Birds
Mammals
Reptile
Feathers
Amphibian
Fur
Fish
Endothermic
Lancelet
Amniotic Egg
Four Limbs
Vertebrae
• What is the symplesiomorphy
or shared primitive character
for this clade?
Ans: Vertebrae
Birds
Reptile
Mammals
Feathers
Amphibian
Fish
Lancelet
Fur
Endothermic
Amniotic Egg
Four Limbs
• What is the synapomorphy or
Vertebrae shared derived character for
amphibians, reptiles, birds &
mammals?
Ans: Four Limbs
• For reptiles, birds & mammals?
Ans: Amniotic Egg
• The outgroup comparison
– Enables us to focus on just those characters that
were derived at the various branch points in the
evolution of a clade.
Tuna
Turtle
Leopard
Salamander
Lamprey
CHARACTERS
Lancelet
(outgroup)
TAXA
Hair
0
0
0
0
0
1
Amniotic (shelled) egg
0
0
0
0
1
1
Four walking legs
0
0
0
1
1
1
Hinged jaws
0
0
1
1
1
1
Vertebral column (backbone)
0
1
1
1
1
1
Turtle
(a) Character table. A 0 indicates that a character is absent; a 1
indicates that a character is present.
Leopard
Hair
Salamander
Amniotic egg
Tuna
Four walking legs
Lamprey
Hinged jaws
Lancelet (outgroup)
Vertebral column
(b) Cladogram. Analyzing the distribution of these
derived characters can provide insight into vertebrate
phylogeny.
Phylogenetic Trees and Timing
• A cladogram is not a phylogenetic tree – why?
• A cladogram represents grouping and
relationships but not the timing of divergences.
• Cladograms stress importance of recent
homologies – derived characters
• A phylogenetic tree from evolutionary
systematics focuses on homologies but does
specify timing or time periods
• Numerical taxonomy doesn’t distinguish
between analogies or homologies
Phylograms
• In a phylogram:
– The length of a
branch reflects the
number of genetic
changes that have
taken place in a
particular DNA or
RNA sequence in that
lineage.
Outgroup
Phylogenetic Trees are Hypotheses
• Among phylogenetic hypotheses
–The most parsimonious tree is the one
that requires the fewest evolutionary
events to have occurred in the form of
shared derived characters.
• The best hypotheses for phylogenetic trees
–Are those that fit the most data:
morphological, molecular, and fossil.
• Overview: Welcome to Your Kingdom
• The animal kingdom
– Extends far beyond humans and other animals we
usually encounter
• Animal are multicellular, heterotrophic
eukaryotes with tissues that develop from
embryonic layers
• Several characteristics of animals
– Sufficiently define the group
• The history of animals may span more than a
billion years
• The animal kingdom includes not only great
diversity of living species
– But the even greater diversity of extinct ones as well
• The common ancestor of living animals
– May have lived 1.2 billion–800 million years ago
– May have resembled modern choanoflagellates,
protists that are the closest living relatives of
animals.
Single cell
Stalk
• Animals can be characterized by “body plans”
• One way in which zoologists categorize the
diversity of animals
– Is according to general features of morphology and
development
• A group of animal species
– That share the same level of organizational
complexity is known as a grade; grade is not
necessarily a clade (may not be monophyletic)
Patterns of Organization
4 Ways of Animal Organization:
• Symmetry (Asymmetry, Radial, Bilateral)
• Tissue Organization (Diploblastic, Triploblastic)
• Body Cavity Development (Acoelomate,
Pseudocoelomate, Coelomate)
• Embryological Development (Protostome and
Deuterostome)
Symmetry
• Asymmetry – arrangement of body parts without a
central axis or point (sponges).
– No complex sensory or locomotion functions.
• Radial Symmetry – arrangement of body parts
such that a single plane passing through the oralaboral axis divides the animal into mirror images
(sea anemones, starfish).
– No blind side.
• Bilateral Symmetry - arrangement of body parts
such that a single plane passing through the
longitudinal axis divides the animal into right and
left mirror images (vertebrates).
– Cephalization – form distinct head to analyze the
environment as they move through it.
Asymmetry
Planes of Radially Symmetrical Animals
• Some animals have radial symmetry
– Like in a flower pot
Radial symmetry. The parts of a radial
animal, such as a sea anemone
(phylum Cnidaria), radiate from the
center. Any imaginary slice through the
central axis divides the animal into
mirror images.
• Some animals exhibit bilateral symmetry
– Or two-sided symmetry
Bilateral symmetry. A bilateral
animal, such as a lobster (phylum
Arthropoda), has a left side and a right
side. Only one imaginary cut divides the
animal into mirror-image halves.
What Kind of Symmetry Do I Have?
What Kind of Symmetry Do I Have?
What Kind of Symmetry Do We Have?
What Kind of Symmetry Do We Have?
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Anatomical Planes and Directions
Fig. 7.9
Sagittal plane
7-9
Bilateral Symmetry
Anatomical Terms of Direction
• Anterior
– Head end (end that meets its environment first in
bilateral animals)
• Posterior
– Tail end
• Dorsal
– Back of an animal; upper surface
• Ventral
– Belly of an animal; lower surface
Anatomical Terms of Direction
• Medial (median)
– On or near the plane that divides a bilateral animal
into mirror images.
• Lateral
– Away from the plane that divides a bilateral animal
into mirror images.
• Distal
– Away from the point of attachment of a structure on
the body.
• Proximal
– Toward the point of attachment of a structure on the
body.
Anatomical Terms of Direction
• Oral
– End containing the mouth.
• Aboral
– End opposite the mouth
• Cephalic (Cranial)
– Toward the head
• Caudal
– Toward the tail
• Inferior
– Below a point of reference
• Superior
– Above a point of reference
Now you do it…
Tissues
• Animal body plans
– Also vary according to the organization of the
animal’s tissues.
• Tissues
– Are collections of specialized cells isolated from
other tissues by membranous layers.
• Early embryonic development in animals
2 Only one cleavage
stage–the eight-cell
embryo–is shown here.
1 The zygote of an animal
undergoes a succession of mitotic
cell divisions called cleavage.
3 In most animals, cleavage results in the
formation of a multicellular stage called a blastula.
The blastula of many animals is a hollow ball of cells.
Blastocoel
Cleavage
Cleavage
6 The endoderm of
the archenteron develops into the tissue
lining the animal’s
digestive tract.
Zygote
Eight-cell stage
Blastula
Cross section
of blastula
Blastocoel
Endoderm
5 The blind pouch
formed by gastrulation, called
the archenteron,
opens to the outside
via the blastopore.
Ectoderm
Gastrula
Blastopore
Gastrulation
4 Most animals also undergo gastrulation, a rearrangement of the
embryo in which one end of the embryo folds inward, expands, and
eventually fills the blastocoel, producing layers of embryonic tissues:
the ectoderm (outer layer) and the endoderm (inner layer).
Development in Classification
• Animal embryos – Form germ layers, embryonic tissues, including
ectoderm, mesoderm, and endoderm.
– Ectoderm develops into the epidermis (outer covering).
– Mesoderm develops into muscle, mesentary, and other
organs between digestive tube and outer covering.
– Endoderm lines the digestive tube and organs that come
from it.
• Diploblastic Animals
– Have two germ layers, ectoderm and endoderm.
(Jellyfish)
• Triploblastic Animals
– Have three germ layers, ecto-, meso-, and endoderm.
(Vertebrates)
Diploblastic Organization
• Body parts are organized
into layers derived from
two embryonic tissue layers
– Ectoderm – gives rise to the
epidermis, outer layer of the
body wall
– Endoderm – gives rise to the
gastrodermis, the tissue that lines the gut cavity
• Mesoglea – middle layer between the epidermis and
gastrodermis; comes from ecto- or endoderm.
Triploblastic Organization
• Third embryological layer
– Mesoderm – is between the ectoderm and
endoderm; develops independently.
• Gives rise to supportive, contractile, and blood
cells
• Most have an organ-system level of
organization
• Usually bilaterally symmetrical and are
relatively active
Triploblastic Organization
• Broken into groups based on presence or
absence of a body cavity
• Body cavity is a fluid-filled space that can
suspend and separate the internal organs
from the body wall
• Many advantages to a body cavity
Advantages to a Body Cavity
1. More room for organ development
2. More surface area for diffusion of gases,
nutrients, & wastes into and out of organs
3. Area for storage
4. Act as hydrostatic skeleton (ie - water filled balloon)
5. A way to eliminate waste products
6. Facilitate increased body size
Triploblastic Body Plans
Body Cavity Development
• Body Cavity (Coelom) – is a fluid-filled space
separating digestive tract from outer body wall.
– Cushions internal organs, allows internal organs to
move independently of the outer body wall,
hydroskeleton in some animals (earthworm).
– Animals with no coelom - acoelomates
– Animals with a true coelom – coelomates – coelom
forms from mesoderm to become mesenteries and
suspend internal organs.
– Animals form a cavity from the blastocoel pseudocoelomates
Acoelomate
• Relatively solid mass of cells between
ectoderm and endoderm
• Organisms without body cavities
– Are considered acoelomates
Body covering
(from ectoderm)
Tissuefilled region
(from
mesoderm)
(c)
Acoelomate. Acoelomates such as flatworms
lack a body cavity between the digestive tract
and outer body wall.
Digestive tract
(from endoderm)
Pseudocoelom
• A body cavity not entirely lined by mesoderm
• “False” cavity
• A pseudocoelom
– Is a body cavity derived from the blastocoel, rather
than from mesoderm
Body covering
(from ectoderm)
Pseudocoelomates such as
nematodes have a body
cavity only partially lined by
tissue derived from
mesoderm.
Pseudocoelom
Digestive tract
(from ectoderm)
Muscle layer
(from
mesoderm)
Ceolom
• A body cavity completely surrounded by
mesoderm
• Thin mesodermal sheet called mesentaries
line visceral organs
• A true body cavity
– Is called a coelom and is derived from mesoderm
Coelom
Coelomate. Coelomates such as
annelids have a true coelom, a
body cavity completely lined by
tissue derived from mesoderm.
Body covering
(from ectoderm)
Tissue layer
lining coelom
and suspending
internal organs
(from mesoderm)
Digestive tract
(from endoderm)