17.3. Evolution
A subsection of Biology, 9700, through 17. Selection and evolution
Listing 10 of 28 questions
MELAS syndrome is an inherited disease caused by a mutation in a gene located in mitochondrial DNA (mtDNA). All mtDNA is inherited from the mother. shows four generations of a family where several individuals are affected by MELAS syndrome. first generation second generation third generation fourth generation = unaffected female = female with MELAS syndrome = unaffected male = male with MELAS syndrome key With reference to , state and explain the evidence that MELAS syndrome is an mtDNA disease and not a disease caused by a mutation in a gene on the X chromosome. Analysis of mtDNA can show how recently species have evolved from each other. Describe the properties of mtDNA that make it suitable for the study of evolution.
9700_m19_qp_42
THEORY
2019
Paper 4, Variant 2
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The European eel, Anguilla anguilla, is a fish. The sizes of eel populations tend to remain relatively stable despite eels producing large numbers of offspring. Suggest two reasons why the population sizes of eels tend to remain relatively stable. Explain what is meant by the general theory of evolution. The generation time of a species is the mean time from one generation to the next generation . For example, the generation time of humans is about 25 years. shows a graph of the relationship between the rate of evolution and the generation time for a wide range of different species. rate of evolution generation time Describe and explain the relationship shown in . The tuatara, Sphenodon punctatus, is a reptile that is native to New Zealand. It is found nowhere else in the wild. shows a tuatara. Tuataras have a slow growth rate and can live for over one hundred years. Fossil evidence shows that there has been little morphological change in the tuatara over the last 200 million years. This is a much lower rate of evolution than would be expected from the generation time of this species. Suggest and explain why the tuatara has remained largely unchanged over the last 200 million years.
9700_m21_qp_42
THEORY
2021
Paper 4, Variant 2
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Complete the following paragraphs using the most appropriate word or words. The theory of evolution describes a process that can lead to the formation of new species from pre-existing species over . DNA sequence data of different species can be compared to show evolutionary relationships. Two species that have a more recent common ancestor share more in the DNA nucleotide sequences of their genomes than two species that are more distantly related. Mitochondrial DNA can also be used in the study of evolutionary relationships. Mitochondrial DNA is inherited only from the female gamete, and its nucleotide sequence is unaffected by during the production of gametes. DNA sequence data can be stored in large biological , allowing faster comparison of the nucleotide sequences of genomes using computer software. DNA sequence data can also be used to predict the sequences of proteins produced by a species. A can be used to detect many different mRNA molecules at the same time in studies that compare gene expression between different species.
9700_m24_qp_42
THEORY
2024
Paper 4, Variant 2
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Anole lizards are found throughout the Caribbean and the surrounding mainland. There are many species. Each species is found only on one island or a small group of islands, apart from Anolis carolinensis which is found in mainland Florida. shows the distribution of four species of anole lizards. Florida U.S.A. Cuba Andros Acklins Anolis smaragdinus Anolis brunneus Anolis carolinensis Anolis porcatus 50 100 km An investigation was carried out into the relationships between these four lizard species, using DNA analysis. The base sequences of a region of mitochondrial DNA from the four species were compared. The results are shown in Table 5.1. The smaller the number, the smaller the differences between the base sequences of the two species. Table 5.1 A. brunneus A. brunneus A. smaragdinus A. smaragdinus 12.1 A. carolinensis A. carolinensis 16.7 15.0 A. porcatus A. porcatus 11.3 8.9 13.2 With reference to Table 5.1, state the species to which A. brunneus appears to be most closely related. The researchers put forward the hypothesis that the three species, A. brunneus, A. smaragdinus and A. carolinensis, have originated from three separate events in which a few individuals of A. porcatus spread directly from Cuba to three different places. Explain how the results in Table 5.1 support the researchers’ hypothesis. Explain how a population of A. porcatus that became isolated on an island could evolve into a new species.
9700_s10_qp_41
THEORY
2010
Paper 4, Variant 1
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The fruitfly, Drosophila, has many different species. Three of these species, Drosophila pseudoobscura, D. persimilis and D. miranda, are thought to be closely related. Samples of these three species were collected from the western United States of America. shows where these species naturally occur. Key D. pseudoobscura D. persimilis and D. miranda The base sequences of four regions of DNA of each species were sequenced. The divergence of these base sequences in D. pseudoobscura and D. persimilis from the sequences in D. miranda was calculated. The results are shown in Table 5.1. Table 5.1 DNA region Drosophila species percentage divergence of base sequence from that of D. miranda pseudoobscura 2.5 persimilis 2.4 pseudoobscura 8.1 persimilis 7.3 pseudoobscura 2.1 persimilis 1.7 pseudoobscura 1.9 persimilis 1.7 With reference to Table 5.1, describe the evidence that D. miranda may be more closely related to D. persimilis than to D. pseudoobscura. Suggest why there is more divergence in some regions of DNA than in others. The area where D. pseudoobscura is found is separated from the areas where the other two species are found by a high range of mountains. Explain how the species D. pseudoobscura could have evolved from a population of D. miranda.
9700_s10_qp_42
THEORY
2010
Paper 4, Variant 2
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The fruitfly, Drosophila, has many different species. Three of these species, Drosophila pseudoobscura, D. persimilis and D. miranda, are thought to be closely related. Samples of these three species were collected from the western United States of America. shows where these species naturally occur. Key D. pseudoobscura D. persimilis and D. miranda The base sequences of four regions of DNA of each species were sequenced. The divergence of these base sequences in D. pseudoobscura and D. persimilis from the sequences in D. miranda was calculated. The results are shown in Table 5.1. Table 5.1 DNA region Drosophila species percentage divergence of base sequence from that of D. miranda pseudoobscura 2.5 persimilis 2.4 pseudoobscura 8.1 persimilis 7.3 pseudoobscura 2.1 persimilis 1.7 pseudoobscura 1.9 persimilis 1.7 With reference to Table 5.1, describe the evidence that D. miranda may be more closely related to D. persimilis than to D. pseudoobscura. Suggest why there is more divergence in some regions of DNA than in others. The area where D. pseudoobscura is found is separated from the areas where the other two species are found by a high range of mountains. Explain how the species D. pseudoobscura could have evolved from a population of D. miranda.
9700_s10_qp_43
THEORY
2010
Paper 4, Variant 3
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Collared lizards, Crotaphytus collaris, show variation in body length and running speed. shows a collared lizard. An investigation was carried out to find out whether body length and running speed affected the number of offspring that a male lizard sired . The lizards reproduce sexually, and females lay eggs after mating with males. A large number of male lizards was captured during the breeding season. For each lizard: • body length was measured • it was chased down a small race track and its fastest running speed over 1 m recorded • a blood sample was taken and DNA sequences at 10 different loci were analysed. The lizards were then released back into the place where they were captured, to allow mating to occur. Several weeks later, after the lizards’ eggs had hatched, as many young hatchlings as possible were captured. DNA testing was carried out on each hatchling to determine which male was the father. The results were used to determine the number of offspring sired by each of the male lizards in the first sample. Outline how DNA analysis can be carried out and then used to establish which male lizard sired each hatchling. shows the number of offspring sired plotted against the body length of the adult male lizards. shows the number of offspring sired plotted against the fastest running speed (sprint speed) of the adult male lizards. number of offspring sired 2.00 2.01 2.02 2.03 2.04 2.05 2.06 body length (log scale) number of offspring sired 0.40 0.45 0.50 0.55 0.60 0.65 0.70 sprint speed (log scale) With reference to and , describe the relationships between • body length and the number of offspring produced • sprint speed and the number of offspring produced. body length sprint speed Research has also shown that, in a population of collared lizards with varying leg lengths, those with longer hind legs are able to run faster. With reference to the results shown in , explain how, over time, this could lead to a change in the mean hind leg length in a population of collared lizards. Small islands often contain species of lizards that are not found on other islands or on the mainland. Explain how a population of collared lizards that became isolated on an island could evolve to form a new species.
9700_s14_qp_42
THEORY
2014
Paper 4, Variant 2
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Researchers investigated the extent to which the founder effect and natural selection affected evolutionary change. shows the brown anole lizard, Anolis sagrei. These lizards live on a number of Caribbean islands and feed on a variety of invertebrates and other small animals. perch diameter A. sagrei spends a lot of time perching on, or moving along, branches of shrubs and trees. The width of the branch that A. sagrei perches on is known as the perch diameter, as labelled in . There is a positive correlation between perch diameter and hind limb length of A. sagrei. • Longer hind limbs allow A. sagrei to run faster on vegetation with a larger diameter. • Shorter hind limbs are needed to provide stability on vegetation of a smaller diameter. In 2004, a hurricane caused the death of all the A. sagrei lizards on seven islands. In 2005, the researchers randomly collected seven male and seven female lizards from a source population on a nearby island. For each of the seven islands affected by the hurricane, a male and female lizard were mated and placed on each island. These islands formed the experimental founder islands where new populations of A. sagrei were successfully established from each founding pair. shows the difference in vegetation between the source island and the seven experimental founder islands. source population experimental founder islands Predict the effect of natural selection on mean hind limb length of A. sagrei on the seven experimental founder islands. Predict how collecting individuals at random for the seven founding pairs affects the mean hind limb length of A. sagrei on the different islands. Many generations of A. sagrei were produced over the four years after the introduction of the founding pairs. shows how the mean hind limb length of A. sagrei changed on the seven experimental islands and on the source island. year mean hind limb length Key: source island island 1 island 2 island 3 island 4 island 5 island 6 island 7 With reference to and , describe and suggest explanations for the results for the islands. In the investigation, one population of A. sagrei was established on each experimental founder island. Outline how speciation may occur on the seven experimental founder islands. Speciation is one possible outcome for the experimental founder populations, but there is also a high risk that they may become extinct. Explain why the experimental founder populations are at high risk of extinction.
9700_s19_qp_41
THEORY
2019
Paper 4, Variant 1
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State the general theory of evolution. Different types of organism have evolved different structures containing light receptors. Eyes are organs containing light receptors. describes the light receptors of several types of organism. Euglena (a single-celled eukaryote) has a simple eyespot that can only detect the intensity and direction of light. Turbellarian flatworms have cup-shaped eyes, each with a layer of light receptor cells. They can detect the intensity and direction of light better than Euglena. They also detect movement. The mollusc Nautilus has eyes with deeper cups and narrower openings for light to enter. They can form a rough image, see shapes and detect the direction of light better than turbellarian flatworms. The mollusc Nucella has eyes with lenses made of jelly. They can form a more detailed image than the eyes of Nautilus and can focus light to a small degree. Mammals have eyes that are more complex than Nucella. They have a fixed lens (the cornea) that bends light and a lens that can change shape to focus on objects at different distances. The lenses focus light onto a deeply cup-shaped layer of light receptor cells. The eyes form a very detailed image. Using the information in , suggest how a complex eye such as that of mammals could have evolved in successive stages. Octopuses are molluscs that have eyes very similar to those of mammals. Octopuses and mammals are not closely related. Octopuses and mammals have lenses that can change shape to focus on objects at different distances. Suggest reasons why octopuses and mammals have evolved similar eye structures. Molecular evidence is used to investigate evolution. One study involved a marine worm, Platynereis dumerilii, that still has characteristics similar to its ancestors from 600 million years ago. Researchers sequenced all the proteins in light receptor cells of P. dumerilii and humans. The results showed that there are many similarities between the protein sequences of P. dumerilii and humans, particularly in the light-detecting protein opsin. State what this molecular evidence indicates about the evolutionary origins of P. dumerilii and humans. Explain how amino acid sequences indicate how close the relationship is between two species.
9700_s19_qp_42
THEORY
2019
Paper 4, Variant 2
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Cats are members of the Felidae family. Two genera of Felidae are Leopardus and Panthera. The genus Leopardus consists of species of wild cats that are small and spotted. In 2013, biologists investigated the evolution of Leopardus tigrinus in South America. shows the locations in South America of two populations of. L. tigrinus, population A and population B. population A population B • Population A lives in grassland and desert habitats and population B lives in forest habitats. • The cats in population A have a lighter coat colour and a different pattern of spots from the cats in population B. • Genetic analysis shows that population A is genetically distinct from population B. • Population B has now been reclassified as a new species, L. guttulus. Define the term species. Explain how the two species, L. tigrinus and L. guttulus, have evolved from one original population in South America. Illegal trade threatens the survival of endangered species. Forensic tests can identify animal species from the DNA of their body parts, for example bones. Cat species differ in the number of repeats of bases C and A (CA repeats) within one particular region of DNA, known as Ple46. Table 3.1 shows the number of repeats in Ple46 for three endangered cat species. Table 3.1 cat species number of CA repeats in Ple46 Asiatic lion Bengal tiger 7–8 leopard 14–15 Gel electrophoresis is used to estimate the length of Ple46 in a sample of DNA to check whether the sample comes from one of the endangered cat species in Table 3.1. Outline how gel electrophoresis is carried out to confirm whether the sample comes from one of these endangered cat species. Customs officials are responsible for checking whether animal body parts come from species on the CITES list of endangered species. Officials can now use a small DNA barcoding kit linked to a computer database to identify a species. Suggest two advantages of using this method to identify a species.
9700_s20_qp_41
THEORY
2020
Paper 4, Variant 1
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Questions Discovered
28