Question 1

Figure 20.2
-Together, the lesser apes and great apes shared a common ancestor most recently with other members of their

Accepted Answer

Both lesser apes and great apes belong to the order Primates, and they share a more recent common ancestor with other members of this order compared to the broader taxonomic categories like class or subclass.

Question 2

Figure 20.1
-Which extinct species should be the best candidate to serve as the outgroup for the clade whose common ancestor occurs at position 2 in Figure 20.1?

Accepted Answer

The outgroup should be the most distantly related species to the clade, so it should be the species that is not closely related to any of the species in the clade. In this case, species A is the most distantly related species to the clade, so it is the best candidate to serve as the outgroup.

Question 3

According to the principle of maximum parsimony,

Accepted Answer

The principle of maximum parsimony states that the preferred tree is the one that requires the fewest evolutionary changes, so option B is correct. Option A is incorrect as phylogenies based on DNA may require only a few base changes if the organisms being compared are closely related. Option C is incorrect as a parsimonious tree for morphology-based phylogenies would require the fewest changes, not the most. Option D is also incorrect as examining a large number of trees does not relate to the principle of maximum parsimony.

Question 4

You discover a fossil with feathers on forelimbs, short hind limbs, and teeth. You conclude that this organism appears early on a phylogenetic tree for which group of organisms?

Accepted Answer

The presence of feathers suggests that this organism is a bird or bird ancestor. The short hind limbs suggest it may not be a modern bird, but rather an earlier ancestor. The presence of teeth also indicate it is not a modern bird, as birds today have beaks instead of teeth.

Question 5

What evidence allowed biologists to conclude that classification of the tree of life required a three-domain system?

Accepted Answer

The phylogenetic tree of the three domains of life is based on sequence data for rRNA and other genes, which provided strong evidence for the need of a three-domain system. Other options are incorrect because they only provide partial information or are not directly related to the evidence for a three-domain system.

Question 6

Figure 20.2
-From Figure 20.2, which other event occurred closest in time to the divergence of gorillas from the lineage that led to humans and chimpanzees?

Accepted Answer

The answer of  Figure 20.2
-From Figure 20.2, which other...

Question 7

A phylogenetic tree shows that birds and crocodiles share many features. A hypothesis based on this tree predicts that these features are present in a common ancestor. Which of these predicted traits is supported by fossil evidence?

Accepted Answer

Fossil evidence shows that both birds and crocodiles laid eggs and built nests, supporting the hypothesis that these features were present in a common ancestor. The other choices (four-chambered heart, singing for territory, singing to attract mates) cannot be directly supported or refuted by fossil evidence.

Question 8

What kind of evidence has recently made it necessary to assign the prokaryotes to either of two different domains, rather than assigning all prokaryotes to the same kingdom?

Accepted Answer

Recent advances in molecular biology, such as ribosomal RNA sequencing, have revealed significant genetic differences between prokaryotes, leading to the need to divide them into two different domains (Bacteria and Archaea) instead of one kingdom.

Question 9

How does a molecular clock measure time?

Accepted Answer

A molecular clock measures time by counting the number of nucleotide substitutions over a fixed period of time. This is based on the assumption that mutations accumulate at a steady rate in the DNA sequence of the gene or region being studied. By comparing the number of differences in the DNA sequence between two species, and knowing the rate of mutation, scientists can estimate the time since the two species diverged from a common ancestor.

Question 10

Which kind of DNA should provide the best molecular clock for determining the evolutionary relatedness of several species whose common ancestor became extinct billions of years ago?

Accepted Answer

DNA coding for ribosomal RNA is highly conserved across different species due to its essential role in protein synthesis. This conservation makes it an excellent molecular clock for studying evolutionary relationships over long periods.

Question 11

The kingdom Protista is obsolete because it contains members of how many other kingdoms?

Accepted Answer

The kingdom Protista is obsolete because it contains members of three other kingdoms: Animalia (e.g. protozoans), Plantae (e.g. algae), and Fungi (e.g. slime molds). Therefore, it is no longer considered a distinct kingdom.

Question 12

Which of these would, if it (they) had acted upon a gene, prevent this gene from acting as a reliable molecular clock?

Accepted Answer

Natural selection can prevent a gene from acting as a reliable molecular clock because it can cause certain mutations to be favored or disfavored, leading to non-constant rates of genetic change over time.

Question 13

When it acts upon a gene, which of the following processes consequently makes that gene an accurate molecular clock?

Accepted Answer

Mutation can accumulate over time in a gene, leading to changes in the sequence. These changes can be used to estimate the divergence time between species, making the gene an accurate molecular clock. Transcription, proofreading, and reverse transcription do not directly affect the sequence of the gene, and directional natural selection can actually cause changes in the gene that disrupt its clock-like properties.

Question 14

Figure 20.2
-Assuming chimpanzees and gorillas are humans' closest relatives, removing humans from the great ape clade and placing them in a different clade has the effect of making the phylogenetic tree of the great apes

Accepted Answer

Placing humans in a separate clade makes the great ape clade paraphyletic, as it excludes one group (humans) that should be included based on evolutionary relationships.

Question 15

Figure 20.1
-If Figure 20.1 is an accurate depiction of relatedness, then which of the following should be correct?
1) The entire tree is based on maximum parsimony.
2) If all species depicted here make up a taxon, this taxon is monophyletic.
3) The last common ancestor of species B and C occurred more recently than the last common ancestor of species D and E.
4) Species A is the direct ancestor of both species B and species C.
5) The species present at position 3 is ancestral to C, D, and E.

Accepted Answer

The entire tree is based on maximum parsimony, a method that infers phylogenetic trees by minimizing the total number of evolutionary changes. If all species depicted make up a taxon, it is monophyletic, meaning it includes an ancestor and all its descendants. The last common ancestor of species B and C occurring more recently than that of species D and E is consistent with typical phylogenetic tree interpretations.

Question 16

The most important feature that permits a gene to act as a molecular clock is

Accepted Answer

A reliable average rate of mutation allows a gene to accumulate changes over time, which can be used to estimate the time since divergence of different species.

Question 17

A phylogenetic tree constructed using sequence differences in mitochondrial DNA would be most valid for discerning the evolutionary relatedness of

Accepted Answer

Mitochondrial DNA is maternally inherited and evolutionarily conserved, making it a useful tool for discerning the evolutionary relatedness of closely related species such as chimpanzees and humans. However, for distantly related species such as archaeans and bacteria or sharks and dolphins, other methods such as comparison of ribosomal RNA sequences or morphological similarities may be more effective. Fungi and animals may have diverged too far back in evolutionary history for mitochondrial DNA to provide sufficient resolution in discerning their relatedness.

Question 18

Which kingdom has been replaced with two domains?

Accepted Answer

Monera, which included prokaryotic organisms, has been replaced by two domains: Archaea and Bacteria, reflecting a more accurate understanding of life's diversity.

Question 19

Neutral theory proposes that

Accepted Answer

Neutral theory proposes that a significant proportion of mutations are not acted upon by natural selection and are instead subject to random genetic drift. This means that many mutations that do not affect an organism's survival or reproduction can still become fixed in a population purely by chance. This idea challenges the traditional notion that natural selection is the sole driving force of evolution.

Question 20

Figure 20.2
- Figure 20.3
In Figure 20.3, phylogeny branch lengths represent genetic changes. Which organism on the tree has undergone the most genetic changes since divergence from common ancestor?

Accepted Answer

The answer of  Figure 20.2
- Figure 20.3
In Figure 20.3,...

Quiz 20: Phylogeny

Figure 20.2 -Together, the lesser apes and great apes shared a common ancestor most recently with other members of their

Figure 20.1 -Which extinct species should be the best candidate to serve as the outgroup for the clade whose common ancestor occurs at position 2 in Figure 20.1?