5.4 Cladistics – Sciences for IGCSE & IB

1.The table shows the number of differences between humans and other selected organisms for the protein cytochrome c oxidase. This protein, consisting of 104 amino acids, is located in the mitochondria and functions as an enzyme during cell respiration.

If the data were used to draw a cladogram, which chordates would be furthest apart from humans?

Chimpanzee because it has zero differences
Fruit fly because it has the most differences
Tuna fish because it is the chordate with the most differences
Horse because it is in the same class

2. Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is based on DNA sequences and the cladogram on the right is based on comparing protein sequences.

What is the reason that cladograms based on DNA sequences are more reliable predictors of the phylogenetic relationship of species than cladograms based on protein sequences?

Amino acids are not as chemically stable as DNA nucleotides
DNA mutates but amino acids do not
Several different triplets of bases can code for the same amino acid
There are 20 different amino acids but only 4 nucleotides

3. The bacterium Neisseria gonorrhoeae causes infections related to the human reproductive system. The graph shows the percentage of samples in which this bacterium showed resistance to six antibiotics over a period of ten years.

What is a possible explanation for the total percentage resistance being larger than 100% in 2010?

People do not take the antibiotics as prescribed
More people have been sampled in that year
There was an epidemic of Neisseria gonorrhoeae in that year
Some bacteria are resistant to more than one antibiotic

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