Biology Chapter 26 Homework

The horizontal line indicating a branch on a phylogenetic tree represents ancestral forms of the named taxon, thereby illustrating the ______ leading to that taxon.

evolutionary lineage

Which species is the basal taxon in this tree?

giant panda

Branch point 2 is the common ancestor shared uniquely by Taxa A, B, and C.

False

Fishes and chimps have no common ancestors.

False

Rotating the tree at branch point 2 would change the relationship between Taxa D and A.

False

The taxon that shares the most recent common ancestor with frogs is fishes.

False

Why do researchers use rRNA in investigations of relationships between taxa that diverged hundreds of millions of years ago? See Concept 26.4 (Page 564)

DNA coding for rRNA changes relatively slowly. Submit

Rank the species from most closely related to horseflies to most distantly related to horseflies. If two species are equally close in their relatedness to horseflies, overlap them.

Most CLOSELY related to horseflies 1: flea 2: katydid, human body louse 3: dragonfly, mayfly 4: silverfish Most DISTANTLY related to horseflies Phylogenetic trees show the evolutionary relationships between organisms. Closely related organisms share more recent common ancestors than distantly related organisms. In this case, fleas are more closely related to horseflies than are any other species on the tree, even though some of the other species look more like horseflies than fleas do.

Branch point 1 represents the common ancestor of Taxa A-F.

True

Frogs and humans are more distantly related than are lizards and humans.

True

In this tree, lizards are the sister taxon of the lineage that includes humans and chimps.

True; Although phylogenetic trees may be drawn in many forms (horizontal, vertical, diagonal), the information conveyed remains the same. Each branch point represents a common ancestor shared by the taxa appearing at the branch tips. The earliest branch point in the tree (shown at the far left of a horizontal tree) represents a common ancestor of all organisms shown in the tree. Sister taxa are groups of organisms that share a common ancestor that is not shared with any other group in the tree.

Taxa D and E arose from a common ancestor and are sister taxa.

True; Branch point 1 shows the divergence in the ancestral lineage that led to all taxa shown. Sister taxa are groups of organisms that share a common ancestor that is not shared by any other group. Rotating the branches of the tree around a branch point does not change the evolutionary relationships. In other words, the order of the taxa at the branch tips does not indicate evolution in a particular direction or toward a specific goal.

Identify the sister taxon to the polar bear.

brown bear

Turtles are not shown on this tree. Turtles are evolutionarily more closely related to lizards than they are to frogs. Select the phylogenetic tree that best represents the position of turtles relative to the other taxa shown.

https://media.cheggcdn.com/coop/7ca/7ca4bca1-5c9e-4d3f-814f-fc3612161ce7/1591340872148_turtlemonophylaticgroup.png Showing turtles and lizards as sister taxa indicates that turtles are more closely related to lizards than they are to frogs. Notice that turtles and lizards share a more recent common ancestor than do turtles and frogs.

Molecular clocks are based on the idea that _____. See Concept 26.5 (Page 564)

on average neutral mutations arise at a constant rate; The idea of a molecular clock rests on the assumption that neutral mutations can arise and become fixed in populations. The rate of occurrence of these mutations is not affected by natural selection, so it is assumed that the rate is relatively constant over time.

Which branch point represents the most recent common ancestor of all bears?

Branch point 1

Which branch point represents the most recent common ancestor of the sloth bear and the spectacled bear?

Branch point 2

Which branch point represents the most recent common ancestor of the Asian black bear and the brown bear?

Branch point 4

Suppose that a phylogenetic tree were constructed using the data shown in this table. Mosses represent the outgroup.

Cherries and peas are each other's closest relatives; Cherries and peas both have flowers and fruits. In fact, they share all the characters listed in the table. That is, they both have vascular systems, seeds, and flowers and fruits, and they both lack cones.

Based on the character table in Part B, which of the following statements about shared derived characters in plants is correct?

Seeds are a shared derived character of pines, cherries, and peas; Seeds are a derived character of pines, cherries, and peas. We can also see that: the vascular system is a derived character of ferns, pines, cherries, and peas; flowers and fruits are a derived character of cherries and peas; and cones are a derived character of pines.

_____________ are groups of organisms that share a unique common ancestor not shared by any other groups.

Sister taxa; Phylogenetic trees graphically represent a hypothesis of how groups of organisms are related. The tree indicates the evolutionary history that gave rise to all of the taxa included in the tree.

Based on this tree, select the correct statement.

Taxon A is the sister taxon of the lineage that includes Taxa B and C.

The tree includes the most recent common ancestor of all living species of bears (branch point 1). What does this tell you about this phylogenetic tree?

The Phylogenetic group is rooted; In a rooted phylogenetic tree, the branch point drawn farthest to the left represents the most recent common ancestor of all taxa in the tree.

Which observation supports the position of eukaryotes at the convergence of the "ring of life"? See Concept 26.6 (Page 566)

The nuclear genome of eukaryotes contains genes from archaeans and from bacteria; A leading hypothesis proposes that eukaryotes are the result of fusion involving a bacterium and an archaean, thereby explaining the presence of both kinds of genes.

According to this tree, is the sun bear more closely related to the sloth bear or the polar bear?

The polar bear

Drag the aliens and shared derived characters to their appropriate locations on this phylogenetic tree.

The presence or absence of characters can be used to build a phylogenetic tree based on morphology. In this example, all aliens other than the outgroup have a spring tail, all but two of the groups have a fourth eye, two of the aliens have two tails, and one of the aliens has a grasping hand. These characters can be used to create a hypothesis about the evolutionary relationships between these organisms.

Based on the revised branch of the tree, what kind of group do brown bears plus ancestral species 7 represent?

a paraphyletic group; The mainland brown bears and the ABC brown bears both share common ancestor 7. But the polar bears also descended from ancestral species 7. Because not all descendants of ancestral species 7 are included in the brown bear group, that group is considered paraphyletic.

The point at which two or more lineages diverge from their common ancestor is called a(n) ________ or node.

branch point

Animals that possess homologous structures probably _____. See Concept 26.2 (Page 556)

evolved from the same ancestor; Homologous structures are similar because of common ancestry.

Select the most parsimonious tree. If there is a tie, select both trees.

phylogenetic tree III; Tree III requires the fewest base-change events, so it is the most parsimonious phylogenetic tree. Based on this genetic evidence, we can hypothesize that group 2b diverged from group 2a at the same time that groups 3, 4, and 5 diverged from group 2a. Either the addition of a fourth eye came after this divergence, or group 2b lost its fourth eye sometime in this group's evolutionary history.

Which of the following groups of species is a monophyletic group, or clade?

sun bear, Asian black bear, American black bear, ancestral species 5, ancestral species 6; This is a monophyletic group, or clade, because it includes ancestral species 5, the common ancestor of all taxa in the clade, and all of its descendents.

Each branch tip on a phylogenetic tree represents a specific group of organisms known as a(n)

taxon

Look at this character table. Rattlesnakes (like turtles) are reptiles, yet they do not have four limbs. In fact, they have no apparent limbs.

The presence or absence of four limbs, on its own, could be misleading when considering the evolutionary relationships of rattlesnakes; The loss of limbs in snakes is an example of a situation where, over the course of evolution, a subgroup of a lineage loses a character that is typically found in other members of that lineage. Snakes evolved from a reptilian ancestor that had four limbs, but over time, these limbs became highly reduced or lost in the snake lineage. The "four limbs" character could be misleading because, on its own, it might suggest a relationship between rattlesnakes and other species that do not have four limbs, such as the lamprey and bass. However, many other traits of rattlesnakes (such as the amnion) show their kinship with other reptiles.

A study published in 2000 sequenced part of the mitochondrial cytochrome b gene from 61 brown bears from two sites in Alaska. One population of brown bears lives on the coastal mainland of Alaska, while a separate population lives on the ABC islands in southeastern Alaska. Mainland and ABC brown bears differ by 11 fixed nucleotide substitutions in the cytochrome b gene. This suggests that the two brown bear populations represent genetically unique clades. The researchers compared the cytochrome b sequences of the two clades of Alaskan brown bears to those of 55 polar bears. The analysis showed that polar bears and ABC brown bears differ at only three nucleotides in this gene, whereas polar bears and mainland brown bears had more differences. Based on the results of the 2000 study, how should the portion of the tree extending from branch point 7 be altered?

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