MYP Biology Pollution and Conservation Notes

What Is Pollution And Why Does It Matter?

1. Pollution occurs when harmful substances or energy enter the environment, disrupting chemical, physical, or biological conditions.
2. Even small changes in air, water, or soil can interfere with respiration, growth, reproduction, and food webs.

How Does Water Pollution Affect Aquatic Ecosystems?

1. Water pollution disrupts aquatic habitats when harmful substances or materials enter rivers, lakes, or oceans.
2. These pollutants interfere with feeding, respiration, reproduction, and the balance of food webs.
3. Water pollution happens through three major pathways.

Chemical contamination

1. Industrial waste, pesticides, heavy metals, and oil dissolve or disperse into water.
2. These chemicals move into organisms and enter food webs.
3. Pollutants accumulate in tissues and become more concentrated at higher trophic levels.

Eutrophication

1. Excess nitrates and phosphates enter water from fertilizers or sewage.
2. Algae grow rapidly, forming dense blooms.
3. When algae die, decomposers break them down, using large amounts of oxygen.
4. Oxygen levels fall (hypoxia).
5. Fish and invertebrates suffocate or leave.
6. The habitat collapses into a low-oxygen “dead zone.”

Microplastics

1. Microplastics (<5 mm) absorb toxic chemicals from the environment.
2. Plankton, shellfish, and fish swallow them unknowingly.
3. Microplastics block digestion and release chemicals that disrupt hormones.
4. These particles move through the food web, affecting many species.

How Does Air Pollution Affect Ecosystems?

1. Air pollution alters the chemistry of the atmosphere.
2. These changes affect plant growth, soil quality, water bodies, and entire food webs.
3. Air pollution impacts ecosystems mainly through acid rain and the greenhouse effect.

Acid rain

1. Factories and vehicles release sulfur dioxide (SO₂) and nitrogen oxides (NOₓ).
2. These gases react with water and oxygen in the atmosphere to form sulfuric and nitric acids.
3. Acid droplets fall as acid rain, lowering the pH of soil and water.
4. Acidic conditions damage organisms and disrupt nutrient cycles.
5. Effects of Acid Rain
   1. Lakes acidify, reducing fish and amphibian populations.
   2. Soil loses essential minerals, weakening plant growth.
   3. Leaves become damaged, reducing photosynthesis.
   4. Roots weaken, making plants less stable and more drought-sensitive.

Greenhouse gases and the greenhouse effect