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-tubeBody wall = outer tube
gut (GI tract) = inside tubemouth
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
Zygote
Cleavage
Eight-cell stage
Cleavage
Blastula Cross section of blastula
Blastocoel
Blastocoel
Gastrula Gastrulation
Endoderm
Ectoderm
Blastopore
Early embryonic development in animals
In most animals, cleavage results in theformation of a multicellular stage called a blastula.The blastula of many animals is a hollow ball of cells.
3
The endoderm ofthe archenteron de-
velops into the tissuelining the animal’s
digestive tract.
6
The blind pouchformed by gastru-
lation, calledthe archenteron,
opens to the outsidevia the blastopore.
5
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).
4
Only one cleavagestage–the eight-cellembryo–is shown here.
2 The zygote of an animal undergoes a succession of mitotic cell divisions called cleavage.
1
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
Body covering(from ectoderm)
Tissue-filled region(from mesoderm)
Digestive tract(from endoderm)
Acoelomate. Acoelomates such as flatworms lack a body cavity between the digestive tract and outer body wall.
A pseudocoelom
a body cavity derived from the blastocoel, rather than from mesoderm
Pseudocoelom
Muscle layer(from mesoderm)
Body covering(from ectoderm)
Digestive tract(from ectoderm)
Pseudocoelomates such as nematodes have a body cavity only partially lined by tissue derived from mesoderm.
A true body cavity is called a coelom and is derived from mesoderm
Coelom
Body covering(from ectoderm)
Digestive tract(from endoderm)
Tissue layerlining coelomand suspendinginternal organs(from mesoderm)
Coelomate. Coelomates such as annelids have a true coelom, a body cavity completely lined by tissue derived from mesoderm.
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)
Deuterostome development(examples: echinoderms,
chordates)
Eight-cell stage Eight-cell stage
Spiral and determinate Radial and indeterminate
(a) Cleavage. In general, protostomedevelopment 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
Anus
Anus
Mouth
Mouth
Mouth developsfrom blastopore
Anus developsfrom blastopore
Digestive tube
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:EpidermisHow Nervous system
gets insidea. 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?
Anatomical Planes and Directions
7-9
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 7.9
Sagittal plane
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 DissectionObjectives: 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.