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IB DP Biology Mock Exam SL Paper 1B Set 2 - 2025 Syllabus

IB DP Biology Mock Exam SL Paper 1B Set 2

Prepare for the IB DP Biology Exam with our comprehensive IB DP Biology Exam Mock Exam SL Paper 1B Set 2. Test your knowledge and understanding of key concepts with challenging questions covering all essential topics. Identify areas for improvement and boost your confidence for the real exam

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Question 

The image shows epidermal tissue from the bulb of an onion plant (Allium cepa) observed using a light microscope.
 
 
 
 
 
 
 
 
 
 
(a) Calculate the magnification of the image. 
(b) State the piece of equipment a student could use to accurately measure the length of an onion cell when viewed through a light microscope. 
(c) Draw a labelled diagram of a nucleus from a eukaryotic cell, such as an onion epidermal cell, as it would appear under an electron microscope. 

▶️ Answer/Explanation

(a)
The scale bar in the image is labelled as 50 µm.
Measured length of the scale bar in the image ≈ 2 cm = 20,000 µm.
Magnification = Image size ÷ Actual size = 20,000 µm ÷ 50 µm = 400.
\(\boxed{400}\)

(b)
The equipment used to accurately measure the length of a cell under a light microscope is an eyepiece graticule.
\(\boxed{\text{Eyepiece graticule}}\)

(c)
A nucleus as seen under an electron microscope should show:
– A double membrane (nuclear envelope)
– Nuclear pores
– Nucleolus
– Chromatin/DNA

Labelled diagram example:

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