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Biology - Organization of the Organism

Grade 10IGCSE

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

🔑Concepts

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Cell Structure: All living organisms are made of cells. Animal cells contain a nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes. Plant cells also possess a cellulose cell wall, chloroplasts, and a large permanent vacuole.

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Functions of Organelles: The nucleus contains genetic material (DNADNA); mitochondria are the site of aerobic respiration (C6H12O6+6O2→6CO2+6H2OC_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O); ribosomes are responsible for protein synthesis.

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Levels of Organization: The hierarchy of complexity is Organelles →\rightarrow Cells →\rightarrow Tissues →\rightarrow Organs →\rightarrow Organ Systems →\rightarrow Organism.

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Specialized Cells: Cells are adapted for specific functions. Examples include: Root hair cells (increased surface area for water uptake), Xylem vessels (hollow tubes for water transport), and Red Blood Cells (biconcave shape and no nucleus to maximize O2O_2 transport).

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Measurement and Units: Biological specimens are often measured in micrometres (μm\mu m). 1 mm=1000 μm1\ mm = 1000\ \mu m. Calculation of magnification is essential using the I=A×MI = A \times M formula.

📐Formulae

Magnification=Size of ImageActual Size of ObjectMagnification = \frac{\text{Size of Image}}{\text{Actual Size of Object}}

Actual Size=Image SizeMagnification\text{Actual Size} = \frac{\text{Image Size}}{Magnification}

1 mm=103 μm1\ mm = 10^3\ \mu m

💡Examples

Problem 1:

A student views a micrograph of a mitochondrion. The image length of the mitochondrion is 30 mm30\ mm. If the magnification of the micrograph is ×15,000\times 15,000, calculate the actual length of the mitochondrion in micrometres (μm\mu m).

Solution:

  1. Convert image size to μm\mu m: 30 mm×1000=30,000 μm30\ mm \times 1000 = 30,000\ \mu m.
  2. Use the formula: Actual Size=Image SizeMagnificationActual\ Size = \frac{Image\ Size}{Magnification}.
  3. Calculation: 30,000 μm15,000=2 μm\frac{30,000\ \mu m}{15,000} = 2\ \mu m.

Explanation:

To find the actual size, we divide the measured image size by the magnification factor, ensuring units are converted to the requested scale (1 mm=1000 μm1\ mm = 1000\ \mu m).

Problem 2:

Describe the levels of organization for the human circulatory system.

Solution:

  1. Cell: Cardiac muscle cell.
  2. Tissue: Cardiac muscle tissue.
  3. Organ: The Heart.
  4. Organ System: The Circulatory System.
  5. Organism: Human.

Explanation:

This demonstrates the progression from a single specialized cell type to a complex multicellular organism.