Introduction
Animal Kingdom Biology Chapter 4 emphasizes the vast diversity of the Animal Kingdom. It explores all the classifications of animals and major phyla. Class 11 Biology chapter 4 notes include all the important details about the Animal Kingdom. The notes are perfect for learning biology in class 11 and essential to understand the features of different animal groups at a breeze.
In this blog article, the key concepts of the Animal Kingdom have been discussed with clear explanations and examples to make it easy to grasp and to excel in the board exam.
Basis of the classification
- Level of body organization
- Body symmetry
- Germinal Layer
- Nature of coelom
- Segmentation of the body
- Presence of notochord
Animals can be classified based on the following features:
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Level of body Organisation
- Tissue level
Cells are arranged into tissues that perform the same function.
- Organ level
Tissues are grouped to form an organ
Each organ has a specific function.
- Cellular level
Cells are arranged in loose cell aggregates.
- Organ system level
Organs are associated with different functional systems, such as mollusks, annelids, and chordates
Closed type
Blood is pumped out through the heart but not circulated through the blood vessels.
Open type
Blood circulation occurs through blood vessels such as arteries and veins.
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Body symmetry
- Asymmetrical
Organisms can not be divided into two halves. Example – sponge
- Radial symmetry
Organisms can be divided into two identical halves by passing a plane through the central axis.
Example – Coelenterates.
- Bilateral symmetry
Organisms can be divided into two identical right and left halves by one plane.
Example – Arthropods.
-
Germinal Layer
- Diploblastic
Cells are arranged in the two embryonic layers, and they are the external ectoderm and the internal endoderm.
Example – Porifers
- Trioploblastic
The developing embryo possesses three layers: ectoderm, endoderm, and mesoderm.
Example – Chordates.
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Nature of Coelom (Body cavity)
- Coelomates: The Coelom can be found.
Example: Annelids, Arthropods.
- Acoelomates: The Body cavity can not be seen
Example – Platyhelminthes.
- Pseudocoelomates: Coelom is absent as mesoderm can be found between ectoderm and endoderm in a scattered pouch.
Example – Aschelminthes.
-
Segmentation
Metamerism – If a body can be divided into segments with serial repetition of some organs. This phenomenon is called Metamerism.
Example – Earthworm, Pseudomereism can be seen in Tapeworm.
-
Notochord
A rod-like structure formed during embryonic development.
It is derived mesodermally. Example – Chordata
Non-Chordates do not possess a notochord.
Read more: Biological Classification Chapter 2 Notes: CBSE Class 11 Biology
Classification of Animals
The classification of animals has been included in Animal Kingdom Biology Chapter 4 to provide a clear concept about the different species of animals and their characteristics.
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Phylum Porifera
- Those are known as Sponges.
- They are asymmetrical and marine.
- They possess cellular level of organisation and are diploblastic.
- Respiratory exchange and waste removal occur through the water canal system.
- The intracellular digestion system can be found.
- Spongocoel or body cavity, Ostia are the mini pores in the body, and Osculum helps in water transport in the body.
Example – Spongilla
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Phylum Coelenterata
- They are marine and radially symmetrical.
- They are called Cnidarians.
- Possesses tissue-level organisation
- They are diploblastic
- Their defence by the nidiblasts on the tentacles.
- It has an opening called the hypostome and the central gastrovascular cavity.
- Intracellular as well as extracellular digestion systems can be found.
- Some of them have a body wall made of calcium carbonate.
Example – Pennatula, Adamsia.
-
Phylum Tenophora
- They are marine and radially symmetrical.
- They are called comb jellies.
- The tissue level of the organisation can be found, and they are diploblastic.
- Locomotion occurs through eight external rows of ciliated comb plates.
- The light-emitting feature, or bioluminescence, can be found.
- They are hermaphrodites.
Example – Ctenoplana.
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Phylum Platyhelminthes
- They are flat worms that are endoparasites.
- They are triploblastic, bilaterally symmetrical
- Organ level of organization.
- Absorb nutrition through the body surface and have suckers and hooks.
- Internal fertilization can be found
- Hooks and suckers are present
- Flame cells are present for excretion
- Sexes are not separated.
Example – Fasciola, Tapeworm..
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Phylum Aschelminthes
- They can be aquatic or terrestrial. They can be parasites or can live freely.
- They are called roundworms
- They are triploblastic, symmetrical.
- Internal fertilisation can be seen.
- They are dioecious, and females are longer than males.
Example – Ancylostoma.
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Phylum Arthropoda
- They are bilateral, symmetrical, and triploblastic.
- Respiration through gills, book gills, and book gills.
- Open circulatory system
- Segmented and coelomate
- Fertilisation is internal
- Excretion through the Malpighian tubules.
- Oviparous
- Sexes are separated
Example — Honey bee, crab, lobster, mosquito.
-
Phylum Annelida
- They can be aquatic or terrestrial.
- They have circular muscles for locomotion.
- They have a closed circulatory system.
- Triploblastic
- Segmentation can be found in Annelida, and Segmentation is both internal and external in Annelida
- They are bilateral, symmetrical
- Organ system level of body organization
- They are Dioecious
Example – Nereis, Pheretima.
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Phylum Mollusca
- They are the largest phylum
- They can be terrestrial or aquatic.
- Spongy and soft layers can be seen on the skin.
- Space between the visceral hump and the mantle can be found.
- Sensory tentacles are on the head
- They are bilateral, symmetrical
- Trioploblastic and coelomate
- Have gills for respiration and excretion
- Oviparous
- They are Dioecious
Example – Octopus, Sepia.
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Phylum Echinodermata
- They are marine and radially symmetrical.
- Organ system level of organisation can be found.
- They are triploblastic, coelomate
- Respiration and locomotion are carried out by the water vascular system
- Spiny skin has an exoskeleton
- The excretory system is absent
- Fertilisation is external
- Dioecious
Example – Sea Cucumber, Starfish.
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Phylum Hemicordata
- They are bilateral, symmetrical, and triploblastic.
- Their circulatory system is open.
- Respiration through gills.
- Sexes are separate
- Organ system of level of organisation.
- The excretory organ is the proboscis gland.
- Fertilization is external
Example – Balanoglossus.
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Phylum Cordata
- Notochord can be found
- Dorsal hollow nerve chords can be found.
- Closed circulatory system can be seen
- The heart is central.
- Segmentation is internal in Chordata
- Closed circulatory system and Post anal tail can be seen
Classification of Phylum Cordata: Phylum Cordata can be classified into three subphyla. They are:
A. Sub-phyla Urocordata
Notochord can be found in the larval tail.
Example – Ascidia, Salpa.
B. Sub-phyla Cephalocordata
The notochord extends from head to tail
Example – Amphioxus.
C. Sub-phyla Vertebrata
- Notochord is present only in the embryonic period.
- Notochord is replaced by a cartilaginous vertebral column.
- Ventral muscular heart
Subphylum Vertebrata is divided into two super classes, and they are:
- Super class: Agnatha (jawless)
- Super class: Gnathostomata (with jaw)
i) Super class: Agnatha
Class: Cyclostomata
- Live as ectoparasites on some fish
- For respiration, 6-25 gill slites are present.
- Marines migrate to fresh water for spawning, and larvae return to the ocean after metamorphosis.
Example – Petromyzon.
ii) Super class: Gnathostomata (with jaw)
- This super class involves all vertebrates with Jaws
Gnathostomata is divided into two superclasses, and they are:
i) Pisces, ii) Tetrapoda
A) Super class: Pisces
This super class is divided into two classes. They are:
- Class: Chondrichthyes
- Ventral mouth
- Placoid scales can be seen on the skin, and they have strong jaws.
- The air bladder is absent.
- They are unisexual
- Sexes are separate, and internal fertilisation can be seen.
Example – Tarpedo, shark.
- Class: Osteichthyes
- Aquatic and have a streamlined body
- Have a bony endoskeleton
- Four pairs of gill slits are covered by an operculum and a two-chambered heart.
- Sexes are separate, and external fertilisation can be seen
- Usually oviparous
Example- Clown fish, Rohu, Katla, Hippocampus
B) Super class- Tetrapod
This superclass can be divided into four classes. They are as follows:
- Class— Amphibian
- Aquatic as well as terrestrial
- Two pairs of limbs
- Skin is moist and smooth with mucus glands
- Respiration through gills in larva and by lungs and skin in adults.
- Oviparous
Example- Frog
- Class— Mammalia
- Mostly terrestrial
- Two pairs of limbs
- 4-chambered heart
- Respiration by the lungs
- Body hair can be seen
- Sexes are separate
- Viviparous
Example- Dolphin, Camalus.
- Class— Aves
- Have feathers to fly
- Forelimbs modified into feathers
- Respiration by the lungs
- The voice box is called syrinx
- 4-chambered heart
- Oviparous
- Fertilisation is internal
Example– Pigeon, crow.
- Class—Reptilia
- Mostly terrestrial
- 12 pairs of cranial nerves
- Heart with three and a half chambers
- Respiration by the lungs
- Fertilisation is internal
- Oviparous
Example– Snake, tortoise.
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Conclusion
Notes for class 11 chapter 4 Animal Kingdom simplify the complex key concepts such as animal classification, phyla, and their features. All the topics of this chapter have been illustrated through clear points that are easy to understand as well as to remember. Going through this note regularly helps boost confidence, and you can be well prepared for this specific chapter.
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