Basis of Animal Classification
Levels of organisation, symmetry, coelom, segmentation and germ layers as classification axes. (Biology › Animal Kingdom, NEET UG syllabus.)
What is Basis of Animal Classification?
The ° of cellular differentiation and arrangement into tissues, organs, or organ systems in an animal's body.
Key points
- Define and differentiate between various levels of organisation in animals.
- Explain different types of symmetry and provide examples.
- Distinguish between diploblastic and triploblastic organisation.
- Describe the types of coelom (acoelomate, pseudocoelomate, coelomate) with examples.
Common exam trap
Confusing pseudocoelom with a true coelom.
Definitions
- Term
Levels of Organisation
- Meaning
The ° of cellular differentiation and arrangement into tissues, organs, or organ systems in an animal's body.
- Term
Symmetry
- Meaning
The arrangement of body parts around a central axis or plane.
- Term
Germ Layers
- Meaning
Embryonic cell layers (ectoderm, mesoderm, endoderm) from which all adult tissues and organs develop.
- Term
Coelom
- Meaning
A fluid-filled body cavity completely lined by mesoderm, located between the digestive tract and the outer body wall.
- Term
Segmentation (Metamerism)
- Meaning
The phenomenon where the body is divided into a series of repeated segments, both externally and internally.
- Term
Notochord
- Meaning
A flexible, rod-like structure derived from mesoderm, located dorsally between the gut and the nerve cord in chordates.
- Term
Diploblastic
- Meaning
Animals whose embryos have two germ layers: ectoderm and endoderm.
- Term
Triploblastic
- Meaning
Animals whose embryos have three germ layers: ectoderm, mesoderm, and endoderm.
- Term
Pseudocoelom
- Meaning
A body cavity that is not completely lined by mesoderm, with mesoderm present as scattered pouches.
- Term
Acoelomate
- Meaning
Animals that lack a body cavity (coelom).
Learning objectives
Define and differentiate between various levels of organisation in animals.
Explain different types of symmetry and provide examples.
Distinguish between diploblastic and triploblastic organisation.
Describe the types of coelom (acoelomate, pseudocoelomate, coelomate) with examples.
Understand the concept of segmentation and notochord.
Classify animals based on these fundamental characteristics.
Prerequisites
Basic understanding of cell structure and function.
Knowledge of basic biological terms like tissue, organ, and organism.
Common mistakes
Confusing pseudocoelom with a true coelom.
Misidentifying examples for different symmetry types (e.g., adult echinoderms).
Not understanding the difference between diploblastic and triploblastic organization.
Assuming all segmented animals are coelomates.
Keywords
Animal Kingdom
Classification
Levels of Organisation
Symmetry
Germ Layers
Coelom
Segmentation
Notochord
Diploblastic
Triploblastic
Acoelomate
Pseudocoelomate
Coelomate
Radial Symmetry
Bilateral Symmetry
Asymmetry
Practice preview
Which of the following phyla exhibits the cellular level of organisation?…
easy
Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm, are called:…
easy
Which of the following phyla exclusively exhibits radial symmetry in its adult form, along with tissue level of organisation?…
easy