krit.club logo

Classification and Biodiversity - Characteristics of Living Organisms

Grade 9IB

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

🔑Concepts

•

Characteristics of Living Organisms (MRS GREN): Movement (action by an organism causing a change of position or place), Respiration (chemical reactions in cells that break down nutrient molecules to release energy), Sensitivity (ability to detect and respond to changes in the environment), Growth (permanent increase in size/dry mass), Reproduction (processes that make more of the same kind of organism), Excretion (removal of toxic materials and waste products of metabolism), and Nutrition (taking in materials for energy, growth, and development).

•

Binomial System: A system of naming species using two parts: the genus (capitalized) and the species (lower case), both usually italicized or underlined, e.g., HomoHomo sapienssapiens.

•

Classification Hierarchy: Organisms are classified into groups based on shared features, following the rank: Kingdom, Phylum, Class, Order, Family, Genus, and Species.

•

Dichotomous Keys: Tools used to identify organisms by asking a series of questions with two possible answers, leading eventually to the name of the organism.

•

The Five Kingdoms: Living organisms are categorized into Prokaryota (Monera), Protoctista, Fungi, Plantae, and Animalia based on cell structure and nutrition.

•

DNA and Classification: Modern classification uses DNA base sequences and amino acid sequences in proteins to determine how closely related organisms are; the more similar the sequences, the more recently they shared a common ancestor.

📐Formulae

Magnification=Image sizeActual sizeMagnification = \frac{\text{Image size}}{\text{Actual size}}

Actual size=Image sizeMagnificationActual \text{ } size = \frac{\text{Image size}}{Magnification}

1 mm=1000 μm1 \text{ mm} = 1000 \text{ } \mu\text{m}

1 μm=10−3 mm1 \text{ } \mu\text{m} = 10^{-3} \text{ mm}

💡Examples

Problem 1:

A biological specimen in a textbook diagram has an image length of 40 mm40 \text{ mm}. If the actual length of the organism is 0.2 mm0.2 \text{ mm}, calculate the magnification used for the drawing.

Solution:

Using the formula: Magnification=IAMagnification = \frac{I}{A} Magnification=40 mm0.2 mmMagnification = \frac{40 \text{ mm}}{0.2 \text{ mm}} Magnification=×200Magnification = \times 200

Explanation:

To find magnification, we divide the measured image size by the actual size of the specimen. Ensure both units are identical (mm in this case).

Problem 2:

A bacterial cell is observed under a microscope with a magnification of ×4000\times 4000. If the image of the cell measures 12 mm12 \text{ mm} in length, calculate the actual size of the cell in micrometers (μm\mu\text{m}).

Solution:

First, find the actual size in mm: A=IM=12 mm4000A = \frac{I}{M} = \frac{12 \text{ mm}}{4000} A=0.003 mmA = 0.003 \text{ mm} Now, convert mm to μm\mu\text{m}: 0.003×1000=3 μm0.003 \times 1000 = 3 \text{ } \mu\text{m}

Explanation:

The actual size is found by dividing the image size by the magnification. Since biological cells are very small, the result is converted from millimeters to micrometers by multiplying by 10001000.