Zoology Project

9
Major

Animal

Phyla

By: Angelyn G, Rosialda
Bachelor of Science in Biology 1-A

1 INTRODUCTION FO ELBAT CONTENTS
PHYLUM MOLLUSCA
2 PHYLUM PORIFERA
4

6 PYHLUM CNIDARIA
9 PHYLUM PLATYHELMINTHES
11 PHYLUM NEMATODA
13 PHYLUM ANNELIDA
16 PHYLUM ARTHROPODA
19 PHYLUM ECHINODERMATA

22 PHYLUM CHORDATA
24 REFERENCES

INTRODUCTION The biological taxonomy, a
phylum (phyla) is a taxon in the
rank below kingdom and above
class. A Phylum is the largest
scientific grouping of life forms
sharing evolutionary certain
requirements of a common
ancestor in evolution.

Phyla can also be considered as a group sharing the same
general body plan, which includes both the external appearance,
but is more importantly dependent of the bodies internal
organization.

There are 36 recognized animal phyla, of which but nine
(Mollusca, Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida,
Arthropoda, Echinodermata, and Chordata) contain the vast
majority of described, extant species. Debate continues regarding
whether the different phyla appeared on earth prior to the
Cambrian Explosion some 544 million years ago that roughly
speaking marks the time when life forms had become large enough
and many had acquired hardened body parts, so that a findable
fossil record could begin to accumulate. The absence of a
Precambrian fossil record greatly worried Darwin. The late
Precambiran and Cambrian are believed to be times when some life
forms that would otherwise deserve the rank of phylum both
evolved only to meet extinction without leaving descendents.

The taxonomic rank of phylum is normally used with specificity
as if science truly knows the placement of life in the tree of life.
Therefore, remember not to put too sharp of a point on the term.
Consequently the number of phyla, both extant and extinct, as well
as what group constitutes a phylum varies from author to author,
and changes over time. Modern molecular science (phylogenetics)
has helped much to clarify the evolutionary descendancy of life
forms, but can not help much to resolve mysteries within the fossil
record.

Body plan is one approach to defining phyla. Development of
the animal body plan was (and is) controlled by large and complex
gene regulatory networks. It follows that evolution of body plans
corresponded to adpative changes in the architecture of these
developmental gene regulatory networks. The many components of
these networks evolve at different rates and in different ways, and
are very much dependent on selection pressures from changing
environments. It is often hypothsized that animal evolution
established essentially all phylum-level body plans by the early
Cambrian. If so, it follows that certain components of the networks
that were essential became immune to change. These highly
conserved network components may well have originated in the
Precambrian.

1

PHYLUM
MOLLUSCA

Mollusca is the second-largest phylum of invertebrate animals
after the Arthropoda. The members are known as molluscs or
mollusks. Around 85,000 extant species of molluscs are

recognized. The number of fossil species is estimated between
60,000 and 100,000 additional species.The proportion of

undescribed species is very high. Many taxa remain poorly studied.
Molluscs are the largest marine phylum, comprising about 23% of all the
named marine organisms. Numerous molluscs also live in freshwater and

terrestrial habitats. They are highly diverse, not just in size and
anatomical structure, but also in behaviour and habitat. The phylum is
typically divided into 8 or 9 taxonomic classes, of which two are entirely
extinct. Cephalopod molluscs, such as squid, cuttlefish, and octopuses,
are among the most neurologically advanced of all invertebrates and

either the giant squid or the colossal squid is the largest known
invertebrate species. The gastropods (snails and slugs) are by far the

most numerous molluscs and account for 80% of the total classified
species.

PHYLUM: MOLLUSCA; LINNAEUS, 1758
SCIENTIFIC NAME: MOLLUSCA
HIGHER CLASSIFICATION:
LOPHOTROCHOZOA
KINGDOM: ANIMALIA
DOMAIN: EUKARYOTA
RANK: PHYLUM

EXAMPLES OF PHYLUM MOLLUSCA:
OCTOPUS,AMMONITES,CEPHALOPOD

2 GASTROPOD
SCIENTIFIC NAME: GASTROPOD

PHYLUM MOLLUSCA (MOLLUSKS) detabed ylivaeh gnieb llits si scsullom ni ynegolyhp ehT eht ,sessalc eht fo erutcurts eht gnidrageR .stsimonoxat neewteb ynam ni dna ecruos siht ni revewoH .eert citenegolyhp detciped ,adopolahpeC
CHARACTERISTICS

The shell provides for muscle attachment

and protection

The mantle (fold of muscular tissue) and

muscular foot

They are essentially aquatic mostly marine,

few freshwater and some terrestrial form. YNEGOLYHP ACSULLOM sessalc

They may be found as hidden parasites in

the interior of other animals.

They vary in size from giant squids and eht

clams to little snails, a millimeter long. .nwonknu era aivlaviB dna ,adoportsaG

They have at least two characters radula fo

and mantle not found elsewhere.

The body is soft, unsegmented (except in ecnegreviD

Monoplacophora), bilaterally symmetrical,

coelomate, triploblastic. tcaxe

PHYLUM MOLLUSCA
CLASSIFICATION

Mollusca (mollusks) are classified
into 6 classes according to their

symmetry and the characters of food:

Shell eht
Nervous system
Muscles ,srehto
Radula.
Mantle
Gills

3

This group of animals is

probably considered as the

PHYLUMo l d e s t a n i m a l g r o u p . T h e y

are also called as Sponges.
PORIFERA
These are by far the

simplest multicellular

animals. Even though they

are multicellular, they do

not have any tissues or

organs.

Sponges live in an aquatic habitat as they have
to have an intimate contact with water. Water
plays a major role in the feeding, exchange of
gases and as well as excretion.  The body of the
sponges has many holes or pores called ostia. The
body structure of sponges is designed in such a
way that water moves through the body, where it
can filter out food and also absorb the dissolved
oxygen, along with eliminating waste material.

Organisms belonging to this phylum do not have
specialized digestive, nervous or circulatory system
.Instead, they have a water transport or canal
system, which achieves the functions of digestion,
excretion and also an exchange of gases.

Kingdom: Animalia
Phylum: Porifera
Grant, 1836
Domain: Eukaryota

Examples of Phylum

Porifera:

Euplectella,Oscarella,

DEMOSPONGE Spongilla

SCIENTIFIC NAME: DEMOSPONGIAE

4

Phylum Porifera
Characteristics

Spend adult life attached Phylum
to hard surface-sessile Porifera three
once though to be plants
distinct
Filter feeders (food groups
suspended in water comes
in through pores) Hexactinellida (glass
sponges)
There is an endoskeleton Demospongia
present with calcareous Calcarea (calcareous
spicules (calcium sponges)
carbonate) or siliceous
spicules (silica) or Porifera
sponging fibres (protein) Phylogeny

Asexual reproduction is The group of
seen through budding, organisms known as
fragmentation. Sexual sponges (Porifera) is
reproduction is seen in considered the
certain species, through earliest branching
gametic fusion. group of Metazoans,
or animals, with
They have the fossils described
characteristic canal from the Vendian
system for the flow of Period, dating back
water through the body. 650-543 million
years ago (Porifera:
The body has many pores Systematics, 2006). 
called the ostia and a
single large opening 5
called osculum at the
top.

Body shape can be
cylindrical, vase-like,
rounded or sac-like.

PHYlUM
CNIDARIA

Phylum Cnidaria or

coelenterate includes diverse

animals like jelly fish, sea

anemones, corals and the

more familiar Hydra. They are

diploblastic eumetazoans with

tissue grade of organization.

The cnidarians are

characterized by the

Sea anemones presence of Cnidocytes, polyp
Scientific and medusa forms.Any member

name: Actiniaria of the phylum Cnidaria are
group made up of more than

9,000 living species. 

Phylum: Cnidaria; All cnidarians share several
Hatschek, 1888 attributes, supporting the
Scientific name: Cnidaria
Kingdom: Animalia theory that they had a single
Higher classification: origin. Variety and symmetry
Radiata
Clade: ParaHoxozoa of body forms, varied
Domain: Eukaryota coloration, and the

sometimes complex life
histories of cnidarians
fascinate layperson and

scientist alike. Inhabiting all

Examples of Phylum marine and some
Cnidaria:
freshwater environments,
 Corals, Hydras, Jellyfish,
Sea anemones, and Sea these animals are most
fans.
abundant and diverse in

tropical waters. 

6

Phylum Cnidaria (Coelenterata)
Characteristics

The body wall is composed of an outer
epithelium called as epidermis, an inner
epithelium called gastrodermis, a gelatinous
mesoglea between the outer and inner
epidermis. Mesoglea consists of amoeboid
cells derived from ectoderm. Mesoglea is
thin in polyps. It is thick in medusa, in which
it is important in buoyancy.
They are diploblastic and show tissue grade
of organization
The blind sac-like central cavity is called
coelenterons or gastro vascular cavity.
Hence the name Coelenterata.  It opens out
by mouth surrounded by tentacles. Mouth
serves for ingestion as well as for egestion.
In medusa form the coelenterons is
specialized into stomach, radial canals and
ring canal. Coelenterons helps in digestion
and circulation.
Digestion is first extracellular in the
coelenterons and then intracellular in the
nutritive muscular cells of gastrodermis.
Exchange of respiratory gases and
elimination f the excretory wates occurs by
diffusion through the body wall.
The body is radially symmetric but sea
anemones show biradial symmetry

Phylum Cnidaria four classes

Hydrozoa (hydrozoans) 7
Scyphozoa (scyphozoans)
Anthozoa (anthozoans)
Cubozoa (cubozoans)

Cnidaria Phylogeny

The exact relationships between the
different cnidarian groups are unknown.
Among theories proposed on the evolution

of the phylum Cnidaria, most treat the
radial symmetry and tissue level of

organization as evidence that the group is
primitive (that is, it evolved before the

evolution of bilateral symmetry) and hold
that the medusa is the original body form,

being the sexually reproductive phase of
the life cycle. 

8

Platyhelminthes is one of the Pseudobiceros hancockanus
most important phylum with Scientific name: Pseudobiceros

thousands genus hancockanus
at the world. Its is composed of

the flatworms: acoelomate
organisms that include many
free-living and parasitic forms.

Most of the flatworms are
classified in the superphylum

Lophotrochozoa, which also
includes the mollusks and

annelids. The Platyhelminthes
consist of two lineages: the
Catenulida and the

Rhabditophora. The Catenulida,
or “chain worms” is a small

clade of just over 100 species.
These worms typically reproduce
asexually by budding. However,
the offspring do not fully detach

from the parents; therefore,
they resemble a chain.

Phylum: Platyhelminthes; Gegenbaur,1859
Scientific name: Platyhelminthes
Higher classification: Platyzoa
Kingdom: Animalia
Domain: Eukaryota
Rank: Phylum

Examples of Phylum Platyhelminthes: 9
Monogenea,Tapeworms,Rhabditophora

Phylum
Platyhelminthes
Characteristics

Bilaterally symmetrical; Phylum
dorso-ventrally Platyhelminthes
flattened
A celomate four classes
Cannot synthesize fatty
acids Turbellaria
Tegument (living Monogenoidea
external layer) (Monogenea)
Digestive tract Trematoda
incomplete or absent Cestoidea
most are parasites
Most are
hermaphrodites-
exchange sperm don't
normally fertilize their
own eggs
Excretory system
protonephridia

Platyhelminthes Phylogeny

The interrelationships of the flatworms
(phylum Platyhelminthes) are poorly
resolved despite decades of
morphological and molecular

phylogenetic studies. (20,000 species)

10

PHYLUM
NEMATODA

Scientific name: Nematoda
Phylum: Nematoda; Diesing, 1861
Higher classification: Ecdysozoa

Kingdom: Animalia
Domain: Eukaryota

Rank: Phylum
Examples of Phylum Nematoda

Ascarids,Filarias,Whipworms

Soybean cyst nematode
Scientific name: Heterodera glycines

Nematodes are commonly referred to as non-

segmented roundworm, threadworm or pinworm, as

distinct from flatworm and higher segmented

annelids.

Commonly known as roundworms, nematodes are a

group of worms that make up the phylum

Nematoda. With well over 15,000 species identified

today, they can be found in different habitats

ranging from terrestrial to marine environments.

Nematodes exist as free living organisms in

terrestrial and aquatic environments or as

parasites of both plants and animals. 11

Phylum Nematoda (Nematodes)
Characteristics

They are widely distributed, aquatic or
terrestrial, parasitic or free-living.
Their body is elongated, cylindrical,
unsegmented, worm-like, bilaterally symmetrical
and tapering at both ends.
They have cellular or syncytial epidermis I.e. the
nuclei are not separated from each other by cell
membranes.
They consist of only longitudinal muscle fibers
with four bands
Circulatory and respiratory systems are absent.
i.e. respiration occurs through general body
surface and aerobic in free-living form and
anaerobic in parasitic form.
Development may be direct, with or without an
intermediate host or indirect.
No asexual reproduction.

Nematoda Phylogeny

The oldest known

nematodes are from Phylum Nematoda

about 400 million years Classification
ago, but I believe they

probably date back to Phasmidia
around 1 billion years. -
Aphasmidia

Poinar . That would mean

they were one of the very

oldest of all life forms,

coming along before

almost all other animals

and just after bacteria, 12
protozoa and fungi.

PHYLUM
ANNELIDA

Examples of Phylum Glycera sp
annelida

Leech,Earthworm,Polychaete
,Clittellata

The annelids from Latin anellus, "little ring" also

known as the ringed worms or segmented worms,

are a large phylum, with over 22,000 extant

species including ragworms, earthworms, and

leeches. The species exist in and have adapted

to various ecologies some in marine environments

as distinct as tidal zones and hydrothermal vents,

others in fresh water, and yet others in moist

terrestrial environments.

The Annelids are bilaterally symmetrical,

triploblastic, coelomate, invertebrate organisms.

They also have parapodia for locomotion. Most

textbooks still use the traditional division into

polychaetes (almost all marine), oligochaetes

(which include earthworms) and leech-like

species. Cladistic research since 1997 has

radically changed this scheme, viewing leeches

as a sub-group of oligochaetes and oligochaetes

as a sub-group of polychaetes.

Scientific name: Annelida

Phylum: Annelida; Lamarck, 1809

Higher classification: Lophotrochozoa

Kingdom: Animalia

Domain: Eukaryota 13
Subkingdom: Eumetazoa

Phylum Annelida
Characteristics

They are mostly aquatic; marine or freshwater some
terrestrial, burrowing or tubicolous, sedentary or
free-living, some commensal and parasitic.
The body is elongated, triploblastic, bilaterally
symmetrical, truly coelomate and vermiform.
The body is metamerically segmented; externally by
transverse grooves and internally by septa into a
number of divisions; each division is called a
segment, metamere or somite.
The epidermis is of a single layer of columnar
epithelial cells, covered by thin cuticle not made of
chitin.
The body wall is contractile or dermo-muscular
consisting of outer muscle fiber circular and inner
longitudinal.
Appendages are jointed when present.
Asexual reproduction occurs in some.

About 8,700 known

species of Annelida are

divided into four main

classes, primarily on the

basis of presence and

absence of: Phylum Annelida
(Annelids)
Parapodia
Setae

Metamere Classification
Other

morphological

features

14

Their interrelationships and evolution have been
the source of much controversy over the past

century with the composition of the annelid crown
group, the relationship of major groups and the
body plan of the ancestral annelid having
undergone major recent revisions. There is a
convincing body of molecular evidence that
polychaetes form a paraphyletic grade and that
clitellates are derived polychaetes. The earliest

€s t e m g r o u p a n n e l i d s f r o m C a m b r i a n L a g e r s t a t t e n

are errant, epibenthic polychaetes, confirming
that biramous parapodia, head appendages and
diverse, simple chaetae are primitive for annelids.
Current evidence from molecular clocks and the
fossil record suggest that crown group annelids

are a Late Cambrian – Ordovician
radiation, with clitellates radiating in the Late

Palaeozoic. Their body fossil record is largely
confined to deposits showing exceptional

preservation and is punctuated by the acquisition
of hard parts in major groups. The discovery of an
Ordovician fossil with soft tissues has shown that

machaeridians are in fact a clade of crown
polychaetes. They were in existence for more than

200 million years and possess unique calcitic
dorsal armour, allowing their mode of life and
phylogeny to be interpreted in the context of the

annelid body plan.

Annelida Phylogeny

15

Phylum: Arthropoda; von Siebold, 1848
Scientific name: Arthropoda

Higher classification: Ecdysozoa
Kingdom: Animalia
Domain: Eukaryota

Subkingdom: Eumetazoa

Examples of Phylum Arthropoda:
Arachnid,Millipedes,Hexapoda

PHYLUM

Arthropoda

Arthropod, (phylum Arthropoda), any member of the
phylum Arthropoda, the largest phylum in the animal

kingdom, which includes such familiar forms
as lobsters, crabs, spiders, mites, insects, centipedes,
and millipedes. About 84 percent of all known species
of animals are members of this phylum. Arthropods are
represented in every habitat on Earth and show a great

variety of adaptations. Several types live in
aquatic environments, and others reside in terrestrial

1 6o n e s ; s o m e g r o u p s a r e e v e n a d a p t e d f o r f l i g h t .

Monarch Butterfly
Scientific name: Danaus plexippus

Phylum Arthropoda
(Antropod)

Characteristics

Body have jointed

appendages or legs (which Phylum Arthropoda
are modified to different

structures to perform Classification

different functions like jaws, Crustace (Crusta)
gills, walking legs, paddle). Myriapoda (Myrios)
There may be 3 pairs, 4 Arachnida (Arachne)
pairs, 5 pairs, many pairs.

Body is covered with Insect (Insectus)

chitinous exoskeleton. Onychophora

They are haemocoelomate. (Onychos)

Coelom i.e. body cavity is

filled with blood or fluid.

Head bears a pair of

compound eyes and antenna.

Locomotion takes place by

jointed appendages.

Sensory organ include NOTE: In some (crustacean

antennae, sensory hairs for and arachnida) body is

touch and chemoreceptor, divisible into cephalothorax

simple and compound eyes, (head and thorax is fused)

auditory organs (in insects) and abdom

and statocysts (in

crustacean).

Body is divisible into head, 17
thorax and abdomen.

Arthropoda Phylogeny

Arthropods are the most diverse animal phylum, and

their phylogenetic relationships have been debated for

centuries. With the advent of molecular phylogenetics,

arthropods were found to be monophyletic and placed

within a clade of molting animals, the ecdysozoans,

with nematodes and six other phyla. Molecular

phylogenetics also provided a new framework for

relationships between the major arthropod groups, such

as the clade Pancrustacea, which comprises insects and

crustaceans. Phylogenomics based on secondgeneration

genomics and transcriptomics has further resolved

puzzles such as the exact position of myriapods or the

closest crustacean relatives of hexapods. It is now

broadly recognized that extant arthropods are split

into chelicerates and mandibulates, and relationships

within the two mandibulate clades (myriapods and

pancrustaceans) are stabilizing. Notably, the phylogeny

of insects is now understood with considerable

confidence, whereas relationships among chelicerate

orders remain poorly resolved. The evolutionary history

of arthropods is illuminated by a rich record of fossils,

often with exquisite preservation, but current analyses

conflict over whether certain fossil groups are stem- or

crown-group arthropods. Molecular time-trees

calibrated with fossils estimate the origins of

arthropods to be in the Ediacaran, while most other

deep nodes date to the Cambrian. The earliest stem-

group arthropods were lobopodians, worm-like animals

with annulated appendages. Confidently placing some

key extinct clades on the arthropod tree of life may

require less ambiguous interpretation of fossil

structures and better integration of morphological data

into the phylogeny. 18

PHYLUM
ECHINODERMATA

Phylum: Echinodermata;
Bruguière, 1791

Scientific name:
Echinodermata

Higher classification:
Deuterostome

Kingdom: Animalia
Domain: Eukaryota

Rank: Phylum

Examples of Phylum
Echinodermata:
Starfish,Brittle

star,blastoid,Crinoids

Starfish
Scientific name: Asteroidea

19

Echinoderm is the common name given to any member

of the Phylum echinodermata of marine animals. The are

recognizable by their radial symmetry, and include such

well-known animals as sea stars, sea urchins,sand dollars,

and sea cucumbers.

The organisms belonging to the phylum Echinodermata

are exclusively marine. Till date, there have been no

traces of any terrestrial or freshwater Echinoderms. These

are multicellular organisms with well-developed organ

systems. All the animals belonging to this phylum share the

same characteristics features. They are colourful

organisms with unique shapes. They are ecologically and

geologically very important. The Echinoderms are found in

sea-depths as well as in the intertidal zones. An

interesting feature of the phylum Echinodermata is that all

the organisms belonging to this phylum are marine. None

of the organisms is freshwater or marine. The water

vascular system present in echinoderms accounts for

gaseous exchange, circulation of nutrients and waste

elimination.

Phylum Echinodermata

(Echinoderm) Characteristics

They have poorly developed sense organs. These

include chemoreceptors, tactile organs, terminal

tentacles, etc

They reproduce sexually through gametic fusion and

asexually through regeneration.  Fertilization  is

external.

They have a simple radial nervous system and the

excretory system are absent.

The body is unsegmented with no distinct head. The

mouth is present on the ventral side while the anus

is on the dorsal side.

They have a star-like appearance and are spherical

or elongated.

They have an open circulatory system.

They respire through gills or cloacal respiratory

tree.

20

Phylum Echinodermata
Classification

Asteroidea
Ophiuroidea
Echinoidea
Holothuroidea
Crinoidea

Echinodermata Phylogeny

All evidence indicates that crinoids are the
most basal. The other four groups all diverged
within a very short geological timeframe around

500 million years ago. Urchins and sea
cucumbers are generally considered to form a
clade of the most derived. It remains unclear

whether the brittle stars group more closely
with this clade or with starfish, due to conflicts

between molecular, morphological, and
embryological evidence.

Echinoderms evolved from symmetrical animals
exhibiting racial symmetry from their bodies at

one point in time. The symmetry is apparent in
adult starfish and sand dollars. Other

echinoderms lack the five point morphology
because it was lost during development.

21

PHYLUM
CHORDATA

Lamprey
Scientific name:
Petromyzontiformes

An important phylum. Its name is derived from

the notochord. Endoskeleton is the chief basic

character of the Chordata phylum. This

endoskeleton is an important factor in the

development and specialization of the higher

animals. Man is the most important chordate. The

chordates show a great variety. They live in  all

kinds of habitat

Phylum: Chordata; Haeckel, 1874

Scientific name: Chordata

Higher classification: Deuterostome

Kingdom: Animalia

Domain: Eukaryota

Rank: Phylum

Examples of Phylum Chordata:
Reptiles, Vertebrate,Amphibians

22

Phylum Chordata (Chordates)
Characteristics

They are backboned animals (vertebrates),
Most of the living chordates are familiar
vertebrate animals.
Presence of dorsal hollow nerve cord
Blood vascular system: Present, closed type
Ventral heart, hepatic portal system and RBC are
present.
Germ layer: Triploblastic.
Symmetry: bilateral symmetry body.

Phylum Chordata
Classification

Sub-Phylum: Urochordata
Sub-Phylum: Cephalochordata
Sub-Phylum: Vertebrata

Chordata Phylogeny

Chordates are the group of animals to which

vertebrates including humans belong. Like so many

other phyla of bilaterian animals, they originated in

the ocean over 520 million years ago, before or

during the Cambrian period. Their early evolution is

of interest to neuroscientists because this was when

the basic structure of the vertebrate brain and

spinal cord was assembled. Early chordates were

soft-bodied so they seldom fossilized, but we

reconstruct their origin using the modern chordates

and their relatives plus some miraculously preserved

fossils.

23

References

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References

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