I. Molecular paleontology – the study of how different body plans evolved ---
comparing DNA among living invertebrates to help determine which phyla are most
II. This shows the evolution of vertebrates:
The Geological Timetable:
ERA: PERIOD: EPOCH: of years EVENTS:
Recent 0.01 Historic time
Pleistocene 2.5 Ice ages; humans appear
Ape-like ancestors of
CENOZOIC Tertiary Origins of most modern
Flowering plants appear;
Conifers, mammals & birds
appear; dinosaurs dominant
Origin of most modern
orders of insects
Origin of reptiles;
Carboniferous 345 amphibians & bony fishes
dominant; first seed plants
Devonian 395 First land plants
Ordovician 500 First vertebrates
Cambrian 570 Origin of most invertebrates
Approximate age of the
The first eon of Earth’s history, from the first coalescence of the planet, about 4500 Mya, to
about 542 Mya, is referred to as the Precambrian. From this hint, one might well suppose
that the Cambrian comes next -- which it does, in a way. Actually, this is the biggest break
point in all of geology. It marks the beginning of the Phanerozoic Eon, the Paleozoic Era,
the Cambrian Period, the Terreneuvian Epoch, and the Fortunian Age (the first age of the
Cambrian). The Cambrian Period was named in 1835 by the geologist Adam Sedgwick,
after the region of Cambria in North Wales, where rocks of this age were first found. The
name "Cambria" is a version of Cumbria, a latinisation the Welsh Cymry (= countryman,
compatriot against the invading Anglo-Saxons).
Long before it was a formal stratigraphic unit, the Cambrian was a concept about Earth
history. It was understood to be the earliest period in which one could find the fossils of
multi-celled animals (Metazoa). Since then, metazoans and their fossilized traces have been
found well before 550 Mya. In particular, Ediacarans, a group of very strange and poorly
understood creatures -- but obviously metazoans -- have been found in many parts of the
world with ages pushing the 600 Mya mark.
Consequently, paleontologists now view the Cambrian as the period when the Bilateria first
appeared and, almost at the same time, the first metazoans with shells. The Bilateria include
all living metazoans except jellyfish, corals, and sponges. Bilaterians have a head at one end
of an elongate body which is bilaterally symmetrical (hence the name). Their embryos all
develop a separate layer of embryonic cells, called mesoderm, between the gut or coelom
and the outer wall of the animal. If this whole description suggests a worm, you’ve got the
right idea. A flatworm is the most basal living form of bilaterian.
Unlike many other, somewhat arbitrary, geological markers, the base of the
Cambrian Period is defined with reference to the underlying paleontological
concept. Small worms rarely leave body fossils, but their burrows are frequently
preserved. The burrows of bilaterian worms are fairly distinctive. Trace fossils are
often given names as if they were organisms, and the earliest well-known bilaterian
trace fossil is a type of fossilized burrow referred to as Treptichnus pedum. The base
of the Cambrian is currently defined as the first occurrence of T. pedum at Fortune
Head, near the town of Fortune, on the north coast of western Newfoundland,
(a) Most animal phyla are invertebrates (in fact, all but one animal phylum contain
nothing but invertebrates)
(b) Extant animals are grouped into approximately 35 phyla
(c) In this survey of the invertebrates we will consider only 10 of these
V. Body Plans or Body Symmetry ---- to see a picture of the animal, click on the link
1. No symmetry –
a. Sponge with belongs to the animal kingdom and the phylum Porifera----this
phylum contains all invertebrates with pore like bodies.
2. Radial Symmetry – body parts extend from the center of the body
a. Portuguese Man Of War---this invertebrate belongs to the animal kingdom and
the phylum Cnidarian----this phylum contains all invertebrates with stinging
cells in the tentacles
Define the following:
b. Starfish---this invertebrate belongs to the animal kingdom and the phylum
Echninodermata----this phylum contains all invertebrates with a spiny type skin
Define the following
1. Tube feet
3. Radial canal
3. Bilateral Symmetry – this basically means that the animal has a mirror image of the left
and right sides.
EXAMPLES – click on link
a. Tapeworms – this invertebrate belongs to the animal kingdom and the phylym
Define the following
b. Hook Worm – this invertebrate belongs to the animal kingdom and the phylum
Nematoda – which means round with NO segments---smooth
c. Earthworm – this invertebrate belongs to the animal kingdom and the phylum
Annelida --- which means segmented body
Define the following
3. Closed Circulatory System
d. Clam – this invertebrate belongs to the animal kingdom and the phylum
Molluska---has one or more shells (THIS IS A POWER POINT)
Define the following terms:
3. Open Circulatory System
e. Black Widow Spider – this invertebrate belongs to the animal kingdom and the
phylum Arthropoda…this phylum contains all insects, spiders; it means to have a segmented
Define the following
1. Difference between an insect and a spider
3. Book Lungs
VI. Body Cavities – COELOM
(Mammals the body cavity is called a Coelom and it is the area that contains all heart and
lungs as well as the gut which is a cavity in its own rite. The words used to define different
body cavities relate to how the cavity comes into being during the development of the
embryo as well as to its final observable structure.)
The key words that you need to understand before learning body cavities are as follows:
These layers are a collection of cells that form when the embryo, itself, is developing.
Germ layers are more known in vertebrates; however, anything more complex than a
Sponge (Porifera), usually have primary germ layers or primary tissue layers.
Cnidarians, like the Portuguese Man of War, has 2 primary germ layers; we call the two
layers the ectoderm and the endoderm. (TWO LAYERS are usually in radial symmetrical
Animals with bilateral symmetry have three primary germ layers:
The germ layers give rise to all of the animals organs and tissues
VII. EXPLANATION of the types of body cavities found in invertebrates
Coelomates (also known as eucoelomates--"true coelom") have a fluid filled body cavity
called a coelom (pronounced /ˈsiːləm/) with a complete lining called peritoneum derived
from mesoderm (one of the three primary tissue layers). The complete mesoderm lining
allows organs to be attached to each other so that they can be suspended in a particular
order while still being able to move freely within the cavity. Most bilateral animals,
including all the vertebrates, are coelomates.
Pseudocoelomate animals have a pseudocoel, (literally “false cavity”) which is a fully
functional body cavity. Tissue derived from mesoderm only partly lines the fluid filled
body cavity of these animals. Thus, although organs are held in place loosely, they are
not as well organized as in a coelomate. All Pseudocoelomate are protosomes; however,
not all protosomes are Pseudocoelomates. An example of a Pseudocoelomate is the
roundworm. Pseudocoelomate animals are also referred to as Hemocoel and
Acoelomate animals, like flatworms, have no body cavity at all. Organs have direct
contact with the epithelium. Semi-solid mesodermal tissues between the gut and body
wall hold their organs in place.
Terms needed for the first part of chapter 29
8. bilateral symmetry
9. radial symmetry
12. names of each of the phylums
13. germ layers
14. Cambrian Era
VI. Each type of invertebrate has systems to keep it living
The simplest animals break down food primarily through intracellular digestion, whereas more
complex animals use extracellular digestion.
Respiratory organs have large surface areas that are in contact with the air or water. In order
for diffusion to occur, these respiratory surfaces must be kept moist.
Most complex animals move fluid through their bodies using one or more hearts and an open
or closed circulatory system.
Most animals have an excretory system that rids the body of metabolic wastes and controls the
amount of water in their tissues.
Invertebrates show three trends in the evolution of the nervous system: centralization,
cephalization, and specialization.
Invertebrates have one of three main kinds of skeletal systems: hydrostatic skeletons,
exoskeletons, and endoskeletons.
Most invertebrates reproduce sexually during at least part of their life cycle. Depending on
environmental conditions, however, many invertebrates may also reproduce asexually.
1. DIGESTIVE SYSTEM
a. Intracellular digestion – this is when the organism brings in food by way of
Phagocytosis; it is found in sponges and the cnidarians…jelly fish, Portuguese
man of War, etc.
http://microbes.arc.nasa.gov/movie/large-qt.html - this link will show you
b. Extra cellular digestion – this is when the organism secretes enzymes through a
membrane to digest the food it took in. These small particles that have been
broken down are small enough now to be phagocyzed. The resulting product is
transported throughout the organism by blood or body fluid.
c. Simplest animals tend to use intracellular digestion. More complex animals tend
to use extra cellular digestion, in which food is broken down in a digestive
d. Simplest digestive systems have just one opening through which food is taken in
and wastes are expelled. More complex digestive systems have two openings -- a
mouth and an anus.
USE THE FOLLOWING POWER POINT TO LEARN MORE OF THESE TYPES OF
VII. RESPIRATORY SYSTEMS
a. Aquatic invertebrates – the oxygen in the water, that the invertebrate lives, has
Oxygen in it. This Oxygen diffuses into the body; carbon dioxide, a waste
product formed in the invertebrates body, diffuses out.
b. Terrestrial invertebrates---these invertebrates bring Oxygen in through
specialized openings OR their skin is moist.
c. Respiratory systems require a thin moist membrane and a large surface area for
effective gas exchange
a. Open circulatory system----this type of invertebrate has no arteries and veins; the
blood is colorless…has no hemoglobin
b. Closed Circulatory system – the fluid/blood stays within arteries and veins; blood
is red because it has the red pigment hemoglobin in it.
IX. RESPONSE – stimulus leads to a response (irritability)
a. Three trends in the evolution of the nervous system are centralization,
Cephalization, and specialization
b. Specialization ---some animals like the Cnidarians (Jelly Fish, Portuguese Man
of War, have a nerve net as its nervous system---it is a loosely organized system
of nerves with NO central control. Impulses are conducted in both directions
causing the movement of the invertebrate.
c. Cephalization---this is an evolutionary trend; it shows that the nervous tissue
becomes more concentrated toward one end of an organism; this leads to sensory
organs. This occurs with bilateral symmetrical invertebrates
Although the ameba is a single-celled
animal, it does appear to be sensitive to
Ameba/Paramecium the environment. This tiny animal moves
away from light, but it has no
photodetectors or eyes. The paramecium,
another single-celled animal, also has no
specialized sensory structures. However,
it avoids cold, heat and chemicals by
backing up and moving away.
Euglena have an eyespot that acts as a
shield for a light sensitive receptor. This
Euglena (flagellate) small animal can detect the strength and
direction of light. It prefers a location
with moderate light and moves away
from darkness and bright light. Euglena
probably use this receptor to keep
themselves in light which they use for
photosynthesis. Euglena use
photosynthesis for energy although they
Image courtesy of Biodidac can eat solid food (like animals) if they
are kept in the darkness.
Sponges are the only multicellular
animals without a nervous system. They
do not have any nerve cells or sensory
cells. However, touch or pressure to the
outside of a sponge will cause a local
contraction of its body.
Image courtesy of Biodidac
The hydra has a nervous system
characterized by a nerve net. A nerve net
Hydra is a collection of separate, but
"connected" neurons. Neurons are
connected by synapse. Communication
between neurons can be in both directions
at the synapse within a nerve net. The
nerve net is concentrated around the
mouth. Unlike higher animals, the hydra
does not have any grouping of nerve cell
bodies. In other words, there are no
The hydra does have specialized
cells for touch and chemical
Like the hydra, the jellyfish has a nervous
system characterized by a series of
interconnected nerve cells (a nerve net).
The nerve net conducts impulses around
the entire body of the jellyfish. The
strength of a behavioral response is
proportional to the stimulus strength. In
other words, the stronger the stimulus, the
larger the response.
Some jellyfish (for example,
Aurelia) have specialized structures
Jellyfish called "rhopalia". These rhopalia
have receptors for:
light (called ocelli)
balance (called statocysts)
chemical detection (olfaction),
touch (called sensory lappets)
st. When the animal moves and body is
tilted, the statocyst makes contact with
the cilium. When the cilium bends, it
causes action potentials to fire in a nerve.
This provides information to move
Like the jellyfish and hydra, the anemone
has a nerve net.
The nervous system of the flatworm has
an organization different from the
invertebrates describe above. It does have
Flatworms (Planaria) a nerve net, but these are connected by
long nerve cords. These cords are
connected to cerebral ganglia located in
the head region. The central nervous
system has been described as "ladder-
like" because of the nerves connecting the
Flatworms have "auricles" that
project from the side of the head.
These auricles contain
chemoreceptors that are used to find
food. Flatworms also have eyespots
called "ocelli". The ocelli are
sensitive to light and are connected
to the cerebral ganglia. Generally,
the flatworm avoids light.
The nervous system of the earthworm is
Earthworm "segmented" just like the rest of the body.
The "brain" is located above the pharynx
and is connected to the first ventral
ganglion. The brain is important for
movement: if the brain of the earthworm
is removed, the earthworm will move
continuously. If the first ventral ganglion
is removed, the earthworm will stop
eating and will not dig. Each segmented
ganglion gets sensory information from
only a local region of its body and
controls muscles only in this local region.
Earthworms have touch, light,
vibration and chemical receptors all
along the entire body surface.
The nervous system of the starfish is very
simple...there is no brain and there are not
even any ganglia to coordinate
Sea Star movement. The nervous system is
("Starfish") characterized by a nerve ring that
surrounds the mouth. A radial nerve
branches off of the nerve ring and extends
to each arm. The picture on the left shows
one of 3 nerve nets that extend
throughout the body.
Starfish have an interesting way of
detecting light. They have
"eyespots" at the tip of each arm.
The eyespot contains light sensitive
pigments that allow the starfish to
detect shadows and changes in the
brightness of light.
Snails The nervous system is characterized by 6
ganglia. Some snails have chemosensors
called "osphradia" in the mantle cavity.
These osphradia are used to detect
chemicals in the air or water.
The aplysia has several ganglia that are
(Sea Hare) connected by long nerves. The cell bodies
of some neurons are very large (1 mm in
diameter). Neuroscientists like these cells
because they are easy to: 1) see 2) record
action potentials 3) inject chemicals.
Image courtesy of BrainSurf
The nervous system is comprised of 3
pairs of ganglia (cerebral, visceral and
(clams, scallops) pedal) each associated with the
esophagus, muscles close to the shell, and
The crab has a condensed central nervous
system consisting of several ganglia.
The lobster has a brain connected to a
first ventral ganglion. This ganglion is
located under its stomach. A double nerve
cord extends from the first ventral
ganglion to a series of paired segmental
ganglia running through the entire body
on the ventral side of the animal.
The grasshopper has a brain located
between its eyes, just above the
esophagus. The brain is connected to the
1st ventral ganglion by a pair of ventral
nerves that surround the gut. The
grasshopper can do many things, like
walking and jumping, WITHOUT its
(such as grasshoppers) brain. The brain is used to relay sensory
information to other parts of the body and
to help with movement. The first ventral
ganglion is used primarily to control
movement of the mouth. The segmental
ganglia throughout the length of the
grasshopper are connected to the first
ventral ganglion by a double nerve cord
and serve to coordinate local activities.
Insects have a compound eye
containing many different units
called "ommatidia". Each ommatidia
is like an individual lens that
samples a small part of the visual
field. There can be thousands of
ommatidia in a single insect eye.
movies that show an insect that sees
thousands of identical images of the
ENTIRE visual field are WRONG --
an insect sees only ONE picture at a
time because each ommatidia sees
only a small part of the entire field.
Some insects are sensitive to
ultraviolet light and others can detect
infrared wavelengths of light.
The octopus has the most complicated
brain of all the invertebrates. The octopus
brain is estimated to have 300,000,000
neurons. These neurons are arranged in
lobes and tracts that are more specialized
than simple ganglia. An octopus has a
"good" memory and can also learn.
Octopus The eye of the octopus is very
similar to that of vertebrates in that it
has a cornea, lens, iris and retina. It
can also focus and form images.
However, the octopus eye is
different from that of vertebrates in
that it focuses light by moving the
lens closer and further away from
the retina. The vertebrate eye
focuses by changing the shape of the
lens. Octopi can perceive shape,
color intensity and texture. Another
difference is that the eye of the
octopus has NO blind spot because
the nerve cells leave from the
outside of the eyeball. The octopus
also has a statocyst located next to
the brain. The statocyst is used to
detect changes in gravity and
respond to acceleration.
Excretory systems regulate the amount of water in the body and dispose of nitrogenous
A. Protozoan and sponges- lack complex excretory organ
1. Contractile vacuoles excrete water and solutes
2. Depends on ambient osmotic conditions- contracts more frequently and expels
more water in fresh H2O
B. Flatworms- branched longitudinal tubules in a hollow bulb
Cilia inside bulb create currents within cell (flame cells)- fluid and waste carried
out through excretory pores.
C. Mollusks- have protonephridia or metanephridia-
1. Freshwater animals- nephridia produce a copious hypo osmotic urine- excrete
water, conserve ions
2. In marine animals- urine- iso-osmotic with body fluid, vol. low to conserve
D. Crustaceans- rely primarily on antennal and maxillary glands for solute excretion.
Urine is formed by filtration at the terminal coelom-sac, which has an arterial;
E. Earthworms- closed circulatory system- excretion is carried out by nephridia.
1. Body fluid enter nephridium through the membrane of the bulb-like
nephrostome, which is ciliated opening into the nephridium
2. The nephridium gives rise to a coiled tubule, which is closely associated with
3. This allows reabsorption of material; the nephridium terminates in a large
bladder that opens to the outside by nephridiopore
F. Insects- excretory structure- Malpighian tubules forms urine by active K+ secretion
into the tubules, water and solutes follow passively.
1. Tubules are out pocketing of the gut at the junction of the midgut and
2. These sacs are washed by the blood, fluids and salts are reabsorbed.
3. The urine formed moves into the hindgut and out of body through
4 Both feces and urine exit through the anus where water is reabsorbed
a. Asexual reproduction makes it possible for one individual to rapidly produce
many genetically identical offspring. Sexual reproduction creates new
combinations of genes.
b. Fertilization may be internal or external.
XII. SUPPORT AND MOVEMENT
a. Hydrostatic Skeleton --- is a structure found in many cold-blooded
organisms and soft-bodied animals consisting of a fluid-filled cavity, the
coelom, surrounded by muscles. The pressure of the fluid and action of the
surrounding muscles are used to change an organism's shape and produce
movement, such as burrowing or swimming. Hydrostatic skeletons have a
role in the locomotion of echinoderms (starfish, sea urchins), coelenterates
(jellyfish), annelids (earthworms), nematodes, and other invertebrates.
b. Sea anemones and earthworms do not have a single bone in their bodies.
Instead, they are supported by pressure from a liquid which consists
mainly of water in their cells and in spaces between their body. The
hydrostatic skeleton allows the earthworm to burrow through the earth.
They have some similarities to muscular hydrostats.
c. Exoskeleton ---- an outer covering is found over the outside of the invertebrate.
An exoskeleton is a type of skeleton that is an external anatomical feature
that supports and protects an animal's body, in contrast to the internal
endoskeleton of, for example, a human. Whilst many, many other
invertebrate animals (such as shelled mollusks) have exoskeletons in the
sense of external hard parts, the character is most associated with the
arthropods (i.e. insects, spiders, myriapods and crustaceans). Exoskeletons
contain rigid and resistant components that fulfill a set of functional roles
including protection, excretion, sensing, support, feeding and (for
terrestrial organisms) acting as a barrier against desiccation. Exoskeletons
first appeared in the fossil record about 550 million years ago, and their
evolution has been seen as a critical driving role in the Cambrian
explosion of animals that took place subsequent to this time.
d. Endoskeleton – a skeletal structure within a body; common to invertebrates