Chapter 7
Animal Classification,
Phylogeny, and
organization
Ms. K. Cox, Zoology
Classification page 97
• A.We have identified about 1.4 million
species on earth; three-fourths of these
species are animals.
– 1. Each species is given a genus and species
name according to the taxonomic system based
on the work of Karl von Linnè.
– 2. The binomial (genus and species names)
nomenclature is universal, and follows rules
from the International Code of Zoological
Nomenclature
• 3. Closely related species are placed in the same genus;
closely related genera are placed in the same family, and
so on.
• 4.Taxon is a general term used to represent a group of
animals at any level of the classification scheme.
• B. To decide how closely related one taxon is to another,
biologists compare the characters or traits present across
groups.
– 1.The traits used may be morphological- physcial
features (fur,no fur, brown eyes, green eyes, scales)
– or
– 2. molecular- DNA or genes that they have in common
– (exact genes they have in common, for example Down
Syndrome is caused by 2 copies of chromosome 21)
• C. Classification of organisms into
higher level taxa has changed
recently.
• 1. A 5 kingdom scheme based on
cellular properties and mode of
nutrition was designed by
Whittaker in1969: Monera, Protista,
Plantae, Fungi, and Animalia.
Bacteria were placed in the
kingdom Monera
Changes
• 2. But new rRNA studies (rRNA
changes very slowly, so it offers
conserved characters for the phylogeny
of ancient groups) indicate that bacteria
is a polyphyletic group.
• 3. Bacteria now belong in two groups:
Archaea and Eubacteria. These two
groups replace the previous Kingdom
Monera.
• 4. Living things are
commonyly grouped into a 3
domain, 6 kingdom system.
• (This is new) Domains:
Archaea, Eubacteria,
Eukarya
5 Kingdoms
1. Monera
2. Protista
3. Plantae
4. Fungi
5. Animalia
Domains: Archaea, Eubacteria,
Eukarya
6 Kingdoms
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1. Plantae
2. Animalia
3. Protista
4. Fungi
5. Archaebacteria
6. Eubacteria
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5. The new taxonomy system.
Domain-3 groups
Kingdom-6 groups
Phylum
Class
Order
Family
Genus
Species
• D. Systematics is the arrangement of organisms
based on evolutionary relationships indicated by
shared characters.
• 1. The groups formed in modern systematics are
designed to be monophyletic; polyphyletic groups
are avoided.
• 2. Monophyletic groups include all organisms that
have arisen from a single ancestral taxon;
• 3. polyphyletic groups are artificial groupings
whose members have arisen from separate
ancestors.
• E. There are 3 main schools of systematics that
differ in their goals and approaches:
• 1. Evolutionary systematics is a traditional approach which
looks for similar characters and homologies to group
organisms into taxa.
• 2. Numerical taxonomy is based on a quantitative analysis
of characters to determine taxa and does not attempt to
distinguish between shared states due to common
ancestry and shared states due to convergence.
• 3. Phylogenetic systematics (cladists) analyzes both
symplesiomorphies (shared ancestral characters) and
synapomorphies (shared derived characters) to determine
cladograms.
Invertebrate or Vertebrate
What are Invertebrates?
Invertebrates are a broad collection of animal groups (they do not
belong to a single subphylum like the vertebrates) all of which lack a
backbone. Some (not all) of the animal groups that are invertebrates
include:
-Sponges (Phylum Porifera)
-Jellyfish, hydras, sea anemones, corals (Phylum Cnidaria)
-Comb jellies (Phylum Ctenophora)
-Flatworms (Phylum Platyhelminthes)
-Molluscs (Phylum Mollusca)
-Arthropods (Phylum Arthropoda)
-Segmented worms (Phylum Annelida)
-Echinoderms (Phylum Echinodermata)
Vertebrate
• bilateral symmetry
• body segmentation
• endoskeleton (bony or
cartilaginous) (they have a
backbone)
• pharyngeal pouches (present
during some stage of
development)
• complete digestive system
• ventral heart
• closed blood system
• tail (at some stage of
development)
The animal classes that are
vertebrates include:
Jawless fish (Class Agnatha)
Armored fish (Class Placodermi) extinct
Cartilaginous fish (Class
Chondrichthyes)
Bony fish (Class Osteichthyes)
Amphibians (Class Amphibia)
Reptiles (Class Reptilia)
Birds (Class Aves)
Mammals (Class Mammalia)
F. Symmetry
• 1. The basic body plans of animals may be
analyzed to illustrate evolutionary trends. The first
consideration is body symmetry:
• Animals may be asymmetrical, as in many protists
and sponges; such animals lack complex sensory
and locomotory functions.
2.
3 Types of Symmetry
• A. asymmetry
• B. bilateral
symmetry
• C. radial
symmetry
3. asymmetry
•The arrangement of
body parts without a
central axis or point.
• (such animals lack complex sensory and
locomotory functions)
Illustration of difference between
symmetrical and asymmetrical.
Tube Sponge
(Callyspongia vaginalis)
The Tube Sponge is one of the
most common varieties of sea
sponge to be found on the reef. It
is distinguished by its long tubeshaped growths, and ranges in
color from purple to blue, gray,
and gray-green. Filtered water is
ejected through the large openings
on the ends. This is one of the few
reef invertebrates that is blue in
color.
Sponges
4. bilateral symmetry
• The arrangement of body parts
such that a single plane passing
between the upper and lower
surfaces and divides the animal
into a right and left mirror
image.(most things fall into this
category)
Hippopotamus
Hippos are herbivores and their diet
consists mainly of grass and some
water plants. Hippos do most of
their eating during the night, while
during the day hippos spend most
of their time basking in the sun on a
sandbar or floating lazily in the
water with just their ears, eyes, and
nostrils, and perhaps their back and
top of the head, exposed. The name
hippopotamus comes from the Greek
"hippos," meaning horse. Hippos were
once called "river horses," even though
they are more closely related to pigs
than horses.
Big male hippos can tip the scales at over
three tons.
The Common Dog
5. radial symmetry
• The arrangement of body parts
such that any plane passing
through the oral-aboral axis
divided the animal into mirror
images.
Cnidarian
Cnidarians are radially
symmetrical. This means that
their gastrovascular cavity,
tentacles, and mouth are aligned
such that if you were to draw an
imaginary line through the center
of their body, from the top of
their tentacles through the base
of their body, you could then
turn the animal about that axis
and it would look roughly the
same at each angle in the turn.
Another way to look at this is
that cnidarians are cylindrical
and have a top and bottom but no
left or right side.
Echinodermata (e.x. starfish)
Sea stars or starfish are marine
invertebrates belonging to phylum
Echinodermata, class Asteroidea.
The names sea star and starfish
are also used for the closely
related brittle stars, which make
up the class Ophiuroidea. They
exhibit a superficially radial
symmetry, typically with five or
more "arms" which radiate from
an indistinct disk (pentaradial
symmetry). In fact, their
evolutionary ancestors are
believed to have had bilateral
symmetry, and sea stars do have
some remnant of this body
structure.
Stopped here on Friday Feb 11
G.
Unicellular Level of Organization page 105
• 1. The second consideration is
the level of cellular organization:
–A. The single celled organisms, or
those formed from aggregates of
single cells, exhibit the cytoplasmic
level of organization; these cells
have very little interdependence
and do not form tissues.
– Diploblastic Organization.
• These organisms, like the cnidarians,
have two tissues layers formed from
the embryonic ectoderm and
endoderm. The cell layers are
interdependent.
– Triploblastic Organization.
• These organisms have 3 tissue layers
derived from the embryonic ectoderm,
mesoderm, and endoderm.
Body Cavity
• 1.The third consideration is the presence of a body
cavity (not the gut cavity, but a cavity external to
the gut):
• 2.The body cavity Functions
• A. provide more room for organ development
• B. Provide more surface area for diffusion
• C. provide an area for storage
• D. often act as hydrostatic skeletons
• E. provide a vehicle for eliminating wastes and for
reproduction
• F. Facilitate increased body size.
Possibilities in the Triploblastic
Organization
• 1. Triploblastic Acoelomate Pattern
• A. see page 106, Figure 7.11 A. Draw this
example in your notes.
• B. Description: thin ectoderm, thick mesoderm,
and thin endoderm, with small opening in the
middle called a gut. The mesoderm touches the
endoderm.
• C. Examples of flat worms, tapeworm. (chapter
10)
-Continued- Possibilities in the
Triploblastic Organization
• 2. Triploblastic Pseudocoelomate Pattern
• A. see page 106, Figure 7.11 B. Draw this
example in your notes.
• B. Description: thin ectoderm, thin mesoderm, thin
endoderm, as an extra space between the
Mesoderm and the Endoderm called the
Pseudocoelom.
• C. Examples: roundworm, filarial worm- causes
elephantiasis see page 174 (chapter 11)
–Continued- Possibilities in the
Triploblastic Organization
• 3. Triploblastic Coelomate Pattern
• A. See page 106, Figure 7.11 C. Draw this
example in your notes.
• B. Description: Thin Ectoderm, thicker mesoderm
that has space to the left and the right. The
mesoderm butts up directly to the Endoderm. In
the center there is a small opening.
• C. Example: Nemertea (ribbon worms)
• ,
Stopped here on feb 14
Higher Animal Taxonomy
• 1. Animalia are considered monophyletic. Due to
cellular organization.
• 2. “The Cambrian Explosion”- about 0.6 billion
years ago an evolutionary explosion occurred
which resulted in the origin of all modern phyla.
(phyla= many groups)
• 3. Three main groups or braches in the animal
kingdom.
– A. Mesozoa
– B. Parazoa (sponges)
Continued
• C. Eumetazoa- divided into further groups based on body
symmetry.
– 1. Radiata
– 2. Bilateria
– A. Protostomia –(Platyhelminthes, Nematoda,
Mollusca, Annelida, Arthropoda)
» 1. Trochophore larva see page 108 figure
7.12 D. draw an example in your notes.
– B. Deuterostomia-(Echinodermata,
hemichordata, chordata)
» 1. Dipleurula larva see page 108 figure 7.12
H. Draw an example in your notes.
Continued
• 4. Scientists use Comparative embryology.
(Definition: the observation that embryological
events may be similar because of shared
ancestry.)