Introduction To Cladistics

Question 1

What is Systematics

Answer 1

Systematics is the branch of biology concerned with the study of organic diversity

Question 2

What was Hennig famous for?

Answer 2

Nowadays, biologists refer to Hennig’s unique approach as “cladistic analysis”, “cladistics”, or “phylogenetic systematics”.

Question 3

evolutionary history (i.e., phylogeny) consists of a series of what ?

Answer 3

evolutionary history (i.e., phylogeny) consists of a series of dichotomies.

Question 4

What does Each dichotomy mark?

Answer 4

Each dichotomy marks the splitting and disappearance of an ancestral species and the formation of two daughter species

Question 5

What is The fundamental product of evolution?

Answer 5

The fundamental product of evolution is the clade, or monophyletic group, which is made up of an ancestral species and all of its descendants.

Question 6

What is a clade, or monophyletic group

Answer 6

which is made up of an ancestral species and all of its descendants.

Question 7

Another word for clade is?

Answer 7

monophyletic group

Question 8

What occurs at a node

Answer 8

a speciation event occurs at the branch point, or node, to give rise to a pair of daughter species

Question 9

any branch that connects two nodes (remember, a node represents a speciation event) corresponds to what ?

Answer 9

any branch that connects two nodes (remember, a node represents a speciation event) corresponds to an ancestor

Question 10

This process of species creation is

known as what?

Answer 10

cladogenesis, or branching evolution.

Question 11

what do you use to Depict phylogenetic history?

Answer 11

a cladogram

Question 12

can the taxa be living and extinct in a cladogram?

Answer 12

These taxa may be living or extinct

.

Question 13

what does a node represent?

Answer 13

a node represents a

speciation event, it corresponds to an ancestor

Question 14

is a cladogram a hypothesis, or a fact?

Answer 14

cladogram is an hypothesis, not a fact.

Question 15

what is the difference between a phylongeny and a cladogram?

Answer 15

A phylogeny provides information about the evolutionary relationships among taxa. It often expresses the geographical distributions or morphological similarities of taxa as well. Most importantly, a phylogeny, unlike a cladogram, has an absolute time axis. In a phylogeny, the taxa under study are not necessarily listed across the top of the diagram, as is mandatory in a cladogram. Instead, the taxa are ordered vertically to indicate when they lived

Question 16

what is the most important diference between a cladogram and a phylogeny?

Answer 16

Most importantly, a

phylogeny, unlike a cladogram, has an absolute time axis.

Question 17

what can be used to determine common ancestry?

Answer 17

the geneological relationships within a suite of taxa can be discovered indirectly by examining their characters.

Question 18

what is a character?

Answer 18

A character is a feature that is an observable part or attribute of an organism. An example of a character is feet in tetrapods.

Question 19

what are the different forms of characters called?

Answer 19

Characters have

different forms or appearances called character states

Question 20

what two things must be considered when choosing characters?

Answer 20

1. the character has to be consistent in all the members of that type of organism.
2. In selecting the suite of characters to be compared, each organism must have at least one character different from the other organisms

Question 21

what is A plesiomorphy?

Answer 21

A plesiomorphy is an “ancestral”, “less specialized”, or “primitive” character

Question 22

what is An apomorphy?

Answer 22

An apomorphy is a “derived”, “specialized”, or “advanced” character.

Question 23

True/ False: Every taxon possesses a

mixture of plesiomorphies and apomorphies.

Answer 23

true:Every taxon possesses a

mixture of plesiomorphies and apomorphies.

Question 24

what is Outgroup comparison ?

Answer 24

Outgroup comparison is a means of determining which character in a transformation series is a plesiomorphy and which is an apomorphy.

Question 25

what is An outgroup?

Answer 25

An outgroup is the most closely related taxon to, but not the ancestor of, the set of taxaunder study.

Question 26

what is a synapomorphy?

Answer 26

A synapomorphy, or “shared derived character”, is an apomorphy that occurs in two or more taxa.

Question 27

what is the main value of synapomorphies?

Answer 27

The beauty of synapomorphies is that they point out clades (monophyletic groups) to the cladist.

Question 28

what is An autapomorphy?

Answer 28

An autapomorphy is an apomorphy that occurs in only one taxon.

Question 29

are Autapomorphies helpful?

Answer 29

Autapomorphies demonstrate the uniqueness of taxa, but they don’t help the cladist identify clades (monophyletic groups).

Question 30

what does the The Principle of Parsimony state?

Answer 30

The Principle of Parsimony states that the simplest explanation of the data is preferable over more complicated explanations. In cladistics it is assumed that the cladogram with the fewest branches is probably the most accurate because it suggests the fewest number of evolutionary innovations.

Question 31

what is a reversal?

Answer 31

A reversal is when an
apomorphic or derived state evolves back into the ancestral or plesiomorphic state. This is
also referred to as an ‘evolutionary loss’ (see diagram below).

Question 32

what is a monophyletic group?

Answer 32

A monophyletic group consists of an ancestor and all of its descendants. A monophyletic group is a clade. It is defined by at least one synapomorphy (all group members have the synapomorphy or synapomorphies).

Question 33

what is a paraphyletic group?

Answer 33

A paraphyletic group consists of an ancestor and some of its descendants. A paraphyletic group is an incomplete clade, or a “grade”. It is defined by the absence of at least one character (all group members lack some particularcharacter[s]

Question 34

what is a polyphyletic group?

Answer 34

A polyphyletic group includes two or more taxa, but not the common
ancestor of those taxa. A polyphyletic group is defined by at least one similar character
that evolved independently (by convergent or parallel evolution) in each group member.
Taxa are placed in a polyphyletic group because they share some superficial similarity, not
because they’re closely related to one another.

Question 35

define : Polytomy vs. dichotomy

Answer 35

Polytomy (vs. dichotomy) – A polytomy is an unresolved node, where three or more branches
come together. A resolved node is dichotomous, meaning it has only 2 daughter branches

Question 36

what are the 2 Types of classification

Answer 36

Linnaean systematics

Phylogenetic systematics

Question 37

what is Linnaean systematics?

Answer 37

Linnaean systematics is the traditional method of classification, based on all kinds of similarity (including homoplasies and plesiomorphies). Because of this, some groups that were made in the
past have turned out not to be monophyletic. Linnaean ranks (genus, family, order, class, phylum,
kingdom) were used to organize groups, but there was no rigorous definition of these ranks.

Question 38

what is Phylogenetic systematics?

Answer 38

cladistics, classification in which items are grouped together based on whether or not they have one or more shared unique characteristics that come from the group’s common ancestor and are not present in more distant ancestors.