Another Basis to Classify the Organisms
These given below criteria provide a structured way to classify the vast diversity of animal life based on their body plans, embryonic development, and other morphological features.
Symmetry
- Asymmetrical: No plane divides the organism into two equal halves (e.g., sponges).
- Radial Symmetry: Any plane passing through the central axis divides the organism into identical halves (e.g., coelenterates, ctenophores, echinoderms).
- Bilateral Symmetry: Only one plane divides the body into identical left and right halves (e.g., annelids, arthropods).
Diploblastic and Triploblastic Organization
- Diploblastic: Animals with two embryonic layers—ectoderm (outer) and endoderm (inner). An undifferentiated layer called mesoglea is present between these layers (e.g., coelenterates).
- Triploblastic: Animals with three germinal layers—ectoderm, mesoderm (middle), and endoderm (inner). These layers form during embryonic development (e.g., all more complex animals).
Coelom
- Coelomates: Animals with a body cavity (coelom) fully lined by mesoderm (e.g., annelids, mollusks, arthropods, echinoderms, hemichordates, chordates).
- Pseudocoelomates: Animals with a body cavity not fully lined by mesoderm, instead having scattered pockets of mesoderm (e.g., aschelminthes).
- Acoelomates: Animals without a body cavity (e.g., platyhelminthes).
Notochord
- Chordates: Animals with a notochord, a mesodermally derived rod-like structure formed on the dorsal side during embryonic development (e.g., all vertebrates).
- Non-chordates: Animals that do not form a notochord (e.g., porifera, cnidaria, echinoderms).
Levels of Organization in Animals
The levels of organization in animals are arranged hierarchically, starting with cells, the basic unit of life. Groups of similar cells form tissues, which perform specific functions. Tissues combine to create organs, each with distinct roles in the body. Organs work together within organ systems to carry out complex functions necessary for survival. The highest level is the organism, a complete, living individual capable of independent existence.
Table of Content
- Levels of Organization in Animals
- Levels of Organization in Animals
- Cellular Level
- Tissue Level
- Organ Level
- Organ System Level
- Organism Level
- Another Basis to Classify the Organisms
- Symmetry
- Diploblastic and Triploblastic Organization
- Coelom
- Notochord
- Importance of Level of Organization in Animals
- Conclusion: Levels of Organization in Animals
- FAQs on Levels of Organization in Animals
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