Classification of Animals – Lecture Notes for 9th Std Homi Bhabha Online Class

This is a brief compilation of the points we have studied in our Zoom Class – Animal Classification.

What is classification?

Why classify into vertebrates and invertebrates? (Why not – those having ears and those not having ears?)

Unicellular animals

Body has got only one cell
No body organs like eyes, hands, head
All functions like breathing, eating through cell
Life is controlled only by chemicals.
Example: Amoeba, paramecium, euglena

Amoeba:

Locomotion by pseudopodia

Euglena:

Locomotion by flagellum

Paramoecium

Multicellular Animals

Non-Chordates / Invertebrates
Hemichordates
Vertebrates

Non-Chordates / Invertebrates

No vertebra, no bones
Examples: Sponge, hydra, sea anemone, tape worm, ascaris (human parasite), earthworm, leech, all insects, spiders, crab, snail, octopus, starfish

Subkingdom Metazoa – Invertebrates (Multicellular, Notochord and vertebra absent)

PORIFERA

The Sponge Skeleton
• An internal support ‘skeleton’ is made of spicules and collagen fibers.
• Spicules are canals made up of cells having crystals of calcium and carbonate ions, or silicate salts.
• These salts are precipitated by scleroblast cells in the sponge tissue.
• Spicules also act as protective device against predation.
• Cells are interchangeable
• They do not have special tissues.

Sponge have three reproduction methods

1) Regeneration: Broken / wounded fragments can grow into new colonies at different place

2) Asexual reproduction :
• Gemmules are formed. They are densely-matted, hardened ball protected by collagen and special spicules.
• In freshwater sponges these balls survive in winter and then form a new clone in the spring.

3) Sexual Reproduction
• In favorable conditions sponge cells develop into sperm
• Sperm flow in water & enter a different sponge body. There they are captured and transferred to an embedded egg.
• The egg develops into a simple larva ( a ball of cells with cilia on the outside.)
• The larvae break out and swim for a few hours
• It settles to the bottom and grows in a new sponge.

COELENTERATA

• Two layered body with radial symmetry
• Both sexual & asexual reproduction
• Alternation of generation fixed (polyp) swimming (medusa)
• Body cavity with single opening
• Tentacles are armed with stinging cells with venom

Hydra

Sea Anemone –

Jellyfish

Corals

PLATYHELMENTHES

• Simplest triploblasts with bilateral symmetry
• Hermophrodites
• Single opening to elementary canal
• Acoelomate
• Flat bodied

Tapeworm

Planaria (a flatworm, microscopic)

Liverfluke –

Nemathelminthes or Aschelminthes

• Triploblasts with bilateral symmetry
• False body cavity preset
• Elementary cannel passes thru body from mouth & anus

Wuchereria Bancrofti

ANNELIDA

• True body cavity
• Body show many segments each having cuticular structure called setae

Leech

Nereis

ARTHROPODA

• Insecta – 6 legs
• Arachnida – 8 legs
• Crustacea – 10 Legs
• Myriapoda – many legs

Insects:
• Potentially over 90% of the animal life forms on Earth are insects!
• Mosquito, fly, cockroach, ant, bee, grasshopper, beetle, silverfish, lice

Arachnida: Spider

Crustacea –

Lobster

Prawn –

Crab

Myriapoda

Millipede-

Centipede-

MOLLUSCA

• Soft body is supported by hard shell made of calcium carbonate
• Breathe through grills. Land molluscans have lungs
• Muscular foot for moving

Snail:

Pila:

Octopus:

Slug:

Oyster:

ECHINODERMATA

• Marine animals with radially symmetrical body
• They have spiny exoskeleton
• Have unsegmented body characterised by absence of head & presence of five regularly arranged arms
• Locomotion is done by tube feet

Starfish

Brittlestar:

Sea Urchin:

Sea Cucumber

Phylum Hemi Chordata

• E.g. Balanoglossus, Saccogloss
• Evolutionary link
• Marine animals
• Body divisible into proboscis, collar & trunk
• Gill slits are in many pairs
• Solitary, show burrowing worm like form
• Straight alimentary canal with terminal anus

Saccoglossus

Balanoglossus

Phylum Chordata

• A rod like structure (notochord) above digestive tract
• A tubular nerve cord above notochord

Phylum: Chordata
Sub Phylum: ProtoChordata
Class: CephaloCordata

Example: Amphioxus

Phylum: Chordata
Sub Phylum: ProtoChordata
Class: UroChordata

• Marine animals
• Many gill slits
• Adult body covered with tunic
• Some produce light
• Fixed or free swimming
• Example: Pyrosoma, Ascidian,

Ascidian:

Phylum: Chordata
Sub Phylum: Vertebrata

Notochord replaced by vertebral column
Bone is enclosed in protective bony box called cranium
Endoskeleton is present in addition to exoskeleton
Heart is in ventral position
Nerve cord is in dorsal position
Red pigment hemoglobin is present in blood
Paired appendages do not exceed two pairs

Class: CYCLOSTOMATA

Example: Petromyzone

Class: PISCES

• Skin is covered with scales. Scales are absent on head
• Head & trunk can not be distinguished
• Fish can smell & hear
• Nostrils do not play a role in respiration
• Eyes are without eye lids
• Cold blooded
• Lateral line pressure sense organs present
• Fins used for locomotion
• Lay eggs. Catfish keep eggs in mouth. Sea horse male keep eggs in pouch.
• Serf fish give birth to young one (viviparous)

Shark:

Sea Horse:

Electric Ray

Phillipine Goby (tiny, size 1cm)

Salmon:
• Born in shallow fresh water
• Adult life in open sea
• Reproduction & death at birth place

Class: AMPHIBIAN

Toad

Class: REPTILIA

Tortoise-

Lizard:

Chameleon:

GArden Lizard

Alligator:

Snake

Snake Venom

Class: AVES

• Exoskeleton is of Feathers
• Lay eggs
• Respiration by lungs & air sac
• Warm blooded
• Presence of Beak
• Hear by tympanic membrane
• Hollow bones for lighter weight

Flightless Birds
•Kiwi
•Emu
•Ostrich
•Rhea
•Penguin (wings are used for swimming)
•Cassoway

Kiwi-