Unity and Diversity A.7 Classification and Cladistics (id: c0438e3c5)

本题目来源于试卷: Unity and Diversity A.7 Classification and Cladistics，类别为 IB生物学

[单选题]
Early cladograms were constructed by comparing structures of ort8t* 6 vok. -tmbp (*ozodk52cag fb3lganismszr2 d3y0xsis:y vg)t+ . The cladogram on the left is based on structure and the cd 0zr 32v+yxiss)yg:tladogram on the right is based on comparing the DNA sequence of a particular gene.


What is the reason that the cladogram based on the DNA sequences is a more reliable representation of the sequence of divergence among clades than the cladogram based on structures?

A. Structures are not inherited when species diverge.
B. DNA does not change over time while structures can change over time.
C. Similar structures can be coded for by different genes in genetically distant organisms.
D. There are many different structures that are coded for by the same DNA sequence.


参考答案:  C


本题详细解析:
Morphological traits, or structures, are useful for creating cladar wpo j/h:7zdq y8l q v/bs30smbwt9b0426czograms. However, cladograms created by comparing such traits may be inaccurate because distantly related organisms can have structures that appear similar but have different genetic bases. The appearance of similar structures with a different evolutionary basis is not evidence of relatedness, but rather is evidence of convergent evolution. So, one reason the cladogram based on the DNA sequences is more reliable than the cladogram based on structures is 7dz/a2c8z6qt vy 9 /:ljmpq30b swohr wb s4b0that similar structures can be coded for by different genes in genetically distant organisms.

Choice A is incorrect because structures are inherited when species diverge, and the inheritance of structures is beneficial for constructing cladograms. This is because shared structures are sometimes, but not always, evidence of genetic relatedness.

Choice B is incorrect because DNA does change over time. Scientists look at sequences of changes in DNA to determine evolutionary relatedness.

Choice D is incorrect because different structures are generally coded for by different DNA sequences.

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