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Gill Sans Bold Biology HSC Course Stage 6 Blueprint of life Part 1: Evolution 0 20 In r e to b T S c O EN g ti n D M a r N o E p r co A M 2 Gill Sans Bold Contents Introduction ............................................................................... 2 Environment and evolution........................................................ 5 Earth’s constantly changing environment ...........................................6 Modelling natural selection ..................................................................9 A case study .......................................................................................13 Evidence for evolution ............................................................. 14 Fossils ................................................................................................15 Transitional forms...............................................................................23 Biogeography .....................................................................................25 Comparative anatomy........................................................................29 Comparative embryology ...................................................................30 Biochemistry .......................................................................................32 Other evidence ...................................................................................33 The evolution of evolution ....................................................... 38 Additional resources................................................................ 41 Suggested answers................................................................. 51 Exercises – Part 1 ................................................................... 57 Part 1: Evolution 1 Introduction Popular culture often depicts the process of evolution as a development of organisms from lower simple forms to higher and more sophisticated states of organisation. These descriptions often place humans at the top of the evolutionary ladder. This is a notion as outdated as the Earth being the centre of the universe. The famous American evolutionary biologist, Stephen Jay Gould said: Darwin’s revolution will be completed when we smash the pedestal of arrogance and own the plain implications of evolution for life’s non-predictable nondirectionality. That is, evolution does not necessarily produce more complex and sophisticated organisms. Rather, it produces different ones. The evolution of species results from changes in the environment. Individual members of a species that can survive the pressures of change have some special features, called adaptations, which enable it to cope and to reproduce. 2 Blueprint of life Gill Sans Bold The first part of this unit deals with the nature of these environmental changes – be they physical, chemical or a result of competition for scarce resources. You will be asked to prepare a case study either on the evolution of the Australian megapods (kangaroos) or the plant Nothofagus, showing how changes in the Australian environment have led to changes in a species. Many sciences today describe and explain how present and past species are related to each other. Evidence that species evolve from a common ancestor has come from studies such as palaeontology (the study of fossils), comparative anatomy and embryology. The sciences of biogeography (the study of the distribution of organisms) and biochemistry (the study of molecules that make up living matter) also reinforce what is understood about evolution. This part of the module will describe, using specific examples, how evolution is supported by these studies. To complete an activity in this unit you will need red and green food colouring, a packet of toothpicks, two small plates, two forks and some paper towel. Please get them ready before you start this part. In this part you will have the opportunity to learn to: • • outline the impact on the evolution of plants and animals of: – changes in physical conditions in the environment – changes in chemical conditions in the environment – competition for resources describe, using specific examples, how the theory of evolution is supported by the following areas of study: – palaeontology, including fossils that have been considered transitional forms • Part 1: Evolution – biogeography – comparative embryology – comparative anatomy – biochemistry explain how Darwin/Wallace’s theory of evolution by natural selection and isolation accounts for divergent evolution and convergent evolution. 3 In this part you will have the opportunity to: • plan, choose equipment or resources and perform a first-hand investigation to model natural selection • analyse information from secondary sources to prepare a case study to show how an environmental change can lead to changes in a species • perform a first-hand investigation or gather information from secondary sources (including photographs/ diagrams/models) to observe, analyse and compare the structure of a range of vertebrate forelimbs • analyse information from secondary sources on the historical development of theories of evolution and use available evidence to assess social and political influences on these developments. Extract from Biology Stage 6 Syllabus © Board of Studies NSW, originally issued 1999. The most up-to-date version can be found on the Board's website at http://www.boardofstudies.nsw.edu.au/syllabus_hsc/syllabus2000_lista.html This version October 2002. 4 Blueprint of life Gill Sans Bold Environment and evolution The fact that species become extinct indicates that its members were not very successful at coping with changes in their environment. Whether they were sudden or gradual changes, the fact remains that the members of the species did not survive the pressures of change and were not able to thrive and reproduce. Adaptations to suit environments Your experiences with nature and living things on Earth have probably come from reading books, watching television and video, and going out in the bush or to the beach. You may have had the opportunity to go to different environments around Australia or even to other parts of the world. The Preliminary course must have also broadened your ideas about life on Earth. Whatever your experiences and observations have been, you would conclude that living things survive best in the environment that they are most suited for. What is less obvious is that all living things evolved to become suited to the environment that they live in. While adaptations are easily observed and described, the evolution of these adaptive features is not usually noticed in a human lifetime. In past times, people thought that species never changed and neither did the environment. Today we know that the environment is constantly changing and that species evolve to make the most of conditions in their background. Species with features most suited to their environment thrive and live to reproduce. Environments on Earth are diverse; therefore there is a diverse range of life on the planet. Some environments change periodically, for example, seasons. Some environments have regular changes over longer periods of time. Sometimes environments change gradually over millions of years; at other times, environments may undergo a sudden drastic change. Part 1: Evolution 5 Whichever way the environment changes, the organisms living there have pressure put on them to survive. The adaptive features of individuals give them survival value. Environmental pressure selects those individuals with the greatest survival value. Using the information you have just read, write a paragraph to state the link between the environment and evolution of organisms. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ Check your answer. Earth’s constantly changing environment Changes to the environment can be grouped into one of the following: 6 • changes in physical conditions These include any non-living natural conditions such as wind, temperature and availability of water. Some changes in physical conditions can occur suddenly or annually. • changes in chemical conditions The concentration of chemicals in the environment that an organism uses or is adapted to may change. For example, the salt concentration (salinity) in soil or in water might increase. • competition for resources Changes to the amount of resources available affects the struggle for survival among the species and within the species. Situations such as the introduction of a successful competitor change the dynamics in a community, often causing a strain on resources. Blueprint of life Gill Sans Bold Think about all the possible changes that can happen in an environment. For example, the climate may become warmer or a new species may be introduced into an area. 1 List as many features in the environment that you can think of that change over a period of time. _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ 2 Now group these changes into physical, chemical and ones caused by changes to competition. List these in the table below. Physical Part 1: Evolution Chemical Changes to competition 7 3 A number of scenarios to do with environmental change are listed below. Describe an adaptive feature of an animal and/or a plant that will help it to survive the change. a) An area dries out because of climatic changes. __________________________________________________ __________________________________________________ __________________________________________________ b) A new species of frog moves in, reproducing and spreading rapidly. It is poisonous to the predators of the new area. __________________________________________________ __________________________________________________ __________________________________________________ c) The salinity (amount of salt) of the soil of an area slowly increases. __________________________________________________ __________________________________________________ __________________________________________________ Check all your answers. Most biologists today agree that major evolutionary changes have been associated with dramatic changes to the Earth’s environment. These changes have mostly been brought about by the drifting continents, causing ocean currents to change as well as affecting volcanic activity and mountain building. More recently, scientists have shown direct links between mass extinctions (where most species on Earth become extinct over a short period of time) and collisions with extraterrestrial objects such as comets and meteoroids. Do Exercise 1.1 now. 8 Blueprint of life Gill Sans Bold Modelling natural selection In the module called Evolution of Australian biota, you learnt that changes in a population are due to selection pressures. Perhaps the best example of this is the classic study of the peppered moth. An example of natural selection This is a historically interesting example of natural selection. The original experiment has been criticised because there is some doubt as to whether the moths are found on tree trunks. The moths are usually found under leaves and branches. Further discredit has come because the original published photographs of the moths were achieved by gluing the moths to the trunk of a tree. However it still serves as an example of how natural selection may occur. There are two forms (light and dark) of the moth occurring naturally in the population. In industrial areas the trees were blackened by soot from the factory chimneys. When the dark moths rested on tree trunks during the day, they were less obvious to the birds that fed on them, while the light variation was easily seen and more often taken by these predators. In these areas, light coloured moths became less and less common. In the non-industrial areas the opposite was the case – the light coloured variation was harder to see against the light backgrounds of the trees so fewer were taken by predators. These were then able to reproduce and form the next generation. It was the dark coloured moths that disappeared. The light variation is easily seen on the dark background and the dark variation is easily seen on the light background. Biologists attempt to explain the evolution of camouflage by using the principles of natural selection. If individuals of a population are obvious to their natural predators, then their numbers would be fewer than those that blend into their environment. Part 1: Evolution 9 An open-ended investigation of natural selection In this experiment you are going to model natural selection by observing which colours are most easily selected against different backgrounds. Plan and perform your own activity if you can, or follow the instructions provided on the following pages. Aim To demonstrate the process of natural selection Equipment You will need: • small bottles of red and green food colouring from the supermarket • a packet of about 100–200 toothpicks • two small plates and two forks • paper towel. Method–preparation 1 Place 50 toothpicks in each plate. Colour one plate red and the other green by pouring enough food colouring over the toothpicks so that they are immersed in the colouring liquid. fork toothpicks OD FO RING OU L O C plate 10 2 Leave the toothpicks in the liquid for at least half an hour. Make sure the toothpicks are stained all over by stirring them around with the fork. 3 Using the fork, scrape the toothpicks out of the plate and onto some paper towels to dry. Blueprint of life Gill Sans Bold 4 Once they are dry you should have a bunch of 100 toothpicks – 50 red, 50 green. 5 Shuffle these around in your hand so that they are randomly mixed. 6 Now you are going to model natural selection by observing which colours are selected against different backgrounds. 7 You should choose either a member of your family or a friend to act as the predator. You will do if you are unable to get anyone else. The toothpicks act as the prey and the background colour will be the environment. Steps 1 Sprinkle the random bunch of toothpicks over an area of green surface, such as a lawn or a green blanket. 2 Get the predator to stand about 5 metres away. When you signal, the predator must run up to the area and randomly pick 10 toothpicks in less than 10 seconds. The predator then runs back, puts down what has been collected, and runs back to do it again. In total, the predator picks up five bunches of 10 toothpicks (50 toothpicks all together). 3 Sort the toothpicks using their colour, count them and record the information in the table below. 4 Do at least 5 trials. 5 Repeat the entire experiment on a neutral coloured background such as a concrete surface or wooden floor. Record these results in the table below. Results Record your results in the table on the following page. Part 1: Evolution 11 On green background Trial Red Green On neutral background Red Green 1 2 3 4 5 Average Write a statement comparing the results for the green background and the neutral background. _________________________________________________________ _________________________________________________________ _________________________________________________________ Conclusion You must account for the difference between the results obtained with the green background compared with the neutral background. Answer the following questions. 1 Predict the results you would obtain if the experiment were repeated on a reddish pink background. ______________________________________________________ ______________________________________________________ ______________________________________________________ 2 Assume that the predator is always present in this environment. If the toothpicks were able to breed, what could be the most frequent colour found in a few generations when: a) the background is reddish-pink __________________________________________________ __________________________________________________ 12 Blueprint of life Gill Sans Bold b) the background is green. _________________________________________________ _________________________________________________ 3 Write an explanation for selection by camouflage. _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ Do Exercise 1.2 now. A case study Your task in this case study is to show how changes in physical or chemical conditions or increased competition for resources have led to changes in an Australian species. Use resources such as the Internet and books, as well as the information given in the Additional resources section of this part. Here are two possible case studies that you may choose for this activity. Case study 1: The evolution of kangaroos Australia has undergone changes in its climate over time. The kangaroo is a good example of a species that has evolved over a long period of time in response to these climatic changes. Case study 2: The distribution of the Southern Antarctic beech This tree had a wide distribution in previous times. Now it is restricted to small pockets in rainforests. Prepare a short case study and present your report in Exercise 1.3. Part 1: Evolution 13 Evidence for evolution For any real links between changes in the environment and the evolution of life, scientists have to make observations that span many millions of years. This can only be done by indirect methods. Since Charles Darwin’s book, On the origin of species, was first published in 18 9, overwhelming support for evolution has came from all areas of science. The science of palaeontology (the study of fossils) has provided evidence for the evolution and history of life on Earth. Palaeontologists have been documenting details of past life forms (the fossil records) and working out when they existed and how they may have evolved. The science of anatomy shows similarities between closely related species by describing features of their body structure that they have in common. Comparisons between the embryos of related species is further support for the idea that species have common ancestors. Advances in technology, especially in biochemical and DNA analysis, have given biochemists the best tools yet to accurately describe the relationships between species. This further supports the theory of evolution. In summary, evidence for evolution comes from: • palaeontology • biogeography • comparative anatomy • comparative embryology • biochemistry. You will investigate some of this evidence in more detail on the following pages. 14 Blueprint of life Gill Sans Bold Fossils A palaeontologist is a scientist who studies fossils. Since the movie, Jurassic Park, palaeontology has become very glamorous but in reality only a few scientists get to study exciting dinosaur fossils. Reconstructed Tyrannosaurus Rex skeleton at the American Museum of Natural History, New York (Photo: R Caddy) Most palaeontologists are busy trying to fill in missing details of the life histories of less spectacular organisms. Fossilised worm burrows (Photo: T Reid) Part 1: Evolution 15 The fossil records have revealed a few interesting facts about the history and evolution of life on Earth. • All the species of living organisms on the Earth today represent only a minute number of the species that have ever lived here over the past three and a half billion years. • The species that exist on Earth today have similarities to some of the pre-existing life forms found in the fossil records. • New fossils are constantly being discovered and their clues are giving scientists a clearer picture of the relationships between past and present life. The work of a palaeontologist involves more than hunting for fossils, digging them out and preparing them for exhibition in museums. Palaeontologists are also concerned with trying to work out what changes took place in organisms over geological time, and what relationships the various fossils bear to one another. This requires careful study of large numbers of fossils (often mere fragments) and detailed comparisons between the fossil material available. Fossilised leaf of an extinct plant called Glossopteris (Photo: M Khun) Palaeontologists, like most other scientists, usually record both their data and their comparisons as measurements. Much of this work is done in the laboratory. To better understand the information available from fossils, you are going to study some of the fossil record of a group of organisms – horses. 16 Blueprint of life Gill Sans Bold The fossil record of horses Some groups of organisms are very well represented in the fossil record. One of these groups is the horse family, for which large numbers of fossils have been found in North America, Europe and Asia. Their skeletal remains, particularly those of the teeth and toes, have given important clues to the relationships between them. It has been possible to suggest the early history of the horse family from this evidence. Background Information Horses have their grinding teeth at the back of the mouth, separated from the front teeth by a toothless space. Their grinding teeth (cheek teeth) consist of three premolars and three molars on either side of the jaw. The skeletal characteristic to be used in this exercise is the distance spanned by the cheek teeth. span of cheek teeth premolars molars Horse skull showing how the span of cheek teeth is measured. Optional This activity is designed to give you an idea about the way that palaeontologists work out the changes that took place in organisms over millions of years. (It is adapted from material by H Messel in Science for High School Students.) Aim To infer likely relationships between various horses of the past, using some of the methods of the palaeontologist Part 1: Evolution 17 Procedure The span of the cheek teeth has been measured in many fossil specimens of horses. The data for seventeen of the twenty or so known genera are presented in the table on the following page. Genera of equidae Time of existence Span of cheek teeth (cm) 1 Early Eocene 4.3 2 Orohippus Middle Eocene 4.3 3 Epihippus Late Eocene 4.7 4 Mesohippus Early Oligocene 7.2 Middle Oligocene 7.3 Late Oligocene 8.4 Early Miocene 8.3 6 Parahippus Early Miocene 10.0 7 Anchitherium Early Miocene 11.3 8 Archaeoshippus Middle Miocene 6.5 9 Merychippus Middle Miocene 10 2 Late Miocene 12.5 10 Hypohippus Late Miocene 14.2 11 Megahippus Early Pliocene 21.5 12 Pliohippus Early Pliocene 15.5 Middle Pliocene 15.6 Early Pliocene 11.0 Late Pliocene 10.7 14 Calippus Early Pliocene 9.3 15 Neohipparion Middle Pliocene 13.1 16 Astrohippus Middle Pliocene 11.8 Late Pliocene 11.8 Late Pliocene 18.8 Pleistocene 17.6 Hyracotherium 5 Miohippus 13 Nannippus 17 Equus 18 Blueprint of life Gill Sans Bold Each measurement has been plotted as short bars on the graph grid below. Beside each bar plotted, write the number from the table of the genus it represents. The first one is done for you. 24 20 S pa n o f c h e e k t e e t h ( i n c m ) 16 12 8 1 4 0 Middle EOCENE 60 Late Early Middle Late 40 OLIGOCENE Early 30 Middle MIOCENE Late Early Middle Late 10 PLIOCENE Millions of years ago PLEISTOCENE Early 1 0 Check your answer before proceeding. How have the spans of cheek teeth changed between genera living at different times? Find out by following the instructions and answering the questions that follow. Start at the oldest genus (Hyracotherium) and work towards the younger fossils. Draw pencil lines between the bar representing each genus and the bar representing another younger genus. Connect the points representing the genera Hyracotherium, Orohippus, Epihippus, Mesohippus, and Miohippus. Part 1: Evolution 19 1 Why can’t you join two or three genera that occurred at the same time? ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ 2 Determine what appears to have happened to the span of the cheek teeth in horses up to late Oligocene times. ______________________________________________________ ______________________________________________________ 3 Continue the graph by showing the relationship between late Oligocene and early Miocene genera. The change in span of cheek teeth can be shown by a single line up to the late Oligocene. What happens from that time to the early Miocene? ______________________________________________________ ______________________________________________________ ______________________________________________________ 4 What does this suggest about the origin of Parahippus and Anchitherium? ______________________________________________________ ______________________________________________________ 5 Working with your pencil, complete the graph to the Pleistocene by indicating what you consider to be the relationships between the various genera. What problem are you confronted with? ______________________________________________________ ______________________________________________________ ______________________________________________________ 20 Blueprint of life Gill Sans Bold 6 When you have completed your graph, compare it with the graphs drawn in the suggested answers. What could you do to help decide which graph was best? _____________________________________________________ _____________________________________________________ _____________________________________________________ Since the fossil material is abundant, particularly in western North America, palaeontologists are able to consider a great many structural characteristics when working out relationships between these horse-like animals. The relationships based on any single characteristic like the span of cheek teeth may conflict with relationships worked out from other characteristics. The most widely accepted hypothesis of relationships, based on all available data to date, is shown in the figure following. Equus Pliohippus Calippus Nannippus Neohipparion Merychippus Astrohippus Megahippus Hypohippus Anchitherium Parahippus Miohippus Archaeohippus Mesohippus Epihippus Orohippus Hyracatherium Part 1: Evolution 21 Are all the relationships proposed by your graph the same as the relationships proposed in the figure you have just studied? Consider any similarities or differences then answer the questions below. Conclusion 7 What was the approximate average change in cheek teeth span per million years from Hyracotherium to Miohippus? ______________________________________________________ ______________________________________________________ 8 What was the approximate average change in cheek teeth span per million years from Miohippus to Equus? ______________________________________________________ ______________________________________________________ 9 From these results, what generalisation can be made about the rate of evolution of horses? (This may serve as an indication of the rates of evolution one might find in other organisms.) ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ 10 There are countless millions of fossils in sedimentary rocks throughout the world. Yet the history of life on Earth is still very incompletely known. List as many reasons as you can why this is so. ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ Check all your answers. 22 Blueprint of life Gill Sans Bold Transitional forms The example you have just examined of the evolution of the horse is well studied because there is an abundance of fossil material. Palaeontologists have been able to describe the relationships between these fossils because the links between one form and another have been found. The ancestral tree of 60 million years of horse evolution shows a gradual development from one genera to the next while giving rise to other groups. However most fossil records tracing the ancestors of groups of organisms are not as complete as the horse. With no fossils showing features intermediate between two forms that are believed to be linked, scientists have a hard time explaining natural selection. You may have seen newspaper headlines like: Scientists find fossil believed to be the missing link! These refer to the discovery of human fossils believed to show our knowledge of human evolution. Intermediate forms or links are called transitional forms. Transitional fossils A transitional fossil is the fossil of a transitional form. A transitional form, as traditionally used, meant an organism halfway between two classes or kinds of organisms. Archaeopteryx is often used as an example of an intermediate form between a reptile and bird. Archaeopteryx was once believed to be an intermediate form between reptile and bird. Part 1: Evolution 23 However, this view of evolution is outdated. Archaeopteryx is not a transitional form between reptile and bird. It is both reptile and bird or a class of its own. (Remember that a classification system is something invented by humans and imposed on nature.) One of the problems Darwin had explaining natural selection was the big difference in features between the classes. Transitional fossils were supposed to bridge the gap or be the missing link in the fossil record. Modern biologists explain these differences by saying there is a gap in the fossil record. As more fossils are found, these gaps will be filled and the gradual progression of change will be shown. Why do palaeontologists continue to look for transitional forms in the fossil record? _________________________________________________________ _________________________________________________________ _________________________________________________________ Check your answer. Equilibrium In 1972, after studying many fossil observations, Eldredge and Gould claimed that most species appear suddenly and their history shows little evidence of change. Individual populations might change both genetically and structurally due to adaptation but overall a species exhibits a net equilibrium. That is, it tends to stay much the same. To explain why transitional fossils are not found, Niles Eldredge and Stephen Jay Gould (1972) came up with the punctuated equilibrium model of evolution. Punctuated equilibrium This view suggests that species originate suddenly whenever rapid changes in the environment occur. This abrupt appearance of new species is a random event and is usually associated with a large number of extinctions called mass extinction. You will learn more about this concept when you do part 4 of this module. 24 Blueprint of life Gill Sans Bold Biogeography Biogeography (sometimes called zoogeography) is the study of the distribution of organisms. It is a science that describes where plant and animal families are found on the Earth today and tries to explain how they came to be where they are. Biogeography explains these distributions by bringing together concepts from biology, geology, palaeontology and chemistry. The science of biogeography had its beginnings in the early part of the last century and depends heavily on the work of Charles Darwin and Alfred Russel Wallace, among others. Notice that these same individuals were prominent in developing the theory of evolution by natural selection. Biogeography as evidence for evolution Each region has similar species occupying similar niches within its borders. However, the species are clearly different from those in adjacent areas. The boundaries between biogeographic zones are drawn according to the distribution of vertebrate groups (in particular, families). The regions are based on the relationships of birds; but the same regional limits work well enough for fish, amphibians, reptiles and mammals. There are six biogeographical zones (or provinces), each with distinct flora and fauna. They are: • Palaearctic – North Africa, North Europe and Northern Asia • Ethiopian – Africa below the Sahara desert • Australian – Australia • Nearctic – North America • Neotropical – South America • Oriental – Southeast Asia and India. These zones are shown on the map of the world following. Part 1: Evolution 25 N 3 3 2 3 Palaearctic Nearctic Oriental Neotropical Ethiopian Australian Biogeographic zones of the world. Look at the map of biogeographic zones above. With what physical features of the Earth do the borders coincide? _________________________________________________________ _________________________________________________________ Check your answer. Populations that become geographically isolated by means of a barrier will tend to change. These barriers include seaways, rivers, mountain ranges, deserts and other hostile environments. They put a wedge between whole groups of organisms, eventually causing related organisms – species, genera, families and so on – to diverge. Wallace’s line Alfred Russel Wallace, the so-called father of animal geography, formulated his ideas on evolution by natural selection while observing and collecting wildlife in the islands of Southeast Asia. He was particularly impressed by the sudden difference in bird families he encountered when he sailed some twenty miles east of the island of Bali and landed on Lombok. On Bali the birds were clearly related to those of the larger islands of Java and Sumatra and mainland Malaysia. On Lombok the birds were clearly related to those of New Guinea and Australia. He marked the channel between Bali and Lombok as the divide between the Oriental and Australian biogeographic zones. 26 Blueprint of life Gill Sans Bold In his honour this dividing line, which extends northward between Borneo and Sulawesi, is still referred to today as Wallace’s Line. Philippines Thailand South China Sea M a l a y s i a Brunei Pacific Ocean Sabah Celebes Sea Borneo Singapore Halmahera Papua New Guinea Kalimantan Sumatra Sulawesi Irian Jaya Java Sea Banda Sea Java Flores Timor Bali Lombok Arafura Sea Timor Sea Indian Ocean 0 100 200 300 400 500 Gulf of Carpentaria Kms Wallace’s Line Australia Map of South-East Asia showing Wallace’s line. To the west, the Asian animal community includes such mammals as the rhinoceros, orangutan, tapir, tiger and elephant. To the east are found animals related to Australian fauna. They include birds such as cockatoos, bowerbirds and birds of paradise as well as marsupials such as bandicoots and cuscus. The core areas of the Oriental and Australian provinces are clearly distinct but overlaps exist on the edges of the boarders. Thus some biogeographers recognise the region of islands between Java and New Guinea as a mixing zone of Oriental and Australian fauna. Rather than try to fix where the line between these two realms should lie, most modern biologists recognise that the whole Indonesian archipelago region represents a zone of changeover. Within this zone, the two faunas progressively replace one another. This changeover zone exists because, as the Asian and Australian landmasses drifted closer together, organisms were able to move out of the places where they originated into new territories. When the world is divided into zones using the distribution of flowering plant groups, the resulting zones do not coincide with biogeographic zones based on vertebrates. What factors could account for the differences in the distribution patterns of vertebrates and flowering plants? _________________________________________________________ _________________________________________________________ Check your answer. Part 1: Evolution 27 Biogeographic distributions There are three important principles used to determine a biogeographic zone. • Environment cannot account for either similarity or dissimilarity, since similar environments can harbour entirely different species groups. • Affinity or similarity of groups on the same continent (or sea) is closer than between continents (or seas). • Geographical barriers, such as seas, oceans and mountain chains, usually divide these different groups. The degree of difference between families relates to the rate of migration or ability to disperse across the barriers. Look back at the world map that shows the biogeographic zones of the world. Think about the different kinds of plants and animals in each zone. Think about the different environmental conditions in each zone. Try to think of some examples to illustrate each of the principles above. For example, environmental conditions in parts of the Ethiopian zone are similar to conditions in the Australian zone. Some organisms in these zones, such as arid area plants, are very similar. However, some organisms, such as gazelle and kangaroos, are very different. Within the Australian zone, species of kangaroo and wallaby are much more similar to each other than they are to organisms in other zones. And notice the positions of the lines separating zones – oceans separate the Australian zone from other zones, whereas the Oriental and Palaearctic zones are separated from each other by the Himalayas. Six degrees of separation Remember that the degree of separation is the amount of difference between similar groups of organisms. Three criteria of mammalian families and their distribution patterns are used to delineate the six regions known as biogeographic zones, or provinces. These are: • the total number of families • the number of families originating from (endemic to) this province. This is a measure of uniqueness of the mammalian fauna • the number and location of other regions with which mammalian families are shared. Rank the biogeographic zones by dividing the number of endemic families by the number of shared families. (Hint: Australia would be first because it only has eight endemic families and only one shared family. The calculations have been done in the first row as an example.) 28 Blueprint of life Gill Sans Bold Biogeographic zone Total number of families Ethiopian Number of endemic families 38 Number of shared families 12 2 Endemic families shared families 12 2 Neotropical 32 16 3 Oriental 30 4 3 Palaearctic 28 2 3 Nearctic 24 4 3 9 8 1 Australian =6 Check your answers. The comparison of endemic to shared families is used as a measure of how much biological separation exists between mammals of the biogeographic zones. Now complete Exercise 1.4. Comparative anatomy Different groups of organisms often have similar structural features. This observation is also used as evidence that species can evolve from a common ancestor. Comparing the mouthparts of insects The mouthparts of insects are an example of a similar structure modified for its function. In various insects, the same basic plan has been functionally modified for biting, piercing, chewing or sucking. Part 1: Evolution 29 Vestigial structures Those structures that functioned in ancestral organisms but are reduced (in structure and function) in the descendant are called vestigial structures. Some examples in humans include vertebrae of coccyx (tailbone) and the appendix on the intestines. In some other mammals, the appendix is a larger organ with a function in digestion. Comparing vertebrate forelimbs The skeletons of vertebrates provide a clear example of structural similarities. The five fingered limbs (called pentadactyl limbs) of vertebrates are considered to be similar structures. The hand of a human, the forefoot of a horse, the flipper of a dolphin and the wing of a bat all have the five-fingered plan. The same basic plan is modified to serve a different function for each type of vertebrate. In your next exercise you will need to observe, analyse and compare the structure of a range of vertebrate forelimbs. You can do this by looking at some in a museum, looking them up on the Internet and/or using information in the diagram in Exercise 1.5. You will find some helpful starting points on the Science online webpage at: http://www.lmpc.edu.au/science Now complete the tasks in Exercise 1.5. Comparative embryology Embryology is the study of embryos and their development. Embryologists have discovered that all vertebrate embryos look alike during their early development. It is almost impossible to distinguish between the early embryos of fish, chickens and humans. They become recognisable later in their development. The common features of embryo development found throughout the vertebrate group include: • 30 gill slits appear even in embryos of fully terrestrial organisms with no sign of gills as adults. • tail • notochord develops into vertebrae in all vertebrates. gill slits notochord tail A vertebrate embryo. (Adapted from Messel, Science for High School Students) Blueprint of life Gill Sans Bold Study the following diagram showing the stages of development of four vertebrate groups and determine which row shows the most similarity. man pig salamander fowl Stages of development of four vertebrate groups. (Adapted from Messel, Science for High School Students) Check your answer. Part 1: Evolution 31 Biochemistry The building blocks of life are fundamentally the same for all living things and they use the same basic biological molecules for similar functions. For example, the amino acid building block molecules are the same in all known species. Biochemists can analyse the sequence of amino acids of a protein common to many species, match the similarities and then compare them with other species. The table below shows the number of amino acids for a common protein called cytochrome c that are different in humans and another species. Species compared Number of different amino acids human/chimpanzee 0 human/horse 7 human/snake 11 human/fly 13 human/cauliflower 19 human/yeast 26 1 Based on the similarities between amino acid sequences for cytochrome c: a) which species is the most similar to humans? _____________ b) which is the least similar to humans? ____________________ 2 What can you infer from this information? ______________________________________________________ ______________________________________________________ ______________________________________________________ Check your answers. There are many more techniques used by biochemists and molecular biologists for showing similarities between species. A good example is DNA sequencing. These techniques are better explained further on in the module after you have learnt about DNA and biotechnology in Part 4. 32 Blueprint of life Gill Sans Bold Other evidence There are two other ways to organise evidence that are used to support the theory of evolution. These use observations from the areas you have already considered (comparative anatomy and so on). These other ways are: • divergent evolution • convergent evolution. Divergent evolution When a new area, such as an island, appears or something causes an area to become vacant, colonising organisms move in. Those with features best suited to the new environment will function more efficiently, thrive and produce offspring because there will be little competition for resources. Adaptations make it possible for these colonising organisms to cope with the new (changed) environmental conditions. Because organisms in a population are slightly different from each other, groups within the population will be able to thrive and reproduce best in different parts of the new environment, so the groups will gradually become different from each other. Or, different species could become more alike to better use the same environment. This is divergent radiation. Divergent radiation commonly occurs immediately following an evolutionary breakthrough. This means a population with an innovative, better adapted feature colonises a vacant ecosystem, speciates (forms species) and radiates to occupy the available space. (Speciation can also occur in the same environment.) An example of divergent radiation – dinosaurs and mammals At the beginning of the Triassic period, some 250 million years ago, the terrestrial surface of Earth had many environments unoccupied by vertebrates. The only vertebrates living on land were amphibians and these were restricted to wet areas close to rivers, lakes and the coast. 1 Why didn’t the amphibians venture inland? _____________________________________________________ _____________________________________________________ _____________________________________________________ 2 Which group of animals would have lived inland? _____________________________________________________ Part 1: Evolution 33 By the middle and toward the end of the Triassic period, a variety of egg-laying vertebrates evolved and diversified to occupy every environment on Earth, including the seas. They were, of course, the dinosaurs. They are well documented in books, museums, videos and movies. Their dominance on the planet was to span the Jurassic period and last some 200 million years. 3 What feature did dinosaurs possess that enabled them to venture away from water? ______________________________________________________ ______________________________________________________ Mammals evolved during the Triassic period but had to be content with occupying the nooks and crannies of a planet dominated by dinosaurs. Fossils of mammals from around these times show them to be small rat-like creatures with little variation among them. They remained this way for 100 million years. A mass extinction event, believed to be due to a collision with an asteroid, caused the dinosaurs to rapidly disappear from their dominant position. Only one variety is thought to have survived to become the ancestor of birds. Around 60 million years ago, with the dinosaurs out of the way, the mammals began to occupy environments and niches left vacant by their previous occupants. The fossil record shows a sudden increase in diversity of mammal forms. Eventually millions of mammals ended up dominating almost every environment on Earth. Some varieties occupying the seas and oceans gradually changed to become the whales and dolphins of today. 4 What factors lead to the sudden increase in mammal’s diversity? ______________________________________________________ ______________________________________________________ ______________________________________________________ 5 Explain what divergent radiation means in your own words. ______________________________________________________ ______________________________________________________ ______________________________________________________ Check your answers. 34 Blueprint of life Gill Sans Bold Darwin’s finches The finches of the Galapagos Islands are examples of many species evolving from one, to take advantage of the available environments. Diversity in a species may eventually result in speciation, which is the creation of new species, when an area or environment has not reached its potential or been fully colonised. The kind of adaptive radiation that leads to the evolution of many divergent forms from one species is called divergent evolution. It is believed that one species of finch may have arrived on a Galapagos island and then divergent evolution lead to the many different species of finch found on the Galapagos Islands today. Different beak structures in finches found on different islands in the Galapogas.This illustrates how the species has diverged from the original form . Charles Darwin explained divergent radiation by using the finches of the Galapagos Islands as an example. Look up this work in a biology book at your local library or on the Internet (use the words Galapagos, finches and Darwin in a search engine). Then complete Exercise 1.6. Convergent evolution Today there is a staggering array of life forms on the Earth and each reflects diverse ways of life. There are probably as many ways of life as there are species. Many organisms that have evolved independently now live in very similar ways. Organisms that live in similar environments have the same selective pressures applied to them. In the example below there are three different vertebrates groups, all showing a similar body structure. This is called convergent evolution. Part 1: Evolution 35 mammal reptile fish The diagrams above show major vertebrate groups that occupied the seas. 1 What physical features do all these animals have in common? _____________________________________________________ _____________________________________________________ _____________________________________________________ 2 Although each sea creature represents a completely different vertebrate group, they all look very similar. How would the theory of natural selection (by Darwin and Wallace) explain what caused each of these vertebrate groups to have the same body shape? ______________________________________________________ ______________________________________________________ ______________________________________________________ Check your answers. 36 Blueprint of life Gill Sans Bold Another example of convergent evolution can be seen in the shape of wings for flying. The diagram below illustrates this example. bat bird pterosaur Adaptation to flight is an example of convergent evolution. Part 1: Evolution 37 The evolution of evolution A requirement for this part of the course is that you assess the social and political influences on the historical development of theories of evolution. What does this mean? You can find out by reading the information below and answering the questions. Then you will have a clearer understanding of how and why theories of evolution develop. Introducing the idea of evolution It is one thing to discover and explain the workings of nature but the rest of society has to understand and accept it. Developing an understanding of how species evolve has been one of the greatest human intellectual endeavours throughout history. This long journey of discovery took humans from considering themselves as the most magnificent of God’s creations to just another species of animal and a very recent arrival at that. The problem with the scientific explanation for evolution is that it challenged the foundations upon which western culture is based. Western societies were governed by religious institutions that controlled not only politics but also the way people viewed nature. The idea that God made ‘man’ in his image to rule over all other living things was indisputable. Therefore any challenge to this idea was seen as a threat to the establishment. What restrictions were there in society to alternative explanations for the nature of life on Earth? _________________________________________________________ _________________________________________________________ Check your answer. 38 Blueprint of life Gill Sans Bold A variation in viewpoint The two statements below contrast the way ‘variations among individuals in a population’ was viewed during ancient Greek times in comparison with modern biology today. Ancient Greek – Plato’s view from ‘The Republic’ Each species is a fixed entity that never changes. All individual variations in a population are unimportant imperfections of the ideal form. The perfect ‘essence of form’ is made up of the best parts of the various individuals. Nineteenth century – Darwin’s view from ‘On the origin of species’ Species have always been changing and always will. Variations among individuals of a population are necessary for natural selection – the chief agent of change. It is these very differences between individuals that make evolution possible and inevitable. The current view Since Darwin/Wallace’s explanations for evolution were first proposed, the science of modern biology was born. Today, biologists use the principles of evolution by natural selection in their everyday work. In the Additional resources section, there is a summary of the major scientific thinkers who have contributed to the modern theory of evolution. Read these now. Then complete Exercise 1.7. Part 1: Evolution 39 40 Blueprint of life Gill Sans Bold Additional resources Case study 1: The evolution of kangaroos Based upon research in Kangaroos: 15 Million years of Australian bounders by Tim Flannery “The kangaroos offer a unique opportunity to study evolutionary changes within a group of Australian mammals”. This is because they have “the best known fossil record and are the most extensively studied of all Australian mammals”. Also because they have undergone rapid evolutionary change and are “commonly good indicators of restricted environments”. Tim Flannery The earliest record of kangaroos is found among the fossils of the Etadunna formation in central Australia. These deposits were formed during the late Oligocene to early Miocene epoch, some 25–15 million years ago. This region, now a hot dry desert, was cool to temperate and the rainfall was consistently moderate, with many freshwater lakes and rivers. It was heavily forested and supported a wide variety of faunas including many types of marsupials, crocodiles, flamingoes and even freshwater dolphins. These early kangaroos were tiny (about the size of a rabbit) and are believed to have descended from arboreal (tree dwelling) ancestors. The Musky-rat kangaroo, which lives in the rainforests of north Queensland, still retains this way of life. By the middle of the Miocene some 10-12 million years ago, Australia began to warm up. As time progressed and Australia moved further north, aridity (dryness) increased and rainfall became seasonal. Forests began to change and were dominated by eucalypts with some pockets of open forests and grasslands thriving in the drier conditions. Kangaroos Part 1: Evolution 41 became abundant, evolving to take advantage of the variety of new environments emerging from these changes. They dominated these emerging grassland areas, increasing in size and rapidly diversifying. The kangaroo fossils of this age show some evidence of hopping. The fifth toe, which is an adaptation to an arboreal way of life, has been lost. This can be seen in the diagram of the fossils showing the paw and toes of a middle Miocene kangaroo. 3 cm 0 A B Kangaroo fossils of the middle Miocene showing the paw on the left and toes adapted for hopping on the right (A, B). These and other fossils from this period show adaptations to a grazing mode of life. Among some of these habitats, the modern types of kangaroo developed. During the Pliocene period, 5–2 million years ago, the continent continued to dry out at a faster rate. Rainforests became restricted to the coastal regions of Victoria, NSW and Queensland. In central Australia and some coastal areas, woodlands and grasslands had replaced the rainforests. The following drawing of a fossil shows the side and top view of kangaroo molars. Scientists say that they are an adaptation to grazing. 42 Blueprint of life Gill Sans Bold A molar 0 molarmolar 3 cm B Top and side view of Pliocene fossil, showing molars adapted to grazing. By the end of the Pliocene and early Pleistocene times, conditions were even drier than today. Kangaroos evolved bounding strides to take advantage of the vast grassland plains that had taken over in the arid areas. This adaptation was to become more important as grasslands emerged. The Pleistocene, 1.6 million years ago to the present, saw the evolution of vegetation that gave rise to the flora that dominates the continent today. Ice ages were a feature of this period of time. Effects on the Australian environment were not as dramatic as in the Northern Hemisphere but they did influence sea levels, which may have fluctuated some 200 metres. This is significant when considering land bridges, especially to the north. This was the time when the well known marsupial megafauna had evolved. Kangaroos were at their most diverse. They varied from the giant kangaroos to small types, being adapted to a variety of environments. As the drying continued, adaptations to overcome long periods of drought evolved. Giant kangaroos, wallabies and wombats and the huge Diprotodon would have been quite a familiar sight among the first humans when they arrived some 40 000 to 60 000 years ago. Their presence is believed to have influenced the demise of the megafauna. The Aboriginal practice of burning further changed the vegetation and favoured grazing species. European settlers have been responsible for further extinctions, both because of hunting and through habitat destruction. Part 1: Evolution 43 Case study 2: Southern Antarctic Beech Forests dominated by southern Antarctic Beech, Nothofagus fusca, persisted in coastal regions of the Antarctic continent until the late Oligocene. They co-existed with the emerging glaciers (similar to the way they exist today in southern Chile) until Antarctica froze over completely. 90 0 0 India Africa South America New Guinea 0 S Antarctica Australia New Zealand Distribution of Nothofagus during the Oligocene. The diagram following shows the distribution pattern of the Southern Antarctic Beech (Nothofagus) as it is today. It is found in rainforests in Tasmania and in the south-eastern Australian mainland. There are also populations in New Zealand, New Caladonia and New Guinea and also on the southern tip of western South America. New Guinea Australia New Caledonia New Zealand Antarctica South America tor Present day distribution of Nothofagus. 44 Blueprint of life Gill Sans Bold Fossil records and the modern distribution pattern of the Southern Beech (Nothofagus) show that it originated on the outer edge of Gondwana during the late Cretaceous period, around 70 million years ago. Theories about evolution For thousands of years, people accepted that living things never change. There was no need to explain evolution until the evidence that creatures have changed became overwhelming. Leonardo Da Vinci (1452–1519) Leonardo made geological and palaeontologic observations of rocks and fossils found in north Italy. The fossils were mostly of Cenozoic molluscs found on the tops of mountains. Leonardo hypothesised these shell fossils had once been living things and that they had been buried at a time before the mountains were raised. It must be presumed that in those places there were sea coasts, where all the shell were thrown up, broken and divided. Leonardo’s contribution to our understanding of life was to suggest that fossils indicated the history of the Earth far beyond human records. Robert Hooke (1635–1703) Robert Hooke observed fossils with a microscope and concluded that shell-like fossils really were ‘the shells of certain shell-fishes.’ He also observed that many fossils represented extinct organisms. Palaeontology had become the science that can be used to help understand the history of life on Earth. George-Louis Buffon (1707–1778) George-Louis Buffon published Les Epoques de Ja Nature (1788), where he suggested that life was much older than 6 000 years as suggested by the Bible. In his 44 volume publication, Histome Naturelle, Buffon questioned the Church’s doctrines by proposing that organisms changed. He did not suggest how but noted that the environment acted directly on organisms. Buffon goes down in history as having paved the way for others. Part 1: Evolution 45 Carolus Linnaeus (1707–1778) A Swedish botanist who was the founder of the binomial (two name) system contributed to evolution by suggesting that species in a genus have arisen through hybridisation. This is where two different individuals produce a new kind of offspring. He originally fought the idea that species had changed and believed they were all created in the beginning and none had become extinct. Later in life, he showed that his ideas were changing. Erasmus Darwin (1731–1802) A leading eighteenth century intellectual and naturalist, Erasmus Darwin formulated the first modern theory of evolution in his book, The laws of organic life. Describing how one species could evolve into another, he suggested that sexual selection and competition could cause changes in species. He wrote: the final course of this contest among males seems to be that the strongest and most active animal should propagate the species which should thus be improved. He also helped to introduce the concept of adaptation by saying that organisms are fit for the environment in which they live and that their structure reflects the functions they perform throughout their lives. Jean-Baptiste de Lamarck (1744–1829) Lamarck is always associated with the discredited theory of evolution where features ‘acquired’ throughout an individual lifetime are inherited by offspring. Lamarck proposed that an organism develops features by use or disuse throughout its lifetime. For example, a giraffe develops a long neck by stretching to eat the leaves of tall trees. This acquired feature is then passed on to its offspring. Although wrong, Lamarck’s ideas did pave the way for natural selection and made a major contribution to the development of evolutionary thought. Sadly his theories were ignored and Lamarck died a poor man. His colleagues even used the eulogy at his funeral to discredit him. 46 Blueprint of life Gill Sans Bold Alfred Russel Wallace (1823–1913) Just north of Australia, through the middle of Indonesia and between the islands of Borneo and Sulawesi, is an imaginary line. This line separates the islands of Bali and Lombok and is called the Wallace line. Biologists use this line to describe the separation of Australia flora and fauna from Asian flora and fauna. It was named after Wallace because of the observations he did in this region. It was in Indonesia that Alfred Wallace concluded that species evolved by a process called natural selection. He wrote to Charles Darwin. Charles Darwin had independently arrived at the same conclusion after his extensive observations and work at the Galapagos Islands. The theory of natural selection was actually proposed by Wallace but has historically become known as the Darwin/Wallace theory of natural selection to incorporate the work done by Charles Darwin. Part 1: Evolution 47 Charles Darwin (1809–1882) Charles Darwin was a founder of modern biology and author of the famous book, On the origin of species. He suggested that plants and animals in nature produce far more offspring than can survive. Each individual has its own variety of features. There is a continual struggle for existence. Those individuals with variations that increase their chance of survival (the fittest) reproduce more. Hence, this interaction between a variety of individuals and the harsh environment is the direct cause of change in species and explains evolution. Charles Darwin was aware of the social and political upheaval his ideas may cause. He did not publish his famous book about evolution for almost 25 years, until Wallace suggested the theory, and Darwin felt more confident about presenting his observations and thoughts. Viewpoints about evolution From the time that the theory of evolution was first presented, it has met with opposition and misunderstanding. People have tended to react to it emotionally and philosophically, rather than assessing it as a scientific explanation that seeks to best explain available evidence. The theory of evolution does not attempt to undermine religious beliefs or ideas about the worth of people. Instead, these are non-scientific arguments that are separate from the debate about whether the theory of 48 Blueprint of life Gill Sans Bold evolution is supported by sufficient scientific evidence and whether it is, indeed, the best explanation of that evidence. The theory of evolution has continued to develop and be refined throughout the twentieth century, as more and more evidence has been collected. The theory will continued to be used and examined into the twenty first century because it remains, to date, the best scientific explanation of many observations of changes in living things, both past and present. Here are some examples of social and political thinking about evolution for you to evaluate. Example 1: Cartoons Cartoons are a common way that social comment is made in newspapers and magazines. There have been many cartoons drawn about evolution. Some show organisms slowly changing form over time. For example, look back at the cartoon in the introduction to this part. Other cartoons were drawn to ridicule evolutionists. (And some have been drawn to ridicule people who oppose evolution too.) A famous cartoon from the 1800s shows Charles Darwin looking like an ape. From "Darwin as an Ape." Cartoon. 1871. Part 1: Evolution 49 Example 2: A view of a nineteenth century scientist What is man? A profound thinker, Cardinal de Bonald, has said, ‘Man is an intelligence assisted by organs.’ We would fain adopt this definition, which brings into relief the true attribute of man, intelligence, were it not defective in drawing no sufficient distinction between man and the brute. It is a fact that animals are intelligent, and that their intelligence is assisted by organs; but their intelligence is infinitely inferior to that of man. …whence comes man? Wherefore does he exist? …the problem is beyond the reach of human thought. …but it will be sufficient for our present purpose to say that it can be shown that man is not derived, by a process of organic transformation, from any animal, and that he includes the ape not more than the whale among his ancestry; but that he is the product of a special creation. …Let us say that the creation of the human species was an act of God, that man is one of the children of the great Arbiter of the universe, and we shall have given to this question the only response which can content at once our feelings and our reason. Louis Figuier in his nineteenth century book, The human race. Example 3: A modern view You may be able to borrow a book by Stephen J Gould that includes information about some of these social and political influences. You could also look at some of the many Internet sites on this subject. You’ll find plenty of information in favour of and opposed to the theory of evolution. You will find some helpful starting points on the Science online webpage at: http://www.lmpc.edu.au/science 50 Blueprint of life Gill Sans Bold Suggested answers Adaptations to suit environments Changes in the environment put pressure on the species living there. Species with features that enable them to survive will thrive and reproduce while those without the adaptations for survival become extinct. Earth’s constantly changing environment 1 2 Part 1: Evolution Features of the environment that may change include: • available water – wetter or drier • temperature – hotter or colder • pH – more acidic or more alkaline • available space - less space or more space • concentration of dissolved minerals • introduction of a new more competitive species • competition from members of the same species. Some other features are also included in the following table. Physical Chemical Changes to competition • changes in temperature • • predatory competition introduction of prey/predator • changes in pressure availability of gases such as oxygen or carbon dioxide • lack of space changes in light • changes to pH • • competition from members of the same species • changes to salinity • disease 51 3 a) Adaptations for an area drying out include: a skin coating or cover to prevent desiccation, more concentrated urine and less surface area of leaves in plants. b) Adaptations for a new species of poisonous frog include: resistance to the poison and seeking alternative food sources. c) Adaptations for increased salinity include: the ability to absorb water by active transport and the ability to excrete salt as a waste. The fossil record of horses 24 11 20 17 17 12 S pa n o f c h e e k t e e t h ( i n c m ) 16 12 10 15 9 12 7 13 6 5 8 4 1 2 16 16 13 9 14 5 4 8 3 4 0 60 Middle EOCENE Late Early Middle Late 40 OLIGOCENE Early 30 Middle MIOCENE Late Early Middle Late 10 PLIOCENE 1 0 Millions of years ago 52 PLEISTOCENE Early 1 They have descended from a common ancestor and did not give rise to one another at the same time. 2 The span is becoming longer in length. 3 There is diversity in the teeth span: some less, some more. 4 They may have originated from the same ancestor as Miohippus. 5 There are many valid interpretations. Blueprint of life Gill Sans Bold 6 Here are two possible alternative answers. 24 11 20 17 S pa n o f c h e e k t e e t h ( i n c m ) 17 12 16 12 10 15 9 12 8 4 1 2 13 9 6 5 16 16 7 13 14 5 4 8 3 4 0 Middle Late EOCENE 60 Early Middle Late 40 OLIGOCENE Early Middle Late MIOCENE 30 Early Middle Late PLIOCENE 10 Millions of years ago PLEISTOCENE Early 1 0 24 11 20 17 S pa n o f c h e e k t e e t h ( i n c m ) 17 12 16 12 10 15 9 12 16 7 6 5 8 4 1 2 13 9 16 13 14 5 4 8 3 4 0 60 Middle EOCENE Late Early Middle Late 40 OLIGOCENE Early 30 Middle MIOCENE Late Early Middle Late 10 PLIOCENE Millions of years ago 6 Part 1: Evolution PLEISTOCENE Early 1 0 To decide which graph is best (yours or either of the ones above), you would need to use data from other characteristics of these organisms, not just the span of their cheek teeth. 53 Your answers for the following questions depend upon how similar your graph is to the ones shown. 7 4 cm 8 About 10.5 cm 9 The horse evolves slowly at first, then, after a series of rapid diversifications, evolves quickly. 10 Many organisms don’t preserve very well. Life forms, as recorded in fossils, are still only a fraction of the number that have ever lived. We are only just finding new techniques for determining the makeup of past life forms. With further development in these areas, more knowledge will be obtained. Transitional fossils Scientists want to find the steps that led from one life form to another. Although most modern scientists do not expect to find real transitional forms – in between organisms – they continue to search for evidence of evolution. Biogeography as evidence for evolution The borders of the biogeographic zones are oceans and mountain ranges. Wallace’s line Most vertebrates, apart from birds and bats, are restricted to regions bordered by coastlines and mountain ranges. Flowering plants have dispersal methods which enable them to be distributed beyond these limiting barriers. Six degrees of separation In order from most different to least different are: 1 Australian (8), 2 Ethiopian (6), 3 Neotropical (5.3), 4 Nearctic (1.3) and Oriental (1.3), and 6 Palaearctic (0.6). Comparative embryology The middle row is the most similar. 54 Blueprint of life Gill Sans Bold Biochemistry 1 a) chimpanzee b) yeast 2 The more closely related the species, the fewer number of amino acid differences. Other evidence – divergent evolution 1 Amphibians reproduce in water and their early stages of development require a life in water. 2 Insects and other arthropod groups could live inland. 3 Dinosaurs reproduced by internal fertilization and laid eggs. 4 Ecosystems left vacant by the perishing dinosaurs enabled mammals to diversify and establish themselves in new specialised niches. They had plenty of food and little competition for resources. 5 Divergent evolution is when one group or species evolves into two or more groups to occupy new niches. Convergent evolution 1 The physical feature that they all have is a streamlined body. This is an adaptation for overcoming the viscosity of water. 2 Moving about through water swiftly is important for the survival of these animals. Natural selection has selected animals which have evolved to this shape so these very different animals look much the same. The evolution of evolution Politics was centred around the beliefs of the church. Alternative explanations were against the dogma of the church; therefore they challenged the establishment. Accepting an idea such as evolution of species required people, including scientists, to sort through many issues, including what science is, what religion is and why human society is organised in particular ways. Part 1: Evolution 55 56 Blueprint of life Gill Sans Bold Exercises – Part 1 Exercises 1.1 to 1.7 Name: _________________________________ Exercise 1.1: Earth’s constantly changing environment a) List some physical conditions that might change in the environment. _____________________________________________________ _____________________________________________________ b) List some chemical conditions that may change in the environment. _____________________________________________________ _____________________________________________________ c) How might these changes impact on the evolution of plants and animals? Choose two physical changes and two chemical changes that you have listed and outline their effects. _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ Part 1: Evolution 57 Exercise 1.2: An open-ended investigation of natural selection Describe an open-ended investigation that you have done that illustrates natural selection. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ Exercise 1.3: A case study Name of Australian species studied: ____________________________ Describe changes in this species that have occurred over time because of environmental changes. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ 58 Blueprint of life Gill Sans Bold Exercise 1.4: Wallace’s line The Wallace line falls between Borneo and Sulawesi and between the tiny islands of Bali and Lombok. The latter pair of islands is separated by a mere 30 km, but for the most part they are inhabited by different families of mammals and even different birds. Philippines Celebes Sea Sabah Limit of native placental mammals other than bats, Muridea, Sus and Cervus Pacific Ocean Limit of marsupials 0 Borneo 1000 km Sulawesi Irian Jaya Wa llac e ’s Lin e Halmahera Papua New Guinea Banda Sea Sumbawa Flores Timor Arafura Sea Timor Sea Australia Gulf of Carpentaria Australia a) How would you account for these differences? _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ b) How did these observations influence Wallace to propose his theory of evolution? _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ Part 1: Evolution 59 Exercise 1.5: Comparative anatomy a) Compare the finger bones labelled 1, 2, 3, 4 and 5 for a bat, human, whale, lizard, cat, frog and bird by filling in the following tables. The first entry in each table is done for you. humerus Bat humerus ulna Human radius humerus carpal radius 1 Bird radius ulna ulna carpal 5 5 carpal humerus 1 4 4 2 radius ulna 1 3 2 carpal Whale 5 3 4 3 1 2 3 2 Lizard humerus humerus Cat Frog ulna humerus radius radius radius 1 ulna ulna carpal 2 3 5 carpal carpal 4 1 2 1 5 3 45 2 4 3 Fingerbones of vertebrates. 60 Blueprint of life Gill Sans Bold ÷) or absent (x) Fingerbone present (÷ Organism frog 1 2 3 4 5 ÷ ÷ ÷ ÷ ÷ lizard bird cat bat whale human Analyse how the structure is related to the function of each by filling in the following table. Organism Function of limb frog limb used for support and cleaning lizard bird cat bat whale human Part 1: Evolution 61 b) Compare the structure of the pentadactyl limb for three of the above vertebrates. ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ c) How would an evolutionary biologist explain the pentadactyl features? ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ 62 Blueprint of life Gill Sans Bold Exercise 1.6: Other evidence Describe how the finches of the Galapagos Islands are an example of divergent evolution. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ Part 1: Evolution 63 Exercise 1.7: The evolution of evolution a) Do your own research on the historical development of theories of evolution. You can also use the material in the Additional resources section titled ‘Theories about Evolution’. Present your information in the table below. Identify the data source(s) you used. ______________________________________________________ ______________________________________________________ ______________________________________________________ Name of scientist Dates Contribution Leonardo Da Vinci Robert Hooke George-Louis Buffon Carolus Linnaeus Erasmus Darwin Jean-Baptiste de Lamarck Alfred Russel Wallace Charles Darwin 64 Blueprint of life Gill Sans Bold b) Do your own research on social and political influences on the development of the theory of evolution. (You can also read the information in the Additional resources section.) How do you think social conditions and political ideas have affected the development and acceptance of an evolutionary explanation for life on Earth? _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ Part 1: Evolution 65