Ch 22: Evolution's Patterns

Question 1

Phylogeny

Answer 1

The history of descent with modification and the accumulation of change over time.

Question 2

Node

Answer 2

In phylogenetic trees, the point where a branch splits, representing the common ancestor from which the descendant species diverged. In plants, the point on a shoot where one or more leaves are attached.

Question 3

Phylogenetic Tree

Answer 3

A tree-like diagram representing a hypothesis about the evolutionary relationships among populations or species.

Question 4

Sister Groups

Answer 4

Groups that are more closely related to each other than either of them is to any other group.

Question 5

Taxon

Answer 5

A named taxonomic group at any rank, such as a species, a genus, or a family.

Question 6

Monophylectic

Answer 6

Describes groupings in which all members share a single common ancestor not shared with any other species or group of species.

Question 7

Paraphylectic

Answer 7

Describes groupings that include some, but not all, the descendants of a common ancestor.

Question 8

Polyphylectic

Answer 8

Describes groupings that do not include the last common ancestor of all members.

Question 9

Genus

Answer 9

A group of closely related species.

Question 10

Family

Answer 10

A group of closely related genera.

Question 11

Class

Answer 11

In the Linnaean system of classification, a group of closely related orders.

Question 12

Phylum

Answer 12

A group of closely related classes, defined by having a distinct body plan.

Question 13

Kingdom

Answer 13

A group of closely related phyla.

Question 14

Domain

Answer 14

One of the three largest limbs of the tree of life: Eukarya, Bacteria, or Archaea.

Question 15

Characters

Answer 15

In the discipline of systematics, an anatomical, physiological, or molecular feature of an organism that varies among taxa.

Question 16

Character States

Answer 16

The observed condition of a character, such as presence or absence of lungs or the arrangement of petals.

Question 17

Homologous

Answer 17

Describes characters that are similar in different species because of descent from a common ancestor.

Question 18

Analogous

Answer 18

Describes similar characters that evolved independently in different groups as a result of similar selection pressures; the noun form is analogy.

Question 19

Synapomorphies

Answer 19

A shared derived character; the basis of cladistic phylogenetic reconstruction.

Question 20

Cladistics

Answer 20

Phylogenetic reconstruction on the basis of shared evolutionary changes in characters, often called synapomorphies.

Question 21

Parsimony

Answer 21

Choosing the simplest hypothesis to account for a given set of observations. In phylogenetic reconstruction, opting for the tree requiring the fewest evolutionary steps.

Question 22

Trace Fossils

Answer 22

A track or trail, such as a dinosaur track or the feeding trails of snails and trilobites, left by an animal as it moves about or burrows into sediments.

Question 23

Molecular Fossils

Answer 23

Sterols, bacterial lipids, and some pigment molecules, which are relatively resistant to decomposition, that can be preserved in sedimentary rocks, documenting organisms that rarely form conventional fossils.

Question 24

Geologic Timescale

Answer 24

The series of time divisions that mark Earth’s long history.

Question 25

Radiometric Dating

Answer 25

Dating ancient materials using the decay of radioisotopes as a yardstick, including the decay of radioactive 14C to nitrogen for time intervals up to a few tens of thousands of years, and the decay of radioactive uranium to lead for most of Earth history.

Question 26

Half-life

Answer 26

The time it takes for an amount of a substance to reach half its original value. Radioactive half-life is the time it takes for half of the atoms in a given sample of a substance to decay.

Question 27

Mass Extinction

Answer 27

A catastrophic drop in recorded diversity, which has occurred five times in the past 541 million years.

Question 28

When several possible phylogenetic trees can be produced from a data set, the most parsimonious tree is the one that shows the:

Answer 28

fewest number of evolutionary changes.

Question 29

The geological timescale was first developed using the fossil record, but this provided only a system of relative dating; absolute dates weren’t established until the discovery of:

Answer 29

radioactive decay.

Question 30

T/F: Even if the geologic record extended back only 5000 years, evidence provided by living organisms alone would support the hypothesis that mammals only diverged following the extinction of dinosaurs.

Answer 30

False

Question 31

Two taxa that are more closely related to each other than to any other taxon are called:

Answer 31

Sister Groups

Question 32

Frogs, birds, rabbits, and lizards all have different forelimbs, which makes sense when you consider their different lifestyles. Interestingly, all of their forelimbs share the same set of bones: the ulna, the radius, and the humerus. These same bones are also seen in fossils of the extinct animal Eusthenopteron, which demonstrates common ancestry among these four groups of animals. Hence, these forelimbs are an example of:

Answer 32

Homologies

Question 33

How do fossils provide evidence of evolutionary history?

Answer 33

Fossils provide a record of extinct species.

Question 34

Fossil data can be used to generate phylogenies that include extinct taxa. Which of the statements indicates how fossil data can be used to refine phylogenies constructed with molecular data?

Answer 34

Fossil data can be used to confirm the time since divergence between extant taxa estimated from sequence data.

Question 35

T/F: Only homologous characters are useful in constructing phylogenetic trees.

Answer 35

True

Question 36

The largest mass extinction occurred at the end of which period?

Answer 36

Permian

Question 37

Taxa that have descended from a common ancestor are expected to:

Answer 37

show a nested pattern of nodes from the common ancestor.

Question 38

Why is agreement between the fossil record and phylogenies constructed from living organisms considered strong evidence of evolution?

Answer 38

It is unlikely that two independent methods of investigation would result in the same pattern by chance alone.

Question 39

In order to be useful for constructing a phylogeny, a character must:

Answer 39

have a genetic basis.

Question 40

T/F: Phylogenetic trees could be considered physical representations of hypotheses that seek to establish the evolutionary relationships between different organisms.

Answer 40

True

Question 41

In a particular layer of rock, a number of fossilized ferns are found, but no fossilized mosses. What conclusions can be drawn from this finding?

Answer 41

The soft tissues of mosses may not have fossilized as readily as the more decay-resistant tissues of ferns, so it is difficult to draw any conclusions from this limited sample.

Question 42

The half-life of 14C is 5,730 years. Archaeologists dig up a seed that contains 0.25 parts per trillion 14C. If it originally contained 1 part per trillion 14C, how old is the archaeological specimen?

Answer 42

11,460 years

Question 43

The half-life of 14C is 5,730 years. If a sample contained 100 percent 14C 17,190 years ago, then what percent of 14C would it contain today?

Answer 43

12.5 percent

Question 44

T/F: Imagine that a taxonomist is provided with several flashcards that contain the names of different species. She would like to organize these flashcards to construct a phylogenetic tree. To do this, she would pay attention to which species belongs to which genus or class.

Answer 44

True

Question 45

T/F: The order of groups along the tips of a phylogenetic tree indicates how closely those groups are related.

Answer 45

False

Question 46

Imagine that you are chatting with one of your friends, who stated that reptiles are obviously a monophyletic group, as this group contains all of the organisms (outside of fish) that possess scales. This statement is:

Answer 46

false, because reptiles are a paraphyletic group; this group does not include birds, even though birds share a common ancestor with reptiles.