Major groups of animals (salient features) (Non-chordates upto phyla and chordates upto classes).

Kingdom V: Animalia
Basis of classification of Animalia kingdom:

• Symmetry
(i) Bilateral symmetry:
It is when an organism can be divided into right and left halves, identical bumirror images, by a single vertical plane.
(ii) Radial symmetry:
It is when an organism is equally spaced around a central point, like spokes oa bicycle wheel.
• Germ layers
→ In embryonic stages there are different layers of cells called germ cells.
• The three different types of germ cells are:
(i) Ectoderm:
It is the outermost layer which forms nail, hair, epidermis, etc.
(ii) Endoderm:
It is the innermost layer which forms stomach, colon, urinary, bladder, etc.
(iii) Mesoderm:
It is the middle layer between ectoderm and endoderm which forms bones,cartilage, etc.

• According to the number of germ layers present in embryonic stage, animal could be:
(i) Diploblastic:
Organisms which are derived from two embryonic germ layers (ecto and endo).
(ii) Triploblastic:
Organisms which are derived from all the three embryonic germ layers.
• Coelom
→ Body cavity or coelom is important for proper functioning of various organs.
→ For example, heart which has to contract and expand needs some cavity or empty space, which is provided by the coelom.
• On the basis of presence or absence of coelom, organisms are divided into:
(i) Acoelomates: These are the simple organisms having no body cavity.
(ii) Coelomates:
These are complex organisms having true cavity lined by mesoderm from all side
→ These are further sub-divided into schizocoelomates or protostomes (coelom formed due to splitting or mesoderm) and enterocoelomates or dueterostomes (coelom formed from pouchespinched off from endoderm).
(iii) Pseudo coelamate:
These are organisms having false coelom. They have pouches of mesoder scattered between endoderm and ectoderm.
 

• Notochord

→ It is a long rod like structure, which runs along the body between nervous tissues and gut and provides place muscle to attach for ease of movement.
→ Organisms could be:
• without notochord
• with notochord
• with notochord in initial embryonic stages and vertebral column in adult phase.
 

Phylum 1: Porifera or Sponges
 

(i) Cellular level of organization
(ii) Non-motile animals
(iii) Holes on body which led to a canal system for circulation of water and food
(iv) Hard outside layer called as skeletons
(v) Examples: Sycon, spongilla, euplectelia
 

Phylum 2: Coelenterata
 

(i) Tissue level of organization
(ii) No coelom
(iii) Radial symmetry, diploblastic
(iv) Hollow gut
(v) Can move from one place to another
(vi) Examples: Hydra, sea anemone, jelly fish (solitary), corals (colonies)
 

Phylum 3: Platyhelminthes

(i) Also called flat worms
(ii) No coelom present
(iii) Bilateral symmetry, triploblastic
(iv) Free living or parasite
(v) Digestive cavity has one opening for both ingestion and egestion
(vi) Examples: Planaria (free living), liver fluke (parasitic)
 

Phylum 4: Mollusca
 

(i) Coelom present
(ii) Triploblastic, bilateral symmetry
(iii) Soft bodies sometimes covered with shell
(iv) Generally not segmented
(v) No appendages present
(vi) Muscular foot for movement
(vii) Shell is present
(viii) Kidney like organ for excretion
(ix) Examples: Chiton, octopus, pila, unio
 

Phylum 5: Annelida

(i) Second largest phylum
(ii) Coelom present
(iii) Bilateral, triploblastic
(iv) Segmented (segments specialized for different functions)
(v) Water or land
(vi) Extensive organ differentiation
(vii) Examples: Earthworm, leech, nereis
 

Phylum 6: Arthropoda
 

(i) Largest phylum (consist of 80% of species)
(ii) Generally known as insects
(iii) Coelom present
(iv) Bilateral, triploblastic
(v) Segmented, sometimes fused
(vi) Tough exo-skeleton of chitin
(vii) Joing appendages like feet, antenna
(viii) Examples : Prawn, scorpio, cockroach, housefly, butterfly, spider
 

Phylum 7: Echinodermata
 

(i) Spiny skin, marine
(ii) No notochord
(iii) Coelom present, bilateral symmetry, triploblastic
(iv) Endoskeleton of calcium carbonate
(v) Water vascular system for locomotion
(vi) Bilateral symmetry before birth and radial symmetry after birth
(vii) Examples : Antedon, sea cucumber, star fish, echinus
 

Phylum 8: Protochordata
 

(i) Marine animals.
(ii) Bilaterally symmetrical, triploblastic and have a coelom.
(iii) Gills present at some phase of life
(iv) Notochord is present which is a long rod-like support structure (chord=string) that runs along back of the animal separating the nervous tissue from the gut.
(v) Notochord provides a place for muscles to attach for ease of movement.
(vi) Examples : Balanoglossus, Herdmania and Amphioxus
 

Phylum 9: Nematoda

(i) Bilaterally symmetrical and triploblastic.
(ii) Body is cylindrical rather than flattened.
(iii) Tissues, but no real organs.
(iv) Sort of body cavity or a pseudocoelom, is present.
(v) Familiar as parasitic worms causing diseases.
(vi) Worms causing elephantiasis (filarial worms) or the worms in the intestines (roundworm orpinworms).
(vii) Examples: Ascaris, Wuchereria
 

Phylum 10: Vertebrata
 

(i) Notochord converted to vertebral column
(ii) 2, 3, 4 chambered heart
(iii) Organs like kidney for excretion
(iv) Pair appendages
(v) Examples: Humans (4-chambered), frog (3-chambered), fishes (2-chambered)
→ Vertebrates are divided into five classes namely Pisces, Amphibia, Reptilia, Aves and Mammalia
• Warm blooded organisms:
These are organisms which maintain same body temperatureirrespective of outside temperature.
Example: Humans. Human’s body temperature is approximately 37º.
• Cold blooded organisms:
These are organisms which change their body temperature as persurrounding temperature.
Example : Frog.
 

Pisces (Fishes)

→ They are fishes living in water.
→ Their skin is covered with scales or plates.
→ They respire using gills.
→ They have streamlined body and fins which help them to move in water.
→ They are cold blooded and their heart has only two chambers.
→ They lay eggs from which the young ones hatch out.
• Fishes are divided into two categories on the basis of skeleton:
(i) Fishes with cartilage skeleton called cartilaginous fishes. Example : Shark, Rays etc.
(ii) Fishes with bony skeleton called bony fishes. Example : Tuna, Rohu etc.

Amphibia (Amphibians)
 

→ They are found in land and water.
→ They do not have scales but have mucous glands on their skin.
→ They are cold blooded and the heart is three chambered.
→ Respiration is through gills or lungs. They lay eggs in water.
Example: Frogs, Toads, Salamanders etc.
 

Reptilia (Reptiles)

→ They have scales and breathe through lungs.
→ They are cold blooded.
→ Most of them have three chambered heart but crocodiles have four chambered heart.
→ They lay eggs with hard covering in water.
→ Example: Snakes, Turtles, Lizards, Crocodiles etc.
 

Aves (Birds)
 

→ They are warm blooded animals.
→ They have four chambered heart.
→ They breathe through lungs.
→ They have an outer covering of feathers.
→ Their two fore limbs are modified into wings for flying. They lay eggs.
→ Example: Crow, Sparrow, Pigeon, Duck, Stork, Ostrich etc.
 

Mammalia (Mammals)

→ They are warm blooded animals.
→ They have four chambered heart.
→ They have mammary glands for production of milk to nourish their young ones.
→ The skin has hairs and sweat glands. Most of them give birth to their young ones.
→ Some of them lay eggs (like Platypus and Echidna).
→ Example: Cat, Rat, Dog, Lion, Tiger, Whale, Bat, Humans etc.

Nomenclature
 

→ An organism can have different names in different languages. This creates confusion in naming
organism.
→ A scientific name is needed which is same in all languages.
→ Binomial nomenclature system given by Carolus Linnaeus is used naming different organisms.

Some conventions in writing the scientific names:
 

(i) Genus should be written followed by the species.
(ii) First letter of the genus should be capital and that of the species should be in small letter.
(iii) When printed the name should be written in italics and when written with hands genus and
species should underlined separately.
Example : Homo sapiens for humans, Panthera tigris for tiger.