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IB MYP Biology Mock Test 4 – 2026 Edition

IB MYP Biology Mock Test 4 – April/May 2026 Exam

IB MYP Biology Mock Test 4: Prepare for the MYP exams with subject-specific Prediction questions, model answers. All topics covered.

Prepared by MYP teachers: Access our IB MYP Biology Mock Test 4 Mock with model answer. Students: Practice with exam-style papers for MYP Exam

Question : Eutrophication and Human Impact [10 marks]

Eutrophication is a natural process that occurs in bodies of water over hundreds of years. Excess nutrients such as nitrogen, phosphorus, and potassium slowly wash from the soil into bodies of water, causing increased growth of algae and aquatic plants.

Question a [1 mark] – Eutrophication: Natural Sources

Suggest one source of nutrients that causes natural eutrophication.

▶️ Answer/Explanation

Possible Answers:

  • Decaying plants/animals (organic matter)
  • Animal waste (e.g., from wildlife)
  • Soil erosion (natural weathering)

Key Point: These sources release nitrogen and phosphorus slowly over centuries.

Question b [2 marks] – Eutrophication: Human Sources

The image below shows human actions that accelerate eutrophication. Suggest one direct and one indirect source of nutrients from human activities.

Direct source:

Indirect source:

▶️ Answer/Explanation

Direct Sources (1 mark): Immediate release of nutrients

  • Sewage treatment plants
  • Fish farms
  • Industrial discharge pipes

Indirect Sources (1 mark): Nutrients transported via runoff

  • Farming (fertilizers/pesticides)
  • Residential areas (lawn chemicals)
  • Urban stormwater

Key Difference: Direct sources enter water immediately; indirect sources are carried by rain or irrigation.

Question c [3 marks] – Algal Blooms: Causes

An algal bloom is caused by a rapid increase in algae population. Using the image in part (b), describe how human-caused eutrophication leads to algal blooms.

▶️ Answer/Explanation

Answer:

  1. Humans add excess nutrients (nitrogen/phosphorus) to water via runoff or waste
  2. Algae use these nutrients to grow and reproduce rapidly
  3. Lack of natural predators allows unchecked population growth

Scientific Terms:

  • Limiting factors: Normally, nutrient scarcity limits algae growth
  • Population explosion: Excess nutrients remove this limitation

Question d [4 marks] – Ecosystem Impact

Explain how a large algal bloom could cause a decrease in biomass in the ecosystem.

▶️ Answer/Explanation

4-Step Process (1 mark per step):

  1. Algal bloom blocks sunlight → Prevents photosynthesis in submerged plants
  2. Plants die → Reduced oxygen production and loss of food source
  3. Decomposers (bacteria) multiply → Break down dead matter using oxygen
  4. Oxygen depletion → Fish/aquatic organisms suffocate (↓ biomass)

Key Terms:

  • Biomass: Total mass of living organisms
  • Hypoxia: Low oxygen levels causing death
  • Dead zones: Areas where most life cannot survive
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