2. BASIS OF CLASSIFICATION
• Levels of organization: all members are multicellular divided as
1. cellular level of organization: loose cell aggregates with some division of
labour e.g., Porifera
2. Tissue level of organization: Coelentrates & Ctenophora
3. Organ level of organization: Platyhelminthes
4. Organ system level of organization: Aschelminthes Chordates
3. BASIS OF CLASSIFICATION
• Digestive system:
1. Open(incomplete): Platyhelminthes(single opening)
2. Closed(complete): Aschelminthes Chordates(two opening as anus & mouth)
• Circulatory system:
1. Open: blood pumped out of the heart and cells and tissues directly bathed in it
2. Closed: blood circulated through series of vessels of varying diameter(arteries,
veins and capillaries)
4. BASIS OF CLASSIFICATION
• Symmetry:
1. Asymmetrical: most of sponges
2. Radial symmetry: any plane passing through central axis divides organism into 2 identical halves e.g.,
cnidaria and ctenophores
3. Bilateral symmetry: body can be divided into identical right and left halves in only 1 plane e.g.,
platyhelminthes chordates (except echinoderms)
• Germinal layers:
1. Diploblastic: external ectoderm, undifferentiated layer mesoglea & internal endoderm e.g., ctenophores
and cnidaria
2. Triploblastic: mesoderm present between ectoderm and endoderm e.g., platyhelminthes chordates
5. BASIS OF CLASSIFICATION
• Coelom: is lined by mesoderm and is cavity between gut wall and body wall
1. Coelomates: annelids chordates
2. Pseudocoelomates: body cavity not lined by mesoderm it present in scattered pouches e.g.,
aschelminthes
3. Acoelomates: body cavity absent e.g., platyhelminthes
• Segmentation: body is externally & internally divided into segments with a serial repetition
of at least some organs e.g., annelids, arthropods & chordates and this phenomenon is called
metamerism
• Notochord: mesodermally derived rod like structure formed on dorsal side during
embryonic development in chordates
6.
7. PORIFERA/SPONGES
• Generally marine
• Mostly asymmetrical
• Primitive multicellular
• Cellular level of organization
• Body is supported by skeleton made of spicules or
spongin fibres
• Hermaphrodite
• Asexual reproduction = fragmentation
• Sexually by gametes
• Intracellular digestion
• Water transport or canal system present and water
moves as:
Ostia Spongocoel (choanocyte/collar cells lined it
and canals)Osculum
Helpful in:
1. Food gathering
2. Respiratory exchange
3. Removal of waste
• Internal fertilization
• Indirect development
9. COELENTERATA/CNIDARIA
• Aquatic, mostly marine, sessile, free swimming,
radially symmetrical animals
• Name cnidaria derived from cnidoblasts or
cnidocytes(contain stinging capsules called
nematocytes) present on tentacles and body.
• Corals skeleton composed of calcium carbonate
• Two basic body forms are:
1. Polyp: sessile and cylindrical e.g., Hydra,
Adamsia
2. Medusa: umbrella shaped & free swimming e.g.,
Aurelia or jelly fish
• Cnidarians which exists in 2 forms exhibit
metagenesis like polyp to medusa asexually and
reverse through sexually e.g., Obelia
• Cnidoblast use:
1. Anchorage
2. Defence
3. Capture of prey
• Tissue level of organization, diploblastic
• Have a central gastro-vascular cavity with single
opening mouth on hypostome
• Digestion is both extra and intra cellular
12. CTENOPHORA/SEA WALNUTS/COMB
JELLIES
• Exclusively marine
• Radially symmetrical
• Diploblastic
• Tissue level of organization
• Body bears eight external rows of
ciliated comb plates help in
locomotion
• Digestion both extra and intra
cellular
• Bioluminescence
• HMB
• Reproduction only by sexual means
• External fertilization and indirect
development
14. PLATYHELMINTHES/FLAT WORMS
• Dorso-ventrally flattened body
• Mostly endoparasites
• Bilaterally symmetrical, triploblastic
and acoelomate animals with organ
level of organization
• Hooks and suckers present in parasitic
forms and absorb nutrients directly
from the host body surface
• Flame cells help in osmoregulation and
excretion
• HMB
• Internal fertilization
• Indirect development
• Planaria has high regeneration capacity
16. ASCHELMINTHES/ROUND WORMS
• Circular cross section
• May be free living aquatic and
terrestrial or parasitic in plants and
animals
• Organ system level of organization
• Bilaterally symmetrical, triploblastic &
pseudocoelomate
• Alimentary canal complete with
developed muscular pharynx
• Excretory tube removes body waste
from body cavity through excretory
pore
• Dioecious females longer than males
• Internal fertilization, development
could be both direct or indirect
18. ANNELIDA
• May be aquatic or terrestrial, free living or
some time parasitic
• Organ system level of organization, bilateral
symmetry, triploblastic, metamerically
segmented, coelomate animals
• Body surface distinctly marked out into
segments/metameres
• Annelida(Latin, annulus: little ring)
• Nereis is dioecious but earthworms and
leeches are monoecious.
• Reproduction is sexual
• Possess longitudinal and circular muscles
help in locomotion
• Aquatic annelids like Nereis possess lateral
appendages, parapodia which help in
swimming.
• Closed circulatory system present
• Nephridia help in osmoregulation and
excretion
• Nervous system consist of paired ganglia
connected by lateral nerves to a double
ventral nerve cord
20. ARTHROPODA
• Largest phylum( over 2/3 of all named
species on earth)
• Organ system level of organization
• Bilaterally symmetrical, triploblastic,
segmented and coelomate animals
• Body covered by chitinous exoskeleton
and divided into head thorax and abdomen
• Have jointed appandages
• Respiratory organs are gills, book gills,
book lungs or tracheal system
• Open circulatory system
• Sensory organs like antennae, eyes(simple
or compound), statocyst or balance organs
are present.
• Excretion through malphigian tubules
• Mostly dioecious, internal fertilization
• Mostly oviparous, development may be
direct or indirect
24. MOLLUSCA
• Second largest
• Terrestrial or aquatic
• Organ system level of organization
• Bilaterally symmetrical, triploblastic and
coelomate.
• Body covered by calcareous shell and
unsegmented with distinct head, muscular
foot and visceral hump
• Usually dioecious, oviparous and indirect
development
• Soft and spongy layer of skin forms a
mantle over the visceral hump
• Space between hump and mantle called
mantle cavity in which feather like gills are
present which have respiratory and
excretory functions
• Anterior head region has sensory tentacles
• Mouth contain file like rasping organ for
feeding called radula
28. ECHINODERMATA
• Endoskeleton of calcareous ossicles
• Spiny bodied organisms
• All marine, organ system level,
coelomate and triploblastic
• Adult are radial and larva are bilateral
• Complete digestive system with mouth
on lower(ventral) side and anus on
upper(dorsal) side
• Water vascular system helps in
locomotion, capture and transport of
food and respiration
• Excretory system absent
• Sexes separate and sexual reproduction
• External fertilization
• Indirect development with free
swimming larva
31. HEMICHORDATA
• Small group of worm like marine
animals with organ system level of
organization
• Bilaterally symmetrical, triploblastic
and coelomate
• Cylindrical body composed of
anterior proboscis, a collar and a
long trunk
• Open circulatory system
• Respiration through gills
• Excretory organ is proboscis gland
• Separate sexes
• External fertilization
• Indirect development
33. CHORDATA
• Bilaterally symmetrical, triploblastic, coelomate, organ system level of
organization
• Three subphyla: Urochordata or tunicata, Cephalochordata and Vertebrata
34. Urochordata and cephalochordata referred as
protochordates and are exclusively marine
• UROCHORDATA: notochord present only in larval tail e.g., Ascidia, Salpa
& Doliolum
• CEPHALOCHORDATA: notochord extends from head to tail and is
persistent throughout their life e.g., Branchiostoma(Amphioxus or Lancelet)
37. VERTEBRATA
• Possess notochord during embryonic period replaced by cartilaginous or
bony vertebral column in the adult thus “all vertebrates are chordates but
all chordates are not vertebrates”
• Ventral muscular heart with 2, 3 or 4 chambers
• Kidneys for excretion or osmoregulation and paired appendages which may
be fins or limbs
39. CYCLOSTOMATA
• All are ectoparasite on fishes
• Have elongated body bearing 6-15 pairs of gill slits for respiration
• Sucking and circular mouth without jaws
• Body devoid of scales and paired fins
• Cranium and vertebral column are cartilaginous
• Closed circulatory system
• Marine but migrate to fresh water for spawning and after it they die in few days and
their larva after metamorphosis returns to ocean
41. CHONDTICHTHYES
• Marine animals with streamlined body and cartilaginous endoskeleton
• Mouth located ventral and notochord persistent throughout life
• Gill slits are separate and without operculum(gill cover)
• Tough skin containing minute placoid scales
• Teeth are modified placoid scales backwardly directed and have powerful jaw
• Predaceous, absence of air bladder, hence swim constantly
• 2 chambered heart(1 auricle & 1 ventricle), cold blooded(poikilothermous)
• Sexes separate, males pelvic fins bears claspers, internal fertilization & many are viviparous
• Some have electric organs (e.g., torpedo) or poison sting(e.g., trygon)
46. Osteichthyes
• Includes both marine and fresh water
fishes with bony endoskeleton
• Streamlined body
• Terminal mouth
• 4 pairs of gills covered by operculum
• Skin covered by cycloid or ctenoid
scales
• Air bladder present regulates buoyancy
• 2 chambered heart(1 auricle & 1
ventricle)
• Cold blooded animals
• Separate sexes
• External fertilization
• Mostly oviparous and direct
development
51. AMPHIBIA
• Live in aquatic as well as terrestrial habitats
• Most have two pairs of limbs
• Body divisible into head and trunk
• Tail may be present in some
• Skin is moist and without scales
• Eyes have eyelids
• Tympanum represents ear
• Alimentary canal, urinary and reproductive tracts
open into a common chamber called cloaca which
opens to the exterior
• Respiration by gills, lungs and through skin
• Heart is 3 chambered(2 auricle and 1 ventricle)
• Cold blooded animals
• Sexes separate
• External fertilization
• Oviparous
• Indirect development
55. REPTILIA
• Creeping or crawling mode of
locomotion(latin, repere or reptum to
creep or crawl)
• Mostly terrestrial and body covered by dry
and cornified skin, epidermal scales or
scutes
• Tympanum represents ear
• Limbs when present are 2 pairs
• Heart usually 3 chambered but 4
chambered in crocodiles
• Poikilotherms
• Snakes and lizards shed their scales as skin
cast
• Sexes separate
• Internal fertilization
• Oviparous and direct development
60. AVES
• Presence of feather and most of them can
fly except flightless birds(e.g.,Ostrich)
• Possess beak, forelimbs modified into wings,
hindlimbs have scales and modified for
walking, swimming or clasping the tree
branches, skin dry without glands except oil
gland at base of tail
• Fully ossified(bony) endoskeleton
• Pneumatic bones present(long bones are
hollow with air cavities)
• Digestive tract have additional chambers
called crop and gizzard
• Heart 4 chambered and warm
blooded(homoiothermous)
• Respiration by lungs, air sacs connected to
lungs supplement respiration
• Sexes separate
• Internal fertilization
• Oviparous
• Direct development
64. MAMMALIA
• Resides variety of habitats
• Presence of mammary glands is
unique
• 2 pair of limbs have diff adaptation
• Skin possess hair, external
ears(pinnae) present
• Heterodont dentition
• 4 chambered heart
• Homoiothermous
• Respiration by lungs
• Sexes separate, internal fertilization
and direct development
• Viviparous with few exception