Ch. 1

Question 1

Binominal nomenclature

Answer 1

Swedish naturalist Carolus Linnaeus

The Linnaean system names species using binomial nomenclature: two names, a genus name and a species epithet.

Question 2

taxonomy

Answer 2

(Greek taxo, “to arrange”; nomos, “order”)

Species are grouped in hierarchical categories (family, order, class, and so on).

These categories are called taxa (singular taxon), and the discipline of naming organisms is taxonomy.

Question 3

Goals for scientific names are threefold:

Answer 3

uniqueness (i.e., no two species can share the same name);

universality (i.e., everyone agrees to use the same name); and

stability (i.e., a species name cannot be changed once it is properly named).

Question 4

If stability of names is a goal of nomenclature, then why do species names seem to change so often?

Answer 4

1. upon further study, a systematist may decide that what was thought to be one species turns out to be two or more species.
2. a species thought to be distinct is found to be the same as another species
3. or that a species originally placed in one genus belongs in another genus;
4. or that the species name was already in use for another organism (often an insect).

Question 5

Another reason for instability of names is the principal of priority,

Answer 5

which means that the first person who recognizes and names a species in an appropriate publication is credited as the author of that species name; any other names that someone else subsequently applies to that species are invalid.

Question 6

phylogeny, or phylogenetic tree

Question 7

Root/base

Answer 7

The root (sometimes called the base)

Question 8

Node

Answer 8

From its root, the tree branches-splits in two at a node. Splits at subsequent nodes, in an earliest-to-most-recent time progression, lead to all the branches in the tree.

Question 9

terminal taxon

Answer 9

Each branch ends in a terminal taxon, the group named at the tip of the branch.

Question 10

classification bracket

Question 11

basal group

Answer 11

the branch closer to the root of a particular tree.

Question 12

Derived

Answer 12

Tax that branch after Basel

Question 13

topology

Answer 13

The arrangement of branches and taxa in a tree are collectively termed the tree’s topology.

Question 14

phylogenetic systematics

Answer 14

(Greek phylon, “tribe”; genesis, “origin”).

Question 15

A core concept of phylogenetic systematics

Answer 15

is the recognition of groups of organisms at different hierarchical levels within an evolutionary lineage, or clade.

Question 16

Clades

Answer 16

Clades must have a single evolutionary origin–that is, they must be monophyletic (Greek mono, “one” or “single”), and include all the descendants of a common ancestor.

Question 17

Members within monophyletic groups

Answer 17

are linked by nested sets of characters that trace the evolutionary history of the group.

Question 18

cladistics

Answer 18

These principles-monophyly and the inclusion of all descendants underpin the discipline of cladistics

Question 19

shared derived characters

Answer 19

that is, characters that have the same evolutionary origin (i.e., are homologous) and that differ from an ancestral condition (are derived).

A shared derived character is a synapomorphy (Greek syn, “together”).

Question 20

derived character

Answer 20

A derived character is called an apomorphy (Greek apo, “away from”; morphe, “form”; thus, “away from the ancestral con-dition”).

Question 21

The basic method is to compare characters…

Answer 21

in the group of interest, the ingroup, to those of an outgroup, a reference group or groups that, although known to be related to the organisms we are studying, is less closely related to any member of the ingroup than the ingroup members are to each other.

Question 22

The most parsimonious phylogeny

Answer 22

(i.e., the branching sequence requiring the fewest number of changes)

Any change in a structure is an unlikely event, so the most plausible phylogeny is the one requiring the fewest changes.

Question 23

molecular scaffolding

Answer 23

Studies that include extant and extinct organisms often employ the technique
of molecular scaffolding: the extant taxa are placed in their phylogenetic position by the relationships established by the molecular data, and then morphological data are used to integrate the fossil taxa with the extant taxa.

Question 24

sister group (or sister taxon),

Answer 24

which refers to the monophyletic lineage most closely related to the mono-phyletic lineage being discussed.

Question 25

extant phylogenetic bracket.

Question 26

Crown group

Answer 26

have all of the derived character states found in extant species. Not all members of a crown group have to be extant; an extinct species with all of the derived characters is a member of the crown group.

Question 27

Stem group

Answer 27

Stem groups are those extinct forms that lack some of the derived characters. Put another way, stem groups are fossils with some derived characters, and crown groups contain extant species plus fossils that have all the derived characters of the extant group. Stem groups are paraphyletic because they do not contain all the descendants of the ancestor of the stem group.

Question 28

gene families

Answer 28

Genes are often grouped in gene families that produce multiple structurally related forms of the same protein, and regulatory genes from a relatively small number of families control a host of developmental processes.

Question 29

developmental regulatory genes

Answer 29

can be expressed in different parts of the body, affect diverse aspects of the phenotype, and can interact.

Question 30

Heterochrony

Answer 30

Heterochrony (Greek heteros, “different”; chronos, “time”) refers to changes in the timing of gene expression during development.

Heterochrony can involve the length of time during which a gene is expressed during development.