Animalia

Animals are multicellular, heterotrophic
eukaryotes.

Except for sponges all animals have tissues which
are specialized collections of cells separated from
other tissues by membranes.

Tissues are arranged together to produce organs
and organs are organized into organ systems (e.g.
digestive system).
Animalia

Most animals are bilaterally symmetrical and form
a large clade called the Bilateria.

Bilateral animals have a left and right side, top and
bottom, as well as front and rear ends.

A smaller number are radially symmetrical (e.g.
jellyfish).
Divisions of the Bilateria

We belong to a division of the Bilateria called the
deuterostomes (a group defined by how the
embryo develops).

It includes us and all chordates as well as the
echinoderms e.g. starfish (which have secondarily
evolved radial symmetry).
33.2
Porifera

The phylum Porifera (the sponges) includes about 5000
species almost all of which are marine (there are about 150
freshwater species).

Sponges occur worldwide at all latitudes from the intertidal
zone to the deep sea.

Range in size from a few millimeters to 2 meters across.

Porifera means “pore-bearing” and refers to the numerous
pores and channels that permeate a sponge’s body.
Yellow tube sponge
Barrel sponge
Porifera

Sponges are the simplest multi-cellular
organisms, but they lack the germ layers of
more complex metazoans.
They have a cellular level of organization
lacking true tissues and organs.
 Body is a mass of cells imbedded in a
gelatinous matrix which is supported by a
framework of spicules.

Glass sponge spicules
Porifera feeding

Sponges are sessile and depend on water
movement to bring in food and oxygen and
remove wastes.

Sponges generate their own flow of water having a
unique water current system.
Porifera feeding

Water enters through many small pores called
ostia and exits through fewer, larger oscula.
Oscula
Porifera feeding

Openings are connected by a series of
canals, which are lined by choanocytes
(flagellated collar cells) that maintain the
current and filter out food particles.
Choanocytes
33.2
Cnidaria
Cnidaria

The phylum Cnidaria includes over 9,000 species
of aquatic, radially symmetrical animals which
have specialized stinging organelles called
nematocysts.

They include the jellyfish, box jellyfish, sea
anemones, fire corals, sea pens and hard corals.
Cnidaria

Cnidarians are the simplest animals equipped with
nerve cells which are arranged into a nerve net,
but there is no central nervous system.
Cnidaria: digestion

Cnidarians have an internal body cavity, the
gastrovascular cavity, but no one-way gut. Food
enters and waste exits through the same opening,
the oral cavity.

Digestion takes place extracellularly within the
gastrovascular cavity.
Body forms


Cnidaria have one of two basic body forms
 Polyp
 Medusa
In some groups one or other body form is used
exclusively, but in others the two forms are used in
a single life cycle.
Polyp and medusa



The polyp or hydroid form is adapted to a sessile
existence and the medusa form to a free-floating
or pelagic life.
In both cases radial symmetry is favored because
stimuli and food are equally likely to come from
all directions.
Polyps and medusae may look quite different, but
are basically inverted versions of each other.
Figure 13.02
Fig. 7.2
Figure 13.16
Giant
Jellyfish
Cyanea
capillata
Fig 7.14
Figure 13.21
Fig 7.19
Sea anemones
Polyp and medusa

Both polyps and medusa are equipped with
tentacles around the oral cavity.

The tentacles are equipped with cnidocytes that
contain stinging nematocysts, which are used to
kill prey.
Figure 13.03
Figure 7.3
Coral Reefs

Coral reefs are found in shallow waters in the
tropics.

They are calcareous structures and what makes
them unique as geological structures is that they
are formed by some of the organisms that live on
them, specifically reef-building corals and
coralline algae.

They are the largest living structures on the planet.
Coral Reefs

Reef-building corals contain symbiotic algae
(zooxanthellae) that supply a significant part of
the coral’s energy in exchange for protection and
access to light.

These algae require light for photosynthesis and so
reef-building corals can live only in clear waters
less than 100m deep (and most species occur in
much shallower waters).
Coral polyps
Brain coral (Anthozoa)
Shumann Island, Papua New Guinea (fringing reef).
33.2
Bilateral Animals

Unlike the radiate animals all of these organisms
are mobile and have evolved cephalization with
their sense organs concentrated at the head end.
There is also the beginning of a ladder-type
nervous system.

In addition, they are bilaterally symmetrical.
Plathyhelminthes

Among the simplest bilateral animals but of
significant economic importance is the phylum
Platyhelminthes, which includes a variety of
parasitic forms such as the flukes and tapeworms.
Plathyhelminthes

They have evolved organs and in some cases
organ systems. The simplest excretory or
osmoregulatory systems and circulatory systems
are found in members of these groups.
Phylum Platyhelminthes

Members of the Platyhelminthes typically have
dorsoventrally flattened bodies that are usually
slender and leaflike or ribbonlike.

There are four classes in the Platyhelminthes. The
Turbellaria are free living whereas as members of
the Monogenea, Trematoda and Cestoda are
parasitic.
Class Trematoda

There are about 9000 species of trematodes
(flukes) all of which are parasitic. Most parasitize
vertebrates.

Adaptations for parasitism include suckers and
hooks for attachment, glands to produce cyst
material and increased reproductive capacity.
Sheep liver fluke
Clonorchis liver fluke

Clonorchis is the most important liver fluke to infect
humans. Common in much of Asia (including China,
Japan and southern Asia).

Adult flukes live in the bile passages and shelled miricidia
pass out in feces. The miricidia enter snails eventually
leave the snails as cercariae and find a fish where they
encyst.

If fish is eaten raw or poorly cooked the person becomes
infected
Figure 14.12
8.8
Class Cestoda (tapeworms)

Tapeworms are parasites of the vertebrate
digestive tract and about 4000 species are known.

Almost all tapeworms require at least two hosts
with the definitive host being a vertebrate,
although intermediate hosts can be invertebrates.
Class Cestoda

Members of the Class Cestoda (tapeworms) are
quite different in appearance from the other
members of the Platyhelminthes.

They have long, flat, tape-like bodies composed of
a scolex for attaching to their host and a chain of
many reproductive units or proglottids called a
strobila. New proglottids form behind the scolex
and the strobila may become extremely long.
Figure 14.18
8.12
Tapeworm scolex
Hooks
Suckers
The scolex is equipped with suckers and hooks that
enable it to grip onto its host’s intestines.
Class Cestoda

Tapeworms live in the intestines and because they
are immersed in digested food lack a digestive
system of their own. Instead they simply absorb
food across their tegument.
Human tapeworms

Humans are definitive hosts to several tapeworms
including the beef tapeworm Taenia saginata,
pork tapeworm T. solium, and fish tapeworm
Diphyllobothrium latum.
Human tapeworms

The lifecycles of these parasites are similar.

Shelled larvae are shed into the environment.

These are consumed by the intermediate host and
the larvae hatch, bury into blood vessels and make
their way to skeletal muscle where they encyst
becoming so called “bladder worms” or
cysticerci.
Human tapeworms

The encysted larva waits, perhaps for years, for its
host to be eaten.

If the meat is uncooked the cysticercus extends its
scolex, attaches to the wall of the intestine and
within 2-3 weeks matures and begins growing and
producing eggs. A tapeworm may be many meters
long and live for years.
Figure 14.19
8.15
Mollusca
Mollusca

The molluscs are a very diverse group with over
100,000 living species including such familiar
organisms as clams, mussels, limpets, snails,
squids and octopi.
Mollusca

Many molluscs possess a hard shell and as a result
there are many fossil molluscs (more than 30,000
species have been described).

Molluscs were abundant in the oceans of the
Cambrian period and must have evolved in the
pre-Cambrian over 570 million years ago.
Molluscs

Living molluscs range in size from small clams
and snails to the giant and colossal squids which
can weigh up to 1,000 lbs and measure 60 feet
long with tentacles extended.

The shells of giant clams may be 1.5 wide and
weigh 225 kg, but most molluscs have shells less
than 5cm across.
Molluscs

The word Mollusca is from the Latin molluscus meaning
soft and describes the soft body, which is one of the key
features of the group.

Most molluscs live in the sea and range from tropical to
Arctic waters. Others occur in freshwater and on land.

There is a great range of life styles that includes bottom
feeding, filter feeding, boring, burrowing and pelagic
forms.
Molluscs

Molluscs have diversified into a great variety of
body forms from the sessile, filter-feeding clam to
the slow-moving grazing snail to the actively
hunting, intelligent octopus.

These different forms are all derived from a basic
molluscan body plan.
Molluscan body plan

At its simplest the molluscan body consists of a
head-foot and a visceral mass.

The head-foot contains the locomotory, feeding,
cephalic, and sensory organs.

The visceral mass includes the digestive,
circulatory, respiratory and reproductive organs.
Molluscan body plan: Head-foot

Many molluscs have a well developed head that
contains a mouth, often tentacles, and some
specialized sensory organs.

Many possess eyes that range from very simple
light sensing structures to the highly developed
eyes of cephalopods.
Figure 16.25
Bay scallop (note the blue eyes).
Figure 16.37
Cuttlefish
Figure 16.28a
Incurrent and excurrent siphons of
Northwest ugly clam
10.26
Mating snails.
Cone shell
Phylum Annelida

The annelids (L. annelus: a little ring) are the
segmented worms.

The annelid body is metameric being composed of
serially repeated segments or metameres.

Each segment is separate from the next segments
being divided by partitions or septa.
Figure 17.03e
Segmentation

Within each segment are components of most
organ systems such as the circulatory, nervous and
excretory systems.

Thus, there is a degree of redundancy in annelids
so that if a segment is damaged it need not be
fatal.
Segmentation

The evolution of segmentation is the great evolutionary
innovation of the annelids.

Because the coelom is divided by septa the force of muscle
contraction in a segment is not transmitted throughout the
body, but instead is confined to the single segment.

Thus, one segment may elongate while the adjacent one
contracts and this allows the animal to make fine,
controlled movements
Annelids

Annelids occur worldwide being found in the sea,
freshwater, and in the soil.

They feed on organic matter in the mud or soil, by
filtering suspended particles from the water, act as
predators, or suck blood.
Figure 17.02b
11.3B
Figure 17.19
World’s largest leech
Haementeria ghilianii
11.17
Phylum Arthropoda

The Arthropoda (from the Greek Arthron, joint
and podus, foot) are the largest group of organisms
and they occur in all environments on earth.

The group includes: spiders, ticks, mites,
centipedes, millipedes, crustaceans, insects and
others.
Characteristics of the Arthropoda

Bilaterally symmetrical with a segmented
(metameric) body divided into head, thorax and
abdomen; cephalothorax and abdomen; or fused
head and trunk.
Characteristics of the Arthropoda

Jointed appendages. Primitively one pair per
segment, but number often reduced.

Appendages often greatly modified for specialized
tasks.
Characteristics of the Arthropoda

Exoskeleton of cuticle.

Exoskelton secreted by underlying epidermis.
Made of chitin, protein, lipid and often calcium
carbonate.

Exoskeleton is shed periodically (ecdysis) as the
organism grows.
Classification of Phylum Arthropoda




Subphylum Chelicerata: horseshoe crabs, spiders,
tick, mites, scorpions,
Subphylum Crustacea: crabs, lobsters, copepods,
barnacles, pill bugs
Subphylum Myriapoda: millipedes and centipedes
Subphylum Hexapoda: springtails, insects
Figure 18.02
12.2
Hobo spider
Brown recluse spider
Female Black Widow spider with egg sac
Figure 18.10a
12.10 a
Figure 18.12
Dust mite
Figure 18.11a
Wood tick
Wood tick
Figure 20.01
12.32B
Figure 19.02a
12.16A
Figure 20.04a
Figure 20.24
12.46
33.2
Phylum Echinodermata

The echinoderms (“hedgehog skin”) are a very unusual
group that includes about 7000 living species.

Members include: starfish, brittle stars, sea urchins, sea
cucumbers, and sea lilies or feather stars.

They are deuterostomes (as are chordates), but have
secondarily evolved radial symmetry from bilateral
symmetry (they still have bilaterally symmetrical larvae).
Characteristics of the
Echinodermata

Exclusively a marine group. They cannot
osmoregulate so rarely occur even in brackish
water.

The body is not segmented, but shows pentaradial
symmetry.

There is no head or brain and the nervous system
is relatively simple.
Characteristics of the
Echinodermata

They possess an endoskeleton of dermal
calcareous ossicles, which are connected together
by connective tissue.

Possess a unique water vascular system that
consists of a series of canals that extend from the
body surface as tube feet.

These tube feet are tentacle-like and enable the
animal to move. In some species movement of the
arms or spines contributes to locomotion too.
Classes of Echinoderms






There are a total of five classes of echinoderms
and about 7300 species.
Class Asteroidea: sea stars or starfishes
Class Ophiuroidea: Brittle stars
Class Echinoidea: Sea Urchins, Sand dollars
Class Holothuroidea: Sea cucumbers
Class Crinoidea: Sea Lilies and Feather stars.
Cushion seastar (Asteroidea)
Figure 22.02b
Figure 22.05a
Brittle star (Ophiuroidea)
Figure 22.15
Sea urchins
Sea cucumber
Figure 22.25