**Structural Organisation in Animals: Frog, Earthworm, and Cockroach in NEET Syllabus**

The structural organization in animals is an essential topic covered in the NEET syllabus. It involves the study of the different levels of organization within an animal’s body, ranging from cells to tissues, organs, and organ systems. Three common organisms discussed in this context are frogs, earthworms, and cockroaches. Let's explore the structural organization of each of these organisms in detail.

**1. Frog:**

Frogs belong to the class Amphibia and possess a complex structural organization. They exhibit a bilateral symmetry and are characterized by the following structural features:

- **Cellular Level:** At the cellular level, frogs have specialized cells such as nerve cells, muscle cells, and epithelial cells that perform specific functions.

- **Tissue Level:** Different types of tissues are present in frogs. Examples include muscular tissue, nervous tissue, connective tissue, and epithelial tissue. These tissues work together to carry out various functions.

- **Organ Level:** Frogs have well-defined organs such as the heart, lungs, liver, kidneys, and reproductive organs. These organs perform specific functions to maintain the body's homeostasis.

- **Organ System Level:** Several organ systems work together to ensure the proper functioning of the frog's body. These include the digestive system, respiratory system, circulatory system, excretory system, reproductive system, and nervous system.

**2. Earthworm:**

Earthworms belong to the phylum Annelida and exhibit a segmented body plan. Their structural organization can be summarized as follows:

- **Cellular Level:** Earthworms have various types of cells, including muscle cells, nerve cells, and epithelial cells, which carry out specific functions.

- **Tissue Level:** Earthworms possess different types of tissues, such as muscular tissue, nervous tissue, connective tissue, and epithelial tissue. These tissues coordinate to perform specific functions.

- **Organ Level:** Earthworms have well-developed organs, including the digestive system (pharynx, esophagus, crop, gizzard, and intestine), circulatory system (blood vessels and hearts), excretory system (nephridia), and reproductive system.

- **Organ System Level:** The organ systems in earthworms work together to ensure the proper functioning of the body. These systems include the digestive system, circulatory system, excretory system, and reproductive system.

**3. Cockroach:**

Cockroaches belong to the class Insecta and possess a simple yet efficient structural organization. The structural features of a cockroach can be described as follows:

- **Cellular Level:** Cockroaches have specialized cells that carry out specific functions such as nerve cells, muscle cells, and epithelial cells.

- **Tissue Level:** Different types of tissues are present in cockroaches, including muscular tissue, nervous tissue, connective tissue, and epithelial tissue. These tissues work together to perform various functions.

- **Organ Level:** Cockroaches have well-developed organs such as the digestive system (foregut, midgut, and hindgut), respiratory system (tracheae and spiracles), excretory system (Malpighian tubules), circulatory system (open circulatory system), and reproductive system.

- **Organ System Level:** The organ systems in cockroaches work together

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