Animal Kingdom Echinoderms exhibit radial as well as bilateral
symmetry at different stages of their life
Animals are classified on the basis of common
fundamental features like the cellular arrangement, Body cavity between the body wall and gut wall,
symmetry of the body, presence or absence of the lined by mesoderm is called coelom
coelom, specific features of the digestive,
Acoelomates: body cavity is absent, e.g.
circulatory and reproductive system
Platyhelminthes
Cellular level of organisation: cells arranged as
Pseudocoelomates: mesoderm is present as
loose aggregates, present in Porifera (sponges)
scattered pouches, e.g. Aschelminthes
Tissue level of organisation: cells performing the
Coelomates: having coelom (body cavity) e.g. from
same function form tissues, present in
Annelida to Chordata
coelenterates
Earthworm’s body shows metameric segmentation
Organ level of organisation: tissues grouped
together to form an organ, which performs particular Animals with notochord are called chordates,
function, e.g. Platyhelminthes animals without notochord are called non-
chordates, e.g. Porifera to Echinodermata
Organ system level of organisation: afew organs
coordinatively perform a certain physiological Also see: Biology syllabus for NEET
function, e.g. Annelids, Arthropods, Molluscs,
Classification of Animals
Echinoderms and Chordates
Open circulatory system: cells and tissue directly
receive the blood pumping out of the heart
Closed circulatory system: blood is circulated
through arteries, veins and capillaries
Diploblastic: embryo with two germinal layers
called external ectoderm and internal endoderm,
e.g. Porifera, Cnidaria
Triploblastic: embryo with three germinal layers,
mesoderm between ectoderm and endoderm, e.g.
Platyhelminthes to Chordates
Asymmetrical: no line of symmetry in the body, Classification of the Animal Kingdom based on common
e.g. sponges fundamental features
Radial symmetry: any plane passing through 1.
centre divides the body in two symmetrical halves, 1. Phylum – Porifera (Sponges)
e.g. coelenterates, ctenophores
Marine, asymmetrical with the
Bilateral symmetry: a plane divides the body in cellular level of organisation
symmetrical left and right halves, e.g. annelids,
arthropods, etc. Food intake, gaseous exchange
and excretion occurs through the
water transport system
Water enters through pores called A polyp is a sessile and
Ostia and goes out through cylindrical form, e.g Hydra,
osculum via central cavity known Adamsia
as spongocoel
Medusa is an umbrella-shaped
Spongocoel is lined by collar cells free-swimming form,
or choanocytes e.g. Aurelia (jellyfish)
Intracellular digestion In some coelenterates,
e.g. Obelia alternation of
Body skeleton is made up of
generation (metagenesis) exist.
spongin fibres or spicules
Polyp form produces medusae
Sponges are hermaphrodite asexually and medusae produce
polyp sexually
Reproduce asexually by
fragmentation and sexually by the Examples: Meandrina (Brain
formation of gametes coral), Adamsia (Sea anemone),
Gorgonia (Sea-fan), Physalia (Po
Fertilisation is internal and the
rtuguese man of war)
development of zygote goes
through a distinct larval stage 1.
Examples: Spongilla (freshwater 1. Phylum – Ctenophora (sea walnuts or
sponge), Euspongia (bath comb jellies)
sponge), Sycon,
Marine, tissue level of
1. organisation, diploblastic and
radially symmetrical and
1. Phylum – Coelenterata (cnidaria)
acoelomate
Aquatic, sessile or free-
Eight rows of ciliated comb plates
swimming, tissue level of
present externally
organisation, diploblastic and
radially symmetrical and Digestion is extracellular and
acoelomate intracellular
The central gastro-vascular cavity Bioluminescence is present
has a single opening called
Hermaphrodite
hypostome, which is surrounded
by sensory tentacles Sexual reproduction, fertilisation
is external with indirect
Cnidoblasts are present on the
development
tentacles, which contain
nematocysts Examples: Ctenoplana,
Pleurobrachia
Digestion is extracellular and
intracellular 1.
Corals have calcium carbonate 1. Phylum – Platyhelminthes (flatworms)
skeleton
Mostly endoparasites, Bilaterally symmetrical,
dorsoventrally flattened body, triploblastic, coelomate, organ
triploblastic, bilaterally system organisation
symmetrical, acoelomate with
Metamerically segmented
organ level of organisation
Longitudinal and circular muscles
Hooks and suckers are present in
help in locomotion
parasites
Nereis, an aquatic animal has
Flame cells are present, which
appendages called parapodia,
help in osmoregulation and
which help in swimming
excretion
Closed circulatory system
Hermaphrodite or monoecious
Nephridia is present for
Internal fertilisation and indirect
osmoregulation and excretion
development through many larval
stages Paired ganglia are present, which
are connected to double ventral
Planaria can regenerate
nerve cord by lateral nerves
Examples: Fasciola (Liver
Reproduction is sexual. Nereis is
fluke), Taenia (tapeworm)
dioecious, earthworm and
1. leeches are monoecious
1. Phylum – Aschelminthes Examples: Pheretima (earthwor
m), Nereis, Hirudinaria (bloodsuc
Free-living or parasitic, aquatic or
king leech)
terrestrial
1.
Round body in cross-section,
bilaterally symmetrical, 1. Phylum – Arthropoda
triploblastic, pseudocoelomate
Largest phylum with two-thirds of
with organ system organisation
all known animals
The alimentary canal is complete
It contains insects
and has a muscular pharynx
Bilaterally symmetrical,
Dioecious, females are longer
triploblastic, coelomate, organ
than males
system organisation
Internal fertilisation with direct or
Their body is covered by
indirect development
chitinous exoskeleton
Examples: Ascaris (roundworm),
The characteristic property of the
Wuchereria (Filarial worm),
group is jointed legs
Ancylostoma (hookworm)
Their body can be divided into
1.
three regions; head, thorax and
1. Phylum – Annelida abdomen
Respiration is by trachea, gills, Loligo (squid), Sepia (cuttlefish),
book gills, book lungs Pinctada (pearl oyster)
The circulatory system is open 1.
type
1. Phylum – Echinodermata
Statocyst or balancing organs are
Adult- radially symmetrical,
present
larvae- bilaterally symmetrical
Eyes are simple or compound
Triploblastic and coelomate
Malpighian tubules help in
Endoskeleton of calcareous
excretion
ossicles
Mostly dioecious, oviparous and
The mouth is present on the
fertilisation is internal
ventral side and anus on the
Examples: economically dorsal side
important
The characteristic feature is the
species- Bombyx (silkworm), Api
presence of Water vascular
s (honey bee) Vector for
system, which helps in feeding,
diseases- mosquitoes
locomotion and respiration
like Anopheles, Aedes,
Culex.Living fossil- Limulus (King Dioecious, external fertilisation
crab) with indirect development
1. Examples: Asterias (starfish),
Ophiura (brittle
1. Phylum – Mollusca
star), Antedon (sea lily),
Bilaterally symmetrical, Echinus (sea urchin)
triploblastic, coelomate, organ
1.
system organisation
1. Phylum – Hemichordata
Unsegmented body covered with
a calcareous shell Presence of stomochord, a
structure similar to the notochord
Distinct head, muscular foot and
the visceral hump is present Bilaterally symmetrical,
triploblastic, coelomate, organ
Respiratory and excretory
system organisation
functions are executed by
feather-like gills Cylindrical body with a proboscis,
a collar and a long trunk
The radula is a rasping organ for
feeding Gills are present and circulation is
open type
They are dioecious, oviparous
with indirect development Proboscis gland works as an
excretory organ
Examples: Pila (apple snail),
Octopus (devilfish),
Dioecious, external fertilisation Amphibia, Reptilia, Aves
with indirect development and mammals
Examples: Balanoglossus,
Saccoglossus
1. Phylum – Chordata
Characteristic features are a dorsal hollow
nerve cord, a notochord and paired gill
slits
Bilaterally symmetrical, triploblastic,
coelomate, organ system organisation
The circulatory system is closed and the
post-anal tail is present
Three subphylums come under Chordata:
1. Urochordata– notochord present
only in the larval tail, e.g. Ascidia,
Salpa, Doliolum
2. Cephalochordata– notochord
present throughout life from head
to tail,
e.g. Branchiostoma (Lancelet or
amphioxus)
3. Vertebrata– Notochord is present
in the embryonic stage, it gets
replaced by Vertebral Column
Vertebrata is further divided into two
divisions
a. Agnatha (without jaws): Class
Cyclostomata
b. Gnathostomata (with jaws): has
two Super Class:
i. Pisces (bear fins): two
Classes-
Chondrichthyes,
Osteichthyes
ii. Tetrapoda (bear
limbs): four classes-
