Ch 22: Evolution's Patterns Flashcards
Phylogeny
The history of descent with modification and the accumulation of change over time.
Node
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.
Phylogenetic Tree
A tree-like diagram representing a hypothesis about the evolutionary relationships among populations or species.
Sister Groups
Groups that are more closely related to each other than either of them is to any other group.
Taxon
A named taxonomic group at any rank, such as a species, a genus, or a family.
Monophylectic
Describes groupings in which all members share a single common ancestor not shared with any other species or group of species.
Paraphylectic
Describes groupings that include some, but not all, the descendants of a common ancestor.
Polyphylectic
Describes groupings that do not include the last common ancestor of all members.
Genus
A group of closely related species.
Family
A group of closely related genera.
Class
In the Linnaean system of classification, a group of closely related orders.
Phylum
A group of closely related classes, defined by having a distinct body plan.
Kingdom
A group of closely related phyla.
Domain
One of the three largest limbs of the tree of life: Eukarya, Bacteria, or Archaea.
Characters
In the discipline of systematics, an anatomical, physiological, or molecular feature of an organism that varies among taxa.
Character States
The observed condition of a character, such as presence or absence of lungs or the arrangement of petals.
Homologous
Describes characters that are similar in different species because of descent from a common ancestor.
Analogous
Describes similar characters that evolved independently in different groups as a result of similar selection pressures; the noun form is analogy.
Synapomorphies
A shared derived character; the basis of cladistic phylogenetic reconstruction.
Cladistics
Phylogenetic reconstruction on the basis of shared evolutionary changes in characters, often called synapomorphies.
Parsimony
Choosing the simplest hypothesis to account for a given set of observations. In phylogenetic reconstruction, opting for the tree requiring the fewest evolutionary steps.
Trace Fossils
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.
Molecular Fossils
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.
Geologic Timescale
The series of time divisions that mark Earth’s long history.
Radiometric Dating
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.
Half-life
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.
Mass Extinction
A catastrophic drop in recorded diversity, which has occurred five times in the past 541 million years.
When several possible phylogenetic trees can be produced from a data set, the most parsimonious tree is the one that shows the:
fewest number of evolutionary changes.
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:
radioactive decay.
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.
False
Two taxa that are more closely related to each other than to any other taxon are called:
Sister Groups
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:
Homologies
How do fossils provide evidence of evolutionary history?
Fossils provide a record of extinct species.
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?
Fossil data can be used to confirm the time since divergence between extant taxa estimated from sequence data.
T/F: Only homologous characters are useful in constructing phylogenetic trees.
True
The largest mass extinction occurred at the end of which period?
Permian
Taxa that have descended from a common ancestor are expected to:
show a nested pattern of nodes from the common ancestor.
Why is agreement between the fossil record and phylogenies constructed from living organisms considered strong evidence of evolution?
It is unlikely that two independent methods of investigation would result in the same pattern by chance alone.
In order to be useful for constructing a phylogeny, a character must:
have a genetic basis.
T/F: Phylogenetic trees could be considered physical representations of hypotheses that seek to establish the evolutionary relationships between different organisms.
True
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?
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.
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?
11,460 years
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?
12.5 percent
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.
True
T/F: The order of groups along the tips of a phylogenetic tree indicates how closely those groups are related.
False
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:
false, because reptiles are a paraphyletic group; this group does not include birds, even though birds share a common ancestor with reptiles.
