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Structural Organisation in Animals - Organ and organ system

Grade 11CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The basic tissues (epithelial, connective, muscular, and neural) organize in specific proportions and patterns to form an organ. This level of organization is essential for more efficient functioning of the body.

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When two or more organs work together to perform a common physical or chemical function, they form an organ system. Examples include the digestive, respiratory, circulatory, and excretory systems.

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The complexity of the organism increases with the hierarchy: Cells→Tissues→Organs→Organ Systems\text{Cells} \rightarrow \text{Tissues} \rightarrow \text{Organs} \rightarrow \text{Organ Systems}.

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Each organ may be composed of one or more types of tissues. For instance, the heart consists of all four types of tissues: epithelial, connective, muscular, and neural.

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The division of labour in complex multicellular organisms is achieved through this structural organization, allowing for specialization and survival of the multicellular body.

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The morphology (external form) and anatomy (internal structure) of organs vary significantly across different animal groups like Earthworms, Cockroaches, and Frogs to represent different evolutionary adaptations.

📐Formulae

Complexity Hierarchy: Cell→Tissue→Organ→Organ System→Organism\text{Complexity Hierarchy: } \text{Cell} \to \text{Tissue} \to \text{Organ} \to \text{Organ System} \to \text{Organism}

Functional Efficiency∝Surface AreaVolume\text{Functional Efficiency} \propto \frac{\text{Surface Area}}{\text{Volume}} (Crucial for organs like lungs and intestines to maximize exchange processes)

💡Examples

Problem 1:

If an organism has a body surface area of 24 cm224 \text{ cm}^2 and a volume of 8 cm38 \text{ cm}^3, calculate the surface area to volume ratio. Explain why highly organized organ systems (like the respiratory system with alveoli) are needed as this ratio decreases.

Solution:

Surface AreaVolume=248=3 cm−1\frac{\text{Surface Area}}{\text{Volume}} = \frac{24}{8} = 3 \text{ cm}^{-1}

Explanation:

In small organisms, the surface area to volume ratio is high, allowing for simple diffusion. In larger multicellular organisms, the ratio decreases (S/V→0S/V \to 0 as size increases). Therefore, specialized organ systems with folded surfaces (like villi in the gut or alveoli in lungs) are required to increase the effective surface area for physiological exchange.

Problem 2:

Identify the primary tissue types present in the heart and explain their roles in the organ system.

Solution:

The heart contains: 1. Muscular tissue (cardiac muscles for contraction), 2. Connective tissue (blood and fibrous valves), 3. Neural tissue (nodes for electrical impulses), 4. Epithelial tissue (pericardium and endocardium).

Explanation:

Though the heart is an 'organ', it is a functional unit of the 'circulatory system'. The coordination between these tissues allows the organ to pump blood, satisfying the definition of an organ system when combined with vessels.