Download Bilateral Symmetry

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?
 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:
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
1.
Embryology Sequence of Events:
1.
2.
3.
4.
Fertilization
Cleavage
Gastrulation
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 
3. Gastrulation
Gastrulation = formation of a gut;
Major MORPHOGENIC event !!!
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”
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)
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).
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
Pseudocoelomates
such as
nematodes have a
body cavity only
partially lined by
tissue derived from
mesoderm.
Body covering
(from ectoderm
Pseudocoelom
Digestive tract
(from ectoderm)
Muscle layer
(from
mesoderm)
A true body cavity is called a coelom and is
derived from mesoderm
Coelomate.
Coelomates
such as
annelids have
a true coelom,
a body cavity
completely
lined by tissue
derived from
mesoderm.
Coelom
Body covering
(from ectoderm)
Tissue layer
lining coelom
and suspending
internal organs
(from mesoderm)
Digestive tract
(from endoderm)
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
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
b. Deep refers to being more internal
7. Plantar
Refers to the sole of the foot
the surface
Body Planes (Sections)
The body can be sectioned in three different planes. Each one gives a
different perspective.
Body Planes (Sections)
1.
2.
3.
Sagittal Section – lengthwise (vertical) cut that divides the
body into right & left halves
Transverse Section – horizontal cut that divides the body
into inferior and superior portions
Coronal Section – vertical cut that divides the body into
anterior & posterior portions