Chapter 1 Animal Kingdom Part 1 (General Account of Animals and Phylum
Chapter 2 Animal Kingdom Part 2 (Phylum Porifera and Coelenterata,
Chapter 3 Animal Kingdom Part 3 (Phylum Platyhelminthes, Nematoda , Annelida
Chapter 4 Animal Kingdom Part 4 (Phylum Mollusca , Echinodermata and
Chapter 5 Animal Kingdom Part 5 (Chordates-General account, Pices and
Chapter 6 Animal Kingdom Part 6 (Reptilia, Aves and Mammalia)
Chapter 7 Structural Organisation in Animals Part 1
Chapter 8 Structural Organisation in Animals Part 2
Animal Kingdom Part 1
(General Account of Animals and Phylum Protozoa)
The Animal Kingdom has been divided into two sub kingdoms:-
1. Protozoa: It includes unicellular eukaryotic animals with a single
Phylum called protozoa. e.g. Euglena, Amoeba, Paramecium etc.
2. Metazoa : It includes multicellular animals. e.g. Porifera,
Coelenterata to Chordata. The Metazoa is further divided into two
branches,namely Parazoa and Eumetazoa.
Parazoa : It includes Porifera/sponges in which cells are loosely
aggregated and do not form true tissues or organs
Eumetazoa : It includes truely multicellular organisms with organ and
organ system level of organization. e.g. Coelenterata to Chordata.
Based on symmetry Eumetazoa is further divided into Radiata and
Radiata : It includes radially symmetrical animals. In radial symmetry,
cthe animal can be divided into two identical halves on by any of the
radial planes along anterior posterior axis of the body. e.g.
Coelenterata and Ctenophora
Bilateria : It includes bilaterally symmetrical animals. In bilateral
symmetry, the animal can be divided into two identical halve only by a
single plane passing from dorsal side to ventral side and along the
anterior posterior body axis. The animal can be divided only into two
Chapter 1 1
identical left and right parts. e.g. Platyhelminthes to Chordata.
All the body tissues of the adult animal are formed from germ layers.
Depending upon no. of germ layers, animals are classified into
i. Diploblastic: Two germ layers. Outer ectoderm and inner endoderms
with a non cellular mesoglea in between the two. eg. Coelenterata
cii. Triplobastic:- Three germ layers. Outer ectoderm, middle mesoderm
and inner endoderm. eg. Platyhelminthes to Chordata
Body Cavity (Coelom):-
Depending upon presence or absence of body cavity Bilateria are
divided into 3 categories
i. Acoelomata : In these animals, coelom (body cavity lying between
the gut and the body wall) is absent. e.g. Platyhelminthes
Chapter 1 2
ii. Pseudocoelomata : In these animals, a false coelom (body cavity not
lined with coelomic epithelium) is present. e.g. Aschelminthes
iii. Eucoelomata: In this group, a true coelom (body cavity lined with
coelomic epithelium) is present. e.g. Annelida to chordata.
Chapter 1 3
The coelom in eucoelomata is of two types:-
a. Schizocoelomata: Coelom develops by splitting up of mesoderm. eg.
Annelida, Arthropoda, Mollusca
b. Enterocoelous coelomata : Coelom is enterocoel which originates by
cfusion of pouches of embryonic gut (archenteron)
The coelomates are two types-
a. Protostomes: In these animals, the embryonic blastopore develops
into mouth eg. annelida mollusca, arthropoda.
b. Deuterostomes: In these animals the embryonic blastopore develops
into anus eg. echinoderms, hemichordates, and chordates
Chapter 1 4
There are three types of body plans in animals
i. Cell aggregate: eg. Sponges
ii Blind sac: In this body plan, the alimentary canal has only one
opening eg. Coelenterates, Platyhelminthes
iii.Tube within tube: Alimentary canal has two openings eg.Nematoda,
Annelida, Mollusca, Arthropoda, Echinodermata and Chordata
Blood vascular system:-
Open type:- It does not have blood capillaries. Therefore, blood comes
Chapter 1 5
in direct contact of tissues. eg. most Arthropods,, some Molluscs and
Closed type:- It has blood capillaries. Therefore, blood does not come
in direct contact of tissues.eg. Many Invertebrates and all Vertebrates
Notochord is a rod like mesodermal structure present on the dorsal
side of some animals. Such animals are called Chordates eg. Fishes,
Amphibians, Reptiles, Birds, Mammals. The animals which do not have
a notochord are called Non-chordates/invertebrates.
The animals which do not have a notochord are called invertebrates.
e.g. sponges. Invertebrates are characterised by the following salient
(1) Absence of vertebral column.
(2) Nerve cord is solid in nature.
(3)Nerve cord is present on the ventral side and never on the dorsal
The invertebrates are grouped into about 30 phyla which are of two
ctypes, namely major phyla and minor phyla.
(a) Major Phyla :
(8) Mollusca, and
Chapter 1 6
(b) Minor Phyla :
(1) Mesozoa (2) Nemertinea (3) Endoprocta (4) Acanthocephala (5)
Rotifera (6) Gastrotricha (7) Kinorhyncha (8) Nematomorpha (9)
Ectoprocta (10) Brachiopods (11) Phoronida (12) Chaetognatha (13)
Priapulida (14) Sipunculida (15) Echiuroidea (16) Pogonophora etc.
Only major phyla are in the syllabus and will be discussed one by one
This phylum includes all unicellular/acellular eukaryotes : (Gr. Porots =
first + zoon = animal). A single cell performs all the vital life activities of
life. About 50,000 species are so far known.
(1) They are simple and primitive organisms, free living or parasitic,
asymmetrical or radially symmetrical or bilaterally symmetrical
(2) They have protoplasmic level of body organization.
(3) Locomotion is by flagella, cilia or pseudopodia.
(4) Nutrition is holophytic, holozoic, saprozoic or parasitic. But mostly
cheterotrophic in nutrition.
(5) Digestion is intracellular
(6) Excretion & Respiration by diffusion through general body surface.
(7) Osmoregulation (water and salt balance) by contractile vacuoles
in fresh water protozoans. Contractile vacoule is absent in parasitic
and marine forms.
(8) Reproduction occurs both by asexual and sexual methods.
Class 1. Flagellata or Mastigophora
Chapter 1 7
(1) Body covered by a thin pellicle or cuticle.
(2) Locomotion by flagella.
(4) Some forms have chloroplast.
Examples : Chrysamoeba, Cryptomonas, Euglena, Volvox,
Chlamydomonas, Noctiluca, Trypanosoma, Leishmania, Proterospongia
Euglena is a connecting link between Plants and animals.
Trychonympha lives symbiotically in the alimentary canal of termites to
digest cellulose for the termite.
Class 2. Sarcodina/Rhizopoda c
(1) Without definite shape, cell wall or pellicle.
(2)Locomotion by pseudopodia
(3) No permanent mouth or anus.
Examples : Amoeba, E. histolytica, E.coli etc.,
Structure of Amoeba
Chapter 1 8
Class 3. Cilliata/Ciliophora
(1) Body covered by a thin pellicle with a fixed permanent shape
(2) The locomotion by cilia. Mouth and cytopharynx are usually
present. Cytopyge is a temporary anal aperture.
(3) Trichocysts for offense and defence are present in certain forms.
Paramecium has two contractile vacuoles. Posterior contractile vacuole
is highly active.
Class 4. Sporozoa
(1) All exclusively endoparasitic
(2) Body covered by pellicle.
(3) Reproducion by spore formation The class is divided into two sub-
Chapter 1 9
classes, namely, Telosporidia and Neosporidia Examples : Monocystis,
Plasmodium, Babesia, etc.,
Plasmodium-the malarial parasite:-
Chapter 1 10
Plasmodium vivax, a malarial parasite, is an intracellular blood parasite
that can affect humans and other vertebrates. Plasmodium vivax is an
endoparasite and is well-adapted to the parasitic mode of life. The life
cycle of Plasmodium vivax is complicated and is completed in two
different types of hosts: definitive and intermediate.
Definitive and Intermediate Hosts
A definitive host provides nutrition to the parasite. Humans beings act
as definitive hosts where the asexual cycle occurs. The asexual cycle
(multiplication) of Plasmodium in man is known as schizogony .
Schizogony takes place in liver and RBCs of man.
An intermediate host helps in transmission from one definitive host to
the other. Mosquitoes (only female Anopheles) are the intermediate
hosts where the sexual cycle occurs. Sexual cycle involves gametogony
The life cycle of Plasmodium vivax is divided into the following stages.
When an infected female Anopheles mosquito bites a healthy person
to feed on his blood, numerous sporozoites enter into the blood stream
of the person along with the saliva of the mosquito. Sporozoite is the
Pre-erythrocytic schizogony happens when the sporozoites first go to
the parenchyma cells of the liver and remain within it for about one
week. During this period, each sporozoite develops into a schizont. The
schizonts undergo multiple fission to form a large no. of merozoites.
The merozoits of the first generation are called cryptozoites. The
cryptozoites enter fresh liver cells, form schizont which will divide to
form merozoites. These merozoites of second generation are called
metacryptomerozoites. This phase is known as pre-erythrocytic cycle
which takes place in liver cells.
Chapter 1 11
This cycle is divided into the following stages:
After entering the blood stream, merozoites start invading the red
blood cells (RBC). Now, the parasite in RBCs is known as trophozoite.
The trophozoite is the adult stage of the parasite.
Signet Ring Stage--
A non-contractile vacuole appears in its cytoplasm and grows by
feeding the haemoglobin of the RBC. The nucleus is pushed on one side
and parasite assumes a ring-like appearance.
The vacuole disappears and the parasite assumes an amoeboid form to
represent this stage.
By thrusting its pseudopodia inside the cytoplasm of RBC, it feeds on
the hemoglobin and increases its size and forms the schizont.
The schizont undergoes asexual multiplication. The nucleus of schizont
divides to form eight to 24 daughter individuals and forms merozoites
which are released by rupture of RBC. These merozoites enter fresh
RBCs to repeat the cycle every 48 hours and form a large no. of
cmerozoites. The toxins are also released by rupture of RBCs and the
accumulation of toxins causes Benign tertian malaria.
Post or Exo-Erythrocytic Cycle
The merozoites from blood may go to liver cells and they may continue
to produce about 1,000 exo-erythrocytic merozoites within the liver
without any symptom, and may live there for some years. After this
dormant stage, they may again become infectious. These merozoites
invade either fresh parenchyma cells or RBCs.
Chapter 1 12
After several generations of multiplication, some merozoites form
gametocytes in the RBC. The female Anopheles mosquito takes a blood
meal from the infected person and thus ingests both
sexual(gametocytes) and asexual forms. In the mosquito, the asexual
forms soon get digested and the sexual forms survive and develop. The
sexual cycle is divided in the following stages:
Gametogony, where some of the schizonts are modified for sexual
reproduction and the resulting merozoites, after entering the RBC, do
not form trophozoites but grow slowly and specialize themselves as
gamonts or gametocytes. Remember, the gametocytes are produced in
man. There are two forms of fully-grown gametocytes--female, or
macrogametocyte, and male, or microgametocyte which form female
gamete and male gamete in mosquito respectively.
The actively moving male gamete(microgamete) is attracted by the
female gamete(megagamete) and unites to form a zygote.
The actively moving zygote moves vibrantly inside the mid-gut, bores
through the wall of the gut wall and comes to rest under epithelium
and the outer wall of the stomach. The zygotes that fail to get shelter in
the stomach wall of the mosquito develop into Ookinete. Ookinete
csecrete a thin membranous cyst wall; this is known as Oocyst. The
nucleus divides repeatedly and ultimately a large number of sickle-
shaped sporozoites are formed from a single Oocyst. The Oocyst
ruptures about 10 days from its formation and sporozoites are liberated
in the hemocoele of mosquito; later they migrate to the salivary gland
and the female Anopheles becomes infected, enabling her to inoculate
the parasite into the blood stream of healthy persons.
Types of malaria:-
Plasmodium species Disease
Chapter 1 13
P. vivax Tertian malaria
Benign tertian malaria
P. ovale Mild tertian malaria
P. falciparum Sub tertian malaria
Malignant tertian malaria
Black water fever
P. malariaeP. vivax is the most extensively distributed and causes much
debilitating disease. P. falciparum, which is also widely spread, results
in the most severe infections and is responsible for nearly all malaria-
related deaths. P. ovale which is mainly confined to Africa is less
prevalent, while P. malariae, which causes the least severe but most
cpersistent infections, also occurs widely.
Practice Test Paper
1. A coelom (body cavity) derived from blastocoel is known as
(a) Enterocoel (b) Schizocoel (c) Haemocoel (d) Pseudocoelom
2. When only single opening is present in the alimentary canal, then
the body plan is
(a) Open (b) Blind sac (c) Cell aggregate (d) Tube in tube
Chapter 1 14
3. Which one of the following is the connecting link between
chordata and non-chordata
(a) Tachyglossus (b) Amphioxus (c) Balanglossus (d) Sphenodon
4. Which phylum belongs to Duterostomia
(a) Echinodermata (b) Mollusca (c) Arthropoda (d) Annelida
5. In protozoa contractile vacuole is generally absent in the class
(a) Rhizopoda (b) Sporozoa (c) Ciliata (d) Flagellata
6. Which is not the locomotory organ of protozoa
(a) Cilia (b) Flagella (c) Pseudopodia (d) Parapodia
7. Which protozoan is unlikely to have a contractile vacuole
(a) Euglena (b) Paramecium (c) Amoeba (d) Plasmodium
8. Class sporozoa of phylum protozoa is characterised by
(a) Flagella (b) Cilia (c) Parasitism (d) None of these
9. Pseudopodia is a characteristic feature of which class
(a) Mastigophora (b) Sarcodina (c) Sporozoa (d) Ciliata
c10.Euglena belongs to
(a) Flagellata (b) Ciliata (c) Sporozoa (d) None of these
11. The unicellular eukaryotes are placed in the phylum……
12. The cell aggregate body plan is found in……….
13. The type of symmetry found in the Ctenophores is ……..
14. Name the phylum in which the body cavity is pseudocoel and
represents a persistant Blastocoel
15. The level of organization found in Protozoa is
16. The type of body plan found in porifera is…..
Chapter 1 15
17. Enlist the function of contractile vacuole in Protozoa. Do all
Protozoans have contractile vacuoles
18. What is open type of blood vascular system
19. Differentiate between radiata and bilateria
20. Differentiate between Blind sac and tube within tube body plan
Answers and Solutions
6. d. Parapodia are found in Annelida
7. d. Plasmodium is parasitic, Therefore, does not have contractile
13. Radial symmetry
15. Protoplasmic level of organization
16. Cell aggregate
Chapter 1 16
17. Osmoregulation (water and salt balance) is performed by
contractile vacuoles in fresh water protozoans. Contractile vacoule is
absent in parasitic and marine forms.
18. The open type blood vascular system does not have blood
capillaries. Therefore, blood comes in direct contact of tissues. eg.
most Arthropods, some Molluscs and Tunicates.
1. It includes radially symmetrical 1. It includes bilaterally
animals symmetrical animals
2. In radial symmetry, the animal 2. In bilateral symmetry, the
can be divided into two identical animal can be divided into two
halves on by any of the radial identical halve only by a single
planes along anterior posterior plane passing from dorsal side to
axis of the body ventral side and along the
anterior posterior body axis.
3. Examples: Coelenterata and 3. Examples: Platyhelminthes to
20. In blind sac body plan, the alimentary canal has only one opening
eg. Coelenterates, Platyhelminthes
Wherease in Tube within tube Alimentary canal has two openings
eg.Nematoda, Annelida, Mollusca, Arthropoda, Echinodermata and
Chapter 1 17
Animal Kingdom Part 2
(Phylum Porifera, Coelenterata and Ctenophora)
Phylum Porifera / Parazoa / Sponges:
The porifera are the lowest multicellular animals (metazoans) without
definite true tissues. In other words, they have “cellular level” of body
organization. The word “Porifera”means pore bearers (Gr., porus =
pore; ferre = to bear); They have numerous minute pores, called ostia,
in their body wall through which a continuous current of outside water
is taken into the body. 5,000 species are
(1) All porifera are aquatic, sedentary/sessile, asymmetrical or radially
symmetrical animals. They are the first multicellular organisms.
(2) The sponge are diploblastic. Ectoderm is composed of pinachocyte
and endoderm is composed of choanocyte. Both these layers are
called pinachoderm and choandoderm respectively.
c(3) The body is perforated by numerous minute pores called ostia.
(4) The ostia open into a large central cavity called spongocoel.
(5) The spongocoel opens to the outside by a large opening called
(6) The most characteristic feature of this phylum is the presence of a
an inter-communicating system of cavities known as canal system.
(6)They have an endoskeleton of calcareous spicules or silicious
spicules or spongin fibres or sometimes none.
Chapter 2 18
(7) Excretion and respiration takes place by diffusion through general
(8)They have a great power of regeneration.
(9) Reproduction takes place both by asexual and sexual methods. The
asexual reproductive bodies are called gemmules
(10) Development is indirect or direct. The common larval are
parenchymula, amphiblastula, etc.
Diagram of a partially sectioned generalized spong
Types of Canal System in sponges:
1. Ascon type- eg. in Leucosolenia
Chapter 2 19
Ascon type canal system
2. Sycon type- eg. in Sycon(=Scypha). It is formed by folding of body
cwall. Choanocytes are limited only to flagellated canals
Sycon type canal system
Chapter 2 20
3. Leucon type- eg. in class Demospongiae. It is formed by further
folding of flagellated canals of the sycon type. Choanocytes are limited
to flagellated chambers only.
Leucon type canal system c
(1) Skeleton of Calcareous spicules.
(2) Choanocyte cells are largeand conspicuous
Examples : Clathrina,Leucosolenia, Sycon, etc.,
Smallest sponge is Leucosolenia.
Class 2. Hexactinellida
(1)Skeleton of six rayed triaxon, silicious spicules,
Chapter 2 21
(2) These are also knownas glass sponges.
Examples : Euplectela, Hyalonema, etc.
Euplectela is given as a precious Gift in Japan.
Hyalonema is also known as Glass rope sponge.
Class 3. Demospongia
(1) Skeleton is either composed of spongin fibres or silicious spicules
or a combination of both.
(2) The silicious spicules never six rayed
(3) The canal system complicated- Rhagon type
Examples : Spongilla, Chalina, Euspongia, Hippospongia, Oscarella, etc.,
Spongillais a fresh water sponge.
cEuspongia is bath sponge
Phylum Cnidaria /Coelenterata
The phylum “Cnidaria” derives its name from the presence of stinging
cells called Cnidoblasts / Nematoblasts. The coelenterates have tissue
level of body organisation. They are the first true metazoans
(eumetazoans) with a radial symmetry. The word“Coelenterata” refers
to the presence of an internal cavity called coelenteron, or gastro-
vascular cavity, which functions both as digestive and body cavities.
About 9,000species are known.
Chapter 2 22
General Characters :-
(1) The coelenterates are aquatic and solitary or colonial
(2) Two basic types of individuals occur in the life cycle. They are
polyps and medusa
(3) They diploblastic. The wall body wall is made up of two layers ofPolypMedusa
cells, namely the ectoderm and the endoderm with a non–cellular layer
in between called mesogloea.Source: http://www.thinkquest.org
(4) They have characteristics cells called Nematocysts or stinging cells.
c(5) The coelenterates are acoelomate animals
(6) A gastrovascular cavity or coelenteron comparable to the gut of
higher animals is present.
(7) Mouth is present; but anus is absent
(8) Digestion is both extracellular as well as intracellular
(9) Respiratory, excretory and circulatory system are absent
(10) Nervous system is diffuse-type, composed of a loose network of
(11) Reproduction is both by asexual and sexual methods
(12) Development is indirect as there are one or two forms of larva
(13) Life history of some forms includes alternation of generations or
Chapter 2 23
metagenesis. i.e. the asexual sessile Polypoid stage alternates with
sexual free swimming Medusoid stage. In plants, the asexual satge is
diploid and sexual stage is haploid, But in coelenterates both poly and
medusa are diploid so this type of alternation of generation is called
Body wall of a Coelenterate c
Chapter 2 24
Cnidoblast Cnidoblast discharged
Class 1. Hydrozoa.
(1) They are both marine and fresh water. Gastro-vascular cavity
without stomodaeum, septa or nematocysts bearing gastric filament
(2) Skeleton is horny perisarc in some forms, while coenosarc secretes a
skeleton of calcium carbonate forming massive stony structure or coral
reefs in other forms.
(3) They are notable to exhibit polymorphism. Medusa is provided with
ctrue muscular velum.
(4) Many hydrozoa exhibit alternation of generation
(5) Gonads ectodermal in origin and discharged externally.
(6) Cleavage is holoblastic, ciliated planula larva.
Examples : Hydra, Tubularia, Bougainvillea, Obelia, Sertularia,
Plumularia Companularia, Millepora, Physalia, Porpita, Velella, Aurelia,
Cynaea, Rhizostoma etc.
Chapter 2 25
Physalia is also known as Portuguese man of war. Aurelia is also known
Anatomy of Hydra showing body wall c
Chapter 2 26
Life cycle of Obelia c
Class 2. Scyphozoa
Chapter 2 27
(1) Scyphhozoa cup shaped animals.
(2) They are exclusively marine.
(3) Medusae are large, bell or umbrella-shaped and without true velum
(acraspedote). They are free swimming or sessile.
(4) Marginal sense organs are tentaculocysts
(5) Polypoid generation is either absent or represented by small polyp-
scyphistoma which gives rise to medusae by strobilization or transverse
(6) Gastrovascular system is without stomodaeum, with gastric
filaments and may or may not be divided by septa.
(7) Mesogloea is usually cellular i.e. it contains some cells
(8) Gonads are endodermal. Sex cells are discharged into the stomach.
Class 3. Anthozoa
(1)They are also known as flower animals, are solitary or colonial and
(2) They are exclusively polypoid. Medusoid stage is absent.
(3) The oral end of the body bears hollow tentacles surrounding the
mouth in the centre.
(4)The stomodaeum is often provided with one or more ciliated
grooves- the siphonoglyphs.
(5) Gastrovascular cavity is divided into compartments by complete or
incomplete septa or mesenteries.
Chapter 2 28
(6) Mesenteries bear nematocysts at their free edges
(7) Mesogloea contains fibrous connective tissue and amoeboid
Examples : Tubipora, Alcyonium, Heliopora, Gorgonia, Corallium,
Metridium, Adamsia, Astraea, Fungia, Zoanthus.
Tubipora is commonly known as organ pipe c
Adamsia is commonly known as sea anemone.
L.S. Sea Anemone( Metridium) showing its structure
Chapter 2 29
Ctenophora is a small phylum containing only about 80 species. They
are exclusively marine animals commonly called comb jellies or sea
walnuts. They resemble Coelenterata as well as platyhelminthes.
Earlier, this phylum was placed under Coelenterata but later
HATSCHEK (1889) placed it under a separate phylum
(1) They are solitary, pelagic and transparent animals having tissue-
grade of organization.
(2) They have biradial symmetry.
(3) Theyare acoelomate, unsegmented,diploblastic animals.
(4) The mesogloea contains cells.
(5) Nematocysts are absent.
(6) Special adhesive cells called colloblasts are present in all
(7) The gastrovascular system is well developed.
(8) Skeletal system is absent.
(9) Excretion and respiration by diffusion through general body surface
(10) The nervous system is in the form of nerve net.(17) An aboral
sense organ- statocys presentt.
(11) Cilia areused for locomation. The cillia are arranged in the form of
bands called comb plates.
Chapter 2 30
(12) They are hermaphrodites, development is indirect.It includes a
Example : Beroe, Cestrum Pleurobachia,Coeloplana, Ctenoplana,
Practice Test Paper
1. The most distinctive character of sponge is
(a) Presence of choanocytes (b) Unicellular (c) Marine (d) Asexual
2. Canal system is only found in the
(a) Coelenterata (b) Porifera (c) Platyhelminthes (d) Nemathelminthe
3. Which sponge is given as a gift in Japan
(a) Hyalonema (b) Euplectella (c) Tethya (d) Leucosolenia
4. Which one is not typical to all porifers
(a) Perforated body (b) Choanocytes (c) System of pores and canal (d)
Presence of spongin fibres
5. Corals belong to the the phylum
c(a) Protozoa (b) Porifera (c) Cnideria (d) Mollusca
6. Phylum coelenterata has remained at
(a) Cellular level of organisation (b) Organ level of organisation (c)
Tissue level of organisation (d) Organ system level of organisation
7. Main cavity in the body of Hydra is called
(a) Gastrovascular cavity (b) Schizocoel (c) Haemocoel (d)
8.The larva of hydra is
Chapter 2 31
(a) Planula (b) Rhabditoid (c) Trochophore (d) None of these
9.Mesogloea is present in the Phylum
(a) Porifera (b) Coelenterata (c) Annelida (d) Arthropoda
10. Hydra is
(a) Triploblastic, radial symmetry & acoelomate (b) Triploblastic, radial
symmetry & coelomate (c) Diploblastic, radial symmetry & acoelomate
(d) Diploblastic, radial symmetry & coelomate
11.The level of body organization found in phylum porifera is ………
12.The comb plates found in the phylum Ctenophora are used for……..
13.The body is perforated by numerous minute pores called…..
14.The ostia open into a large central cavity called
15.Name the larva found in coelenterates
16.Portuguese man of War is the name given to …….
17.What is metagenesis
c18.The spongocoel opens to the outside by a large opening called…...
19.What is canal system
20.Briefly explain about skeleton in Porifera
Answers and Solutions
Chapter 2 32
11. Cellular level of body organization
17. Life history of some Coelenterates includes alternation of
generation i.e. the asexual sessile Polypoid stage alternates with sexual
free swimming Medusoid stage. In plants, the asexual satge is diploid
and sexual stage is haploid, But in coelenterates both poly and medusa
care diploid so this type of alternation of generation is called
19. The characteristic feature of the phylum porifera is the presence of
a an inter-communicating system of cavities known as canal system.
The canal system is vital for performing life activities of the sponge like
respiration, circulation, excretion etc.
Chapter 2 33
20. They have an endoskeleton of calcareous spicules or silicious
spicules or spongin fibres or sometimes none
Chapter 2 34
Animal Kingdom Part 3
(Phylum Platyhelminthes, Nematoda, Annelida and Arthropoda)
The phylum Platyhelminthes includes flatworms (Gr., platys =flat;
helmins = worms); They have a dorsoventrally flattened body like a
leaf. About10,000 species known.
(1)They show organ level of body organization.
(2) They are acoelomate animals.The cavity in platyhelminthes is filled
with mesenchyme or parenchyma
(3) First time in animal kingdom, triploblastic condition is established
having three germ layers namely ectoderm, mesoderm and endoderm
(4) First time, bilaterally symmetrical animals.
(5) Some members have segmented body but the segmentation in
platyhelminthes is called as pseudometamerism
c(6)Some of the parenchyma cells give rise to muscle fibres. The muscle
fibres are arranged in circular, longitudinal and vertical layers.
(7) The digestive system is incomplete i.e. it does not have anus.
Alimentary canal is absent in absent in Cestoda and Acoela. The
alimentary canal is branched in Turbellarians.
(8) The respiratory organs are absent. In parasites, respiration is
(9) There is no circulatory system
Chapter 3 35
(10) The excretory system consists of protonephridia (flame cells)
(11) The nervous system is formed of longitudinal nerve cords with
ganglia. A pair of anterior ganglia form the brain. The longitudinal nerve
cords are connected together by transverse connectives.
(12)They are monoecious / hermaphrodites, i.e., both the male and
female sex organs are present in the same organism
(13) Fertilization is internal. Self or cross fertilization takes place, cross
fertilization is more common, development is direct or indirect.
Endoparasites normally show indirect development with many larval
cstages. Their life cycle is completed involving one or two hosts.
(14) They are free living or parasitic. The parasitic worms have adhesive
organs like hooks, spines, suckers and adhesive secretions.
(a) Class 1. Turbellaria
Chapter 3 36
(1) Most turbellarians are free living but some of them are ecoto-
commensal or parasitic
(2) The epidermis is either cellular or syncytial and covered with cilia.
Epidermis contains rhabdites
(3) No Segmentation
(4) Alimentary canal is present except in a few
(5) Suckers are absent c
(6) Life cycle is simple
Example : Dugesia (= Planaria)
Class (2) – Trematoda
(1) They are ecto or endoparasites of vertebrates; commonly called
Chapter 3 37
(3) Body without cilia, but covered by a thick, resistant cuticle.
(4) Suckers, hooks and spines, present for attachment to the host
Examples : Polystomum,Fasciola, Schistosoma (blood fluke of man and
Life Cycle of Fasciola hepatica c
Class (3) – Cestoda
(1)All cestodes are endoparasites. Mostly in alimentary canal of
vertebrates; commonly called tapeworms.
(2) Body long, slender, tape-like, usually divided into small segments
(3) Body non-ciliated but with a thick
Chapter 3 38
(4) Anterior end with suckers.
(5) Mouth and digestive system absent ; digested food is absorbed
from host tissues by diffusion through body wall.
(7) Each proglottid contains one or two complete sets of hermaphrodite
(bisexual) reproductive organs.
(8) Life-cycle usually complicated with alternation of hosts. Embryo
chooked. Examples – Taenia
Chapter 3 39
The most important characteristics of phylum nematoda is that the
space between body wall and alimentary canal is not lined by
peritonium / mesoderm. Such a body cavity is known as a false body
ccavity, or pseudocoel. The pseudocoel represents the persistant
embryonic blastocoel. The term “Nematoda” literally means
“threadworms” (Gr., nema = thread + eidos = form) or“roundworms”
About 12,000species are known.
(1) The nematodes have a soft, cylindrical, unsegmented and elongated
body usually tapering at both ends.
Chapter 3 40
(2) Body wall is composed of a cuticle, asyncytial hypodermis beneath
cuticle, and an innermost layer of large peculiar longitudinally
extended muscle cells arranged in four
(3) The pseudocoel is filled with a fluid without free
(4) The alimentary canal is complete with a terminal mouth and anus
and has a triradiate pharynx
(5) The Circulatorysystem and respiratory organs are
(6) A simple excretory system in the form of a Rennete cell is present.
(7) The nervous system is well–
(8) Reproductive system well–developed. Usually unisexual with sexual
(9) Many Nematodes areparasites of many useful plants and domestic
canimals. Some of them are pathogenic causing serious diseases. Even
man is a host for more than 50species,out of which Ascaris
lumbricoides and enterobius vermicularis (pinworm) are quite
common. Other common human nematodes are Wuchereria which
causesFilaria, Trichinella causing trichinosis, and Ancylostoma causing
Chapter 3 41
T.S. Body of a roundworm c
On the basis of the presence or absence of some specialized sense
organs and caudalglands, nematodes are classified intotwo classes:
Class (1) Phasmidia
(2) They have a pair of unicellular, pouch-like caudal sense organs,
(3) A pair of reduced, pore like sense organs, called amphids are
presentnear anterior end.
(4) Excretory system has paired lateral
(5) Caudalglands are
cExamples – Ascaris, Enterobius, Ancylostoma, Wuchereria, etc.
(1) Mostly small, free-
Chapter 3 43
(3) Amphids spiral, cord like or disc like, rarely pore
(4) No lateralexcretory
(5) Caudal glands
Examples – Tichinella,
The annelids have a long, narrow, worm like body which is divided into
ring-like, true (metameric) segments (Gr., annelus = little ring.
Therefore, they are also known as “segmented worms”. About 9,000
species are known.
(1) They are bilaterally symmetrical animals having organ-system level
of body organization
c(2) They are triploblastic, coelomate animals. First time true coelom
appears in annelida in the animal kingdom
(3) The body wall has thick muscle layers hence called as dermo-
(4) The body is divided into a no. of segments called the metameres.
The segmentation is known as metamerism
(5) Locomotory takes place by unjointed chitinous appendages called
(6) Digestive system complete
(7) Blood vascular system is a closed type
(8) Excretory system consists of segmentally arranged nephridia.
Chapter 3 44
(9) Nervous system consists of a pair of cerebral ganglia (brain) and a
double ventral nerve cord
(10) The annelids are mostly hermaphrodites. The gonoducts are
derived from coelom (coelomoducts). The coelomoducts are connected
with nephridia The development is direct or indirect
Class 1. Polychaeta
(1) They are marine and carnivorous.
(2) Head region consists of prostomium and peristomium and bear
eyes, tentacles, cirri and palps, etc.
(3) Setae are numerous and are born up on lateral appendages of the
body wall known as parapodia
(4) Clitellum absent
(5) Alimentary canal has an eversible buccal region and protrusible
pharynx with jaws.
(9) Excretory organs are segmentally paired nephridia
(10) Saxes are separate
(11) Fertilization is external; free swimming larval stage is trochophore
(12) Asexual reproduction occurs by budding.
cExamples : Nereis, Aphrodite, Polynae, Chaetopterus.
Trochophore larva present in polychaeta (Neries). Aphrodite is
commonly known as Sea mouse.
Chapter 3 45
T.S. of a polychaeta showing the presence of a pair of parapodia.
Class 2. Oligochaeta
(1) They are mostly terrestrial, some fresh water forms.
(2) Their body has conspicuous external and internal segmentation.
(3) Dsitinct head, eyes and tentacles are absent.
(4) Parapodia absent.
(5) Setae usually arranged segmentally.
(6) Clitellum is mostly present.
c(7) Pharynx is not eversible and without jaws.
(8) They are hermaphrodites, development direct and takes place
within cocoons secreted by clitellum.
(9) No free larval stage Examples : Tubifer, Pheretima, (Earthworms).
Class 3. Hirudinea
(1) The members of this class are mostly ecto-parasitic and fresh water
forms, a few marine.
(2) Body consists of definite number of segments, each segments
further breaks up into 2 to 4 rings or annuli
(3) Parapodia and setae absent
Chapter 3 46
(4) Body has an anterior and a posterior sucker, both located ventrally
(5) They are hermaphrodite i.e., sexes united. Reproduction sexual.
Eggs are usually laid in cocoons. Development is direct without free
swimming larval stage
Examples : Acantaobdella, Hirudinaria (Leeches)
Class 4 Archiannelida
(1) They are small, marine exclusively marine,worm-like annelids
(2) Setae and parapodia are usually absent
(3) Prostomium bears two or three tentacles
(4) Larva is typical trochopore
Examples : Polygordius
The arthropods are metamerically segmented animals with each body
segment having a pair of jointed locomotory appendages. “Arthopoda”
literally means jointed feet (Gr., arthron = jointed + podos = foot)
animals. They also have a protective chitinous exoskeleton.
c(1)The pair of lateral jointed appendages in each segment is adapted
for food ingestion, locomotion, respiration, copulation, etc.
(2) Muscular system well-developed whose muscle fibres are always
(3) Digestive tract complete. Most head appendages form mouth parts
with lateral jaws for chewing or sucking.
(4) Coelom restricted to small cavities in excretory and reproductive
organs; It is replaced elsewhere by blood sinuses which fuse together to
form a large perivisceral cavity known as haemocoel. The Sinuses form
an “open blood vascular system” and are filled with haemolymph which
Chapter 3 47
may contain haemocyanin. Haemocoel communicates with a long
tubular mid–dorsal heart.
(5) Respiration takes by gills, book gills ( in aquatic forms), or tracheae
or book lungs (in terrestrial forms) and by diffusion through general
body surface in some forms
(6) Excretion takes place by specialized green glands or coxal glands, or
(7) Nervous system annelidan type; head with a brain-ring which is
connected to a double ventral nerve cord, having paired segmental
(8) Sexes mostly separate with sexual dimorphism
(9) Fertilization internal, in female's body. Eggs megalecithal. Oviparous
(10) Life–cycle includes one or more larval stages that metamorphose
Chapter 3 48