Cladistics NES 11

What does the length of the branch in a phylogenetic tree represent?

• Evolutionary time between two nodes

• Complexity

• More evolved organisms

• Analogous structures

The diagram represents a cladogram of the family Procyonidae. What would justify classifying these organisms into four different genera?

• They live in different habitats.

• They do not share any common ancestors.

• There are enough differences between them.

• The number of times that the species have split.

Molecular evidence is often used to construct a cladogram. Describe one type of molecular-based evidence to identify members of a clade

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.

• There are 20 different amino acids but only 4 nucleotides.

• Several different triplets of bases can code for the same amino acid.

Discuss the use of cladograms in phylogenetic studies.