Animals are multicellular and heterotrophic.
Animal kingdom is most diverse than the plant kingdom.
Based on the organization of the cells, there are 3 levels of organization
Cellular level of organization: Cells are arranged as loose cell aggregates. E.g. sponges
Tissue level of organization: Cells are arranged into tissues. E.g. coelenterates, ctenophores
Organ level of organization: Tissues are arranged into organs and the organs are associated to
form organ systems. Each system performs a specific physiological function. E.g. All higher
animals (from platyhelminthes to chordates).
Organ systems of different animals show complexities. For example,
The digestive system of cnidarians and platyhelminthes is incomplete (only a single opening
functioning as mouth and anus). Complete digestive system has 2 openings (mouth and anus).
Circulatory system is 2 types (open and closed).
It is the arrangement of similar body parts on 2
sides of main axis of body.
Based on symmetry, animals are 2 types:
Symmetry is 2 types:
Radial symmetry
Bilateral symmetry
Radial symmetry: Body can be divided into 2 similar parts by any plane along oral- aboral axis
of body. E.g. some Sponges, Coelenterates, Echinoderms.
Bilateral symmetry: Body can be divided into 2 right and left halves by a section passing
through the longitudinal axis.
Such animal has
An upper or vertebral dorsal side
A lower ventral side
Left and right lateral sides
Anterior (cephalic) side and
Posterior (anal) side.
E.g. All vertebrates and many invertebrates.
The layers of gastrula from which body organs
are formed.
Based on the number of germ layers, animals
are 2 types- Diploblastic and Triploblastic.
Diploblastic animals: 2 germ layers- outer
ectoderm and inner endoderm. E.g. Sponges
and Coelenterates.
Triploblastic animals: 3 germ layers- Outer
ectoderm, middle mesoderm and inner
endoderm. E.g. Flat worms to mammals.
It is the space between body wall and gut wall.
Coelom separates the muscles of gut and body wall.
On the basis of nature of coelom animals are 3 types.
Acoelomate
Pseudocoelomate
Eucoelomate (True coelomate)
Acoelomate: No coelom. The space between
body wall and digestive cavity is filled with
matrix (parenchyma). E.g. Porifers,
Coelenterates and flat worms.
Pseudocoelomates: Here, blastocoel becomes
the coelom. It is not lined by peritoneal layer.
E.g. roundworms.
Eucoelomates (True coelomates): The
coelom in animals except the roundworms
arises from the mesoderm. Coelom is lined by
peritoneal layer and filled with coelomic fluid.
E.g. Annelids to mammals.
Functions of coelom:
It accommodates visceral organs
Coelomic fluid provides moist environment to visceral organs
Acts as shock absorber
Friction is minimized.
In some animals, the body is formed of
similar parts (segments or metameres).
This segmentation is called metamerism.
E.g. Annelids, Arthropods.
In vertebrates: only internal metamerism.
It is a supporting rod formed on the dorsal
side during embryonic development in some
animals. Animals with notochord are called
chordates and those without notochord are
called non-chordates.
Levels of
organisation
Germ
layers
Symmetry
Coelom
Phylum
Cellular level
Diploblastic
Asymmetrical
/ radial
Acoelomate
Porifera
Tissue
Diploblastic
Radial
Acoelomate
Cnidaria
Ctenophora
Acoelomate
Platyhelminthes
Pseudocoelomate
Aschelminthes
Coelomates
Annelida
Arthropoda
Mollusca
Echinodermata
Hemichordata
Chordata
Organ/
Organ system
Triploblastic
Bilateral
Habit: Aquatic. Sedentary. Solitary or colonial.
Digestive system: Absent. Digestion is intracellular. Water
transport (canal system) to gather food.
Respiratory system: Absent. Respiration by canal system.
Circulatory system: Absent. Circulation by canal system.
Excretory system: Absent. Excretion by canal system.
Nervous system: Absent
Reproductive system:
Hermaphrodite.
ARP by fragmentation.
SRP by the formation of sperms and ova.
Fertilization internal.
Development is indirect.
Other features:
Millions of minute pores (ostia).
Body wall with outer layer of flat cells
(pinacocytes) and inner layer of flagellated cells
(choanocytes or collar cells).
Body is supported by spicules & spongin fibres.
Highest degree of regenerating capacity.
Habit: Aquatic. Solitary or colonial. Sessile or free
swimming.
Digestive system: Incomplete. Intracellular and
extracellular digestion.
Respiratory system: Absent
Circulatory system: Absent
Excretory system: Body surface
Nervous system: Only a network of neurons.
Reproductive system:
Polyp reproduces asexually (budding) and medusa sexually.
Fertilization external.
Development is indirect.
Other features:
Tentacles for food collection and defence.
Tentacles possess cnidoblasts (stinging cells) with
poison filled capsule (nematocyst).
Cnidoblast is used to kill or paralyse the enemies &
prey.
CNIDOBLAST
Polyp and Medusa are 2 kinds of body
forms.
Show polymorphism and alternation of
generation.
Habit: Marine, solitary and pelagic.
Digestive system: Incomplete. Intracellular & extracellular
digestion.
Respiratory system: Absent
Circulatory system: Absent
Excretory system: Body surface
Nervous system: Only a network of neurons.
Reproductive system:
Only SRP.
Hermaphrodite.
Fertilization external.
Development is indirect.
Other features:
Locomotion is by 8 vertical external rows of ciliated comb plates.
Tentacles present.
Shows Bioluminescence.
Habit: Parasites. Some are free-living. Mainly aquatic.
Digestive system:
Branched alimentary canal with mouth.
Anus absent.
In parasites alimentary canal absent.
Respiratory system: Absent
Circulatory system: Absent
Excretory system:
Protonephridia with flame cells (solenocytes).
Ammonotelic
Nervous system:
Ladder-like.
A brain and nerve cords,
connected by transverse nerves.
Reproductive system:
ARP by fragmentation and regeneration.
Most are hermaphrodite.
In SRP fertilization is internal.
Development is indirect
Other features:
Unsegmented flat leaf like body (except tape
worms).
The first group showing cephalization.
Examples: Taenia solium, Planaria, Liver fluke
Habit: Free living or parasitic
Digestive system:
Tubular alimentary canal with mouth, pharynx,
intestine and anus.
Mouth may possess teeth
Respiratory system: Absent
Circulatory system: Absent
Excretory system: H-shaped Renett cells.
Ammonotelic
Nervous system: Consists of circumpharyngeal
ring with dorsal and ventral nerves.
Reproductive system:
SRP.
Internal fertilization.
Development is direct.
Other features:
Syncitial epidermis.
Thick cuticle.
Sexual dimorphism.
Examples: Ascaris, Ancylostoma,
Wuchereria, Enterobius
Habit: Terrestrial, fresh water or marine or
parasitic.
Digestive system: Pharynx, oesophagus,
stomach, intestine.
Respiratory system: Cutaneus respiration.
Some have branchial (gill) respiration
Circulatory system: Closed type
Excretory system: Nephridia. Aq. forms are
ammonotelic and terr. forms ureotelic.
Nervous system: A pair of cerebral ganglia
(brain) and a double ventral nerve cord.
Reproductive system:
Earth worms and leeches are
hermaphrodites.
Free swimming trochophore larva.
Other features: True segmentation.
Covered by thick cuticle.
Locomotory organs are setae or parapodia.
Examples: Earthworm, Leech, Neries,
Aphrodite, Chaetopterus
Habit: Cosmopolitan
Digestive system:
Well developed.
Mouth parts are different types.
Respiratory system: Gills, trachea, book gills or book
lungs.
Circulatory system: Open type
Excretory system:
Either Antennary glands or Malpighian tubules or coxal
glands.
Aq. forms are ammonotelic. Ter. forms are uricotelic.
Nervous system: A nerve ring followed by
a double ventral nerve cord, which is
ganglionated.
Reproductive system:
Sexes are separate.
External fertilization in aq.forms.
Internal fertilization in land forms.
Oviparous. Some are viviparous.
Other features:
Jointed appendages.
3 regions: head, thorax and abdomen.
Body is covered by cuticle.
Ecdysis (moulting) present.
Metamorphosis present.
Examples: Spider, Scorpion, Crab, Prawn,
Lepisma, insects etc.
Habit: Generally aquatic. Few are terrestrial.
Digestive system:
Well developed.
Salivary glands and liver present.
Respiratory system: Gills in aq.forms and pulmonary
sac in terrestrial forms.
Circulatory system: Open type
Excretory system:
Organs of Bojanus.
Ammonotelic or ureotelic.
Nervous system: Paired ganglia and their connectives.
Reproductive system:
Sexes are separate.
Development direct or indirect.
Larval forms are glochidium, trochophore and veliger.
Other features:
Body is divisible into head, visceral mass (visceral hump) &
foot.
Univalve or bivalve shell.
Mantle and radula present.
Examples: Pila, Achatina, Pinctada, Sepia, Loligo, Octopus,
Habit: Exclusively marine.
Digestive system: Simple and complete.
Respiratory system: Dermal branchiae (gills) or
papulae and tube feet.
Circulatory system: Reduced
Excretory system:
Diffusion through gills.
Ammonotelic
Nervous system:
Circum oral nerve ring and some radiating nerves.
No brain.
Reproductive system:
Fertilization external.
Development indirect.
Ciliated free swimming larva.
,
Other Features:
Body is covered with spines for protection.
Head absent.
Endoskeleton (ossicles) present.
Water vascular system for locomotion and
food capture.
Great power of autotomy and regeneration.
Examples: Star fish, Echinus,
Echinocardium, Antedon, Cucumaria
Habit: Marine
Digestive system: Complete
Respiratory system: Gills
Circulatory system: Open type
Excretory system: Proboscis gland
Nervous system:
Reproductive system: infra-epidermal type
Sexes are separate.
Fertilization external.
Development is indirect.
Other features: Cylindrical body composed of an
anterior proboscis, a collar and a long trunk.
Examples: Balanoglossus, Saccoglossus
These are animals with
notochord, dorsal tubular
nerve cord and pharyngeal gill
slits.
Notochord is a flexible rod
located in the mid dorsal line
between the alimentary canal
and the nerve cord in the
embryo.
Chordata
Non-chordata
Notochord is found in the embryonic stage
Absent
Central nervous system is dorsal, hollow and single
Pharyngeal gill slits present
Ventral heart
A post-anal tail is present
Endoskeleton and exoskeleton present
Hepatic portal system present
Ventral, solid and double
Absent
Dorsal heart (if present)
Absent
Only exoskeleton
Absent
Marine
Heterocercal caudal fin
Cartilaginous
Gill slits without operculum
Skin with placoid scales
Teeth are modified placoid scales which are
backwardly directed
No air bladder so they have to swim constantly to
avoid sinking
Sexes are separate. In males pelvic fins bear
claspers
Internal fertilization
Many of them viviparous
E.g. Scoliodon (Dog fish), Pristis (Saw fish),
Carcharodon (Great white shark), Trygon (Sting
ray), Torpedo (have electric organ).
Marine and fresh water
Homocercal caudal fin
Bony endoskeleton
Terminal mouth
Gills (4 pairs) covered by an operculum on each side
Cycloid, ctenoid or ganoid scales
Air bladder for buoyancy
Sexes are separate
Fertilisation external
Mostly oviparous
Development direct
Marine
Fresh water
Aquarium
Exocoetus (flying fish)
Labeo (Rohu)
Betta (Fighting
Hippocampus (sea horse)
Catla (Katla)
fish)
Sardine
Clarias (Magur)
Pterophyllum
Mackeral
Tilapia
(Angel fish) etc.
Tuna
Anabas (Climbing
Remora (sucker fish)
perch)
Pomfret
Cybium
Aquatic larval life and terrestrial adult life
For breeding they require a watery environment
Pentadactyl limbs
Moist skin without scales
A tympanum represents the ear
Alimentary canal, urinary and reproductive tracts open into a common chamber (Cloaca)
which opens to exterior
Respiration is by gills (in larva), lungs and through skin.
3-chambered heart (2 auricles + 1 ventricle)
Poikilotherms
Sexes are separate. Fertilisation external. Oviparous. Development is indirect
E.g. Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis
(Limbless amphibia), Ambystoma (Tiger salamander), Rhacophorus (Flying frog)
Dry & cornified skin, epidermal scales or scutes Snakes and lizards shed their scales as skin
cast.
Tympanum represents ear.
Limbs- 2 pairs (if present)
3-chambered heart (but a septum partially separates ventricle). Heart is 4-chambered in
crocodiles.
Poikilotherms
Fertilisation internal
Oviparous
Development is direct
Examples:
Chelone (Turtle), Testudo (Tortoise)
Chameleon (Tree lizard), Calotes (Garden lizard)
Crocodilus (Crocodile), Alligator, Gavialis (gharial)
Hemidactylus (Wall lizard), Sphenodon (Tautara), Draco (flying dragon or flying lizard),
Phrynosoma (horned lizard), Varanus (monitor),
Poisonous snakes: Naja (Cobra), Bangarus (Krait), Vipera (Viper), Crotalus (rattle snake),
Enhydrina (sea snake) etc.
Non-poisonous snakes: Python, Typhlos (blind snake), Dryophis (tree snake)
Presence of feathers
Possess beak
Forelimbs are modified into wings
Hind limbs have scales and are modified for walking, swimming, or clasping tree branches
Skin is dry without glands except the oil gland at the base of tail
Long bones are hollow and pneumatic
Digestive tract with additional chambers, the crop and gizzard
Heart is 4-chambered
Homoiotherms (warm-blooded).
Double respiration. Air sacs connected to lungs.
No urinary bladder.
Fertilisation is internal.
Oviparous.
Development is direct.
E.g. Corvus (Crow), Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock),
Gullus (Fowl), Bubo, Aptenodytes (Penguin), Neophron (Vulture) etc.
Presence of mammary glands (milk producing glands).
2 pairs of limbs for walking, running, climbing, burrowing, swimming or flying.
Skin with hair.
External ear (Pinnae)
Heterodont, thecodont, diphyodont.
4-chambered heart.
Homoiotherms.
Respiration by lungs.
Sexes are separate.
Fertilisation internal.
Viviparous (except Echidna and Platypus).
Development is direct.
E.g. Ornithorhynchus (Platypus), Macropus (Kangaroo), Pteropus (flying fox), Camelus
(Camel), Macaca (Monkey), Rattus (Rat), Canis (dog), Felis (Cat), Elephas (Elephant), Equus
(Horse), Delphinus (Common Dolphin), Balaenoptera (blue whale), Panthera tigris (Tiger),
Panthera leo (lion)
Protochordata (Acraniata)
Urochordata (Tunicata)
Vertebrata (Craniata)
Cephalochordata
Notochord present
Notochord extends from
Possess notochord during the
only in larval tail
head to tail region and is
embryonic period
Body is covered by
persistent throughout
Notochord is replaced by a
test made up of
the life
cartilaginous or bony
tunicin
Exclusively marine
vertebral column in the adult
Exclusively marine
Fish-like
Ventral muscular heart
Retrogressive
No definite coelom
Kidneys for excretion and
metamorphosis
Sexes are separate
osmoregulation
Hermaphrodite
E.g. Branchiostoma
Paired appendages which
E.g. Ascidia, Salpa,
(Amphioxus or Lancelet)
may be fins or limbs
Doliolum.
Ascidia