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StudyPacks STUDY. KS4 SCIENCE Evolution Theories of Evolution This Study Pack aims to cover: 1. Theories of Evolution. 2. Natural selection. SB17 Study Packs are prepared by Qualified Teachers and Specialists and are a complete range of comprehensive compiled resources based on the UK National Curriculum covering the Primary and Secondary Frameworks including SATs and GCSE examinations. Student Name Contents Evolution Notes 2-7 Practice questions 8-16 Exam questions 17-28 Mark scheme 29-35 1 Evolution Darwin's theory of evolution explains how species of living things have changed over geological time. The theory is supported by evidence from fossils, and by the rapid changes that can be seen to occur in microorganisms such as antibiotic-resistant bacteria. Many species have become extinct in the past and the extinction of species continues to happen. Charles Darwin Charles Darwin (1809 - 1882) Charles Darwin was an English naturalist. He studied variation in plants and animals during a five-year voyage around the world in the 19th century. He explained his ideas about evolution in a book called On the Origin of Species, which was published in 1859. Darwin's ideas caused a lot of controversy, and this continues to this day, because the ideas can be seen asconflicting with religious views about the creation of the world and creatures in it. Darwin's finches Darwin studied the wildlife on the Galápagos Islands - a group of islands on the equator almost 1,000 kilometres west of Ecuador. He noticed that the finches - songbirds - on the different islands there were fundamentally similar to each other, but showed wide variations in their size, beaks and claws from island to island. For example, their beaks were different depending on the local food source. Darwin concluded that, because the islands are so distant from the mainland, the finches that had arrived there in the past had changed over time. Darwin's drawings of the different heads and beaks he found among the finches on the Galapagos Islands Darwin studied hundreds more animal and plant species. After nearly 30 years of research, in 1858 he proposed his theory of evolution by natural selection. Darwin's theory of evolution The basic idea behind the theory of evolution is that all the different species have evolved from simple life forms. These simple life forms first developed more than three billion years ago - the Earth is about 4.5 billion years old. The timeline below shows some of the key events in the evolution of life forms on Earth, from the first bacteria to the first modern humans. Natural selection The theory of evolution states that evolution happens by natural selection. Here are the key points: Individuals in a species show a wide range of variation. This variation is because of differences in genes. Individuals with characteristics most suited to the environment are more likely to survive and reproduce. The genes that allowed the individuals to be successful are passed to the offspring in the next generation. 2 Individuals that are poorly adapted to their environment are less likely to survive and reproduce. This means that their genes are less likely to be passed to the next generation. Given enough time, a species will gradually evolve. Evidence for evolution - fossils Fossils of ammonites - sea creatures that became extinct about 65 million years ago Most of the evidence for evolution comes from the fossil record. Fossils show how much, or how little, organisms have changed over time. One of the problems with the fossil record is that it contains gaps. Not all organisms fossilise well, and there will be many fossils that have been destroyed by the movements of the Earth, or simply not yet been discovered. The horse One of the few animals for which we have a fairly complete evolutionary record is the horse. All the main stages of the evolution of the horse have been preserved Over 60 million years, the horse evolved from a dog-sized creature that lived in rainforests into an animal adapted to living on the plains and standing up to 2 metres high. In the process its multi-toed feet, that were adapted for walking across the forest floor, evolved into single-toed hooves more suited for running over open country. The evolution of the horse time period height 1 million years ago 1.6 metres Modern horse 10 million years ago 1.0 metres Pliohippus 30 million years ago 1.0 metres Merychippus 40 million years ago 0.6 metres Mesohippus 60 million years ago 0.4 metres Eohippus 3 Evidence for evolution - rapid changes Rapid changes in species have been observed. These support the theory of evolution. Peppered moths Before the industrial revolution in Britain, most peppered moths were of the pale variety. This meant that they were camouflaged against the pale birch trees that they rest on. Moths with a mutant black colouring were easily spotted and eaten by birds. This gave the white variety an advantage, and they were more likely to survive to reproduce. Airborne pollution in industrial areas blackened the birch tree bark with soot. This meant that the mutant black moths were now camouflaged, while the white variety became more vulnerable to predators. This gave the black variety an advantage, and they were more likely to survive and reproduce. Over time, the black peppered moths became far more numerous in urban areas than the pale variety. The pale peppered moths camouflage well against the pale birch tree The darker mutant peppered moths camouflage well against the blackened birch tree Antibiotic-resistant bacteria E. coli bacteria (Photo from Rocky Mountain Laboratories, NIAID, NIH) Microorganisms such as bacteria and viruses reproduce very rapidly and can evolve in a relatively short time. One example is the bacterium E. coli. Its DNA can be damaged or changed during replication, and most of the time this causes the death of the cell. But occasionally, the mutation is beneficial - for the bacteria. For example, it may allow resistance to an antibiotic. When that antibiotic is present, the resistant bacteria have an advantage over the bacteria that are not resistant. Antibiotic-resistant strains of bacteria are an increasing problem in hospitals Extinction Individuals that are poorly adapted to their environment are less likely to survive and reproduce than those that are well adapted. Similarly, it is possible that a species that is poorly adapted to its environment will not survive and will become extinct. Here are some of the factors that can cause a species to become extinct: 4 changes to the environment, such as a change in climate new diseases new predators new competitors The fossil record shows that many species have become extinct since life on Earth began. Extinction is still happening and a lot of it occurs because of human activities. We compete with other living things for space, food and water, and we are very successful predators. The dodo Engraving of the extinct dodo The dodo was a large flightless bird that lived on Mauritius, an island in the Indian Ocean. The island was uninhabited and the dodo had no natural predators. Then Mauritius was colonised by the Dutch in 1638. Dodos were hunted for food and easy to catch because they were not afraid of people. New competitors were brought onto the island, including pigs, cats and rats, which ate the dodos' eggs and their young. Within 80 years, the dodo was extinct. 5 6 7 The evolutionist no one believed Aim To understand how Lamark’s theory of evolution was different from Darwin’s. Jean Lamark had many jobs. As a soldier, his bravery under fire led to his promotion. He wrote about plants and worked for nothing in a Botanical Garden. He was the first scientist to study worms and insects properly. He invented the word ‘invertebrate’. None of this paid well, and he died in poverty. While he was studying invertebrates, he came up with his theory of evolution. Very few people believed him. In fact his boss, a famous scientist of the time, did his best to stop people taking Lamark’s ideas seriously. Lamark was one of the first modern scientists to believe in evolution. His ideas were fifty years before Charles Darwin and Alfred Wallace. In fact we know that Darwin’s grandfather wrote about evolution with ideas similar to Lamark. Fifty years after Lamark’s work, Darwin and Wallace said that evolution happened because of natural selection. Lamark thought that evolution happened by ‘acquired characteristics’. He thought that if an animal used a body part, it would get bigger, and that this bigger organ would be passed on to its offspring. He thought that giraffes evolved because they kept stretching their necks to reach higher. He thought that moles have small eyes because they never used them. He also did not believe in extinction. He thought evolution had a purpose. Now that we understand more about genetics, we know that acquired characteristics are not inherited. We also know about mutations, and that they happen by chance. Complete the following sentences: Both Lamark and Darwin believed in ………….…………. Lamark published his ideas about evolution ............. years before Darwin. Darwin said that evolution had taken place by ………..…...................... Lamark thought that evolution took place by the inheritance of ....................................................... ……………………..………….. What did Darwin and Lamark believe about extinctions? ....................................................................... ......................................................................................................................................................... ......................................................................................................................................................... How are modern ideas about evolution different from Lamark’s? ........................................................... ......................................................................................................................................................... 8 How to become extinct Aim To understand why living things become extinct. List five reasons why living things may become extinct, with an explanation for each one. Reason for extinction Explanation 9 Summary questions Use the following words to complete the sentences below. extinction predators minerals ice fossils evolved competitors generation breed earth mutation mutation species species fossils environment diseases fossils animal adaptation organism natural selection climate survive plant environment natural billion decay evidence related One important piece of …………..………….. for how life has developed on earth is ………….……. The most common type are formed when parts of the ……………… or ………….……. are replaced by ……….………. as they decay over long periods of time. Some ……………… were formed when an organism did not …….……. after it died. …….. …………… are very rare. The theory of evolution states that all the ………………… which are alive today – and many more which are now extinct – ………………. from simple life forms, which first developed more than three …………….……. years ago. Darwin’s theory is that evolution takes place through ……………..…….. selection. Studying the similarities and differences between species helps us to understand how they have evolved and how closely ……………..…….. they are to each other. When a ………….…………. has a good effect it produces an …………..………….. which makes an ………..……….. better suited to its …………..………….. This makes it more likely to ………….……. and ………….……. The ……………..…….. then gets passed on to the next ………….………….………….…………. This is ……………….. ……………………… …………..………….. is the permanent loss of all the members of a ……………… from the ………...…... It may be caused by changes to the …………….……………. or ……….………., to new ……………………, new ………………. or possibly new ………………………. 10 Evolution 1 The list contains factors that have played a part in the development of the species we see on Earth today: A Extinction ………. B Evolution ………. C Natural selection ………. D Mutation ………. Match words A, B, C and D with the processes 1, 2, 3 and 4 in the table. Process 1 Change and development of organisms over a long period of time 2 Change to the amount or arrangement of genetic material within a cell 3 Permanent loss of all members of a species 4 Passing of genes to offspring by the organisms most suited to their environment (4) 2 3 Which of the following does not play a part in evolution by natural selection? A Inheritance of acquired characteristics. B Mutation of existing genes. C Variation of individuals within a species. D Production of offspring by individuals best suited to their environment. (1) Which of the following would not normally cause the extinction of a species? A Environmental change B Fewer competitors C New diseases D More predators (1) 11 4 Not all scientists agree on the exact evolutionary relationship between different primates. The diagram shows a timeline for one version of this relationship. (a) Which group is the closest relative to humans? A Old world monkeys B Orang-utans C Gorillas D Chimpanzees (b) How many million years after the old world monkeys evolved from the common ancestor did the gorillas evolve? A 27 B 20 C 10 D 7 (c) How many of the primate groups shown in the diagram were on Earth 20 million years ago? A 6 B 5 C 3 D 1 (d) Many of the ancestors of the present-day primates are now extinct. How do we know these ancestors once lived? A By studying DNA samples. B By studying fossil records. C By studying blood samples. D By studying cell structure. (4) 12 5 The Galapagos Islands are a group of islands in the Pacific Ocean. The nearest country on the mainland is Ecuador, 1000 km away. By some means, a few seed-eating finches were the first birds to reach the islands. This single ancestral species has since evolved into many different species. Charles Darwin visited the islands and noted that each species had a beak adapted to the type of food it ate. Using the theory of natural selection, explain how the ancestral species might have evolved into birds with different-shaped beaks. ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ 13 Evolution Exam style 1 a This diagram shows a timeline for the evolution of some dinosaurs. The mass of each dinosaur is shown in the brackets by its name. Choose the correct answer to complete each sentence. Dinosaur evolution timeline i A dinosaur which lived between 100 and 150 million years ago is .................... . Agilisaurus ii Saturnalia Tyrannosaurus Camarasaurus evolved from ................. .......... . Agilisaurus Alamosaurus (1) (1) Saturnalia iii The difference in mass between Agilisaurus and the smallest dinosaur is ....... kg. 1.82 b i 5.5 7.32 The earliest life forms developed on Earth more than 3 ................... years ago. billion ii million (1) thousand The earliest life forms can be described as ................... bony c (1) complex (1) simple Darwin suggested a theory of evolution. His theory is described as evolution by ...................................... acquired characteristics (1) a god natural selection 14 2 Giraffes have developed their long necks over millions of years. Two scientists tried to explain why the giraffes have long necks. They are called Darwin and Lamarck. Match the name in List A to the correct statement in List B. (3) List A List B Name Statement Darwin only Noticed that the neck of the giraffe changed over time Lamark only Had enough evidence to prove why the giraffe’s neck got longer Both Lamark and Darwin Thought that natural selection worked on variations in neck length present at birth Thought the giraffe stretched its neck while eating leaves in trees. Then its young inherited the longer neck 3 The photograph shows a snake eating a toad. Cane toads were first introduced into Australia in 1935. The toads contain toxins and most species of Australian snake die after eating the toad. The cane toad toxin does not affect all snakes the same way. Longer snakes are less affected by toad toxin. Scientists investigated how redbellied black snakes had changed in the 70 years since cane toads were introduced into their area. They found that red-bellied black snakes had become longer by around 3–5%. Suggest an explanation for the change in the body length of the red-bellied black snakes since the introduction of the cane toads. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (4) AQA, 2005 15 Evolving oysters Aim To explain natural selection for a new example. Use this writing frame to explain the natural selection of Malpeque Bay Oysters. A disease killed most of the Oysters in Malpeque Bay, Canada Key word: mutation Key idea: survive to breed 16 Exam Questions Q1. A particular species of snail has a shell which may be pink, yellow or brown. It may also be plain or have bands running round it. The snails are eaten by song thrushes. Explain why snails with plain brown shells are the most common in hedgerows. ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... (Total 4 marks) Q2. Cepaea nemoralis is a snail which is found on sand dunes. It may have a plain or banded shell. The snails are found on grass stalks and leaves. Plain Banded When a scientist collected snails on the sand dunes he got 450 banded 280 unbanded. Snails are eaten by birds. Sand dunes have clumps of grasses growing on them. Suggest why there were more banded than unbanded snails on the sand dunes. ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... (Total 4 marks) 17 Q3. The peppered moth is an example of a mutation which gives the mutant variety an advantage in certain environmental conditions. Normally the peppered moth is light coloured. In 1848 the first dark form of the peppered moth was caught in the Manchester area. By 1895, 98% of the population was the dark form. In an area where a smokeless zone was established in 1972 the percentage of light-coloured peppered moths changed. In 1961 it was 5.2% but in 1974 it had risen to 10.5%. Use the information above to explain the term natural selection. ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... (Total 4 marks) Q4. The map shows: the most densely populated industrial areas; the frequency of pale and dark forms of the peppered moth; the direction of the prevailing winds in the British Isles. Peppered moths usually rest on trees covered with lichen, and they are preyed upon by many birds. In areas of low air pollution the lichen on trees is usually pale in colour. In areas of high air pollution the lichen turns black. (a) (i) State a pattern of the distribution of the mutant dark form shown on the map. ...................................................................................................................... ...................................................................................................................... (1) (ii) Suggest a reason for your pattern. 18 ...................................................................................................................... ...................................................................................................................... (1) (b) The dark form of peppered moth developed after a mutation in the pale form. What is a mutation? .................................................................................................................................... .................................................................................................................................... (1) (c) Using the idea of Natural Selection explain why the dark form of the moth is restricted to the areas shown. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (4) (Total 7 marks) Q5. A scientist called Lamarck proposed a theory of evolution. The passage gives Lamarck’s explanation of the evolution of the long legs of wading birds. Change occurs because an animal passes on to its offspring changes it acquires during its lifetime. The long legs of wading birds arose when those animals’ ancestors responded to a need to feed on fish. In their attempt to get into deeper water, but still keep their bodies dry, they would stretch their legs to the full extent, making them slightly longer in the process. This trait would be passed on to the next generation, who would in turn stretch their legs. Over many generations, the wading birds’ legs became much longer. Darwin’s theory of natural selection would give a different explanation for the evolution of the long legs of wading birds. Describe the differences between Lamarck’s and Darwin’s explanations of the evolution of the long legs of wading birds. ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... 19 ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... (Total 4 marks) Q6. Giraffes feed on the leaves of trees and other plants in areas of Africa. Lamarck explained the evolution of the long neck of the giraffe in terms of the animals stretching their necks to eat leaves from tall trees. Darwin also explained the evolution of the long neck in terms of getting leaves from tall trees. Neither scientist used any evidence to support their explanation. Recently, scientists have tried to explain how the long neck of the giraffe might have evolved. These are some of their observations. • Giraffes spend almost all of the dry season, when food is scarce, feeding from low bushes. • Only in the wet season do they feed from tall trees when new leaves are plentiful. • Females spend over 50 % of their time feeding with their necks horizontal. Both sexes feed faster and most often with their necks bent. • Long giraffe necks are very important in male-to-male combat. Males fight each other with their long, powerful necks! • Female giraffes prefer male giraffes with longer necks. (a) Do the observations support or reject the explanation that the long neck of the giraffe evolved to get leaves from tall trees? Explain the reasons for your answer. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... 2) (b) Use the recent observations to give another explanation for the evolution of the long neck of the male giraffe. ..................................................................................................................................... ..................................................................................................................................... 20 ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 4 marks) Q7. Modern humans belong to the species Homo sapiens. Many people think that modern humans evolved from more primitive species. Three of these primitive species were Australopithecus, Homo habilis and Homo erectus. These three species are now extinct. The graph shows the brain size of several specimens from each of the species. (a) Estimate the mean brain size of Homo habilis. .................... cm3 (1) (b) Suggest how we know about the brain size of Australopithecus. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (c) Suggest an explanation, in terms of natural selection, for the change in brain size during the evolution of Homo sapiens. ..................................................................................................................................... 21 ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (Total 6 marks) Q8. Giraffes feed on the leaves of trees and other plants in areas of Africa. They are adapted, through evolution, to survive in their environment. (a) Use the information in the picture to give one way in which the giraffe is adapted to its environment. .................................................................................................................................... (1) (b) Explain how Jean-Baptiste Lamarck (1744–1829) accounted for the evolution of the long neck in giraffes. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (3) (c) Another scientist, August Weismann (1834 -1914) wanted to check Lamarck’s explanation. To do this he cut off the tails of a number of generations of mice and looked at the offspring. His results did not support Lamarck’s theory. Explain why. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (2) 22 (d) Explain how Charles Darwin (1809–1882) accounted for the evolution of the long neck in giraffes. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (4) (Total 10 marks) Q9. (a) The theory of evolution via natural selection was proposed by Darwin. Explain how evolution occurs via natural selection. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (4) (b) Darwin’s theory was only gradually accepted. Give two reasons why. 1 ..................................................................................................................... ........................................................................................................................ 2 ..................................................................................................................... ........................................................................................................................ (2) (Total 6 marks) Q10. (a) What does the theory of evolution state? ..................................................................................................................................... 23 ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (b) Daphnia are microscopic water fleas. Midge larvae prey on Daphnia. The midge larvae release a hormone into the water. Daphnia respond to these hormones by growing larger protective ‘helmet’like structures Scientists were surprised to observe that the offspring of Daphnia females who had been exposed to these hormones always had larger helmets than offspring whose mothers had never been exposed to the hormones. The offspring with the large helmets went on to produce offspring with large helmets. Explain why the scientists’ observations seem to contradict the theory of natural selection. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 4 marks) Q11. The drawings show two different species of butterfly. • Both species can be eaten by most birds. • Amauris has a foul taste which birds do not like, so birds have learned not to prey on it. • Hypolimnas does not have a foul taste but most birds do not prey on it. (a) Suggest why most birds do not prey on Hypolimnas. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (b) Suggest an explanation, in terms of natural selection, for the markings on the wings of 24 Hypolimnas. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (Total 5 marks) Q12. The vole is a small, mouse-like animal. Voles found on some cold islands to the north of Scotland are much larger than voles found in warmer areas such as southern France. Explain how natural selection may have caused the northern voles to be larger in size. ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... (Total 5 marks) Q13. (a) Explain, as fully as you can, how natural selection leads to evolution. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... 25 ..................................................................................................................................... (3) (b) Most penguins live in cold climates. The modern penguin best adapted for cold conditions is the emperor penguin. Scientists have found fossils of a ‘giant’ penguin which they have called Icadyptes. The diagram shows how the size of modern penguins compares with Icadyptes. The scientists were surprised to discover that Icadyptes lived in warm seas at a time when the Earth’s climate was much warmer than it is now. Explain why the scientists were surprised that Icadyptes lived in warm seas. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 5 marks) 26 Q14. The diagram shows an evolutionary tree for a group of animals called primates. The names of extinct animals are printed in italics e.g. Nycticeboides. The drawings show animals that are alive today. Illustration by Lucrezia Beerli-Bieler (a) (i) How many million years ago did Karanisia first appear? ............................. millions of years ago. (1) (ii) During which geological period did the Apes and Monkeys begin to evolve? .......................................................................................................................... (1) (iii) Which group of primates alive today are the closest relatives of the Lorises? .......................................................................................................................... (1) (b) Darwin was the first scientist to state that humans and other primates had common ancestors. Many people were against Darwin’s ideas at that time. Give two reasons why they were against his ideas. 1 ................................................................................................................................. .................................................................................................................................... 2 ................................................................................................................................. .................................................................................................................................... 27 (2) (Total 5 marks) Q15. The photograph shows a Crossbill. A Crossbill feeds by using its bill (beak) to force apart the scales on conifer cones. It then uses its tongue to extract the seeds. If the bill is clipped it grows back again. Scientists were interested in the evolution of the bill of the Crossbill. In an investigation, they clipped the bills of several Crossbills so that their bills no longer crossed. They observed that Crossbills with clipped bills took much longer to get seeds. Use information from the investigation to suggest an explanation for the evolution of the bill in the Crossbill. In your explanation, use the ideas of selection, competition and mutation. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. (Total 4 marks) 28 Mark scheme M1 idea brown colour/plain shell inconspicuous for 1 mark less likely to be eaten gains 1 mark but less likely to be eaten before breeding gains 2 marks so alleles (genes) passed on for 1 mark (N.B accept inverse of any of the above) [4] M2. idea • banded snails camouflaged/less easily seen • fewer banded eaten [by birds] • more banded survive to breed • more genes for banded passed on or more banded snails in population for 1 mark each N.B. Accept reverse of all above for plain snails *All 4 marks may be gained by a relatively short response [4] M3. any four from dark were better adapted to survive or dark ones can hide in dirty environment dark is the survival of the fittest or they are better camouflaged those which survive breed they are able to pass on their genes light ones more easy to see on smoky surfaces (so get eaten) birds can see light ones more easily as environment becomes cleaner or less smoky light ones hide easier those which survive breed or increase the population accept the converse argument [4] M4. (a) (i) dark form lives in the industrialised/ densely populated areas or dark form lives to the East/downwind/North East of industrialised are 1 (ii) more pollution/discolouration in those areas or pollution blown by prevailing winds 1 29 (b) a change to the genetic material/DNA/chromosomes/genes in an organism do not accept fault. error 1 (c) survival in polluted areas: one mark for each mark point to a maximum of 4 (pollution) lichen/trees/buildings become(s) blackened credit an answer given in terms of survival in polluted areas or non-survival in other areas (camouflage) black formed camouflaged / more difficult to see (predation) not preyed upon eaten by thrushes (survival) survive to breed or non survival (no pollution) lichen/trees/buildings remain(s)pale/non-blackened (no camouflage) black formed not camouflaged / easier to see (predation) preyed upon/eaten by thrushes (survival) do not survive to breed 4 [7] M5. idea of variation Darwin’s theory based on range of variation in organisms accept some (birds) have long legs and some have short legs do not credit inherited characteristics mention of genes etc – neutral 1 idea of acquisition Lamarck’s based on characteristics or long legs acquired during lifetime e.g. legs stretch during lifetime do not credit grow 1 idea of survival of fittest Darwin’s theory based on survival of organisms with beneficial variation accept reference to survival of the fittest accept ones with longer legs will survive 1 idea of inheritance Lamarck’s based on inheritance of acquired characteristics accept reverse point that Darwin recognised that acquired characteristics are not inherited do not credit reference to other animals e.g. giraffes 1 M6. (a) (reject) if support then zero marks any two from: giraffe spend almost all of the dry season feeding from low bushes only in the wet season do they feed from tall trees, when new leaves are plentiful females spend over 50% of their time feeding with their necks horizontal both sexes feed faster and most often with their necks bent 2 30 (b) any two from: mutations produce male giraffes with longer necks either male giraffes with longer neck more likely to win fight / more likely to mate with female or females prefer long necks / more likely to mate with long necked male their genes more likely to pass to next generation accept long necks inherited or offspring have long necks 2 [4] M7. (a) 550 – 650 for one mark 1 b) skulls preserved as fossils / measure skull volume for 1 mark each 2 c) range of brain size / bigger brains arose by mutation more with large brains more likely to survive because more intelligent / survival advantage described their genes passed to next generation / offspring inherited large brains any three for 1 mark each 3 [6] M8. (a) long neck or legs 1 (b) change in environment or reaching for food or stretching led to more use of neck (and legs) [1] use led to increased size or characteristic acquired during lifetime [1] this characteristic was passed to offspring [1] 3 (c) phenotypic changes do not affect genotype or genes [1] acquired characteristics are not passed to offspring or the offspring were bom with tails or inheritance has to be genetic [1] 2 (d) one mark awarded for each of the following general points: variation exists in all populations or mutation occurred [1] or if written specific to giraffes: all giraffes are different or reference to short necked giraffes[1] 4 some individuals will have an advantage in certain areas or will be better adapted or there is survival of fittest [1] taller giraffes or those with longer necks will have an advantage in being able to reach high vegetation or there is survival of fittest [1] 31 advantaged individuals breed more or are more successful [1] these giraffes will breed more or will be more successful [1] the genes or units of heredity or DNA of these individuals are passed on [1] (look for idea of genetic information being passed on) the genes or units of heredity or DNA of these giraffes are passed on [1] [10] M9. (a) organisms within species may show variation 1 because mutation(s) occur in individuals 1 this results in the individuals with characteristics most suited to the environment being more likely to survive / to breed 1 as a consequence the genes that have enabled these individuals to survive are passed on to the next generation 1 (b) any two from • the theory undermined the idea that God made all the animals and plants that live on earth • there was insufficient evidence at the time • the mechanism of inheritance / variation was not yet known 2 [6] M10. (a) present day organisms have evolved from simpler organisms ignore answers in terms of natural selection 1 over long periods of time or millions / billions of years 1 (b) (natural selection operates on successful) characteristics produced by chance / (random) mutation 1 in this experiment caused by hormones / environment allow this example indicates inheritance of acquired characteristics for 2 marks allow this is Lamarckism only for 1 mark 1 [4] M11. (a) wing pattern similar to Amauris 1 birds assume it will have foul taste 1 (b) mutation / variation produced wing pattern similar to Amauris do not accept breeds with Amauris do not accept idea of intentional adaptation 1 these butterflies survived 32 1 breed / genes passed to next generation 1 [5] M12. any five from: • genetic variation exists in a population or variation caused by mutation / change in gene / in DNA • larger voles have smaller or have more fat ‘they’ accept as larger voles • larger voles lose less heat / are better insulated or more energy stored • larger voles survive • larger voles breed • larger voles pass on (beneficial) gene / allele / mutation / DNA ignore characteristic [5] M13. (a) variation / mutation 1 individuals with characteristics most suited to environment survive allow survival of the fittest 1 genes passed to next generation or these individuals reproduce 1 (b) any two from: • similar in size to Emperor penguin or bigger than all penguins • large size is adaptation to cold climate • since less heat loss per unit of body volume or smaller surface area / volume ratio 2 [5] M14. (a) (i) 40 – 42 1 (ii) Palaeocene 1 (iii) bush babies 1 (b) any two from: • religious objections • insufficient evidence allow ‘could not prove’ ignore ‘no evidence’ 33 • mechanism of heredity not known 2 [5] M15. any four from: max two marks for a Lamarck explanation • mutation produced a bird whose bill was crossed do not allow birds decide to mutate • birds compete for food / seeds • mutant crossbill able to obtain food faster / easier / more successfully • selected for or more likely to survive • reproduce / mate / breed / produce offspring [4] Evolutionary trees Teacher notes Answers to questions Fill in the table with the main features of each of the subgroups of vertebrates. Fish has been done for you: Fish Amphibians Reptiles Birds Mammals Scales Moist skin Scales Feathers Fur Lays soft eggs Lays eggs in jelly Lays eggs with leathery shell Lays eggs with hard shells Gives birth to live young Gills Lives part of its life in water Cold-blooded Wings Warm-blooded Fins Cold-blooded Warm-blooded Cold-blooded Feel free to remind students that there are always exceptions to the rule – challenge them to think of any exceptions (such as the duck-billed platypus). According to the evolutionary tree given above, are reptiles more closely related to birds or mammals? The line branches off more recently to birds than it does to mammals; this tells us that reptiles are more closely related to birds than mammals. 34 Which group of organisms has become extinct? Using evidence from the evolutionary tree, explain how you know this. The dinosaurs. Their line stops before the ‘present’ level at the top of the evolutionary tree, which tells us that they are extinct. There is much controversy about whether or not birds evolved from dinosaurs or mammals. What does this evolutionary tree suggest? This evolutionary tree suggests that birds evolved from dinosaurs and not from mammals. What feature do reptiles and birds have in common? They both lay eggs. What feature do birds and mammals have in common? They are both warm-blooded. Exam style Questions 1 a i Agilisaurus ii Saturnalia iii 7.32 b i billion ii simple c Natural selection 1 1 1 1 1 1 2.Darwin only – Thought that natural selection worked on variations in neck length present at birth. Lamark only – thought the giraffe stretched its neck while eating leaves in trees. Then its young inherited the longer neck. Both Lamark and Darwin – noticed that the neck of the giraffe changed over time. 3 3.Accept any four from: • mutation (do not accept ‘had to mutate / decided to mutate’) • produces longer snake or there is variation in snake length (do not accept ‘had to adapt and became longer’) • longer snake less susceptible to toxin or longer snake survives • survivors reproduce • gene passed to next generation (allow characteristic passed to next generation) 4 35