to the exceptional a process from Chapter 1 where work Recall your described to account for the origins of Earth’s was describe this atmosphere. Concisely oxygen-rich that supports it. process and the fossil evidence is it why to 5.a., explain answer Based upon your shale preservation Era Paleozoic Explain why trace fossils, such as burrows, are not trace fossils, such as burrows, Explain why Shale. found in the Burgess lasted have The Cambrian Explosion is thought to like Although this sounds about 20 million years. Scale this is a Time a long time, on the Geological short Determine time span. percentage of the relatively history that corresponds to this time interval. Earth’s What triggered the burst of animal origins called has to the Cambrian Explosion? One explanation finally reaching levels do with atmospheric oxygen concentrations adequate enough to support the mobile organisms. metabolisms of active Define the following key terms.Define key the following fossil Shale is a site of exceptional The Burgess to this degree lies preservation of The key preservation. the fossilization process occurred. in the way c. a. b. 3. 4. 5. a. b. Shale the Burgess of that organisms suspect Geologists helped that mud avalanche underwater in an caught were and the most extensive are considered to be to create what best-preserved Earth. Cambrian fossils on rapid In the the Cambrian Explosion, as the diversification of life known all modern groups of nearly for the origin sown seeds were of animals. Knowledge 1. a. c. e. Applying Concepts 2.

545 to 525 million years ago: Cambrian Explosion Summary fossils indicate that the interpretation of fossil 2.1 Because of these priorities, you can take guided tours of the can take Because of these priorities, you protect natural artifacts in all fossil sites. Strict laws various national parks. of Canada’s a rare, fragile, and scientifically important site. But this is the need for Canadians and visitors from other balanced by opportunities to learn about their heritage. countries to have are of great scientific importance, but the site is also in a to all Canadians. accessible is national park, which for the protection of such is responsible Canada Parks was happening during this significant event in Earth’s happening during this significant in Earth’s was event this reason, the United Nations has declared the For history. These fossils Heritage Site. World Shale to be a Burgess A World Heritage Site World A snapshot of what a wonderful Shale provides The Burgess the past half-billion on the basic designs that variations seems to involve years first the Cambrian Explosion. from emerged this question, it is that remarkable life on Earth for oxygen levels finally high enough to reached a concentration levels oxygen metabolism of these mobile animals. support the more active to answers possible While scientists continue to investigate Cambrian Period. Cambrian Period. diversification at this occur did so much biological Why suggested that the atmospheric have time? Some researchers origins, so some evolutionary biologists refer to this rapid biologists origins, so some evolutionary all modern groupsdiversification Nearly as an explosion. of the their origins to the beginning of animals can trace variety of animals with hard body parts of animals with shells. On the like variety time interval Scale, this 20-million-year Time Geological short time to see such a burst of animal is a relatively of organisms was limited to soft-bodied organisms, such organisms, limited to soft-bodied was of organisms the beginning that marks Cambrian Period The as worms. the first Era signals of the Paleozoic appearance of a wide plans for animals that have lived on Earth in can be found lived that have plans for animals ago. to 525 million years rocks dating from 545 Cambrian variety suggests that the time, the fossil record Prior to this The Cambrian Explosion Cambrian The or body basic designs for all the examples The earliest case of the Burgess Shale, the wealth of data from the fossil of Shale, the wealth case of the Burgess ecosystem from insights into an underwater beds provides ago. more than 500 million years Hallucigenia from follow that The explanations is challenging. evidence In the be treated as tentative. should always scant evidence In this lesson you reviewed the process of fossilization. reviewed In this lesson you with the Evidence” and the investigation “Interpreting Fossil Photo Credits and Acknowledgements All photographs, illustrations, and text contained in this book have been created by or for Alberta Education, unless noted herein or elsewhere in this Science 20 textbook. Alberta Education wishes to thank the following rights holders for granting permission to incorporate their works into this textbook. Every effort has been made to identify and acknowledge the appropriate rights holder for each third-party work. Please notify Alberta Education of any errors or omissions so that corrective action may be taken. Legend: t = top, m = middle, b = bottom, l = left, r = right

330 Photodisc/Getty Images 331 (bl) © Mark R. Boardman (remainder) © Reproduced with the permission of the Minister of Public Works and Government Services Canada, 2005 and Courtesy of Natural Resources Canada, Geological Survey of Canada 332 (br) © Tom Larsen (remainder) © Reproduced with the permission of the Minister of Public Works and Government Services Canada, 2005 and Courtesy of Natural Resources Canada, Geological Survey of Canada