Chapter 26 Biology Homework

If you were using cladistics to build a phylogenetic tree of cats, which of the following would be the best outgroup?

Wolf

The best classification system is that which most closely _____.

eflects evolutionary history

Animals that possess homologous structures probably _____.

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

The lakes of northern Minnesota are home to many similar species of damselflies of the genus Enallagma. These species have apparently undergone speciation from ancestral stock since the last glacial retreat about ten thousand years ago. Sequencing which of the following would probably be most useful in sorting out evolutionary relationships among these closely related species?

mitochondrial DNA

By definition a clade is _____.

monophyletic A clade is defined as a group that includes an ancestral species and all of its descendants.

Phylogenetic trees constructed from evidence from molecular systematics are based on similarities in _____.

mutations to homologous genes

Which of the following would, if it had acted upon a gene, prevent this gene from acting as a reliable molecular clock?

natural selection

Choosing the most parsimonious tree The geneticists studying the alien organisms have deciphered their genetic code. For familiarity, they have used A, C, G, and T to indicate the bases in this code. A comparable genetic sequence in each alien has been identified in the genes that code for eye growth. This genetic sequence has allowed the aliens to be divided into six groups, with the single-tail, three-eye group split in half. The geneticists also studied several outgroup species (not shown) to compile a likely ancestral DNA sequence. From this information, they have constructed four possible phylogenetic 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.

Linnaeus believed that species remained fixed in the form in which they had been created. Linnaeus would have been uncomfortable with _____.

phylogenies

Which of the following is (are) problematic when the goal is to construct phylogenies that accurately reflect evolutionary history?

polyphyletic taxa and paraphyletic taxa

The legless condition that is observed in several groups of extant reptiles is the result of _____.

several instances of the legless condition arising independently of each other

Fossil evidence indicates that some dinosaurs had feathers. If birds are indeed descended from dinosaurs, feathers are what kind of character?

shared ancestral character A shared ancestral character is one that originated in an ancestor of the taxon. In this case it appears that feathers originated in some dinosaur lineages and were passed down to birds.

Prokaryotic cells are found in the domain(s) _____.

Bacteria and Archaea Both of these domains are composed of prokaryotic cells.

Lizards and Snakes

Because lizards and snakes have the most ancient common ancestor with the rest of the organisms shown here, we would expect their DNA sequences to be most different.

Refer to the figure above. Which of the following forms a monophyletic group?

E, F, and G

A branch point represents a species that is the ancestor of all species that fall on lines to the right. So point #2 is the only branch point that includes those 3 groups of organisms but not lizards and snakes. Click here to review the figure.

2

The species that is a common ancestor to all species shown on the tree

Any point along a line in a phylogenetic tree represents a species that is ancestral to all species to the right of that point. Thus, the far left point on this figure represents a species that is an ancestor of every species shown on the tree.

Which of the following taxonomic categories contains all the others listed here?

Class Class includes all categories except phylum, kingdom, and domain.

Why do researchers use rRNA in investigations of relationships between taxa that diverged hundreds of millions of years ago?

DNA coding for rRNA changes relatively slowly.

A human is classified in domain _____ and kingdom _____.

Eukarya ... Animalia Humans are animals, and animals are eukaryotes.

A rose bush is classified in domain _____ and kingdom _____.

Eukarya ... Plantae Rose bushes are plants.

Which tree depicts the microsporidians as a sister group of the ascomycetes?

I

Which of the following would be useful in creating a phylogenetic tree of a taxon? I) morphological data from fossil species II) genetic sequences from living species III) behavioral data from living species

I, II, and III

Which tree depicts the closest relationship between zygomycetes and chytrids?

III

Which tree depicts the microsporidians as a sister group of the fungi, rather than as a fungus?

IV

Birds

In the bottom right, you can see that birds and Saurichian dinosaurs share the most recent common ancestor.

Which of these are homologous structures?

Ivy leaf and pine needle The leaves of all living plants evolved from leaves of early plants. There are many homologous plant structures. For instance, all plant leaves and modified leaves (such as thorns and tendrils) are homologous structures derived from the leaves of early plants. Read about homology.

In the five-kingdom system, prokaryotes are placed in the kingdom _____.

Monera All monerans are prokaryotes.

A large proportion of archaeans are extremophiles, so called because they inhabit extreme environments with high acidity, salinity, and/or temperature. Such environments are thought to have been much more common on the primitive Earth. Thus, modern extremophiles survive only in places that their ancestors became adapted to long ago. Which of the following is, consequently, a valid statement about modern extremophiles, assuming that their habitats have remained relatively unchanged?

On a phylogenetic tree whose branch lengths are proportional to the amount of genetic change, the branches of the extremophiles should be shorter than the non-extremophilic archaeans.

There is(are) _____ eukaryotic domain(s).

One The only eukaryotic domain is the domain Eukarya.

Part A - Reading a phylogenetic tree This is one possible phylogenetic tree representing the relationships between some members of phylum Arthropoda. Use this phylogenetic tree and your knowledge of cladistics to determine the relationships between these species. 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.

Phylogenetic trees show the evolutionary relationships between organisms. Closely related organisms have more 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.

Which eukaryotic kingdom includes members that are the result of endosymbioses that included an ancient aerobic bacterium and an ancient cyanobacterium?

Plantae

In the five-kingdom system, which kingdom consists primarily of unicellular eukaryotes?

Protista Protists are mostly unicellular eukaryotes, though they also include multicellular algae.

Answer: Lizards are more closely related to salamanders than to humans.

Question:

Which observation supports the position of eukaryotes at the convergence of the "ring of life"?

The nuclear genome of eukaryotes contains genes from archaeans and from bacteria.

Constructing a hypothetical phylogenetic tree based on morphology Imagine that you are studying alien life-forms discovered on a distant planet. While geneticists are working out the genetic code of these organisms, you are asked to construct a phylogenetic tree based on four morphological features, or characters: presence or absence of a spring tail, presence or absence of a grasping hand, presence or absence of a second tail, and number of eyes. The organisms have been divided into five groups based on these characters. If we assume the alien with a tail stalk is an outgroup, what is the most likely phylogenetic tree based on these shared derived characters? When did these characters appear during the aliens' evolutionary history? Drag the aliens and shared derived characters to their appropriate locations on this phylogenetic tree. Use only the blue labels for the blue targets and the white labels for the white targets

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.

In the two-kingdom system, why were fungi classified in the kingdom Plantae?

They are sedentary. This is why fungi were placed in the same kingdom as plants.

Time

Time is shown along the X axis of a phylogenetic tree, with the most ancient time on the left, and the present day on the right.

Given that phylogenies are based on shared derived characteristics, which of the following traits is useful in generating a phylogeny of species W, X, Y, and Z? Species W Species X Species Y Species Z Trait 1 A A A A Trait 2 A A B B Trait 3 A B C D

Trait 2

Three living species X, Y, and Z share a common ancestor T, as do extinct species U and V. A grouping that consists of species T, X, Y, and Z (but not U or V) makes up

a paraphyletic group.

In a comparison of birds and mammals, having four limbs is

a shared ancestral character.

Systematists have used a wide variety of traits to reconstruct the phylogenies of particular groups of organisms. Which one of the following traits produces a good estimate of phylogeny?

biochemical traits behavioral traits molecular traits gross morphological traits Most researchers today appreciate that both morphology and molecular biology are essential sources of data for phylogenetic study.

Eukaryotes that are not closely related and that do not share many anatomical similarities can still be placed together on the same phylogenetic tree by comparing their _____.

homologous genes that are highly conserved

The common ancestors of birds and mammals were very early (stem) reptiles, which almost certainly possessed three-chambered hearts (two atria, one ventricle). Birds and mammals, however, are alike in having four-chambered hearts (two atria, two ventricles). The four-chambered hearts of birds and mammals are best described as _____.

homoplasies

Molecular clocks are based on the idea that _____.

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.

Your professor wants you to construct a phylogenetic tree of orchids. She gives you tissue from seven orchid species and one lily. What is the most likely reason she gave you the lily?

to serve as an outgroup