Phyla Level And Chordates Upto Class Level (1)

CBSE Biology Class 11 I Phyla Level and Chordates up to Class LevelCBSE Biology Class 11 I Phyla Level and Chordates up to Class Level

Phyla Level and Chordates up to Class Level

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B IOLOGY

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CBSE Biology Class 11 I Phyla Level and Chordates up to Class Level

Topics Covered

Phyla Level and Chordates up to Class LevelBasics of Non-Chordates

Phylum - Chordata

Characteristics of Sub-Phylum Vertebrates

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Introduction

Based on common fundamental characteristics, the broad classification of Kingdom-Animalia has eleven phyla.

Porifera, Coelenterata, Ctenophora, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, Hemichordata and Chordata are the phyla divisions.


Basic Characteristics of Non-Chordates

Non-chordates do not have the notochord.

All animals from phylum Porifera to phylum Hemichordata belong to this group.

Non-chordates are classified according to the level of organisation, symmetry and body cavity.


Phylum-Porifera

Commonly known as sponges, these are

marine, asymmetrical, multi-cellular animals.

They have a cellular level of organisation with a canal

system.

Water enters spongocoel through ostia and leaves

through the osculum.

Collar cells or choanocytes line the

spongocoel and the canals.

A skeleton made of spongin fibres or spicules

supports the body.

Sponges are hermaphrodite and

fertilisation is internal.

Examples are Sycon, Spongilla and Euspongia.


Phylum-Coelenterata (Cnidaria)

These are marine, sessile and radially symmetrical

animals.

Cnidocites or cnidoblasts present on the body and tentacles give the name

cnidaria.

Cnidoblasts contain nematocytes and help in defence, the capture of prey and anchorage.

Cnidarians possess a gastrovascular cavity

starting at the mouth on hypostome.

Basic body forms are of two types – polyp and

medusa.

Polyps are sessile and cylindrical, for example,

Hydra and Adamsia.

Medusa is umbrella-shaped and free-

swimming, for example, Aurelia.

Corals have a skeleton made of calcium

carbonate.

Cnidarians exhibit metagenesis between polyps and medusa.

Examples are, Physalia, Pennatula, Gorgonia and

Meandrina.


Phylum-Coelenterata (Cnidaria)

Gorgonia

Physalia

Meandrina

Medusa


Phylum-Coelenterata (Cnidaria)Commonly called sea walnuts or comb jellies, these are marine, radially symmetrical organisms.

They are diploblastic with tissue level of organisation of the body.

Locomotion occurs with eight external rows of ciliated comb

plates.

Ctenophores are bioluminescent and digestion is extracellular as well

as intracellular.

Reproduce sexually with external fertilisation.

Examples are, Pleurobrachia and Ctenoplana.


Phylum-Platyhelminthes

Commonly called flatworms since the body is

dorsoventrally flattened, these are endoparasites.

They are triploblastic, acoelomate, bilaterally symmetrical animals.

Flatworms have organ level of body organisation and

some members can regenerate.

Hooks are suckers are present while some absorb

nutrients from the host through the body surface.

Flame cells help in excretion and osmoregulation.

Internal fertilisation and development show many

larval stages.

Examples are Taenia and Fasciola.


Phylum-Aschelminthes

Commonly called roundworm,

aschelminthes have a circular cross-section.

They may be aquatic or terrestrial; free-living or

parasitic organisms.

Roundworms are triploblastic,

pseudocoelomate, bilaterally symmetrical

animals.

They have an organ-system level of body

organisation with complete alimentary

canal.

The alimentary canal has muscular pharynx

and excretory canal and excretory pores

remove waste.

Roundworms are dioecious with female longer than males and

internal fertilisation.

Examples are Ascaris, Wuchereria and Ancylostoma.

Ascaris


Phylum-Annelida

The name Annelida is from annulus due to segmental division of body known as

metameres.

Annelids may be terrestrial or marine; free-living or

parasitic.

Triploblastic, bilaterally symmetrical, coelomate

organisms, they have organ-system level of organisation.

Aquatic annelids have parapodia for locomotion,

for example, Nereis.

Terrestrial annelids use longitudinal and circular muscles for locomotion.

They have nephridia for excretion and

osmoregulation while having a closed circulatory system.

The neural system consists of double ventral nerve cord connected to paired ganglia

by lateral nerves.

Nereis is dioecious while leech (Hirudinaria) and

earthworm (Pheretima)are monoecious.


Phylum-Arthropoda

Largest phylum of Animalia, Arthropoda

contains two-third of the classified species.

Triploblastic, segmented, coelomate and bilaterally

symmetrical animals.

They exhibit an organ-system level of organisation

with an open circulatory system.

The body has a head, thorax, abdomen and jointed appendages

covered by a chitinous exoskeleton.

The respiratory system includes gills, book gills and

tracheal system while Malpighian tubules help in

excretion.

Sensory organs include antennae, eyes and

statocysts.

Mostly, dioecious and oviparous, fertilisation is

internal.

Economically important insects are Apis, Bombyx

and Laccifer whereas Limulus is a living fossil.

Disease vectors are Anopheles, Culex and

Aedes while Locusta is a gregarious pest.


Phylum-Mollusca

The second largest animal phylum, molluscs may be

marine or terrestrial.

They are triploblastic, coelomate, bilaterally

symmetrical organisms with the organ-system level of

organisation.

The body has a head, muscular foot and

visceral hump, but no segmentation.

A soft, spongy layer of skin over the visceral hump is

the mantle with gills below it.

The body has a calcareous shell covering while mouth has a rasping organ called

a radula.

Fully functional respiratory and excretory systems and

the anterior head has sensory tentacles.

Most molluscs are dioecious and oviparous

with indirect development.

Examples are Pila, Sepia, Loligo, Octopus, Pinctada,

Dentalium, Aplysia and Chaetopleura.


Phylum-Echinodermata

Endoskeleton of calcareous ossicles gives the name Echinodermata.

They are marine, triploblastic, coelomate animals with the organ-

system level of organisation.

Larvae are bilaterally symmetrical while adults are radially symmetrical.

They have a complete digestive system with

ventral mouth and dorsal anus.

Water vascular system helps in locomotion,

respiration, capture and transport of food.

Separate sexes and sexual reproduction is followed by external

fertilisation.

They exhibit indirect development with free-

swimming larvae.

Examples are Asterias, Ophiura, Antedon, Echinus

and Cucumaria.


Phylum-Hemichordata

Initially considered part of phylum-Chordata,

Hemichordates are now a phylum under non-

chordates.

They are triploblastic, bilaterally symmetrical, coelomate, worm-like

marine animals.

They have organ-system level of organisation with a cylindrical body consisting

of anterior proboscis, collar and a long trunk.

They have an open circulatory system,

respiration is through gills and excretion is through

the proboscis.

They have indirect development after external

fertilisation.

Examples are, Saccoglossus and

Balanoglossus.


Phylum-Chordata

The organisms of this phylum have a

dorsal hollow nerve cord, a notochord

and paired pharyngeal gill

slits.

They are triploblastic, coelomate, bilaterally

symmetrical animals with organ-system

level body organisation.

A closed circulatory

system and post-anal tail are their

other characteristics.

Chordata is divided into three subphyla

Urochordata/Tunicata

Cephalochordata

Vertebrata


Characteristics of Sub phyla-Urochordata and Cephalochordata

Subphyla Urochordata and Cephalochordata,

called protochordate, are

marine animals.

Notochord is present in larval tail of Urochordata.

Notochord in Cephalochordates

extends from head to tail and remains throughout the

lifespan.

Examples of Urochordates are, Salpa, Ascidia and

Doliolum.

Example of Cephalochordates is

Branchiostoma or Amphioxus.

Amphioxus


Characteristics of Subphylum-Vertebrata

The notochord during the embryonic stage is

replaced by a vertebral column in adults.

The vertebral column may be bony or cartilaginous.

They have a ventral heart with two, three or

four chambers.

Kidneys help in osmoregulation and

excretion in vertebrates.

Externally, they have paired appendages –

fins or limbs.


Characteristics of Subphylum-Vertebrata

Class division of subphylum-Vertebrata

Agnatha (jawless) Class – Cyclostomata

Gnathostomata (Has jaw)

Superclass – Pisces (has fins)

Class – Chondrichthyes

Class – Osteichthyes

Superclass – Tetrapoda (has limbs)

Class – Amphibia

Class – Reptilia

Class – Aves

Class – Mammalia


Class – Cyclostomata

Characteristically marine

ectoparasites, they have a

sucking, circular mouth.

They have 6 to 15 pairs of gill

slits but no scales or fins.

Vertebral column and cranium are cartilaginous

while circulation is closed type.

Examples are, Myxine and Petromyzon.


Class – Chondrichthyes

Marine fish with cartilaginous endoskeleton and powerful jaws.

Tough skin with tiny placoid scales with modified placoid as teeth directed backwards.

The notochord is persistent throughout life but no air bladder.

They are poikilothermic (cold-blooded) animals with two-chambered heart.


Class – ChondrichthyesSome members have electric organs, for example Torpedo, and some have poison sting, for example Trygon.

Viviparous animals with internal fertilisation, the males have claspers on pelvic fins.

Examples are, Scoliodon, Carcharodon and Pristis.


Class – Osteichthyes

Both marine and fresh-water fishes, they have a

bony endoskeleton.

Streamlined body with a terminal mouth and skin covered with cycloid or

ctenoid scales.

They have four pairs of gills covered by a pair of

operculum and air bladder to regulate

buoyancy.

They are clod-blooded with two-chambered heart.

Oviparous animals with external fertilisation and

direct development.

Examples of marine Osteichthyes are Exocoetus and Hippocampus.

Freshwater fishes are Labeo, Catla, Clarias etc.

Examples from the aquarium are Pterophyllum

and Betta.


Class – Amphibia

Amphibians have dual life – aquatic as well

as terrestrial.

The body is divided into head and trunk

with two pairs of limbs and tails in some.

Skin is moist, eyes have eyelids and ears

have tympanum.

Respiration occurs through skin and gills

or lungs.

Alimentary canal, urinary and

reproductive tracts open into the cloaca.

Two auricles and one ventricle make a three-chambered

heart for these cold-blooded animals.

They are oviparous with external

fertilisation and indirect development.

Examples are, Hyla, Rana, Bujo,

Salamandra and Ichthyophis.


Class – Reptilia

The name is derived from the Latin word for creep and crawl related to locomotion of these

animals.

Chiefly, terrestrial animals, their bodies have dry, cornified

skin covered with scales or scutes.

They are poikilotherms and heart is three-chambered except in crocodiles (four-

chambered).

Tympanum represents the internal ear while limbs are

two pairs if present.

Oviparous animals with internal fertilisation and direct

development.

Example are Crocodilus, Chameleon, Chelone,

Testudo, Calotes, Hemidactylus, Alligator,

Bangarus, Naja, Vipera etc.


Class – Aves

Aves are animals characterised by forelimbs

modified into wings and body covered by feathers.

Most of them can fly while hind limbs have scales for

swimming, clasping or walking.

Endoskeleton is ossified and long bones have air cavities.

The digestive tract has gizzard, the crop and additional chambers.

They are homeothermic with four-chambered heart and

Respiration is through lungs and supplementary air sacs

help with respiration.

Oviparous animals, they have internal fertilisation and direct

development.

Examples are, Columba, Corvus, Pavo, Psittacula,

Neophron, Struthio, Aptenodytes etc.


Class – Mammalia

The unique characteristic of these animals is the presence

of mammary glands producing milk for young ones.

Most of them have two pairs of limbs and skin covered with

hair.

External ear or pinnae and different types of teeth are

present.

Homeothermic animals, mammals have a four-

chambered heart.

Viviparous animals having internal fertilisation and direct

development.

Examples are, Felis, Canis, Panthera leo, Elephas, Equus,

Macaca, Rattus, Macropus, Delphinus etc.

Ornithorhynchus are oviparous mammals.


Did You Know?

The smallest bird is Mellisugo helenae while the largest bird is Struthio camelus.Struthio is also the fastest runner bird.Fastest swimming bird is Pygoscelis papua.



Q1

When did the reptiles dominate the earth?


A1Mesozoic era

The Jurassic period of the Mesozoic era about 200 million years ago was the time for

class-Reptilia dominating the animal world.


• The animal kingdom is broadly divided into eleven phyla.• Ten of the phyla are non-chordates while phylum Chordata is the only true chordates.• Porifera are simple multicellular organisms with a cellular level of organisation.• Coelenterates are aquatic, mobile animals having cnidoblasts while Ctenophores have comb plates and are marine.• Platyhelminthes are flat, parasitic worms while Aschelminthes are pseudocoelomate roundworms.• Annelids are coelomate, metamerically segmented animals.• Arthropods are the largest group of animals with a segmented body and a chitinous exoskeleton.• Molluscs are the second-largest animal group with calcareous shell and unsegmented body.• Hemichordates are marine animals with proboscis, collar and trunk.• Chordates have a notochord during development or throughout.• Chordates are divided into classes – Cyclostomata, Chondrichthyes, Osteichthyes, Amphibia, reptilia, Aves and

Mammalia.

Summary


The 2-min Test

Question 1: Which type of body scales are present on bony fishes?

Question 2: Describe the mouth of cyclostomes.

Question 3: Name a flightless bird and an oviparous mammal.

Let’s Crack IT!


The 2-min Test

Question 1: Which type of body scales are present on bony fishes?Answer: Ctenoid or Cycloid scales are present on bony fishes.

Question 2: Describe the mouth of cyclostomes.Answer: A cyclostome has round, sucking mouth without jaws.

Question 3: Name a flightless bird and an oviparous mammal.Answer: Struthio (Ostrich) is a flightless bird and Ornithohynchus (Platypus) is an oviparous mammal.

Let’s Crack IT!

CBSE Biology Class 11 I Phyla Level and Chordates up to Class LevelCBSE Biology Class 11 I Phyla Level and Chordates up to Class Level

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Phyla Level And Chordates Upto Class Level (1)