IB Biology HL Paper 1 Practice Questions

Preparing for the IB Biology HL exam can be challenging. To help you succeed, we've put together a set of three practice questions from different areas of the syllabus, including Evolution, Human Physiology, and Plant Biology. Accompanying these questions are clear, step-by-step solutions to enhance your understanding and boost your exam readiness.

Dive in and test your knowledge with these targeted practice questions!

Question 1:

• Topic: Evolution and Biodiversity

• Question: Which mechanism of speciation is most likely to occur when a physical barrier divides a population of organisms?

  • A) Sympatric speciation

  • B) Allopatric speciation

  • C) Parapatric speciation

  • D) Artificial speciation

1. Question 2:

   • Topic: Human Physiology

   • Question: Which hormone is primarily responsible for regulating blood glucose levels?

     • A) Insulin

     • B) Glucagon

     • C) Adrenaline

     • D) Both A and B

2. Question 3:

   • Topic: Plant Biology

   • Question: What is the primary function of xylem in plants?

     • A) Transport of nutrients

     • B) Transport of water and minerals

     • C) Photosynthesis

     • D) Gas exchange

And here are the worked solutions for each question:

1. Solution to Question 1:

   • The question involves understanding different mechanisms of speciation.

   • Sympatric speciation occurs without physical separation.

   • Allopatric speciation occurs when populations are geographically separated, leading to speciation.

   • Parapatric speciation is a mix of sympatric and allopatric, occurring when populations are adjacent but not overlapping.

   • Artificial speciation is a result of human intervention.

   • In this scenario, where a physical barrier divides a population, allopatric speciation is most likely.

   • Answer: B) Allopatric speciation

2. Solution to Question 2:

   • This question pertains to hormones regulating blood glucose levels.

   • Insulin is produced by the pancreas and helps lower blood glucose levels by facilitating cellular uptake of glucose.

   • Glucagon, also produced by the pancreas, has the opposite effect, raising blood glucose levels by promoting the release of glucose into the bloodstream.

   • Adrenaline affects glucose levels indirectly but is not primarily responsible for its regulation.

   • Since the question asks about the primary hormone for regulating blood glucose levels and both insulin and glucagon play crucial but opposite roles, the correct answer is both.

   • Answer: D) Both A and B

3. Solution to Question 3:

   • This question is about the function of xylem in plants.

   • The primary function of xylem is to transport water and minerals from the roots to the rest of the plant.

   • Nutrients (like sugars) are primarily transported through the phloem, not xylem.

   • Photosynthesis occurs in the chloroplasts, mainly in leaves, and is not a function of xylem.

   • Xylem is not involved in gas exchange, which primarily occurs through stomata in leaves.

   • Answer: B) Transport of water and minerals

These solutions aim to clarify the reasoning behind each answer, providing an understanding of the key concepts in IB HL Biology.