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Zoology – the study of animals.
 There are 1.5 million+
animals (estimates as
high as 3 million
undescribed).
 Classified into 35
current Phylums
 Phylum Arthropoda =
1.2 million+ named
species.
 Mammals represent
only about 5, 000
named species!
Zoology Disciplines
 Comparative Anatomy – the study of structures
and functions of various animal groups.
 Taxonomy – the science of finding, describing, and
classifying animals.
 Entomology – the study of insects.
 Ichthyology – the study of fish
 Herpetology – the study of reptiles and
amphibians.
 Ethology – the study of animal behavior.
 Malacology – the study of molluscs.
 Myrmecology – the study of ants.
 Helminthology – the study of worms
What is an Animal?
Petunia is a plant
and
Wolf spider is an
animal.
What is an Animal?
 Coral
sessile (“rooted”?)
stem, branches,
greenish.
Resembles plant;
but this IS an
animal! Why?
What IS an Animal?
 Definition of "Animal"
Multicellular (so are plants, fungi)
Eukaryotic (so are plants, fungi)
Diploid (usually) (so are plants, fungi)
Meiosis produces gametes called
sperm and egg
Sperm, egg are the only haploid cells
Heterotrophic by ingestion
Cells lack cell walls.
What IS an Animal?
Basic structure (not definition) = Tube-in-tube
 Body wall = outer tube
 gut (GI tract) = inside tube
mouth
anus
Embryological Development
in Animals
 Every animal begins as ZYGOTE
 How do animals develop tube-in-tube
body form?
 Important in understanding
relationships, classification of Phyla.
Three fundamental
processes:
1.
Morphogenesis
(morph- = shape, + genesis = origin)
Origin of shape, form
2. Differentiation
Process of cells becoming different,
and specializing for different functions
3. Growth
Increase in size, requires input of
matter, food
Embryology Sequence of Events:
1. Fertilization
2. Cleavage
3. Gastrulation
4. Organogenesis
1. Fertilization
Gametes join in fertilization
gametes are produced
(gametogenesis) through meiosis
What process produces every other
cell in the human body?
MITOSIS
Let the Division Begin!
2. Cleavage
 Cleavage is a series of rapid mitotic divisions
(without cell growth)
 The two-celled zygote divides repeatedly until
a ball of 32 cells is formed
 This is the morula - 32 cells 
 Continued divisions make the hollow blastula
 These few cells are pluripotent (have the potential to become
ANY of the 220 types of cells in the human body).
 These are embryonic stem cells
3. Gastrulation
Gastrulation = formation of a gut;
 Major MORPHOGENIC event !!!
 At the end of the cleavage stage, cells making up the
blastula move about and surface proteins help cells
recognize each other
 Location of cells after GASTRULATION determines further
development
 The gastrula is formed, which can consists of 3 “germ
layers”
1. Endoderm “inside skin”
2. Mesoderm “middle skin”
3. Ectoderm “outside skin”
 Will yield Archenteron in primitive animals
“ancient gut” = first formation of "inside tube."
Development in Classification
Tissues -collections of specialized cells
working together and isolated from
other tissues by membranous layers.
(germ layers)
• Diploblastic Animals
– Have two germ layers, ectoderm and
endoderm. (Jellyfish)
• Triploblastic Animals
– Have three germ layers, ecto-,
meso-, and endoderm. (Vertebrates)
Gastrulation
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).
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
Organisms without body cavities
Are considered acoelomates
Acoelomate.
Acoelomates such as
flatworms lack a body
cavity between the
digestive tract and
outer body wall.
Body covering
(from ectoderm)
Tissuefilled region
(from
mesoderm)
Digestive tract
(from endoderm)
A pseudocoelom
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)
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)
Coelomates will further branch into
either a Protostome or
Deuterostome
Based on certain features seen in early development
3 Characteristics Determine the Group:
Cleavage Pattern (Cell Division)
Coelom Formation
Fate of the Blastopore
Cleavage Pattern (Cell Division)
In protostome development
Cleavage is spiral (mitotic spindles at diagonals to embryo axis) and
determinate (cells fixed on a developmental pathway)
In deuterostome development
Cleavage is radial (spindles parallel and perpendicular) and indeterminate
(cells can adjust)
Protostome development
(examples: molluscs, annelids,
arthropods)
Eight-cell stage
Spiral and determinate
Deuterostome development
(examples: echinoderms,
chordates)
Eight-cell stage
Radial and indeterminate
(a) Cleavage. In general, protostome
development begins with spiral,
determinate cleavage.
Deuterostome development is
characterized by radial, indeterminate
cleavage.
Coelom Formation
In protostome development, the solid
mass of mesoderm cells split to form
the coelom
In deuterostome development,
mesoderm buds from endoderm
Fate of the Blastopore
 In protostome development the blastopore becomes the mouth
 In deuterostome development the blastopore becomes the anus
Mouth
Anus
Digestive tube
Mouth
Mouth develops
from blastopore
Anus
Anus develops
from blastopore
4. Organogenesis
Organogenesis Purpose:
 Formation of organs from three germ layers
 Differentiation & continued Morphogenesis
1. Ectoderm will form the following:
 Epidermis
 Lining of mouth & rectum
 Cornea of eye
 Lens of eye
 Nervous system
 Thin linings of gut & branches
 lining of excretory ducts, bladder
 Lining of
lungs, trachea
 Lining of reproductive ducts, uterus, vas deferens
 liver
 pancreas
Organogenesis
2.
Mesoderm will form the following:
Skeleton,
Muscles (skeletal, smooth, cardiac)
Dermis of skin
Heart, blood, blood vessels
Kidneys,
Ovaries/testes, etc.
Organogenesis
3. Ectoderm forms the
following:
Epidermis
 How Nervous system
gets inside
a. Dorsal surface of
embryo forms Neural
plate
b. Plate sinks inward
forming Neural groove
c. Edges of groove fuse to
separate Neural tube
from epidermis
Extraembryonic Membranes
These membranes develop from the
germ layers, but are NOT part of the
embryo (they are lost at birth)
They lie outside of the embryo &
provide protection and nourishment
Four exist in terrestrial vertebrates:
Chorion, amnion, allantois (stores
nitrogenous waste in reptiles), &
yolk sac (not found in humans, but
yolk aids in formation of RBC
Human Development
 The gestation period lasts 266 days from
fertilization to birth
 Organogenesis (development of the organs and
organ systems) begins with the nervous
system
 Think on this:
Do all animals have the same gestation
period?
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 oral-aboral 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.
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?
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Anatomical Planes and Directions
Fig. 7.9
Sagittal
plane
7-9
Bilateral Symmetry
Directional Terms
1. Anterior and Posterior
a. Anterior refers to being towards the front
b. Posterior refers to being towards the
back
2. Dorsal and Ventral
a. Dorsal refers to the upper back region
b. Ventral refers to the bottom region,
relating to the underside
Directional Terms
3.
Superior and Inferior
a. Superior refers to being
above
b. Inferior refers to being
below
Directional Terms
4. Proximal and Distal
a. Proximal refers to being
closer to a point of attachment
or the trunk
b. Distal refers to being farther
away from a point of
attachment or the trunk
Directional Terms
5. Medial and Lateral
a. Medial refers to being closer to
a vertical midline
b. Lateral refers to being closer to
the sides with relation to the
midline
Directional Terms
6. Superficial and Deep
a. Superficial refers to being
closer to the surface
b. Deep refers to being more
internal
7. Plantar
Refers to the sole of the foot
Body Planes (Sections)
The body can be sectioned in three different planes. Each
one gives a different perspective.
Body Planes (Sections)
1. Sagittal Section – lengthwise (vertical)
cut that divides the body into right & left
halves
2. Transverse Section – horizontal cut that
divides the body into inferior and
superior portions
3. Coronal Section – vertical cut that
divides the body into anterior & posterior
portions
Hot Dog Dissection
Objectives:

The student will become familiar with directional terminology.

The student will become familiar with body section cuts.
Procedure:

Identify the superior and inferior position on your specimen.
Label these regions on your paper plate.

Identify the anterior and posterior position on your specimen.

Using a permanent marker, draw a sagittal body plane on the
anterior portion of your specimen. Specimen must be dry for
this!

Discuss with your partner how medial & lateral relate to this
sagittal plane.

Make a medial superficial incision on the posterior side from the
superior to the inferior position.

Now make a superficial transverse incision on the anterior side
proximal to the arms.

On the inferior, anterior tip, remove a 1-inch section. Use this
section to cut a coronal section.

Label the plantar region.

Using the examples in your notes, relate the body terminology
to the relative position terminology.