A Short Note On Animalia

The Five kingdom classification has Animalia also known as the animal kingdom as one of the categories. Animals are heterotrophic and their mode of nutrition is described by the term known as Holozoic which means ingestion of food. The animal kingdom has various sub-groups that are classified based on the following -:

• The pattern of organisation of cells. They can be cellular level, tissue level, organ level or organ system level.
• Symmetry – they can be asymmetric as in the case of phylum Porifera or radial symmetry in the case of cnidaria or bilateral symmetry in the case of Platyhelminthes.
• They can be Diploblastic or triploblastic.
• They can have a notochord or it may be absent.
• Presence of segmentation.

Based on the above-mentioned characteristics the organisms are classified into  the following Phylum-:

1. Porifera
2. Cnidaria
3. Ctenophora
4. Platyhelminthes
5. Aschelminthes
6. Annelida
7. Arthropoda
8. Mollusca
9. Echinodermata
10. Hemichordata
11. Chordata
    1. Subphylum – Urochordara
    2. Subphyla-Cephalochordata
    3. Subphylum- Vertebrata
       1. Division – Agnatha- class – Cyclostomata
       2. Division-Gnathostoma- superclass- Pisces ( class – Chondrichthyes, Osteichthyes) and Tetrapoda ( class – Amphibia, Reptilia, Aves, Mammals)

This is the overall hierarchy of the Animal kingdom.

Phylum 

1. Porifera – Members of the phylum are pore bearing and hence the name Porifera.
   1. They are marine
   2. Presence of water canal system.
   3. Presence of collar cells – choanocytes.
   4. Digestion – intracellular
   5. Skeletons are made from – spicules and spongin fibres.
   6. Asymmetric body with the cellular level of organisation.
   7. Hermaphrodite
   8. Examples – Sycon, Spongilla.

1. Cnidaria or Coelenterata – Members are marine and radially symmetric.
   1. Presence of cnidoblasts which are stinging capsules.
   2. Tissue level of organization
   3. Mouth on hypostome
   4. Two basic forms – polyp and Medusa.
   5. Metagenesis is observed.
   6. Calcium carbonate skeleton.
   7. Examples – Polyp – Adamsia, Medusa – jellyfish

1. Ctenophora – They are also known as sea walnuts or comb jellies 
   1. Radially symmetry
   2. Diploblastic
   3. Tissue level organization
   4. Right rows of comb plates for locomotion
   5. Show bioluminescence.
   6. Reproduction – sexual 
   7. Examples – Ctenoplana

1. Platyhelminthes – They are commonly known as flatworms.
   1. Endoparasite
   2. Bilaterally symmetric
   3. Triploblastic
   4. Hooks and suckers are present.
   5. Flame cells for osmoregulation.
   6. High regeneration capacity
   7. Taenia Solium and Fasciola are examples.

• Aschelminthes- They are commonly known as Roundworms.

1. 1. Parasitic
   2. Sexual dimorphism is seen
   3. Pseudocoelom
   4. Separate sexes
   5. Development of alimentary canal
   6. Ascaris- Roundworm is an example.

• Annelida-They has a segmented body.

1. 1. Metamers are present.
   2. Organ system level of organization
   3. Presence of nephridia for excretion
   4. Paropdia is present in Nereis for swimming
   5. Sexual reproduction
   6. Nereis and earthworms are examples.

• Arthropoda- The largest phylum of the animal kingdom.

1. 1. Presence of chitinous exoskeleton.
   2. Coelomate 
   3. Segmentation is present
   4. Paired appendage
   5. Respiratory organs – book gills, book lungs etc.
   6. Malpighian tubules are present.
   7. Locusts and honey bees (Apis indica) are examples.

1. Mollusca – is the second-largest phylum
   1. Bilaterally symmetric
   2. Marine and freshwater organisms
   3. Unsegmented body
   4. Triploblastic
   5.  Head, muscular food and hump are parts.
   6. The presence of a rasping organ is seen.
   7. Pila, Octopus, and Pinctada are some examples.

• Echinodermata-They is spiny bodied organisms.

1. 1. Marine organisms
   2. Presence of water vascular system.
   3. Triploblastic
   4. Radially symmetry in the adult stage 
   5. Complete digestive system
   6. Excretory system absent.
   7. Sexual reproduction
   8. Development is indirect
   9. Starfish -Asterias, and ophiura are some examples.

• Hemichordata- It contains a small group of worms.

1. 1. 1. Open circulatory system
      2. Bilaterally symmetric
      3. Triploblastic
      4. Organ system level of organization
      5. Proboscis is present
      6. External fertilization.
      7. Balanoglossus is an example.

• Chordata- Presence of notochord and nerve cord.

1. 1. Urochordata – presence of notochord in larval tail . Example- salpa
   2. Cephalochordata- notochord is present from head to tail throughout life. example-amphioxus
   3. Vertebrata notochord is replaced by the vertebral column. 

Vertebrata

Division

1. Agnatha– has a class Cyclostomata under it.

Cyclostomata- ectoparasite, closed circulation, gill slits are present, marine organisms. Some examples include – Petromyzon and Myxine.

1. Gnathostoma is divided into two superclasses-

Pisces – divided into chondrichthyes and osteichthyes

Chondrichthyes –

•  Marine animals 
• Mouth is ventral
• Cartilaginous exoskeleton
• Placoid scales are present.
• Tough skin
• Scoliodon and Trygon are examples.

Osteichthyes-

• Marine and freshwater
• Streamlined body 
• Terminal mouth
• The air bladder is present
• Two-chamber heart
• Exocetus and Betta are examples.

Tetrapoda – divided into classes – Amphibia, Reptilia Aves, Mammals.

Amphibia –

• Amphi means dual.
• Live in terrestrial and aquatic environments.
• Pair of eyelids is present
• Cloaca, a common chamber, is a distinct feature. 
• Respiration through skin, gills and lungs 
• The Head and trunk are the divisions of the body.
• Three chambered hearts.
• Frog, toads are examples

Reptilia 

• Creepy and crawly organisms.
• Three chambered hearts with exception of crocodiles with four chambers.
• Scales are present in the body
• Fertilization is internal.
• Oviparous
• Examples – turtle, tortoise, crocodile.

Aves 

• • Feathers fly but some exceptions of kiwi and ostrich.
  • Presence of beak and wings.
  • Presence of glands oil glands 
  • Ossified endoskeleton
  • Crop, gizzard and four chambers of the heart.

• Warm-blooded

• Lungs are present.
• Internal fertilization.
• Crow – crovus and peacock – Pavo are examples.

Mammalia

• Mammary glands are present.
• Two pairs of limbs
• Body hair
• Pinnae is present 
• Four chambers heart
• Respiration by lungs
• Elephas – elephant, canis – Dog are some examples.

Conclusion 

The Five kingdom classification has Animalia as one of the categories. Animals are eukaryotic organisms that are heterotrophic and don’t have a cell wall. They are dependent on plants for their food. The animal kingdom is divided into various categories based on the organization, symmetry segmentation and other features. Each phylum has a certain Distinct feature in terms of its respiratory system or locomotion. There are eleven categories to the kingdom or one can say eleven phyla.