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Levels of Organization in Animals

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In the animal kingdom, all animals are multicellular, and all animals don’t follow the same pattern of cellular organization. Depending on the organization of cells they are divided into different types of organizations.

Levels of Organization in Animals

The animal’s fundamental unit is a cell and it is the very basic unit of life. When a big mass of cells (same type of cell )aggregate in one place then they make a type of tissue. Tissues aggregate and form organs. Later on, organ systems are formed. Many organs work together to work properly.

Cells-Tissue-Organ-Organ System

Structural Organization in Animals


Cellular Level of Organizations

The cell is the basic fundamental unit of life. The cell has all the cell organelles which are required to perform all the basic functions to survive and regenerate. Cell-level organization animals have aggregation of a loose arrangement of the cells. Example: Sponges

What is Structural Organization in a Cell?

The cell is the basic unit of life. The cell contains all the organelles which are required for a cell to survive. All the organelles are placed and form a structural organization in the cell.

Animal Cell


Cell Organelles and their Functions

  1. Nucleus: Storage of genetic material i.e DNA.
  2. Endoplasmic Reticulum: They help in the synthesis of protein and lipids.
  3. Golgi Apparatus: It mainly helps in tagging and transportation.
  4. Ribosome: They synthesize the protein with the help of mRNA.
  5. Mitochondria: Mitochondria generate ATP, and because of that mitochondria are known as the Powerhouse of cells.
  6. Lysosome: Helps in digestion within the cell via decomposing.
  7. Cytoplasm: Cytoplasm is a thick substance in which all the cell organelles are embedded.
  8. Plasma Membrane: It is the outer layer of the cell, and helps in maintaining the equilibrium of the cell.

Tissue Level of Organizations

Tissue is the most important layer that plays a major role in the protection of the organ, and tissues allow only the required one into the organ and keep the organ safe. Example: Coelenterates.

Tissues are groups of similar cells from the same origin that work together to perform a specific function. Basic tissues in humans are classified into:

  1. Connective Tissues: Tissues are made up of fibrous cells that give organs shape and structure. 
  2. Muscle Tissue: Tissue is composed of cells that can contract and allow movement. 
  3. Epithelial Tissues: The outer layers of organs, the skin, and the stomach are made up of epithelial tissues. 
  4. Nervous Tissue: The spinal cord and the brain are made up of specialized cells that transform information through electrochemical signals.

Organ and Organ Systems

An organ is a structure composed of various tissues that carry out specific bodily functions. Most organs contain tissues. The organ level is composed of the level combination of tissues together in one to perform a specific function. Organs can be solid or hollow, and their size and complexity vary greatly. Organs include the heart, lungs, and brain next this level organism level is a very complex level composed of different organs to perform a particular thing to maintain the body. Example: Platyhelminthes

Organ System: This level of organization is present in animals where different organs join and perform functions. Here each system has its own specific function. Organs systems like- Cardiovascular system, Lymphatic system, and Nervous system. Examples: Annelida, Chordates, Echinoderms, Arthropoda, and Mollusca.

Another Basis to Classify the Organisms


Creatures on the order based on their symmetry. Sponges are mostly asymmetrical, any plane that goes through the middle doesn’t partition them into two halves. When any plane going through the focal hub through the body partitions the life form into indistinguishable halves, it is called radial symmetry. Coelenterates, ctenophores, and echinoderms have this sort of body plan. Creatures like annelids, and arthropods. Where the body can isolate indistinguishable left and right parts as if it were one plane, exhibiting bilateral symmetry.

Diploblastic and Triploblastic Organization

Animals in which the cells are arranged in two embryonic layers, external ectoderm, and internal endoderm, are called diploblastic animals e.g.coelenterates. An undifferentiated layer, mesoglea, is present in between the ectoderm. Those animals in which the developing embryo has a third germinal layer, mesoderm in between the ectoderm and endoderm are called trophoblast animals.


The presence or absence of a hole between the body divider and the stomach divider is vital in classification. The body cavity is lined by a mesoderm called coelom. Animals possessing coelomates are called coelomates. Annelids, Mollusca, Arthropods, Echinoderms, hemichordates, and chordates. In a few creatures, the body hole isn’t lined by the mesoderm and is available as dissipated pockets between the ectoderm and endoderm. Such a body depression is called pseudocoelom such body pits are called pseudocoelomates, e.g. aschelminthes. The creatures in which the body pit is missing are called acoelomates. e.g. Platyhelminthes.


The notochord is a mesodermally determined pole-like design framed on the dorsal side during early-stage development in some animals. Animals with notochord are called chordates and that creature that doesn’t shape this design is called non-chordates, e.g. Porifera to Echinoderms.

FAQs on Levels of Organization in Animals

Question 1: What are the 5 levels of the organization?


The level of organization in any living thing:

  • Chemical Atom
  • Cellular Level
  • Tissue Level
  • Organ Level
  • Organ System

Question 2: What are the 12 levels of organization from smallest to largest?


The 12 levels of the organization in the living organism:

  • Atoms
  • Molecules
  • Organelles 
  • Cells Level
  • Tissue Level
  • Organ Level
  • Organ System Level
  • Organism
  • Population
  • Communities
  • Ecosystem
  • Biosphere

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Last Updated : 24 Feb, 2023
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