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DP IB Biology: SL

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Home / IB / Biology: SL / DP / Topic Questions / 5. Evolution & Biodiversity / 5.2 Classification & Cladistics / Structured Questions: Paper 2


5.2 Classification & Cladistics

Question 1a

Marks: 3
a)

Ailuropoda melanoleuca, the giant panda, and Ailurus fulgens, the red panda, are both native to China. They share the following similarities:

  • They live in similar environments
  • They both digest bamboo as a primary source of food
  • They both have a pseudo-thumb (a sixth digit) used to grip and shred food such as bamboo

The following table shows the differences between a comparable sequence of mitochondrial DNA of the giant panda and the red panda.

Mammal DNA sequence
Giant panda ATT GGA GCA GAC TTA
Red panda ATT GGC ACT GAC CTA

A group of students concluded that the giant panda and the red panda are closely related.

Use the information provided to evaluate this conclusion.

[3 marks]

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    Question 1b

    Marks: 2
    b)

    After careful deliberation, the group of students decided that the giant panda and red panda were, in fact, not closely related.

    Suggest an explanation for the existence of a pseudo-thumb in both species.

    [2 marks]

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      Question 1c

      Marks: 2
      c)

      The base sequence of a different section of mitochondrial DNA (mtDNA) were analysed to determine the differences between giant panda and red panda DNA. In total, there were eight differences between the mtDNA of the two species.

      Mitochondrial DNA is estimated to mutate at a rate of 1.87 x 10-7 mutations site-1 year-1. Use the information given to calculate how long ago the giant panda and the red panda evolved from a common ancestor. Show your working and round your answer to three significant figures.

      [2 marks]

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        Question 1d

        Marks: 2
        d)

        Explain the difference between a taxon and a clade.

        [2 marks]

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          Key Concepts
          Clades

          Question 2a

          Marks: 4
          a)

          Cetaceans is an order of carnivorous aquatic mammals which include dolphins, whales and porpoises. The following diagram shows two proposals that have been put forward regarding the closest living relative of the cetaceans, represented by diagrams R and S.

          5-2-hard-q2a

          Compare and contrast the information in diagrams R and S.

          [4 marks]

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            Question 2b

            Marks: 3
            b)

            Casein is a protein found in the milk of most mammals. Scientists investigated the differences in the DNA base sequence of the gene coding for casein in the mammals shown in diagrams R and S. The following table shows their results.

            jeJc6~re_h-2b

            Scientists concluded that diagram S best represents the currently accepted theory regarding the evolutionary origin of cetacean.

            Based on the information provided, evaluate this conclusion.

            [3 marks]

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              Question 2c

              Marks: 1
              c)

              More recently, scientists decided to merge the order Cetacea and Artiodactyla into a single order called Cetartiodactyla based on new sequencing results.

              Explain the importance of classifying organisms correctly according to their clade.

              [1 mark]

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                Question 2d

                Marks: 1
                d)

                Based on the information provided in part a), deduce four other taxonomic groupings/levels of classification that would be similar for dolphins and whales.

                [1 mark]

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                  Question 3a

                  Marks: 2
                  a)

                  DNA hybridisation is a technique used to determine the genetic similarity between species. The double stranded DNA of two different species is mixed and then heated until the strands separate. This provides an opportunity for hybridisation between the different DNA strands to occur. The mixture is then cooled in order to allow new hybrid double stranded DNA molecules to form. The greater the degree of hybridisation, the more genetically similar the two species are.

                  Scientists investigated the genetic similarity between four species of bacteria (A to D) by allowing their DNA to hybridise with each other. The results of this investigation are shown in the table below.

                  5-2-hard-q3a

                  i)

                  Identify the species of bacteria that is most closely related to the other bacterial species.

                  [1 mark]

                  ii)

                  Explain your answer at part i).

                  [1 mark]

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                    Question 3b

                    Marks: 2
                    b)

                    Scientists concluded that species D was the first to branch off from the common ancestor that they all share.

                    Based on the information provided, comment on this conclusion.

                    [2 marks]

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                      Question 3c

                      Marks: 1
                      c)

                      The group of scientists also investigated the similarity of the protein molecules that make up peptidoglycan in the cell walls of the bacterial species. The amino acid sequence of species A was compared to those of species B to D.

                      The results are shown in the table below:

                      Bacterial species Percentage similarity
                      A 100
                      B 99.4
                      C 98.7
                      D 97.8

                      Based on the information provided and your knowledge of protein synthesis, explain the reason why the bacterial species show such a high level of similarity between the protein molecules, even though there are differences in their DNA.

                      [1 mark]

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                        Question 4a

                        Marks: 1
                        a)

                        The following diagram shows a cladogram that indicates the evolutionary relationship of plants. Note that different taxonomic groups are represented in the cladogram.w5KuTyjO_h-4a

                        Identify the plant phyla which are the most closely related.

                        [1 mark]

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                          Question 4b

                          Marks: 2
                          b)

                          Bryophyta are found in a variety of environments and are typically very small in size. Filicinophyta are able to grow to much larger sizes than Bryophyta.

                          Using your knowledge of plant phyla characteristics, explain the difference in size between Bryophyta and Filicinophyta.

                          [2 marks]

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                            Key Concepts
                            Plant Phyla Features

                            Question 4c

                            Marks: 2
                            c)

                            The common names of some plant genera and species were given in this cladogram.

                            Using the information given in part a), explain how using the common names could cause confusion when studying this cladogram.

                            [2 marks]

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                              Key Concepts
                              Binomial System

                              Question 4d

                              Marks: 1
                              d)

                              Gemniferous spikemoss, tooth-leaved clubmoss, spikemoss and the resurrection plant can all be considered members of the same clade.

                              Explain this statement.

                              [1 mark]

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                                Question 5a

                                Marks: 3

                                One mark is available for clarity of communication throughout this question.

                                a)

                                The binomial naming system is an important tool to facilitate cooperation and collaboration between groups of scientists.

                                Discuss how the binomial system will facilitate cooperation and collaboration between scientists.

                                [3 marks]

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                                  Key Concepts
                                  Binomial System

                                  Question 5b

                                  Marks: 5
                                  b)

                                  Compare and contrast the domain Eubacteria with the domain Eukaryotes.

                                  [5 marks]

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                                    Key Concepts
                                    Domains

                                    Question 5c

                                    Marks: 7
                                    c)

                                    Constructing the evolutionary relationship between organisms based on morphology alone will not always deliver accurate results.

                                    Outline the advancements that have been made in constructing cladograms in the field of cladistics.

                                    [7 marks]

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