The Animal Kingdom is an essential topic in Biology syllabus. It is one of the five kingdoms according to the scheme of classification by Whittaker that comprises multicellular eukaryotic animals. The weightage of Animal Kingdom in NEET is around 7 to 8% and candidates can also expect direct questions from this section which makes it one of the top-scoring topics. 

• Some of the sub-topics from which candidates can expect questions are Patterns of circulatory, Body symmetry, Nature of Coelom, Arrangement of cells, Notochord, digestive and reproductive frameworks, Segmentation and Arrangement of cells in germ layers. Check NEET Biology Syllabus

• As the dates for NEET 2021 are revised, it’s the right time to prepare and have a grip on every topic.

We are providing the revision notes of Animal Kingdom to help candidates in their preparation that consists of all the essential concepts and facts. We have also added some quick notes with all the vital information so that you can quickly go through the entire topic. Other than that, you can also get the sample questions along with tips and tricks that will help you in the exam.

Arrangement of Cells/ Body Walls

• Animals in which Cells are arranged in two embryonic layers, external ectoderm and internal endoderm are known as Diploblastic. For, eg. Cnidaria and Porifera

• Animals with developing embryo having a third germinal layer, mesoderm besides ectoderm and endoderm are called triploblastic. E.g. Chordates

Patterns of Circulatory System

•  When Blood is pumped out of heart and cells and tissue are directly bathed in it is known as Open circulatory system.

• When Blood is circulated through arteries, veins and capillaries, it is known as Closed circulatory system.

Digestive System:

• Incomplete Digestive System-This Digestive system works with only one opening that performs all the functions of the outside of the body, the mouth and the rear end.

• Complete Digestive System- This works with two openings to play all the functions of the body. The mouth and the rear end.

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• NEET Study Notes for Strategies of Enhancement of Food
• NEET Study Notes for Genetics

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Body Symmetry and its types

Animals are categorised on the symmetry of their body. Mainline or point around body parts decides the symmetry.

Asymmetrical- When the body is partitioned in two equivalent parts along any plane going through the focal point of an organism like sponges

Radial- Animals are displaying spiral symmetry going through the focal axis of body partitions into two equal part—for example, Ctenophores, Coelenterates and Echinoderms.

Bilateral- Animal Body that can be partitioned into right and left indistinguishable. It consists of Annelids, Arthropods and more.

Nature of Coelom

The Body cavity that is lined by the mesoderm is known as Coelom. Appearance or Non-Appearance in between the gut wall and body wall has importance in Body cavity.

They are three kinds of Coelom:

Acoelomates- The body cavity is truant in such an animal. Example: Platyhelminthes

Pseudocoelomates- When the body cavity is not lined by the mesoderm and is available in scattered pockets in the middle of endoderm and ectoderm, these organisms are called Pseudocoelomates. Example: Aschelminthes

Coelomates- The mesoderm lines the body cavity. Example: Mollusca, Arthropods, Chordates and Echinoderms.

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Level of Organization and its types

Animal Kingdom organisms are multicellular, but they don’t display the similarities of cell organisation.

Examples of cellular organisation found an animal:

Cellular Level of Organisation: The cells are organised as free cell lumps in such animals. This type of organisation is seen in sponges.

Tissue Level of Organisation: Cells show Division of Exercises among themselves that carry out the same capacity and are organised tissues. It can be seen in Coelenterates.

Organ Level of Organisation: Tissues that carry out similar capacity grouped to shape organs and is specific of particular capacity. It can be seen in Platyhelminthes

Organ system Level of Organisation: Organs that collectively perform a physiological function comes under the organ system level of organisation. This type of organisation is seen in Annelids, Molluscs, Arthropods and Chordates.

Sample Question

Question: Name the Animal swimming or floating in the surface film of water?

A) Neuston

B) Nekton

C) Pelagic

D) Seston

Answer: A

Segmentation

The segmentation of body in few animals from inside and outside is with serial redundancy of few organs and is known as Metamerism. An example of Metameric Segmentation is Earthworm.

Notochord

A Mesodermally determined pole-like structure shaped on the dorsal side is known as Notochord in few animals. The Notochord is divided into Chordates and Non-Chordates.

Chordates are those who have Notochord

Non-Chordates are those who don’t have Notochord.

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• NEET Study Notes for Ecosystem
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Animal Kingdom and its classification

Animals are distinctive to each other in various characteristics and can be compared. Those from a specific group share some similarities.

Organisms are divided into groups according to their similarities and characteristics, and this orderly type of classification is known as Taxonomy.

Carolus Linnaeus (1707-1778) discovered the Modern system of Scientific Classification in which the arrangement of classification was planned that only one animal or plant would be assigned a name that would not relate any other organism.

The animals are classified from top to bottom with the help of Kingdom, Phylum, Class, Order, Family, Genus and Species.

• The kingdom is the largest group and involves all the animals.
• The phylum is the second largest group and is further divided into subdivisions known as phyla.
• Class- Organisms that relate to Organisms from the same class and are not found in any other organism from a different class.
• Order- Organisms that have more features alike and is more specified than class.
• Family- This group contains more than one genus, and these are a class that is separated into families.
• Genus- These are subdivisions of Families and are called Genera. Organisms with the same genus are not the same but are developed from a common predecessor.
• Species- It contains just one kind of animal. And is the smallest group in animal kingdom classification

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Phylum and its types

A phylum is divided into Vertebrae and Invertebrae.

Invertebrae 

• Phylum Porifera
• Phylum Cnidaria
• Phylum Platyhelminthes
• Phylum Nematoda
• Phylum Annelida
• Phylum Mollusca
• Phylum Arthropoda
• Phylum Echinodermata
• Phylum Hemichordata

Vertebrae

• Class Aves
• Class Fish
• Class Reptilia
• Class Mammalia
• Class Amphibia

Phylum Porifera ( Sponges)

• These are marine organisms with the asymmetrical cellular level of organisation
• Water transport system helps in Food intake, Gaseous exchange and Excretion.
• Spongocoel is a central cavity from which Water enters through pores called Ostia and out of Osculum.
• Intracellular Digestion
• Skeleton is made of Spicules and Spongin fibres.
• Hermaphrodite
• Asexual Reproduction by Fragmentation and Sexual by the formation of gametes.
• Internal Fertilisation and development of Zygote start from a larval stage.

Example: Spongilla, Euspongia, Sycon.

Phylum Cnidaria( coeloenterata)

• Organisms that are Aquatic, sessile and shows tissue level of organisation.
• Radial Symmetry, Diplobalstic and Acoelomate.
• Central Gastro vascular cavity with a single opening is known as Hypostome and surrounded by sensory tentacles.
• Cnidoblasts present on tentacles containing nematocysts.
• Extracellular and Intracellular Digestion.
• Calcium Carbonate skeleton of corals
• Sessile and cylindrical forms known as a polyp, e.g. Hydra
• Umbrella Shaped free-swimming form is known as Medusa, e.g. Aurelia( jellyfish)
• Polyp form produces Medusa asexually, and Medusae produce polyp sexually.

Examples: Adamsia ( sea anemone), Physalia, Meandrina ( brain coral)

Phylum Ctenophora

• Marine and tissue level of organisation
• Radial symmetry, Diploblastic and coelomate.
• Extracellular and Intracellular Digestion
• Hermaphrodite
• Bioluminescence present
• Reproduction is Sexual but external Fertilisation with indirect development.

Example: Pleurobrachia, Ctenoplana

Phylum Platyhelminthes

• Organisms that are Endoparasites and have Flattened Body showing organ level of organisation.
• Triploblastic, acoelomate and bilateral symmetry
• Parasites have Hooks ad suckers
• Osmoregulation and Excretion happen through Flame cells.
• Hermaphrodite and Monoecious
• Internal Fertilisation with indirect development
• Planaria can regenerate

Example: Taenia, Fasciola

Phylum Aschelminthes

•  Parasites, Terrestrial, Aquatic and free-living showing organ system organisation comes under this phylum.
• Bilateral symmetry, Triploblastic and Pseudocoelomates
• Have muscular pharynx and complete alimentary canal
• Dioecious and female longer than males.
• Internal Fertilisation with indirect development.

Example: Wucheria, Ascaris

Phylum Annelida

• Bilateral symmetry and organ system organisation
• Triploblastic, Coelomate
• Metameric Segmentation
• Longitudinal and circular muscles helping in locomotion
• Parapodia help in swimming
• Closed circulatory system
• Nephridia is present for Excretion and osmoregulation
• Paired ganglia are presently connected to double ventral nerve cord by lateral nerves.
• Sexual reproduction.
• Dioecious- Nereis and Monoecious- Leeches and Earthworms

Phylum Arthropoda

• Consists of Insects
• Bilateral symmetry with organ system organisation
• Triploblastic and Coelomate
• The body is covered with Chitinous Exoskeleton
• They have Jointed legs.
• The body is divided into three: Head, Thorax and Abdomen
• Trachea, Gills, Book Gills and Book Lungs help in Respiration
• Open type of circulatory system
• Excretion happens from Malpighian tubules.
• Balancing organs or Statocyst is present
• Oviparous and Fertilisation is internal
• Dioecious

Example: Apis ( Honey bee), Anopheles, Aedes, Bombyx ( Silkworm)

Phylum Mollusca

• Bilateral Symmetry and Organ system Organisation
• Triploblastic and Coelomate
• Feathers like gills for Respiration and Excretion
• Unsegmented body with a calcareous shell.
• Head, Muscular Foot and Visceral Hump are present.
• A rasping organ is known as radula for feeding.
• Dioecious
• Oviparous and Indirect development

Examples: Octopus, Sepia, Squid, Pila( Apple snail)

Phylum Echinodermata

• Bilateral Symmetry in Larvae and Radial Symmetry in Adults
• Triploblastic and coelomate
• Endoskeleton of Calcareous ossicles
• The mouth is on the ventral side and Anus on the dorsal side
• Water vascular system helps in feeding, Respiration and locomotion
• External Fertilisation with internal development
• Monoecious

Example: Antedon, Echinus

Phylum Hemichordata

• Bilateral symmetry with organ system organisation
• Cylindrical body with a proboscis, collar and a long trunk
• Triploblastic and coelomate
• Open type circulation and gills are present
• Functions of Excretory organ are managed by Proboscis gland.
• Monoecious
• External Fertilisation with indirect development

Example: Saccoglossus, Balanoglossus

Phylum Chordata

• Dorsal hollow nerve cord, a notochord and paired gill slits
• Bilateral symmetry and organ system organisation
• Closed circulatory system
• Post anal tail is present
• There are three subphyla:

Urochordata- Notochord present only in the larval tail

Cephalochordata- Notochord present from head to tail throughout life

Vertebrata- Notochord is present but later gets replaces by vertebral column after embryonic stage.

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Some Sample Question on Phylum

Question: Which is the matching pair of body feature and animal?

1. Ventral nervous system- Leech
2. Ventral heart- Scorpio
3. Gill slits absent in embryo- Chameleon
4. Post anal tail- Chameleon

Answer: A

Question: What are the essential characteristics hemichordates share with chordates?

1. Pharynx with Gill Slits

2. Ventral Tubular Nerve Cord

3. Absence of Notochord

4. Pharynx without Gill Slits

Answer: A

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Vertebrata and its types

Vertebrata has two divisions:

1. Agnatha ( without jaws) and is known as Class Cyclostomata

2. Gnathostomata (with jaws) has two superclasses Pisces(Chondrichthyes, Osteichthyes) and Tetrapoda (Amphibia, Reptilia, Aves, Mammalia)

Class I: Cyclostomata (Circular Mouthed Fishes)

• Circular and sucking mouth without jaws

• Gill slits pairs(6-15)

• Ectoparasites on fishes

• Scales and fins are present

• Closed type circulation

• Marine but migrate to fresh Water while in larvae state, later come back to the ocean.

Example: Petromyzon, Myxine(Hagfish)

Class II- Chondrichthyes (Cartilaginous Fishes)

• The mouth on the ventral side

• Gills without operculum

• Cartilaginous endoskeleton

• Notochord present 

• Placoid scales present to make tough skin

• Constant swimmer to avoid sinking due to the absence of air bladders

• Two chambered heart and cold-blooded

• Separate sexes

• Internal Fertilisation and viviparous

• Male’s pelvic fin has claspers

• Electric organs are present with poison sting.

Example: Dogfish, Trygon, Pristis, Carcharodon

Class III- Osteichthyes (Bony Fishes)

• Endoskeletal and streamlined body

• Gills with an operculum ( 4pairs)

• Cycloid scales cover the skin

• Two chambered heart and cold-blooded

• Air bladder for buoyancy

• Separate sexes and external Fertilisation

Example: Marine: Hippocampus(sea horse)

Freshwater- Labeo, Catla

Aquarium- Betta

Super class: Tetropoda

Class IV- Amphibia

• Aquatic as well as terrestrial bodies

• Moist skin and absence of scales

• Two pairs. Limbs

• Respiration by skin, lungs or gills

• Three chambered heart and cold-blooded

• Oviparous

• Separate sexes and external Fertilisation

Example: Frog, salamander

Class V- Reptilia

• Terrestrial

• Limbs are present

• Dry skin with scales

• Respiration through lungs

• Three chambered heart and cold-blooded ( four-chambered in crocodile)

• Oviparous

• Separate sexes and internal Fertilisation

Example: Crocodile, Chameleon, Alligator

Class VI- Aves

• Feathers

• Forelimbs modified to wings and high limbs for walking, swimming and clasping

• Dry skin with oil glands at the base of the tail

• Respiration through lungs

• Four chambered heart and warm-blooded

• Oviparous

• Separate sexes and internal Fertilisation

Example: Birds

Class VII- Mammalia

• Terrestrial, few can fly or live in Water.

• Two pairs of limbs

• Hairy skin and mammary glands to feed young ones

• Respiration through lungs

• Four chambered heart and warm-blooded.

• Viviparous (platypus- oviparous)

• Separate sexes with internal Fertilisation

• Example: Kangaroo, cat, dolphin

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Previous Year Solved Sample Questions

Question: Metamerism is characteristic of 

A) Platyhelminthes

B) Mollusca

C) Porifera

D) Annelida

Answer: D

Question: The spongocoel is lined with flagellated cells known as:

1. Oscula

2. Choanocytes

3. Mesenchymal Cells

4. Ostia

Answer: D

Question: Which phylum represents both Marine and Freshwater species?

1. Ctenophora

2. Cnidaria

3. Echinoderms

4. Platyhelminthes

Answer: B

Question: Which animal among mentioned below have a single opening that works as mouth as well as Anus?

1. Fasciola

2. Asterias

3. Ascidia

4. Octopus

Answer: D

Question: How does the infection of Ascaris occur:

1. Mosquito bite

2. Tse Tse fly

3. Eating uncooked pork

4. Water containing eggs of Ascaris

Answer: D

All the candidates are advised to refer to these notes and other notes you have prepared to do a thorough study of Animal kingdom while preparing for NEET. Clear the basic terminologies and study first. Complete the phylum and classes and thoroughly revise. Focus on remembering the common names because most of the questions asked are very common and direct. You can also NEET 2021 Practice paper so that by solving those questions you can work on your speed and accuracy level.