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

IB DP Biology Mock Exam SL Paper 1A Set 2

Prepare for the IB DP Biology Exam with our comprehensive IB DP Biology Exam Mock Exam SL Paper 1A 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

IB DP Biology Mock Tests -All Sets

Question 

Which row below provides the correct combination of gland, hormone, and its main action in the endocrine system?
OptionGlandHormoneAction
Apinealmelatonincontrols circadian rhythm
Badrenalepinephrine (adrenaline)controls circadian rhythm
Cadrenalmelatoninprepares the body for vigorous activity
Dpinealepinephrine (adrenaline)prepares the body for vigorous activity
▶️ Answer/Explanation
Detailed solution

The pineal gland produces melatonin, a hormone that helps regulate the body’s circadian rhythm. This makes row A the only correct match. ✅ Answer: (A)

Question 

The diagram illustrates the male reproductive system from a front perspective.

The structures labelled X, Y, and Z correspond to three major components.

OptionXYZ
Atestissperm ductseminal vesicle
Bepididymissperm ductprostate gland
Ctestisurethraprostate gland
Depididymisurethraseminal vesicle
▶️ Answer/Explanation
Detailed solution

Label X points to the testis, which produces sperm. Label Y indicates the sperm duct (vas deferens), which transports sperm toward the urethra. Label Z corresponds to the seminal vesicle, a gland that contributes fluid to semen. ✅ Answer: (A)

Question 

The images below show an Ichthyosaurus and a dolphin. The Ichthyosaurus was an extinct aquatic reptile known from fossils, whereas dolphins are modern mammals.

How can the evolution of these two species best be described?

A. Their streamlined bodies show divergent evolution.
B. Their streamlined bodies are analogous structures.
C. Their pentadactyl limbs are an example of convergent evolution.
D. Their pentadactyl limbs are analogous structures.

▶️ Answer/Explanation
The Ichthyosaurus (a reptile) and the dolphin (a mammal) evolved independently but developed similar streamlined body shapes for efficient swimming. These similarities arose due to similar environmental pressures, not because of shared ancestry. Hence, their streamlined forms are analogous structures — a result of convergent evolution.
✅ Answer: (B) Their streamlined bodies are analogous structures.
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