Question 1

An assumption for the use of molecular clocks is that neutral mutations accumulate at a rapidly increasing rate over time between two species.

Accepted Answer

The assumption for the use of molecular clocks is that neutral mutations accumulate at a constant rate over time between two species, not at a rapidly increasing rate.

Question 2

How does the phenomenon of horizontal gene transfer muddle the concept of monophyletic groups?

Accepted Answer

Horizontal gene transfer introduces genes from sources other than the common ancestor, complicating the genetic lineage and making it difficult to define monophyletic groups based solely on descent from a common ancestor.

Question 3

Consider the following DNA sequences for four different species:
1: AATCG
2: TAATG
3: ATACC
4: ATAGG
Based on the principle of parsimony,which species shares a most recent common ancestor with a species having the sequence TTACC?

Accepted Answer

Species 3 shares the most similarities with TTACC as they only differ by one base pair, whereas species 1 and 4 differ by two base pairs and species 2 by three base pairs. Therefore, based on the principle of parsimony, it is more likely that species 3 and the unknown species share a more recent common ancestor.

Question 4

The figure shows a simplified phylogeny of closely related species of primates.This tree was proposed by comparing DNA sequence changes in the gene for cytochrome oxidase subunit II.The vertical scale represents time and the branch points represent common ancestors.What species did ancestor B give rise to?

Accepted Answer

Ancestor B gave rise to all of the species except siamangs. The siamangs branched off earlier, before the common ancestor of the rest of the species.

Question 5

A phylogenetic tree is a diagram that describes a phylogeny.A phylogeny is

Accepted Answer

A phylogeny is the evolutionary history of a species or group of species. A phylogenetic tree is a diagram that represents the relationships between these organisms based on their ancestry and evolutionary relationships.

Question 6

Consider the following cladogram and list of characteristics: 
$$\begin{array}{r}
\text { Moss Fern Conifer Flowering Plant }\
\begin{array} { l c c c c } 
\text { Chlorophylls } a \& b & \text { Yes } & \text { Yes } & \text { Yes } & \text { Yes } \
\text { Vascular tissue } & \text { No } & \text { Yes } & \text { Yes } & \text { Yes } \
\text { Seeds } & \text { No } & \text { No } & \text { Yes } & \text { Yes } \
\text { Flowers } & \text { No } & \text { No } & \text { No } & \text { Yes }
\end{array}
\end{array}$$
Based on what you know about the principle of parsimony,which of the following is most likely a shared derived character of conifers and flowering plants?

Accepted Answer

The principle of parsimony states that the hypothesis with the fewest assumptions should be selected. Therefore, the shared derived character that requires the fewest number of evolutionary changes is most likely to be correct. In this cladogram, seeds are found only in conifers and flowering plants, which suggests that the last common ancestor of these two groups had seeds. Therefore, seeds are the most likely shared derived character of conifers and flowering plants. Vascular tissue and chlorophylls a & b are shared by three or four groups, requiring more evolutionary changes, while flowers are a unique feature of flowering plants, making them less likely to be a shared derived character. Thus, the best choice is C, seeds.

Question 7

What kind of molecular information is commonly used to study phylogeny among species that diverged from a common ancestor relatively long ago?

Accepted Answer

The small ribosomal subunit (SSU) RNA is found in all living organisms and evolves relatively slowly, making it a useful molecular marker for studying phylogeny among species that diverged from a common ancestor relatively long ago. It is also conserved across taxa, meaning that it is unlikely to have undergone significant changes in function.

Question 8

The firefly (Photinus granulatus)and the zebra mussel (Dreissena polymorpha)are both members of the kingdom Animalia.This indicates that they must also both be members of the same

Accepted Answer

Both the firefly and the zebra mussel belong to the domain Eukarya, as all animals are eukaryotic organisms.

Question 9

If the genus Quercus (oaks)is monophyletic,then this means that all species of oaks

Accepted Answer

Monophyletic means that all species share a common ancestor. Therefore, if the genus Quercus is monophyletic, it means that all species of oaks have descended from a common ancestor.

Question 10

Molecular clocks are based primarily on rates of

Accepted Answer

Molecular clocks are primarily based on rates of neutral mutations, which are changes in DNA sequence that do not affect the function of the protein encoded by that gene. These mutations can accumulate over time and can serve as a measure of the time since the organisms being compared last shared a common ancestor.

Question 11

Members of the plant family Cactaceae (cacti)are native to the Americas and thrive in dry environments.They have a number of specialized adaptations,including reduced leaves,succulent (fleshy)stems for water storage,and spines for defense against herbivores.Some members of the family Euphorbiaceae are native to Africa and resemble cacti,having similarly reduced leaves,succulent stems,and thorns.However,their common ancestor likely did not have these traits.Based on this information,what can you say about the morphological traits of Cactaceae and Euphorbiaceae indicated above?

Accepted Answer

The traits of reduced leaves, succulent stems, and spines/thorns are not shared primitive traits because their common ancestor likely did not possess these specific traits. They are also not homologous traits because they evolved independently in each family due to similar environmental pressures. Therefore, they are analogous traits, meaning they evolved independently but share a similar function.

Question 12

Horizontal gene transfer is the transfer of genes between

Accepted Answer

Horizontal gene transfer occurs between different species, both prokaryotic and eukaryotic, through mechanisms such as transformation, transduction, and conjugation. It can also occur between different domains of life, such as between bacteria and archaea.

Question 13

Horizontal gene transfer is less prevalent in eukaryotic species because

Accepted Answer

Multicellularity and sexual reproduction provide barriers that limit the transfer of genetic material between individuals, unlike in prokaryotic species where horizontal gene transfer is more prevalent. Organelles do not play a significant role in limiting horizontal gene transfer between individuals.

Question 14

When comparing the sequences of a homologous gene in four different species,one pair of species shows a 1% difference,whereas the other pair shows a 3% difference.Which pair diverged longer ago from their common ancestor and why?

Accepted Answer

A larger difference (3% instead of 1%) indicates that there has been more time to accumulate mutations, implying that the pair with a 3% difference diverged longer ago from their common ancestor.

Question 15

Consider the following cladogram and list of characteristics:

$\begin{array}{r}
\text { Moss Fern Conifer Flowering Plant }\
\begin{array}{lccc}
\text { Chlorophylls } a \& b & \text { Yes } & \text { Yes Yes } & \text { Yes } \
\text { Vascular tissue } & \text { No } & \text { Yes Yes } & \text { Yes } \
\text { Seeds } & \text { No } & \text { No Yes } & \text { Yes } \
\text { Flowers } & \text { No } & \text { No No } & \text { Yes }
\end{array}\end{array}$
Based on what you know about the principle of parsimony,which of the following is most likely a shared primitive character of mosses,ferns,conifers,and flowering plants?

Accepted Answer

The answer of Consider the following cladogram and list of...

Question 16

Molecular clocks are usually calibrated based on

Accepted Answer

Molecular clocks are calibrated based on the date when two species diverged from a common ancestor. This allows for estimation of the time elapsed since the divergence of the two species based on the accumulation of mutations in their genomes over time.

Question 17

A modern goal of systematics is to classify organisms based on similarity of form and function,regardless of their evolutionary relationships.

Accepted Answer

A modern goal of systematics is to classify organisms based on their evolutionary relationships and phylogenetic history, using various types of data such as morphology, genetics, and behavior. Form and function may still be considered, but they are not the sole basis for classification.

Question 18

The mitochondrial genome would be most useful for studying evolutionary relationships among which group of organisms?

Accepted Answer

The mitochondrial genome is inherited maternally and has a high mutation rate, which makes it very useful for studying closely related organisms. Therefore, it would be most useful for studying evolutionary relationships among whales (members of the order Cetacea) which are closely related to each other.

Quiz 21: Taxonomy and Systematics