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.