Reference: Zoology 7th edition by Stephen A. Miller and John P. Harley

1. Animal Morphology Lesson 2

2.  Systematics or Taxonomy
 The study of the kinds and diversity of organisms
and of the evolutionary relationship among
them
 Nomenclature
Is the assignment of a distinctive name to each
species
“systema” = system
“ikos” = body of facts
“taxis” = arrangement
“nominalis” = belonging to a name
“nomalis” = belonging to a name
“calator” = to call

3.  Carolus Linnaeus or Karl
von Linné
 Binomial nomenclature
 Different species can be
grouped into broader
categories based on shared
characteristics
 Any grouping of animals that
shares a particular set of
characteristics forms an
assemblage called taxon

4. Domain (Archea, Eubacteris and Eukarya)
Kingdom (Monera, Protista, Fungi, Plantae and Animalia)
Phylum
Class
Order
Genus
Family
Species

6.  Robert H. Whittaker
 Described a system of
classification that
distinguished between
kingdoms according to
cellular organisation
and mode of nutrition

9.  Goal : to arrange animals into groups
that reflect evolutionary relationships
 Monophyletic group
 Is a group of organisms that consists of all
the descendants of a common ancestor
 Character
 Animal attributes which indicates
relatedness
 Has genetic basis and can be measured

10.  Polyphyletic groups
 Have members that can be traced to
separate ancestors
 Paraphyletic group
 Includes some, but not all, members of a
lineage
 Resulted when knowledge of the group is
insufficient

12.  Evolutionary systematics
 Oldest of the three approaches
 “Traditional approach”
 Basic assumption is that organisms closely related to
an ancestor will resemble that ancestor more closely
than they resemble distantly related organisms
 2 kinds of similarities
 Homologies – resemblances that result from
common ancestry (classifying animals)
 Analogies – resemblances that result from organisms
adapting under similar evolutionary pressures

14.  Numerical taxonomy
 Represents the opposite end of the
spectrum from evolutionary systematics
 Use mathematical models and computer-
aided techniques to group samples of
organisms according to overall similarity
 Limits discussion of evolutionary
relationships to closely related taxa

15.  Phylogenetic systematics (cladistics)
 Goal : the generation of hypotheses of
genealogical relationships among
monophyletic groups of organisms
 More open to …analysis and testing, and
thus more scientific
 Ancestral characters
 Attributes of species that are old and have
been retained from common ancestors

16.  Symplesiomorphies
 “sym” together, “plesio” near, “morphe” form
 Ancestral characters are homologies that are common to all
members of group and indicate a shared ancestry
 Outgroup
 Used to help decide whether a character is ancestral or has
arisen within the study group
 Derived characters
 Characters that have arisen since common ancestry with the
outgroup
 Synapomorphies
 “syn” together, “apo” away, “morphe” form
 Derived characters shared by members of a group

17.  Clade
 “klados” branch
 Cladogram
 Depict a sequence in the origin of derived
characters
 Interpreted as family tree showing a hypothesis
regarding monophyletic lineages
 Hierarchical nesting
 Groups of related organisms share suites of similar
characteristics and the number of shared traits
increases with relatedness

20.  The bodies of animals and protists are
organized into almost infinitely diverse
forms
 Symmetry
 Describes how the parts of an animal are
arranged around a point or an axis

22. Sponges display a cell-aggregate organization, and as this red encrusting
sponge (Monochora barbadensis) shows, many are asymetrical.

24. Planes that pass through the oral-aboral axis divide radially symmetry
animals, such as this tube coral polyp (Tubastraea sp.), into equal
halves. Certain arrangements of internal structures modify the radial
symmetry of sea anemones.

26.  Unicellular (Cytoplasmic) Level of Organization
 Organisms whose bodies consist of single cells or cellular
aggregates display the unicellular level of organization
 All unicellular organisms must provide for the functions of
locomotion, food acquisition, digestion, water and ion
regulation, sensory perception, and reproduction in a single
cell
 Cellular aggregates (colonies) consist of loose associations of
cells that exhibit little interdependence, cooperation, or
coordination of function (cannot be considered a tissue)
 Absence of interdependence – division of labors
(reproductive, nutritive, or structural functions)

27.  Diploblastic Organization
 “diplóos” twofold, “blaste” to sprout
 Cells are organized into tissues
 Has simplest tissue-level organization
 Body parts are organized into layers
(ectoderm and endoderm) derived from
two embryonic tissue layers

29.  Tripoblastic Organization
 “treis” three, “blaste” to sprout
 Tissues are derived from three embryological
layers (ectoderm, endoderm and mesoderm)
 Has organ-system level of organization
(excretory, nervous, digestive, reproductive,
circulatory and other systems)
 Has body cavity, fluid filled space in which
the internal organs can be suspended and
separated from the body wall

30.  Advantage of body cavities
 Provide more room for organ development
 Provide for more surface area for diffusion of
gases, nutrients, and wastes into and out of
organs
 Provide an area for storage
 Often act as hydrostatic skeletons
 Provide a vehicle for eliminating wastes and
reproductive products from the body
 Facilitate increased body size

31.  3 Patterns
 Tripoblastic acoelomate pattern
▪ Tripoblastic animals whose mesodermally derived tissues form a
relatively solid mass of cells between ectodermally and
endodermally derived tissues
 Tripoblastic pseudocoelomate pattern
▪ Body cavity not entirely lined with mesoderm
▪ No muscular or connective tissues are associated with the gut
tract, no mesodermal sheet covers the inner surface of the body
wall, and no membranes suspend organs in the body cavity
 Tripoblastic coelomate pattern
▪ A coelom is a body cavity completely surrounded by mesoderm