Introduction to Animals
Section 1: Nature of Animals
I. Vertebrate vs. Invertevrate
A. Vertebrate – has vertebrae or backbone
surrounding nerve cord (spinal cord)
B. Invertebrate – no backbone surrounding
nerve cord; 95% of animal species!!!
II. What is an animal?
A. Multicellular – each cell depends on the
functions of all other cells
1. Specialization – a cell has developed to
perform one specific function; a division of
labor among the cells
2. Cell Junctions – connections between cells
that hold them together to make a tissue
• Review: Tissue – group of specialized
cells working on one function together
B. Heterotroph – animals must obtain
organic molecules (a.k.a. food) through
ingestion.
C. Sexual Reproduction & Development
1. The 1st cell is a fertilized egg – diploid zygote
2. Differentiation – zygote divides to produce
more cells, which grow & “learn” the
function(s) they will be responsible for.
***Differentiation is the process that results in
Specialization!!
D. Movement
1. Animals have muscle and nerve tissue (or at
least cells).
2. Neurons (nerve cells) use electrical signals
to trigger muscle movements.
III. Origin & Classification of Animals
A. Flagellated, Colonial Protist gave rise to
early invertebrates.
B. An invertebrate gave rise to vertebrates
Section 2: Animal Bodies
I. Symmetry – describes organization of an
animal’s body, if parts are arranged in
mirror images of one another.
A. Asymmetry – body shows no symmetry
•
Ex: sponges, corals
B. Radial Symmetry – body has 2 or more
planes of symmetry, body is arranged in
a circular fashion
•
Ex: star fish, anemones, sand dollars
C. Bilateral Symmetry – body has only one
plant of symmetry
•
Ex: fish, mammals, birds (all vertebrates!)
II. Anatomical Positions – term that describes
areas of the body
1. Anterior – towards the head
2. Posterior – towards the tail
3. Dorsal – towards the upper part or back of a
standing animal
4. Ventral – towards the lower part or belly of the
standing animal
5. Medial – towards the midline plane that
separates right and left sides of a body
6. Inferior – below or under a body part
7. Superior – above or over a body part
8. Caudal – toward the back or tail
9. Cranial – toward the front or head
III. Body Tissues & Cavities
A. Germ Layers – tissue types found in embryos
1. Sponges have none
2. Cnidarians & Ctenophores have 2 germ
layers (anemones and jellies)
3. All other animals have 3 germ layers
• Are mostly bilaterally symmetrical
• Show Cephalization – concentration of
sensory organs toward the anterior end
(in the head)
B. Body Cavities – fluid-filled space
between digestive tract
and outer wall of the body
IV. Animal Phyla
A. Ten Invertebrate Phyla
•
•
Very diverse in symmetry & body
organization
Ex: sponges, insects, starfish
B. One Vertebrate Phylum (Chordata) – all
animals have the following structures at one
point in life, but many lose them as they
mature
1. Notochord – firm, flexible rod of tissue
2. Dorsal Nerve Chord – located just above the
notochord; gives rise to spinal cord
3. Pharyngeal Pouches – our pockets of
digestive tract at anterior end
4. Postanal Tail – muscles near posterior end
Section 3: Invertebrates vs.
Vertebrates
I. Invertebrates – over 95% of animals
A. Symmetry – radial or bilateral
1. Sponges are asymmetrical
2. Bilateral allows for cephalization
B. Segmentation
1. Some invertebrates are segmented, the
body is made of repeating units (earthworm)
2. Segments can be almost identical
(earthworm) or very different (lobster).
Segmentaion
C. Body Support – what holds the body up
1. Simple skeletons (sponges)
2. Fluids inside the body cavity push out on the
outer covering of the animal (roundworms)
3. Exoskeleton: rigid, outer covering that
protects body & must be shed as the animal
grows. A new exoskeleton will grow in its
place (animal is very vulnerable at that time).
D. Respiratory & Circulatory Systems
1. Respiratory – exchange of gases (CO2 & O2)
• Most invertebrates exchange gases
directly through their outer covering or gills
2. Circulatory – moving fluid through the body to
transport O2 and nutrients
• Open Circ. System: blood is pumped into
body cavity (no blood vessels)
• Closed Circ. System: blood travels through
body cavity in vessels
Open vs. Closed Circulatory
Systems
E. Digestive & Excretory System
1. Digestion – break down of food to gain
nutrients
• Sponges: digestion occurs in each cell
• Digestion can occur in a central chamber
(Cnidarians)
• Digestion can occur in a gut
E. Digestive & Excretory System (cont)
2. Excretion – release wastes from the body
• Aquatic invertebrates: waste is released as
ammonia
• Land invert.: ammonia is converted into a
less toxic substance
F. Nervous System
1. Using electrical impulses to control body
functions
2. Large amounts of diversity among
invertebrates!!
G. Reproduction & Development
1. Hermaphrodites – single animal produces
both male and female gametes (earthworm)
2. Indirect Development – enter a larval stage,
then mature into an adult
• Ex: ?
3. Direct Development - no larval stage; at
birth, animal already resembles adult form
• Ex: ?
II. Vertebrates – all have bilateral symmetry!!
A. Body Support
1. Endoskeleton: internal skeleton that
supports large, heavy bodies
B. Segmentation
1. All vertebrates are segmented somewhere
on or in their bodies (ribs, vertebrae)
C. Body Coverings – Integument System
1. Aquatic Vertebrates: have moist skin which
allows for gas exchange through the skin
2. Land vertebrates: skin is watertight
3. Feathers & Fur: expel water & insulate body
D. Respiratory & Circulatory Systems
1. Respiratory: aquatic vert. use gills; land
vert. use lungs
2. Circulatory: closed system with a
chambered heart
E. Digestive & Excretory Systems
1. Digestive: have a gut running anterior to
posterior
2. Excretion: converts ammonia to less toxic
substance; filters blood through kidneys
F. Nervous System
1. Brain & nervous tissue is organized into an
efficient system.
G. Reproduction & Development
1. Embryos can develop in an egg outside
mother’s body or inside body in a uterus.
2. All vertebrates undergo direct development!