GENERAL FEATURES OF ANIMALS
By Pranjal Gupta, Ramjas College
BASIS OF CLASSIFICATION
Level of organization
>Protoplasmic or acellular or unicellular
>Cellular-aggregation of cells not reformed into
tissues
>Tissue level-proper division of labor, various
tissues perform different functions
>Organ(system) level-various tissues aggregate
to form separate organs which are entirely
dedicated for a separate function, they later form
organ systems. These organ systems though have
separate functions work collaboratively.
Body plans>cell aggregate plan: Cluster of cells form a body
e.g.. Sponge
>Blind sac plan: single cavity(endocoel) with one
opening for both mouth and anus.
>Tube within tube plan: One tube here refers to
body wall & other the alimentary canal-two
openings mouth and anus
This pattern is further categorized as
deuterostomes and protostomes.
Dueterostome Protostome
Anus forms first in embryo Mouth forms first
Indeterminate cleavage( mosaic
cleavage blastomere separation early
stages may give rise to complete embryo)
Determinate cleavage( complete
embryo forms only if all blastomere remain
together)
enterocoelomates schizocoelomates
Echinoderms and chordates Other animals( sponges-
mollusks)
Symmetry
Asymmetry radial symmetry biradial symmetry bilateral symmetry
Body sections
ANATOMICAL DIRECTIONS
Based on germ layers
>Diploblastic: Two germ layers-endoderm and
ectoderm with fluid filled mesoglea
>Triploblastic:three layers of ectoderm, endoderm
and mesoderm.
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Coelom
ACOELOMATE FASCIOLA SECTION
endoderm
ectodermmesodermlumen
No Coelom
Pseudocoelom in Ascaris
female
cuticle
Cuticle(ectoderm)
Nerve cord
Longitudinal
muscles(mesoderm)
Intestinal lumen
Intestinal lining(endoderm)
Pseudocoel
Uteri
eggs
True coelom
Intestinal
lining(endoderm)
Muscles
surrounding the
intestine
typhlosole
ectoderm
Schizocoelom Enterocoelom
Develop as a split in mesoderm Mesoderm arises from wall of embryonic gut or
enteron as a hollow out growth which form coelom
In annelids, arthropods and mollusks In higher animals
Types of true coeloms
Body segmentation
Metamerism Pseudometamerism
True body segmentation False segmentation
Segmentation is visible
both when body is divided
internally and externally
Segmentation is only
external
Segments are fused and
cannot be separated on
will
Segments are loosely
bound and can be
separated on will
Most distinctive in
annelids and also seen in
Arthropods, chordates
(segments called tagma)
Proglottids of tapeworm
True segmentation
As in earthworm
False segmentation
Composing of
Proglottids in tapeworm
Cephalization- Differentiation of head at anterior
end with sense organs and nervous tissue. It is a
benchmark for bilaterally symmetrical animals.
Appendages- locomotary projections
Sexual dimorphism- differences in male and female
Polymorphism- condition of occurring in different
forms
Fertilization- process of fusion of sperm and egg.
>External fertilization-gametes are released outside
body where process occurs
>Internal fertilization-sperms are released inside the
female
CEPHALIZATION
No cephalizationCephalization
APPENDAGES
Tentacles of jellyfish
Wings and antennae of moth Wings and feet of birds
Foot of gastropod
Tube feet of starfish
Fins in fishes
Parapodia in polychaete
SEXUAL DIMORPHISM
Male(small) and female
Golden orb weaver spider
Peacock and peahen
male
Angler fish female(large) and male
FERTILIZATION
External fertilizationInternal fertilization
ORGAN SYSTEMS
Blood vascular system
Blood flow in open
Spaces called sinuses
Or lacunae and
It bathes cells in blood
E.g.. Arthropods and mollusk
Blood flow in closed vessels
And it allows efficient transport
Of blood to cells where the size
Of vessels reduce greatly
And empty their contents.
Respirati
on type
example
Body surface Hydra
Pulmonary
respiration(throu
gh lungs)
Amphibian-
mammals
Branchial
respiration(throu
gh gills)
Mollusks, fishes,
tadpoles, prawns
Cutaneous
respiration(
through skin)
Annelids, frog
Book lungs and
book gills
Arachnids
Tracheal
respiration(
through network
of tubular
tracheae)
Most arthropods
Buccopharyngeal
respiration(
through that
cavity)
Some frogs and
toad
Respiratory system
EXCRETIONExcretory
structure
example
Malphigian
tubules
Insects
Green or
antennal
gland
Crustaceans
Complex of
renette cells
Ascaris
Nephridia Annelids
Flame cells or
protonephridi
a
Flatworms
Diffusion Sponges,
cnidarians,
some
echinoderm
Kidneys Mollusk,
vertebrates
Gizzard
Crop
Hepatic ceca
Mesenteron
Malphigian
tubules
Colon
ANIMALS ON THE BASIS OF REMOVAL OF WASTE PRODUCTS
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edited/chap19/tab1a.gif
Certain animals like earthworm are both ammonotelic or ureotelic depending
On availability of water.
NEURAL SYSTEM
neuron and glial cells compose
The major mass of the nervous
Tissue
Ganglia- It is a cluster of different
neurons and associated glial cells
forming into a solid
nerve cord like mass if found
in the PNS; it is called
nucleus if found in CNS
Commisure-connect two similar
ganglia/nuclei
Connective- connect two different
ganglia/nuclei.
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SKELETON
Exoskeleton-Outside body; formed by ectoderm and mesoderm. E.g.. Shell of mollusks, scales, feathers, hairs, cuticle, carapace
Endoskeleton-Inside body; formed by mesoderm and endoderm. E.g.. Spicules of sponges, cartilage and bones.