Chapter 27.1-27.221 cards

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1

Phylogeny

The evolutionary history of a group of organisms.

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Phylogenetic tree

A diagram that depicts the evolutionary history of a group of species and the relationships among them.

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Branch

(1) A part of a phylogenetic tree that represents populations through time. (2) Any extension of a plant’s shoot system.

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Node

(1) In animals, any small thickening (e.g., a lymph node). (2) In plants, the part of a stem where leaves or leaf buds are attached. (3) In a phylogenetic tree, the point where two branches diverge, representing the point in time when an ancestral group split into two or more descendant groups. Also called fork.

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Tip

The end of a branch on a phylogenetic tree. Represents a specific species or larger taxon that has not (yet) produced descendants—either a group living today or a group that ended in extinction.

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Phenetic approach

A method for constructing a phylogenetic tree by computing a statistic that summarizes the overall similarity among populations, based on the available data

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Cladistic approach

A method for constructing a phylogenetic tree that is based on identifying the unique traits of each monophyletic group

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Synapomorphies

A shared, derived trait found in two or more taxa that is present in their most recent common ancestor but is missing in more distant ancestors. Useful for inferring evolutionary relationships.

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Monophyletic groups, clades, or lineages

An evolutionary unit that includes an ancestral population and all of its descendants but no others.

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Homology

Similarity among organisms of different species due to their inheritance from a common ancestor. Features that exhibit such similarity (e.g., DNA sequences, proteins, body parts) are said to be homologous.

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Homoplasy

Similarity among organisms of different species due to convergent evolution.

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Convergent evolution

The independent evolution of analogous traits in distantly related organisms due to adaptation to similar environments and a similar way of life.

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Parsimony

The logical principle that the most likely explanation of a phenomenon is the most economical or simplest. When applied to comparison of alternative phylogenetic trees, it suggests that the one requiring the fewest evolutionary changes is most likely to be correct.

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SINEs (Short interspersed nuclear elements)

The second most abundant class of transposable elements in human genomes; can create copies of itself and insert them elsewhere in the genome.

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Fossil

Any trace of an organism that existed in the past. Includes tracks, burrows, fossilized bones, casts, etc.

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Fossil record

All of the fossils that have been found anywhere on Earth and that have been formally described in the scientific literature.

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Paleontologists

The study of organisms that lived in the distant past.

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Precambrian era

The interval between the formation of the Earth, about 4.6 billion years ago, and the appearance of most animal groups about 543 million years ago. Unicellular organisms were dominant for most of this era, and oxygen was virtually absent for the first 2 billion years.

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Paleozoic era

The period of geologic time, from 543 million to 250 million years ago, during which fungi, land plants, and animals first appeared and diversified. Began with the Cambrian explosion and ended with the extinction of many invertebrates and vertebrates.

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Mesozoic era

The period of geologic time, from 250 million to 65 million years ago, during which gymnosperms were the dominant plants and dinosaurs the dominant vertebrates. Ended with extinction of the dinosaurs. Also called Age of Reptiles

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Cenozoic era

The most recent period of geologic time, beginning 65 million years ago. during which mammals became the dominant vertebrates and angiosperms became the dominant plants. Also called Age of Mammals.