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Characteristics and Classification of Living Organisms - Characteristics of living organisms

Grade 11IGCSEBiology

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

🔑Concepts

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Movement: An action by an organism or part of an organism causing a change of position or place.

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Respiration: The chemical reactions in cells that break down nutrient molecules and release energy for metabolism. This often involves the consumption of O2O_2 and the release of CO2CO_2.

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Sensitivity: The ability to detect or sense stimuli in the internal or external environment and to make appropriate responses.

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Growth: A permanent increase in size and dry mass by an increase in cell number or cell size or both.

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Reproduction: The processes that make more of the same kind of organism.

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Excretion: The removal from organisms of the waste products of metabolism (chemical reactions in cells including respiration), toxic materials, and substances in excess of requirements, such as CO2CO_2 and urea.

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Nutrition: Taking in of materials for energy, growth, and development. Plants require light, CO2CO_2, H2OH_2O, and mineral ions; animals need organic compounds, ions, and usually H2OH_2O.

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Metabolism: The sum of all chemical reactions occurring within a cell or organism, facilitated by enzymes.

📐Formulae

C6H12O6+6O2→6CO2+6H2O+EnergyC_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}

Magnification=Measured size of imageActual size of specimen\text{Magnification} = \frac{\text{Measured size of image}}{\text{Actual size of specimen}}

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

💡Examples

Problem 1:

Explain why the removal of undigested food (egestion) is not considered excretion in the context of IGCSE Biology.

Solution:

Egestion is the removal of undigested food through the anus, whereas excretion is the removal of waste products of metabolism.

Explanation:

Excretion specifically refers to substances that have been produced by chemical reactions inside cells (metabolism), such as CO2CO_2 from respiration or urea from the breakdown of proteins. Undigested food has never entered the cells to be metabolized.

Problem 2:

A plant seedling grows towards a light source placed to its left. Identify the two characteristics of living organisms shown here.

Solution:

Sensitivity and Movement.

Explanation:

The plant detects the light stimulus (Sensitivity) and responds by changing its growth direction (Movement), a process known as phototropism.

Problem 3:

An image of a cell is 40 mm40 \text{ mm} wide. If the actual width of the cell is 0.05 mm0.05 \text{ mm}, calculate the magnification.

Solution:

Magnification=40 mm0.05 mm=800×Magnification = \frac{40 \text{ mm}}{0.05 \text{ mm}} = 800\times

Explanation:

Using the formula M=IAM = \frac{I}{A}, we divide the image size by the actual size. Ensure both units are the same before calculating.

Characteristics of living organisms Revision - Grade 11 Biology IGCSE