chapter 20

ancestral lineage splits

(at the branch point) into two branches, one for each of the two-descendant lineage

By applying a molecular clock, researchers have proposed that the first HIV-1 M invasion into humans occurred in the __________. (Section 20.4) 1830s 1890s 1930s 1950s 1980s

1930s This is the point in time when some scientists estimate that HIV jumped from simians to humans.

What does a branch point in a phylogenetic tree represent? (Section 20.1) A branch point represents a gene duplication event. A branch point represents a point at which two evolutionary lineages split from a common ancestor. A branch point represents a place where one species branches off from another. A branch point represents a split between two phyla. A branch point represents the absolute time at which two evolutionary lineages split from a common ancestor.

A branch point represents a point at which two evolutionary lineages split from a common ancestor. right answer feedback: A branch point shows evolutionary relationships as a dichotomy.

Clade

A group of species that includes an ancestral species and all its descendants.

CLADE

A monophyletic taxon is equivalent to a

Binomial

A polynomial with two terms

maximum parsimony

A principle that states that when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts.

A taxon __________. (Section 20.1) of one type of organism at one level is comparable to another type of organism at the same level is a formal grouping in any level from phylum to species is a clade is a formal grouping at any given level is a species

A taxon is a formal grouping of organisms at any given level, such as species, genus, or phylum.

1. Prokaryotic cells are found in the domain(s) ________. Question 6 options: Bacteria and Archaea Protista and Archaea Bacteria Bacteria and Protista Bacteria and Eukarya

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

The three domains are

Archaea, Bacteria, and Eukarya

composed entirely of single-celled prokaryotes

Bacteria and Archaea

the three-domain system are

Bacteria, Archaea, and Eukarya

Which of the following are the best examples of homologous structures? Question 9 options: Owl wing and hornet wing Eyelessness in the Australian mole and eyelessness in the North American mole Bones in the bat wing and bones in the human forelimb Bat wing and bird wing

Bones in the bat wing and bones in the human forelimb

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? Question 2 options: Singing to attract mates Singing for territory Eggs and nests Four-chambered heart

Eggs and nests

Universal phylogenetic trees built from different genes sometimes give inconsistent results. What assumption, on which phylogenetic trees are based, has probably been violated during the history of life, causing this confusion? (Section 20.5) Homologous traits come about because of common ancestry. Genes are often passed from one organism to another without the occurrence of reproduction. Genes are passed vertically from one generation to the next. The greater the difference in gene sequences, the longer two species have diverged. Analogous traits come about because of convergent evolution.

Genes are passed vertically from one generation to the next. Phylogenetic trees assume vertical gene transfer, but many organisms also use horizontal gene transfer. Many scientists postulate that horizontal gene transfer was far more prevalent during the early history of life.

sister taxa

Groups of organisms that share an immediate common ancestor and hence are each other's closest relatives. Not shared by any other group

The idea of using molecules as clocks to time evolutionary events is very attractive, but there are many problems in applying the technique. What is the best way to get reliable results? (Section 20.4) It is important to use one gene in which the changes are clearly neutral. It is important to use a gene that has been affected by natural selection to ensure that evolution will be observed. It is best to use a gene that is essential to survival because they change more slowly. It is important to use as many genes as possible. With this approach, fluctuations in evolutionary rate will tend to average out. All of the choices are correct.

It is important to use as many genes as possible. With this approach, fluctuations in evolutionary rate will tend to average out. It is almost impossible to find a gene that has been unaffected by natural selection during its entire existence. Using many genes has been shown to give dates that match the fossil record fairly closely.

To which domain is the domain Eukarya most closely related? (Section 20.5) Archaea Bacteria Protista It is not clear whether eukaryotes are more closely related to bacteria or archaea. Fungi

It is not clear whether eukaryotes are more closely related to bacteria or archaea. right answer feedback: Studies of rRNA genes indicate that eukaryotes and archaea are more closely related, but genes that influence metabolism indicate a closer relationship between eukaryotes and bacteria. Horizontal gene transfer has likely been at work here.

five kingdoms were recognized: as

Monera (prokaryotes), Protista, Plantae, Fungi, and Animalia

Which is the correct taxonomic name for the leopard? (Section 20.1) Panthera pardus panthera pardus Panthera Pardus Panthera pardus Panthera Pardus

Panthera pardus

monophyletic

Pertaining to a taxon derived from a single ancestral species that gave rise to no species in any other taxa.

Rabbits and guinea pigs both belong to Class Mammalia. This means they must also both belong to __________. (Section 20.1) Phylum Chordata Family Caviidae Genus Cavia Order Rodentia All of the choices are correct.

Phylum Chordata Class is less inclusive than phylum; organisms that are in the same class are also in the same phylum.

three lineages in the domain Eukarya are dominated by multicellular organisms:

Plantae, Fungi, and Animalia

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments

What is true of parsimonious trees? (Section 20.3) Trees can be constructed that are parsimonious or the most likely, but not both at the same time. The best tree requires the fewest evolutionary events to have occurred in the form of shared ancestral characters. Given the rules of how DNA changes over time, a tree can be found that reflects the most likely sequence of evolutionary events. Given the rules of how morphological traits change over time, a tree can be found that reflects the most likely sequence of evolutionary events. The best tree requires the fewest evolutionary events to have occurred in the form of shared derived characters.

The best tree requires the fewest evolutionary events to have occurred in the form of shared derived characters. This statement is true regarding trees based on morphological characters. For phylograms based on DNA, the most parsimonious tree requires the smallest number of base changes in DNA

Birds and mammals have a four-chambered heart, but most reptiles have a three-chambered heart. How does this fact affect the construction of phylogenetic trees for these groups? (Section 20.3) It shows that the common ancestor of birds and mammals must have had a four- chambered heart. This represents a problem with the principle of parsimony, rather than a problem with the analogy-homology issue. The most likely tree is always the most parsimonious. The most likely tree is not always the most parsimonious.

The most likely tree is not always the most parsimonious. Evidence shows that birds diverged from reptiles before mammals did; therefore, there is no common ancestor of birds and mammals that had a four-chambered heart. This character must have evolved twice.

What is true about an outgroup? (Section 20.3) The outgroup would be found at one of the highest branches of a phylogenetic tree. The outgroup and ingroup display a mixture of shared and derived characters. Outgroup comparison is based on the assumption that homologies present in both the outgroup and ingroup must be derived characters. The outgroup should be less closely related to any members of the ingroup than those members are to each other. None of the choices is correct.

The outgroup should be less closely related to any members of the ingroup than those members are to each other. The outgroup should be known to be less closely related than any ingroup members are to each other based on other evidence such as paleontology, embryonic development, and gene sequences.

5. What is one common mistake taxonomists may make when attempting to place seemingly closely related species into a shared classification group? Question 4 options: The two species share many structural proteins, genes, and metabolic pathways. The two species seem to be located in the same region on the planet. The two species share an evolutionary history based upon matching DNA. The two species share similar morphology or character traits.

The two species share similar morphology or character traits.

• Kingdom

a taxonomic category, the second broadest after domain

amnion

a thin membrane forming a closed sac about the embryos or fetuses of reptiles, birds, and mammals and containing the amniotic fluid

The wings of a hummingbird and a bee are __________. (Section 20.2) analogous taxonomic binomial phylogenetic homologous

analogous Structures that are similar as a result of convergent evolution are referred to as analogous structures.

Which would be the least useful in determining the relationships among various species? (Section 20.2) analogous structures amino acid sequences of proteins a comparison of DNA base sequences homologous structures fossils

analogous structures right answer feedback: Analogous structures are the result of convergent evolution and may not reflect the relationships among the species that share them.

similarity due to convergent evolution

analogy

A lineage that diverges from all members of its group early in the group's history is called a

basal taxon

Cladistics

classifies organisms by common descent

Which method for establishing phylogenetic relationships among organisms has been developed most recently? (Section 20.2) comparing morphology (shape and structure) comparing embryonic development comparing the component sequences of proteins and nucleic acids comparing physiology (the functioning of structures and systems) comparing behavioral patterns

comparing the component sequences of proteins and nucleic acids The comparison of nucleic acids and proteins has become a powerful addition to the other comparative methods that systematists use to measure evolutionary relationships among species.

paraphyletic group

composed of some but not all members descending from a common ancestor

A potential source of confusion in constructing a phylogeny tree is similarity between organisms that is due to Question 3 options: homology shared ancestry adaptation. convergent evolution

convergent evolution

lineage

direct descent from an ancestor; derivation. a sequence of species each of which is considered to have evolved from its predecessor.

Each branch point represents

divergence of two species divergence of two evolutionary lineages from a common ancestor

basal taxon

diverges early in the history of a group and originates near the common ancestor of the group

3. In addition to naming species, Linnaeus also grouped species into a hierarchy of increasingly inclusive categories. The largest category that would include closely related species is the Question 1 options: genus. class. domain order.

domain

The two-part format of the scientific name, referred to as binomial, ensures that ______

each species is assigned a unique name systematists can easily specify the closest relatives of any species each species has a name that is understandable regardless of language barriers among scientists

A phylogenetic tree of bird families constructed by cladistic analysis would be a hypothesis about what? (Section 20.3) analogous structures shared by various species relative ages of living species of birds families that look most alike characteristics shared by all bird families evolutionary relationships among bird families

evolutionary relationships among bird families Phylogenetic trees are constructed to reflect the evolutionary relationships among organisms.

. Animals that possess homologous structures probably __________. Question 8 options: evolved from the same ancestor are not related are the result of convergent evolution are the result of similar environmental pressures in different evolutionary lineages have increased genetic diversity

evolved from the same ancestor

What process actually increases the number of genes in an organism's genome? Question 5 options: parsimony cladistics independent assortment gene duplication mutation

gene duplication Mutations that lead to duplications actually increase the number of genes in a genome. When an organism has two copies of a gene, one can perform its function while the other is free to accumulate mutations to the point that it may take on a new and advantageous function.

Each __________ is assigned a two-part Latin name, or binomial. The first word is the ______ , and the second word is the _______. Species that are very similar are grouped into the same genus.

genus and species

The binomial system assigns to each organism a unique name that describes its

genus and species

monophyletic group

group that consists of a single ancestral species and all its descendants and excludes any organisms that are not descended from that common ancestor

Phenotypic and genetic similarities due to shared ancestry are called

homologies

similarity due to shared ancestry

homology

rooted tree

includes a branch to represent the last common ancestor of all taxa in the tree

Clasistics

method where organisms are grouped together based only on traits that are shared due to common descent, derived relative to an out group

A taxon is equivalent to a clade only if it is

monophyletic

10. By definition a clade is _________ Question 7 options: parsimonious monophyletic analogous paraphyletic polyphyletic

monophyletic; defined as a group that includes an ancestral species and all of its descendants

Paraphyletic

pertaining to a group of taxa that consists of a common ancestor and some, but not all, of its descendants

polyphyletic

pertaining to a group of taxa that includes distantly related organisms but does not include their most recent common ancestor

8. Some molecular data place the giant panda in the bear family (Ursidae) but place the lesser panda in the raccoon family (Procyonidae). Consequently, the morphological similarities of these two species are probably due to Question 10 options: inheritance of acquired characteristics. possession of analogous structures. sexual selection. inheritance of shared derived characters

possession of analogous structures.

The tree of life is based on slowly evolving ___________genes that code the ___________components of___________________

rRNA ------RNA------ribosomes

Unlike a regular phylogenetic tree, phylogenetic trees with branch lengths proportional to time can be used to __________. (Section 20.3) tie polyphyletic clades to a common ancestor represent the chronological time that has passed since two groups diverged from a common ancestor hypothesize the relative relatedness between different taxa reflect the rate of evolutionary change reflect the number of evolutionary changes that have taken place in a lineage

represent the chronological time that has passed since two groups diverged from a common ancestor In this type of tree, called an ultrametric tree, the branching pattern is the same as in a normal phylogenetic tree, but all the branches that can be traced from the common ancestor to the present are of equal length.

phylogenic trees show

represents a hypothesis about evolutionary relationships

Consider three different species: A, B, & C. Species A and B are in the same phylum. Species A and C are in the same order. From this information you can conclude that __________. (Section 20.1) all three species are not members of the same phylum species B and species C share a less recent ancestor than do species A and B species A and species B are in the same family species C could be in the same class as species A and B all three species are members of the same genus

species C could be in the same class as species A and B If species A and species C are in the same order, then they must also be in the same class. Because you know that species A and species B are in the same phylum, it is possible that they are in the same class, but different orders.

systematics

study morphological and behavioral resemblances as well as molecular similarities and differences to devise theories about relationships.

Question 1: A discipline that is focused on classifying organisms and determining their evolutionary relationships is

systematics

What is the focus of the branch of biology called taxonomy?

the classification of life-forms by their similarities and differences

taxonomy

the classification of life-forms by their similarities and differences

Using cladistic analysis, a taxonomist wishes to construct a phylogenetic tree showing the relationships among various species of mammals. Which would be least useful for this purpose? (Section 20.3) the fact that teeth vary among types of mammals descriptions of various types of limbs (wings, legs, flippers, etc.) DNA base sequences the fact that all mammals have hair data about skull bones

the fact that all mammals have hair As a shared derived character, hair cannot be used to determine the phylogeny of mammals.

branch point

the representation on a phylogenetic tree of the divergence of two or more taxa from a common ancestor

Phylogenetic bracketing allows us to

used to predict features of ancestors and their extinct descendants based on the features of closely related living organisms: For example, characters of dinosaurs are inferred from characters shared by living birds and crocodiles