TORRESMA.GERALDINEL_BIOSCI2_PROJECT

VOL. 1 ISSUE 1 | NOVEMBER 2020

ZOOLOGY

ANIMAL SCIENCE

9 MAJOR ANIMAL PHYLA

Discovering group of classes with similar distinctive characteristics.

TABLE OF

CONTENTS

21    39 18   
Phylum Mollusca Phylum Chordata Phylum Nematoda
Molluscs Roundworms

3
Introduction to Animal Phyla

4
9 Major Animal Phyla and their
Representatives

5  
Phylum Porifera
Sponges

9   
Phylum Cnidaria
Hydroids, Sea Anemones, Jellyfish, Horn,
and Stony Corals

14   
Phylum Platyhelminthes
Flatworms

26   
Phylum Annelida
Segmented Worms

30
Phylum Anthropoda
Spiders, Scorpions, Ticks, Mites, Crustaceans,
Millipedes, Centipedes and Insects

43   
REFERENCES

34
Phylum Echinodermata

Sea Stars, Brittle Stars, Sea
Urchins, Sea Cucumbers, and Sea Lilies

The Animal Phyla

In biological taxonomy, a phylum (plural phyla) is a taxon in the rank The kingdom Animalia can be
below kingdom and above class. A Phylum represents the largest sub-divided into two main
scientific grouping of life forms sharing evolutionary certain groups – invertebrates (no
requirements of a common ancestor in evolution. Phyla can also be backbone) and vertebrates (
considered as a group sharing the same general body plan, which with backbones, mostly
includes both the external appearance, but is more importantly chordata).
dependent of the bodies internal organization.
Examples of invertebrate phyla
There are 36 recognized animal phyla, of which but nine (Mollusca, include porifera, cnidaria,
Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, platyhelmintha, annelida,
Arthropoda, Echinodermata, and Chordata) contain the vast mollusca and arthropoda.
majority of described, extant species.
All vertebrates belong to the
The taxonomic rank of phylum is normally used with specificity as if phylum chordata – however
science truly knows the placement of life in the tree of life. Therefore, not all chordata are vertebrates
remember not to put too sharp of a point on the term. Consequently (e.g. invertebrate sea squirts).
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.

9 MAJOR ANIMAL PHYLA  |  03

9 MAJOR
ANIMAL
PHYLA

AND THEIR REPRESENTATIVES

9 MAJOR ANIMAL PHYLA  |  04

PHYLUM PORIFERA

9 MAJOR ANIMAL PHYLA  |  05

18

PHYLUM PORIFERA

SPONGES

Phylum Porifera are the lowest multicellular Cells in the sponge walls filter goodies from the

animals belonging to the kingdom Animalia. water as the water is pumped through the body and

out other larger openings. The flow of water through

The word “Porifera” mainly refers to the pore the sponge is unidirectional, driven by the beating of

bearers or pore bearing species. Based on the flagella which line the surface of chambers

embryological studies, sponges are proved as connected by a series of canals. Sponge cells perform

animals and are classified into a separate Phylum in a variety of bodily functions and appear to be more

the animals. independent of each other than are the cells of other

This phylum includes about 5000 species. Poriferans animals.

are pore-bearing first multicellular animals. The

pores are known as Ostia.The poriferans have a They were initially regarded as plants due to the

spongy appearance and are therefore called green colour and their symbiotic relationship with

sponges. They are attached to the substratum and algae. Later, their life cycle and feeding system were

do not move. They have the ability to absorb and discovered, and they were included in the animal

withhold fluids. kingdom.

9 MAJOR ANIMAL PHYLA  |  06

The Characteristics of

Phylum Porifera

Multicellular; body an aggregation of Skeletal structure of fibrillar collagen
1 several types of cells differentiated for 6 (protein) and calcareous or siliceous

various functions, some of which are crystalline spicules, often combined
organized into incipient tissues of a with variously modified collagen
low level of integration. (spongin).

Body with pores (ostia), canals, and No organs or true tissues, digestion
2 chambers that form a unique system of 7 intracellular; excretion and respiration

water currents on which sponges by diffusion
depend for food and oxygen.
Reactions to stimuli apparently local
Outer surface of flat pinacocytes, most 8 and independent in cellular sponges,
3 interior surfaces lined with flagellated
but electrical signals in syncytial glass
collar cells (choanocytes) that create sponges wherein nervous system
water currents with a gelatinous probably absent.
protein matrix called mesohyl contains
amebocytes of various types and All adults are sessile and attached to
skeletal elements. 9 substratum.

4 Radial symmetry or none. Asexual reproduction by buds or
10 gemmules and sexual reproduction by
5 Mostly marine but all aquatic.
eggs and sperm and free-swimming
9 MAJOR ANIMAL PHYLA  |  07 flagellated larvae in most.

EXAMPLES OF PHYLUM PORIFERA

Spongilla

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Euplectella

These are also known as Venus flower
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Cliona

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Hyalonema

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9 MAJOR ANIMAL PHYLA  |  08

PHYLUM CNIDARIA

9 MAJOR ANIMAL PHYLA  |  09

PHYLUM
CNIDARIA

HYDROIDS, SEA ANEMONES, JELLYFISH, HORN, AND STONY CORALS

The term Cnidaria came from the Greek The phylum takes its name from cells called
word knide which means nettle and cnidocytes, which contain cnidae, a
Latin aria which means connected with. As unique organelles of the phylum. As such,
such, Phylum Cnidaria is an interesting cnidocytes are formed only by cnidarians,
group of more than 9,000 species whose but some ctenophores, molluscs, and
members some of nature’s strangest and flatworms eat hydroids bearing nematocysts,
loveliest creatures. These includes then store and use these stinging structures
branching, plant-like hydroids, flowerlike for their own defense.
sea anemones, jellyfishes, and those
architects of the ocean floor, horn corals (sea In addition, Cnidarians are most abundant in
whips, sea fans, and others) and stony corals shallow marine habitats, especially in warm
whose thousands of years of calcareous temperatures and tropical regions. Note that
house-building have produced great reefs there are no terrestrial species of Cnidarians.
and coral islands.

9 MAJOR ANIMAL PHYLA  |  10

The Characteristics of

Phylum Cnidaria

Cnidocytes present, typically housing stinging
1 organelles called nematocysts.

Entirely aquatic, some in freshwater, but most
2 marine.

Radial symmetry or biradial symmetry around a
3 longitudinal axis with oral, aboral ends and with

no definite head.
Two types of individuals namely polyps and
4 medusae.
Adult body two-layered (diploblastic) with
epidermis and gastrodermis derived from

5

embryonic ectoderm and endoderm,
respectively.

Mesoglea, an extracellular matrix (jelly) lies
6 between body layers with septa.

Extracellular digestion in gastrovascular cavity
7 and intracellular digestion in gastrodermal cells.

Extensible tentacles usually encircle mouth or
8 oral region.

9 MAJOR ANIMAL PHYLA  |  11

Muscular contractions via epitheliomuscular
cells, which form an outer layer of longitudinal
9 fibers at base of epidermis and an inner layer of
circular fibers at base of gastrodermis;
modifications of plan in hydrozoan medusa
(independent ectodermal muscle fibers) and
other complex cnidarians
Sense organs include well-developed statocysts
10 (organs of balance) and ocelli (photosensitive
organs); complex eyes in members of Cubozoa.
Nerve net with symmetrical and asymmetrical
11 synapses; diffuse conduction; two nerve rings in
hydrozoan medusae.

Asexual reproduction by budding in polyps
12 forms clones and colonies whereas some

colonies exhibit polymorphism.

Sexual reproduction by gametes in all medusae
13 and some polyps.

14 No excretory or respiratory system.

15 No coelomic cavity.

9 MAJOR ANIMAL PHYLA  |  12

Examples of
PHYLUM CNIDARIA

Hydroids

Hydroids are colonies of tiny stinging
jellies, best described as hundreds of
inverted jellyfish attached to a feather-
or seaweed-like base, known as the
organism's polyp phase.

Sea Anemones

These are the marine, predatory
animals of the order Actiniaria. They are
named after the anemone, a terrestrial
flowering plant, because of the
colourful appearance of many.

Jellyfish

Jellyfish are mainly free-swimming
marine animals with umbrella-shaped
bells and trailing tentacles, although a
few are anchored to the seabed by
stalks rather than being mobile.

Horn

Horn corals, which are named for the
hornlike shape of the individual
structures built by the coral animal,
were either solitary or colonial forms.

Stony Muscle

The individual animals are known as
polyps and have a cylindrical body
crowned by an oral disc in which a
mouth is fringed with tentacles

9 MAJOR ANIMAL PHYLA  |  13

PHYLUM PLATYHELMINTHES

9 MAJOR ANIMAL PHYLA  |  14

PHYLUM
PLATYHELMINTHES

FLATWORMS

Platyhelminthes are commonly known as The most distinguishing feature of these
flatworms or tapeworms. They are a group invertebrates is their flat body. As the
of soft-bodied invertebrate animals. As a body does not have any cavity, they are
matter of fact, there are around 20,000 flat. The body is also not segmented and
species of these animals. A few of these they do not have specialized systems.
live as parasites on humans and other Around eighty percent of the flatworms
animals. Furthermore, it is because of this are parasitic in nature, while a few free-
parasitic nature that they do cause some form flatworms are also present.
amount of trouble for the host animal. A
few species belonging to this phylum can The animals in this phylum have a diverse
be a major cause of certain diseases. range in size. Some are microscopic, while
a few go up to two feet long. They are
The most distinguishing feature of these also hermaphrodites, which mean that
invertebrates is their flat body. As the body both the sexes are present in the same
does not have any cavity, they are flat. The organism.
body is also not segmented and they do not
have specialized systems. Around eighty
percent of the flatworms are parasitic in
nature, while a few free-form flatworms
are also present.

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CLASSIFICATION OF PLATYHELMINTHES

Turbellarians

Turbellarians (Turbellarian worms) are free-
living organisms in their natural environment.
However, a few species exist as commensals or
parasites in certain hosts (some marine fish and
turtles, etc). They are also very colorful with
different species exhibiting a variety of colors
ranging from brown and black to blue and green

etc.

Trematoda

also called flukes, have oral suckers, sometimes
supplemented by hooks, with which they attach

to their vertebrate hosts. Trematodes have
retained the same body form and digestive
cavity as the turbellarians. However, practically

the entire interior is occupied by the
reproductive system; the organism is capable of

producing huge numbers of offspring.

Monogenea

Monogeneans are a group of ectoparasitic
flatworms commonly found on the skin, gills, or
fins of fish. They have a direct lifecycle and do

not require an intermediate host. Adults are
hermaphrodites, meaning they have both male

and female reproductive structures

Cestoda

Most of the species—and the best-known—are
those in the subclass Eucestoda; they are
ribbon-like worms as adults, known as

tapeworms. Their bodies consist of many similar
units, known as proglottids, which are

essentially packages of eggs which are regularly
shed into the environment to infect other
organisms.

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CHARACTERISTICS OF

Phylum Platyhelminthes

1 No clear defining feature Muscular contractions via epitheliomuscular
9 cells, which form an outer layer of longitudinal
Commonly found in marine,freshwater, and
2 moist terrestrial habitats. fibers at base of epidermis and an inner layer
of circular fibers at base of gastrodermis;
Radial symmetry or biradial symmetry around a modifications of plan in hydrozoan medusa
3 longitudinal axis with oral, aboral ends and with (independent ectodermal muscle fibers) and
other complex cnidarians.
no definite head.
Sense organs include well-developed statocysts
Bilateral symmetry with definite polarity of 10 (organs of balance) and ocelli (photosensitive
4 anterior and posterior ends, and body flattened
organs); complex eyes in members of Cubozoa.
dorsoventrally.
Adult body two-layered (diploblastic) with Nerve net with symmetrical and asymmetrical
epidermis and gastrodermis derived from 11 synapses; diffuse conduction; two nerve rings in
5 embryonic ectoderm and endoderm,
respectively. hydrozoan medusae.

Mesoglea, an extracellular matrix (jelly) lies Asexual reproduction by budding in polyps
6 between body layers with septa. 12 forms clones and colonies whereas some

Extracellular digestion in gastrovascular cavity colonies exhibit polymorphism.
7 and intracellular digestion
Sexual reproduction by gametes in all medusae
in gastrodermal cells 13 and some polyps.

Extensible tentacles usually encircle mouth No excretory or respiratory system.
8 or oral region.
14
9 MAJOR ANIMAL PHYLA  |  17
No coelomic cavity.

15

PHYLUM NEMATODA

9 MAJOR ANIMAL PHYLA  |  18

PHYLUM

NEMATODA

ROUNDWORMS

Phylum Nematoda consists of the nematodes, or roundworms. Both terms are
apt descriptions. Visually, the members of this phylum are described as being

long, thin, and hair-like. This is how they received their scientific name.
Nematode is from the Greek roots nemat-, meaning thread, and -odes, meaning

like or resembling. They have also been described as similar to a long, thin,
round tube hence, roundworms. Most species are microscopic, however a few
are over a meter long. The largest known nematode infects sperm whales and
can grow up to 9 meters. That's almost 30 feet long! The root-knot nematode,

Meloidogyne incognita, is a parasite that infects plants.
Phylum Nematoda is one of the most prolific phyla in the animal kingdom.
Although there are only slightly more than 25,000 known species, scientists
estimate there are probably another 900,000 species waiting to be discovered.
They have been found in nearly every possible environment, including as
parasites in a wide variety of plants and animals. They don't, however, like dry
locales. One species of nematode, the sour paste nematode, has been found in

book binding paste and German beer mats!

9 MAJOR ANIMAL PHYLA  |  19

EXAMPLES
OF

PHYLUM
NEMATODA

Plectus Parvus

Plectus parvus is a species of nematode (roundworm)
found in freshwater and terrestrial environments. It has
been sampled in Europe and New Zealand.Adults of this
species are reported to grow to 0.4–0.6 mm long.They
possess two alae. The body is defended by a thin cuticle.

The males possess asymmetrical spicules

Caenorhabditis elegans

C. elegans is a non-hazardous, non-infectious, non-
pathogenic, non-parasitic organism. It is small,

growing to about 1 mm in length, and lives in the soil
—especially rotting vegetation—in many parts of the
world, where it survives by feeding on microbes such
as bacteria. It is of no economic importance to man.

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PHYLUM MOLLUSCA

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PHYLUM

MOLLUSCA

MOLLUSCS They are a source of food as well as jewellery.
The hard shells are used to make beautiful
Many organisms belonging to this phylum jewellery pieces. In some regions of the world,
have a calciferous shell. The bodies are these are also raised as pets, even though it
generally very soft and are covered by the hard sounds bizarre. Pearls that are obtained from
exoskeleton. They can be found in terrestrial bivalves and gastropods are valuable as these
regions as well as in the depths of the seas. pearls are lined with nacre. Natural pearls are
You will be amazed to know that the size of the formed when a small foreign object gets stuck
molluscans can range from 20 metres to one in between the mantle and shell of the mollusc.
millimetre, with a few microscopic animals too.
These animals continue to have an important The bivalve molluscs are used as bioindicators
role in the lives of humans.an contain of the freshwater and marine environments. But
photographs. not all molluscans are good for humans. Some
are pests like the snails and slugs.

9 MAJOR ANIMAL PHYLA  |  22

THE CHARACTERISTICS OF

Phylum Mollusca

Dorsal body wall forms pair of folds called the mantle, which encloses the mantle cavity, is modified
1 into gills or lungs, and secretes the shell (shell absent in some). Ventral body wall specialized as a

muscular foot, variously modified but used chiefly for locomotion; radula in mouth.
2 Live in marine, freshwater, and terrestrial habitats.

Free-living or occasionally parasitic.

3

4 Body bilaterally symmetrical (bilateral asymmetry in some); unsegmented; often with definite head.
Coelom limited mainly to area around heart, and perhaps lumen of gonads, part of kidneys, and

5 occasionally part of the intestine.
6 Surface epithelium usually ciliated and bearing mucous glands and sensory nerve endings.

Complex digestive system; rasping organ (radula) usually present; anus usually emptying into
7 mantle cavity; internal and external ciliary tracts often of great functional importance.

9 MAJOR ANIMAL PHYLA  |  23

Circular, diagonal, and longitudinal muscles in the body wall; mantle and foot highly muscular
8 in some classes (for example cephalopods and gastropods).

Nervous system of paired cerebral, pleural, pedal, and visceral ganglia, with nerve cords and sub-
9 epidermal plexus; ganglia centralized in nerve ring in gastropods and cephalopods.

Sensory organs of touch, smell, taste, equilibrium, and vision (in some); the highly developed direct
eye (photosensitive cells in retina face light source) of cephalopods is similar to the indirect eye

10

(photosensitive cells face away from light source) of vertebrates but arises as a skin derivative in
contrast to the brain eye of vertebrates.

11 No asexual reproduction.

Both monoecious and dioecious forms; spiral cleavage; ancestral larva a trochophore, many
12 with a veliger larva, some with direct development.

13 Has tripoblastic body.

One or two kidneys (metanephridia) opening into the pericardial cavity and usually emptying
14 into the mantle cavity.

15 Gaseous exchange by gills, lungs, mantle, or body surface.

Open circulatory system (secondarily closed in cephalopods) of heart (usually three
16 chambered), blood vessels, and sinuses; respiratory pigments in blood.

9 MAJOR ANIMAL PHYLA  |  24

EXAMPLES OF

Phylum Mollusca

Cuttlefish

Cuttlefish or cuttles are marine
molluscs of the order Sepiida. They
belong to the class Cephalopoda, which
also includes squid, octopuses, and
nautiluses. Cuttlefish have a unique
internal shell, the cuttlebone, which is

used for control of buoyancy.

Snails

A snail is, in loose terms, a shelled
gastropod. The name is most often
applied to land snails, terrestrial

pulmonate gastropod molluscs

9 MAJOR ANIMAL PHYLA  |  25

PHYLUM ANNELIDA

9 MAJOR ANIMAL PHYLA  |  26

A n n e lPHYLUM i d a

SEGMENTED WORMS

Phylum Annelida contains the class Polychaeta (the polychaetes) and the class
Oligochaeta (the earthworms, leeches, and their relatives). These animals are
found in marine, terrestrial, and freshwater habitats, but a presence of water or
humidity is a critical factor for their survival, especially in terrestrial habitats.
The name of the phylum is derived from the Latin word annellus, which means a
small ring. Animals in this phylum show parasitic and commensal symbioses with
other species in their habitat. Approximately 16,500 species have been described
in phylum Annelida. The phylum includes earthworms, polychaete worms, and
leeches. Annelids show protostomic development in embryonic stages and are
often called “segmented worms” due to their key characteristic of metamerism, or

true segmentation.

Annelids display bilateral symmetry and are worm-like in overall morphology.
They have a segmented body plan where the internal and external morphological

features are repeated in each body segment. Metamerism allows animals to
become bigger by adding “compartments,” while making their movement more
efficient. This metamerism is thought to arise from identical teloblast cells in the
embryonic stage, which develop into identical mesodermal structures. The overall
body can be divided into head, body, and pygidium (or tail). The clitellum is a
reproductive structure that generates mucus that aids in sperm transfer and gives
rise to a cocoon within which fertilization occurs; it appears as a fused band in the

anterior third of the anima.

9 MAJOR ANIMAL PHYLA  |  27

THE CHARACTERISTICS OF

Phylum Annelida

Unique annelid head and paired epidermal
1 setae present (absent in leeches) parapodia

present in the ancestral condition.

Marine, freshwater, and terrestrial.

2

Most free-living, some symbiotic, some
3 ectoparasitic.

Body bilaterally symmetrical, metameric, often
4 with distinct head.

5 Triploblastic body.

Coelom (schizocoel) well developed and
6 divided by septa, except in leeches; coelomic

fluid functions as hydrostatic skeleton.

Epithelium secretes outer transparent moist
7 cuticle.

Digestive system complete and not
8 segmentally arranged.

Body wall with outer circular and inner
9 longitudinal muscle layers.

Nervous system with a double ventral nerve
10 cord and a pair of ganglia with lateral nerves in

each segment; brain a pair of dorsal cerebral
ganglia with connectives to ventral nerve cord.

Sensory system of tactile organs, taste buds, Hermaphroditic or separate sexes larvae, if
11 statocysts (in some), photoreceptor cells, and 13 present, are trochophore type; asexual

eyes with lenses (in some). Specialization of reproduction by budding in some.
head region into differentiated organs, such as
tentacles, palps, and eyespots of polychaetes Excretory system typically a pair of nephridia
14 for each segment. Nephridia remove waste
Asexual reproduction by fission and
12 ragmentation while some are capable of from blood as well as from coelom.

complete regeneration. Respiratory gas exchange through skin, gills, or
15 parapodia.

9 MAJOR ANIMAL PHYLA  |  28

Glycera dibranchiata

The marine proboscis worm Glycera (class Polychaeta, family
Glyceridae) is sometimes called bloodworm. G. dibranchiata is
found along the eastern coast of North America. It grows to 37

centimetres (about 15 inches) in length.

Alittta succinea

A. succinea, the pile worm, is an aquatic sedentary polycheate
annelid that can grow up to 19 cm long. It can be found in open
seas, but appears to be able to tolerate a range of salinities and
is common in estuaries and ports. It is considered native to parts

of Europe’s Atlantic coast, but has been introduced widely
around the world, most likely due to fouling on ships.

Earthworms

Earthworms' bodies are made up of ring-like segments called
annuli. These segments are covered in setae, or small bristles,

which the worm uses to move and burrow.

EXAMPLES OF

"P h y l u m A n n e l i d a

PHYLUM ANTHROPODA

9 MAJOR ANIMAL PHYLA  |  30

phylum

The name “arthropoda” means “jointed legs”
(in the Greek, “arthros” means “joint” and
“podos” means “leg”); it aptly describes the
enormous number of invertebrates included
in this phylum. Arthropoda dominate the
animal kingdom with an estimated 85 percent
of known species included in this phylum and
many arthropods yet undocumented. The
principal characteristics of all the animals in
this phylum are functional segmentation of
the body and presence of jointed appendages.
Arthropods also show the presence of an
exoskeleton made principally of chitin, which
is a waterproof, tough polysaccharide.
Phylum Arthropoda is the largest phylum in
the animal world, and insects form the single
largest class within this phylum. Arthropods
are eucoelomate, protostomic organisms.

Phylum Arthropoda includes animals that
have been successful in colonizing terrestrial,
aquatic, and aerial habitats. This phylum is
further classified into five subphyla:
Trilobitomorpha (trilobites, all extinct),
Hexapoda (insects and relatives), Myriapoda
(millipedes, centipedes, and relatives),
Crustaceans (crabs, lobsters, crayfish, isopods,
barnacles, and some zooplankton), and
Chelicerata (horseshoe crabs, arachnids,
scorpions, and daddy longlegs). Trilobites are
an extinct group of arthropods found chiefly
in the pre-Cambrian Era that are probably
most closely related to the Chelicerata.

9 MAJOR ANIMAL PHYLA  |  31

THE CHARACTERISTICS OF

Phylum Anthropoda

Jointed appendages; ancestrally, one pair to each
1 segment, but number often reduced and

appendages often modified for specialized
functions.
Living in marine, freshwater, and terrestrial
2 habitats but many capable of flight

Free-living and parasitic taxa and has tripoblastic
3 body..

Bilateral symmetry; segmented body divided into
4 functional groups called tagmata consisting of

head and trunk; head, thorax, and abdomen; or
cephalothorax and abdomen; definite head.

Reduced coelom in adult; most of body cavity
5 consisting of hemocoel filled with blood.

Cuticular exoskeleton containing protein, lipid,
6 chitin, and often calcium carbonate secreted by

underlying epidermis and shed (molted) at
intervals; although chitin occurs in a few groups
other than arthropods, its use better
developed in arthropods.

Complete digestive system; mouthparts modified
7 from ancestral appendages and adapted for

different methods of feeding; alimentary canal
shows great specialization by having, in various
arthropods, chitinous teeth, compartments, and
gastric ossicles.

Complex muscular system, with exoskeleton for
8 attachment, striated muscles for rapid actions,

smooth muscles for visceral organs; no cilia.

Nervous system similar to that of annelids, with
9 dorsal brain connected by a ring around the gullet

to a double nerve chain of ventral ganglia; fusion
of ganglia in some species.

Sexes usually separate, with paired reproductive
10 organs and ducts; usually internal fertilization;

oviparous, ovoviviparous, or viviparous; often
with metamorphosis.

PHYLUEMxaAmNplTeHs RoOf PODA

Crabs

Crab, any short-tailed member of the crustacean
order Decapoda (phylum Arthropoda)—especially
the brachyurans (infraorder Brachyura), or true
crabs, but also other forms such as the anomurans

(suborder Anomura), which include the hermit
crabs. Decapods occur in all oceans, in fresh water,

and on land; about 10,000 species have been
described.

Dragonfly

Dragonfly, (suborder Anisoptera), also called
darner, devil’s arrow, or devil’s darning needle, any

of a group of roughly 3,000 species of aerial
predatory insects most commonly found near
freshwater habitats throughout most of the world.
Damselflies (suborder Zygoptera) are sometimes
also called dragonflies in that both are odonates

(order Odonata).

Caterpillar

Caterpillars have chewing mouth parts and feed on
vegetation, generally leaves of a specific type of

plant. Some caterpillars have such specific diets that
they will only eat one kind of plant, while others
may feed on a wide variety of plants. Some
specialist caterpillars feed on animal dung, are
predators on other insects, or are even aquatic,
feeding on algae.

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PHYLUM ECHINODERMATA

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PEhcyhliun mo d e r m a t a
SEA STARS, BRITTLE STARS, SEA URCHINS, SEA CUCUMBERS AND SEA LILIES

Echinoderms are animals that you must be knowing. If you know a starfish, then you are well aware of
what an echinoderm is. Echinoderms are animals that are invertebrates. The name actually means spiny
skin! All the animals in this phylum exhibit spiny skin and hence are grouped together. Let us find out
more about them.

Echinoderms are marine animals and can be found in the depths of the ocean as well as in the intertidal
zone. An interesting feature of this phylum is that all animals belonging to Echinodermata are marine.
There are no freshwater or terrestrial organisms in this phylum. Water vascular system present in the
echinoderms is a unique circulatory system. This accounts for the gaseous exchange, circulation of
nutrients, waste elimination as well as locomotion. This system has a central ring canal and radial canals
that extend along each arm. Through these structures, water circulates. The madreporite is a structure
present on top of the body. This is responsible for regulation of the water in the water vascular system.

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THE CHARACTERISTICS OF

Phylum Echinodermata

Unique water-vascular system of coelomic origin extends from body surface as series of tentacle-like
1 projections (podia, or tube feet) protracted by increase of fluid pressure within them; opening to

exterior (madreporite or hydropore) usually present.

2 Living in marine habitats and is a free living taxa.

Body unsegmented with pentaradial symmetry with body rounded, cylindrical, or star-shaped, with
3 five or more radiating areas, or ambulacra, alternating with interambulacral areas and no distinct

head
Coelom extensive, forming perivisceral cavity and cavity of water-vascular system; coelom of
4 enterocoelous type; coelomic fluid with amebocytes
Endoskeleton of dermal calcareous ossicles with spines or of calcareous spicules in dermis; covered
5 by either epidermis or pedicellariae.
Triploblastic body and excretory organs are absent.

6

9 MAJOR ANIMAL PHYLA  |  36

Endoskeleton of dermal calcareous ossicles with spines or of calcareous spicules in dermis; covered
7 by either epidermis or pedicellariae.

Skeletal elements connected by ligaments of mutable collagenous tissue under neural control,
8 ligaments can be “locked” into rigid posture or relaxed to allow free movement at will;

locomotion by tube feet, which project from ambulacral areas, by movement of spines, or by
movement of arms, which project from central disc of body.
Nervous system with circumoral ring and radial nerves; usually two or three
9 systems of networks located at different levels in the body, varying in degree of
development according to group.
No brain, only few specialized sensory organs; sensory system of tactile and chemoreceptors, podia,
10 terminal tentacles, photoreceptors, and statocysts.
Autotomy and regeneration of lost parts conspicuous while asexual reproduction by fragmentation in
11 some.
Sexes separate (except a few hermaphroditic) with large gonads, single in holothuroids but multiple in
12 most. Some with simple ducts, with no elaborate copulatory apparatus or secondary sexual
structures. Fertilization usually external wherein eggs brooded in some and development through
free-swimming, bilateral, larval stages. Metamorphosis to radial adult or sub-adult form.
13 Respiration by papulae, tube feet, respiratory tree (holothuroids), and bursae (ophiuroids).

Blood-vascular system (hemal system) much reduced, playing little if any role in circulation, and

2

surrounded by extensions of coelom (perihemal sinuses). Main circulation of body fluids (coelomic
fluids) by peritoneal cilia.

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Examples of

PHYLUM ECHINODERMATA

Starfish

Starfish are marine invertebrates. They typically
have a central disc and usually five arms, though
some species have a larger number of arms. The
aboral or upper surface may be smooth, granular
or spiny, and is covered with overlapping plates.

Sea Urchins

Are typically spiny, globular animals,
Echinoderms in the class Echinoidea. Like other
echinoderms, urchins have fivefold symmetry as

adults, but their pluteus larvae have bilateral
(mirror) symmetry,

Sea Cucumbers

Sea cucumbers are echinoderms from the class
Holothuroidea. They are marine animals with a
leathery skin and an elongated body containing

a single, branched gonad.

Brittle Stars

Brittle star, also called serpent star have their
long, thin arms—usually five and often forked
and spiny—are distinctly set off from the small
disk-shaped body. The arms readily break off but

soon regrow—i.e., are regenerated

Sea Lilies

Sea lily, any crinoid marine invertebrate animal
(class Crinoidea, phylum Echinodermata) in

which the adult is fixed to the sea bottom by a
stalk.The sea lily stalk is surmounted by a

bulbous body with frondlike tentacles, and the
animal resembles a plant.

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PHYLUM CHORDATA

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CHOPRhyDlumATA

Chordata is a familiar phylum that includes organisms like mammals, fish, birds, reptiles, and amphibians
(all vertebrates); sea squirts (tunicates); and lancelets (cephalochordates). All chordates have a notochord,
a dorsal nerve cord, and pharyngeal slits at some point in their development.
People tend to think that the terms "chordate" and "vertebrate" are interchangeable, but that's not true.
While all vertebrates are chordates, not all chordates are vertebrates (for example, the tunicates and
cephalochordates).
So for examples, any vertebrate you can think of is in the phylum Chordata. That means pandas, crows,
sharks, salamanders, alligators, humans, etc.!

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THE CHARACTERISTICS OF

Phylum Echinodermata

Bilateral symmetry; segmented body; three
1 germ layers; well developed coelom.

Notochord (a skeletal rod) present at some
2 stage in the life cycle.

Single, dorsal, tubular nerve cord; anterior Endostyle in floor of pharynx or a thyroid
3 end of cord usually enlarged to form brain. 5 gland derived from the endostyle.

Pharyngeal pouches present at some stage Postanal tail projecting beyond the anus at
4 in the life cycle; in aquatic chordates these 6 some stage but may or may not persist.

develop into pharyngeal slits. Asexual reproduction by budding in polyps
7 forms clones and colonies whereas some

colonies exhibit polymorphism.

Segmentation, if present, restricted to outer
8 body wall, head, and tail and not extending

into coelom.

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EXAMPLES OF

Phylum Chordata

Turtles Sea Squirts

Turtles are reptiles with hard shells that protect Sea squirts are primarily sessile (permanently
them from predators. They are among the oldest fixed to a surface), potato-shaped organisms
found in all seas, from the intertidal zone to the
and most primitive groups of reptiles, having
evolved millions of years ago. Turtles live all over greatest depths.

the world in almost every type of climate. Crows

Sharks Crows are generally smaller and not as thick-
billed as ravens, which belong to the same
Sharks are a group of elasmobranch fish
characterized by a cartilaginous skeleton, five to genus. A large majority of the 40 or so Corvus
species are known as crows, and the name has
seven gill slits on the sides of the head, and
pectoral fins that are not fused to the head. been applied to other, unrelated birds.

Giant Panda

Giant panda, (Ailuropoda melanoleuca), also
called panda bear, bearlike mammal inhabiting

bamboo forests in the mountains of central
China.

Sea Cucumbers

Salamander, (order Caudata), any member of a
group of about 740 species of amphibians that

have tails and that constitute the order
CaudataThey most commonly occur in
freshwater and damp woodlands, principally in
temperate regions of the Northern Hemisphere..

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