7. STRUCTURAL ORGANISATION IN ANIMALS

In the preceding chapters you came across a large variety of organisms, both unicellular and multicellular, of the animal kingdom. In unicellular organisms, all functions like digestion, respiration and reproduction are performed by a single cell. In the complex body of multicellular animals the same basic functions are carried out by different groups of cells in a well organised manner. The body of a simple organism like Hydra is made of different types of cells and the number of cells in each type can be in thousands. The human body is composed of billions of cells to perform various functions. How do these cells in the body work together? As you have already learnt in your earlier classes, in multicellular animals, a group of similar cells alongwith intercellular substances perform a specific function. Such an organisation is called tissue.

This chunk introduces the concept of tissues and how cells function together in multicellular organisms. Unicellular organisms rely on a single cell for all life functions, while multicellular organisms have specialized groups of cells (tissues) that collaborate to perform complex functions. For example, different types of cells in the stomach work together to help digest food, each performing a specific role.

Think of a multicellular organism like a factory. Just as a factory has different workers specialized in various tasks (like assembly, quality control, and shipping), multicellular organisms have different types of cells that specialize in specific functions. This specialization allows the organism to perform complex tasks efficiently, just like a well-organized factory.

You may be surprised to know that all complex animals consist of only four basic types of tissues. These tissues are organised in specific proportion and pattern to form an organ like stomach, lung, heart and kidney. When two or more organs perform a common function by their physical and/or chemical interaction, they together form organ system, e.g., digestive system, respiratory system, etc. Cells, tissues, organs and organ systems split up the work in a way that exhibits division of labour and contribute to the survival of the body as a whole.

This section explains that all complex animals are made up of four basic types of tissues: epithelial, connective, muscular, and neural. These tissues come together to form organs, each with a specific function. When multiple organs work together, they create an organ system, which performs a broader function for the organism. For instance, the digestive system includes the stomach, intestines, and liver working together to digest food.

Imagine a sports team where each player has a specific role: a striker, a defender, a goalkeeper, etc. Each player must work together, leveraging their skills to win the game. Similarly, in our bodies, various tissues and organs work together, with each having a unique role, to keep the organism alive and functioning.

The basic tissues as you have learnt in earlier classes, organise to form organs which in turn associate to form organ systems in the multicellular organisms. Such an organisation is essential for more efficient and better coordinated activities of millions of cells constituting an organism.

This chunk emphasizes the efficiency brought by the organization of tissues into organs and organs into systems. This hierarchical structure allows for better coordination in the body, enabling it to perform complex functions seamlessly. For example, the heart works with blood vessels to transport nutrients and oxygen throughout the body, demonstrating the necessity of this organization.

Think of how a city is organized. A city has different departments (like police, fire department, hospitals) that specialize in specific areas of public service. Each department must work with others to keep the city running smoothly, just like organs must work together to keep living organisms functioning properly.

In this chapter, you are being introduced to morphology and anatomy of frog. Morphology refers to study of form or externally visible features. ... The word anatomy conventionally is used for the study of morphology of internal organs in the animals.

Morphology and anatomy are key concepts in understanding living organisms. Morphology focuses on the external structure of an organism, such as the body shape and appendages, while anatomy deals with the internal structures, such as organs and tissues. In the case of the frog, important features such as skin texture and the arrangement of organs give insights into its classification and functioning as a living being.

Consider a car: morphology is like observing the car's design and body shape, which gives you a clue about its brand and functionality, while anatomy is like taking the car apart to look at the engine and wiring to understand how it works under the hood. Each perspective is important for a complete understanding.

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