Evolution__3rd_Edition

470 PART 4 / Evolution and Diversity
3 Under what conditions (of evolutionary rates) are
distance statistics reliable guides to phylogenetic
relations?
4 What would you look at in some superficially similar
structure, such as the tail of a dolphin and a salmon, to
decide whether it was homologous or homoplasious?
5 Here are the character states of species 1–6.
(a)
(b)
(c)
Species
Character state
Species
Character state
Species
Character state
1 2 3 4 5 6
A A' A A A A
1 2 3 4 5 6
A' A A A A' A
1 2 3 4 5 6
A A' A A' A A'
Which of A and A′ is ancestral, and which derived, in the
group of species 1 + 2? Assess the relative certainty of
the inference in the three cases.
6 Compare the attributes of molecular and
morphological evidence that make character analysis, or
statistical inference from unanalyzed characters, more or
less applicable to evidence of each kind.
7 What is meant by the problem of multiple hits?
8 The simplest model of sequence evolution assumes
that the chance that any nucleotide changes to any
other nucleotide is the same, p. Here is a simple
unrooted tree.
T
A
1 2
(a) What is the probability of the tree (in terms of p), if
both internal nodes (labeled 1 and 2) are G? (b) If the
nucleotide states of the internal nodes (labeled 1 and 2)
are unknown, how many possible nucleotide states at
the internal nodes need to be considered in calculating
the probability of the tree?
9 Here are the orders of genes (or some other markers)
along the chromosomes of three species: (1) adebcfg;
(2) abcdefg; and (3) abedcfg. What is the unrooted tree
of the three species?
G
G
..