This document discusses evolutionary models and mechanisms including punctuated equilibrium, phyletic gradualism, anagenesis, cladogenesis, and chronoclines. It examines two lineages of automobiles over 60 years to identify speciation events and applies evolutionary concepts. It also discusses early tetrapod and fish limb structures, the development of joints to bear weight on land, and compares skull features in early mammals and therapsids. A diagram shows morphological characters of four hypothetical organisms and tasks are to complete the chart and identify closest related taxa and their synapomorphy.

1. 2. Evolutonary theory predicts that orgunisms should apgear in a secpence over time and that it
shoulc be posside to link younger forms to older firme. The model of "punctealec equilitrium"
predicts that newy terms (species) sheuld often appear "suddeally" and then expeience iong
pericd of stasis (or stugnation). The modei of "Phyletic gradualsem" peedicts that most species
should change grad taily throuphout time and many species-to-bposies trantilione will be part of
the recorc. Several terms are usec to describe the mechanisms invoived in thene modeln.
Anagenesis is the ide that an oice species, os a whoie, changes into a new deseendent species in
eliect, the ancestor is transiormed into the descencient Cladogenesis is the concept that a
daughter species aplia of from a populalion of ar vicie species, after which both the old and new
spedes coexist in time (and posaitly spocet. A chronocline is defined as the gradual change in
one linesge ovez time. A. Examine the two lineages of "fossil" aulonobiles ove the past 60 yens.
Con you icientify any "epedation events" in eithee lineage? If sa, maric each spedation erent by
drawing a. line acrcos the aute lineage at the appropriate level of thenge. B. How mamy
speciation events can you diertify within the V V lineage? C. How many gpeciation events can
youidentify within the Mustung lineage? D. What is the rate (numioe of apeciation evcnss t timel
of evclutlonary thange in the VW linesge? E. What is the rate of evolutionary change in the
Mustrng lineage? F. Which evolutionary model best describes the changee, or lack therrod, in the
VW lineage? G. Which ewolutionary model best describes the changes documened in the
Muatang lineage? H. Which of the foliowirg evolujicnary mecharisms wouid best apply when
describing the Mustang lineage? (Anagenesis) (Cladogenesia) (Chronocline?
B. The earliest tetrapods retained a limb structure similar to that of the fins of ancestyal fish.
Rather than having limbs based upon in fve-toed foot, as do modern tetrapods, these animals had
more than five ":oes." This gave the feet the look of a short, stout flipper with mary "ine rays"
similar to fin rays. "dentify the eady tetrapod by writing ICTHY on the cliagram. How does the
toe strueture of this hind linb differ trom that of the mammat? G. Toe fins of mast ibe finred
fiahes have a simple bifureate devign. That is, bones ceevelop in a fattern of twos during
embryogenesis. The mid-late Devorian rhipidistian posessed this limb architecture. II fins were
very similar to eazy amphibian feet in the overall layout of the major bones, except that there
were no perceptibie "toes," just a set of identical fin rays, Identify the limb structure of
Eistimapteren by writing EU on the diagram. How does the bone scructure of this figh compare
with that of the early tet:spod? D. Land-ewelling arimals must bear weight on their limibs in
order to move efficientiy on terra firma. One feature that helped early vertrates move on land,
and allowed for weight to be borne, was the development of imb joints (elbows and knees). All
but one of the eariy tetraoods are from concinentai deposits, and all posieas similar arrangements
of 'onee in the limis as depicted in the drawing. Compare the skeletal arrangement of the semi-

2. acuatic mammai and the early totrapod. What can you infies about the ability of each to move
about on hand.
C. What differenoes tan yoed see in the skull of the early mammal and those of the therapsids? 8.
Four hypothetical organiams are shown in the figure below along with the distribution oi some of
their impoutant morphologic characters. Characters are shown on the table as present it) or abient
(-). (Refer back to Figuye 9.2 and the accompanying texi). A. Compicte the chadogrum provided
hene by assigning the comrect characters at the "nodes" ithe black dobs at the brasxheng points),
and assign taxa by plicing the correct letbur on the blark at the end of each line (only one ietter
per blanki. B. Which two taxa are the mrost dosely relatedi? C. Which chatacter is the
synapomorphy for these two taxa?