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Classification - The Five Kingdoms

Grade 6IGCSE

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

🔑Concepts

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Classification is the process of sorting living organisms into groups based on their shared features and characteristics.

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The Five Kingdom system includes: Animalia, Plantae, Fungi, Protoctista, and Prokaryotae (Bacteria).

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Kingdom Animalia: Multicellular organisms that gain energy by ingesting organic material (heterotrophs). They lack cell walls and typically have nervous system coordination.

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Kingdom Plantae: Multicellular organisms that carry out photosynthesis to make their own food (autotrophs) using the pigment chlorophyll, found in chloroplasts. Their cell walls are made of cellulose.

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Kingdom Fungi: Organisms that can be multicellular (mushrooms) or unicellular (yeast). They absorb nutrients from dead or decaying matter (saprophytic nutrition) and have cell walls made of chitin.

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Kingdom Protoctista: A 'catch-all' group of eukaryotic organisms that are mostly unicellular (e.g., AmoebaAmoeba, ParameciumParamecium) but can include multicellular forms like seaweed.

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Kingdom Prokaryotae: Unicellular organisms that lack a distinct nucleus and membrane-bound organelles. Their genetic material consists of a single loop of DNA. Cells are typically very small (0.5μm0.5 \mu m to 5μm5 \mu m).

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Binomial Nomenclature: Every organism is given a two-part scientific name consisting of the GenusGenus (capitalized) and speciesspecies (lowercase), usually written in italics, e.g., HomoHomo sapienssapiens.

📐Formulae

6CO2+6H2O→lightC6H12O6+6O26CO_2 + 6H_2O \xrightarrow{\text{light}} C_6H_{12}O_6 + 6O_2

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

1mm=1000μm1 mm = 1000 \mu m

💡Examples

Problem 1:

An organism is observed under a microscope. It is unicellular, has a cell wall, but no visible nucleus. To which kingdom does it belong?

Solution:

Kingdom Prokaryotae (or Monera).

Explanation:

The absence of a nucleus is the defining characteristic of prokaryotes. While plants and fungi also have cell walls, they are eukaryotic (possess a nucleus).

Problem 2:

A scientist finds a multicellular organism growing on a fallen log. It does not perform photosynthesis and has a cell wall. Is it a plant or a fungus?

Solution:

It is a Fungus.

Explanation:

Plants are autotrophs and perform photosynthesis using CO2CO_2 and sunlight. Fungi are heterotrophs (specifically saprotrophs) that absorb nutrients from decaying organic matter and do not contain chlorophyll.

Problem 3:

Calculate the actual length of a bacteria cell if the image length is 20mm20 mm and the magnification is ×4000\times 4000. Give the answer in micrometers (μm\mu m).

Solution:

ActualSize=20mm4000=0.005mm=5μmActual Size = \frac{20 mm}{4000} = 0.005 mm = 5 \mu m

Explanation:

Using the formula ActualSize=ImageMagnificationActual Size = \frac{Image}{Magnification}, we get 0.005mm0.005 mm. Since 1mm=1000μm1 mm = 1000 \mu m, we multiply 0.0050.005 by 10001000 to get 5μm5 \mu m.

The Five Kingdoms - Revision Notes & Key Formulas | IGCSE Grade 6 Science