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The Invisible Living World: Beyond Our Naked Eye - What Are the Levels of Organisation in Multicellular Organisms?

Grade 8CBSE

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

🔑Concepts

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The structural hierarchy in multicellular organisms follows a specific sequence: Cell→Tissue→Organ→Organ System→Organism\text{Cell} \rightarrow \text{Tissue} \rightarrow \text{Organ} \rightarrow \text{Organ System} \rightarrow \text{Organism}.

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Cell: The basic structural and functional unit of life. In multicellular organisms, cells are specialized to perform specific tasks.

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Tissue: A group of similar cells that work together to perform a specific function. Examples include muscular tissue and nervous tissue.

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Organ: Different types of tissues grouped together to perform a specific physiological function, such as the stomach or the lungs.

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Organ System: A group of organs working together to perform a major life process. For example, the digestive system includes the stomach, intestines, and esophagus.

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Division of Labour: In multicellular organisms, different cells and organs perform different functions, allowing for higher efficiency and complexity.

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Microscopic observation is required to see the lower levels of organization. The magnifying power is denoted by the symbol ×\times (e.g., 100×100\times).

📐Formulae

Total Magnification=Magnification of Eyepiece×Magnification of Objective Lens\text{Total Magnification} = \text{Magnification of Eyepiece} \times \text{Magnification of Objective Lens}

Actual Size of Specimen=Observed Size (under microscope)Total Magnification\text{Actual Size of Specimen} = \frac{\text{Observed Size (under microscope)}}{\text{Total Magnification}}

💡Examples

Problem 1:

A student is observing a cheek cell using a compound microscope. The eyepiece has a magnification of 15×15\times and the objective lens being used is 45×45\times. Calculate the total magnification.

Solution:

Total Magnification=15×45=675×\text{Total Magnification} = 15 \times 45 = 675\times

Explanation:

To find the total magnification, we multiply the power of the ocular lens (eyepiece) by the power of the objective lens.

Problem 2:

In the human body, the stomach consists of epithelial tissue, connective tissue, and muscular tissue. To which level of organization does the stomach belong?

Solution:

The stomach belongs to the Organ level.

Explanation:

An organ is defined as a structure composed of different types of tissues working together to perform a specific function. Since the stomach uses multiple tissues for digestion, it is an organ.

Problem 3:

If a biological structure is measured to be 0.05 mm0.05\text{ mm} under a microscope with 100×100\times magnification, what is the actual size of the structure in micrometers (μm\mu m)?

Solution:

Actual Size=0.05 mm100=0.0005 mm\text{Actual Size} = \frac{0.05\text{ mm}}{100} = 0.0005\text{ mm} Conversion: 0.0005×1000=0.5 \mum\text{Conversion: } 0.0005 \times 1000 = 0.5\text{ \mu m}

Explanation:

First, divide the observed size by the magnification factor. Then, convert millimeters to micrometers using the factor 1 mm=1000 \mum1\text{ mm} = 1000\text{ \mu m}.