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Class 11 CBSE and NEET Notes: Animal Kingdom Classification
Table of Contents
- Basis of Classification
- Levels of Organisation
- Symmetry
- Diploblastic and Triploblastic Organisation
- Coelom
- Segmentation
- Notochord
- Classification of Animals
- FAQs
Basis of Classification
When you look around, you will observe different animals with different structures and forms. With over a million species of animals described till now, the need for classification becomes all the more important. Classification helps in assigning a systematic position to newly described species.
Levels of Organisation
Despite differences in structure and form, there are fundamental features common to various animals in relation to the arrangement of cells, body symmetry, nature of coelom, and patterns of digestive, circulatory, or reproductive systems. These features form the basis of animal classification.
Cellular Level of Organisation
In sponges, cells are arranged as loose cell aggregates.
Tissue Level of Organisation
In coelenterates, cells performing the same function are arranged into tissues.
Organ Level of Organisation
In Platyhelminthes and other higher phyla, tissues are grouped to form organs.
Organ System Level of Organisation
In Annelids, Arthropods, Molluscs, Echinoderms, and Chordates, organs form functional systems.
Symmetry
Animals can be categorized based on their symmetry.
Asymmetrical
Sponges, where no plane divides the body into equal halves.
Radial Symmetry
Coelenterates, ctenophores, and echinoderms, where any plane passing through the central axis divides the body into identical halves.
Bilateral Symmetry
Annelids, arthropods, etc., where the body can be divided into identical left and right halves in only one plane.
Diploblastic and Triploblastic Organisation
Diploblastic: Animals with two embryonic layers (ectoderm and endoderm), such as coelenterates.
Triploblastic: Animals with three germinal layers (ectoderm, mesoderm, and endoderm), ranging from platyhelminthes to chordates.
Coelom
Coelomates: Animals with a body cavity lined by mesoderm, such as annelids, molluscs, arthropods, echinoderms, hemichordates, and chordates.
Pseudocoelomates: Animals with a body cavity not fully lined by mesoderm, such as aschelminthes.
Acoelomates: Animals without a body cavity, such as platyhelminthes.
Segmentation
Some animals have bodies divided into segments with serial repetition of organs. For example, earthworms exhibit metameric segmentation, known as metamerism.
Notochord
The notochord is a rod-like structure formed on the dorsal side during embryonic development in some animals.
Chordates: Animals with a notochord.
Non-chordates: Animals without a notochord, ranging from porifera to echinoderms.
Classification of Animals
The broad classification of Animalia based on common fundamental features is crucial for understanding the diversity and complexity of life forms.
FAQs
What is the basis of animal classification?
Animal classification is based on fundamental features such as cell arrangement, body symmetry, coelom nature, and digestive, circulatory, or reproductive systems.
What are the different levels of organization in animals?
The levels of organization include cellular, tissue, organ, and organ system levels.
What is the significance of body symmetry in classification?
Body symmetry helps categorize animals into asymmetrical, radial symmetry, and bilateral symmetry groups.
What are diploblastic and triploblastic animals?
Diploblastic animals have two embryonic layers (ectoderm and endoderm), while triploblastic animals have three layers (ectoderm, mesoderm, and endoderm).
How is the coelom important in classification?
The presence or absence of a coelom (body cavity) is crucial for classifying animals into coelomates, pseudocoelomates, and acoelomates.
What is segmentation in animals?
Segmentation is the division of the body into segments, as seen in earthworms, which is called metamerism.
What is a notochord?
A notochord is a rod-like structure formed during embryonic development. Animals with a notochord are called chordates.
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