Biology: Ecology and Sustainability - Human Impacts on Ecosystems (Pollution, Habitat Loss, Overexploitation, and Invasive Species)

Pollution: The introduction of harmful substances (pollutants) into the environment. This includes air pollution (CO$_2$, SO$_2$), water pollution (plastics, fertilizers), and soil pollution. High levels of fertilizers lead to Eutrophication, where excess nutrients cause algal blooms that deplete oxygen ($O_2$) levels.

Bioaccumulation and Biomagnification: Bioaccumulation is the build-up of toxins within a single organism over time. Biomagnification is the increase in concentration of toxins, such as mercury or DDT, as they move up the food chain. If $C$ is the concentration, then $C_{predator} > C_{prey}$.

Habitat Loss and Fragmentation: The process where natural habitats are rendered unable to support the species present, often due to deforestation or urbanization. Fragmentation divides large habitats into smaller, isolated patches, reducing biodiversity and increasing edge effects.

Overexploitation: Harvesting a renewable resource to the point of diminishing returns. This occurs when the harvest rate ($H$) exceeds the natural replacement rate ($R$), leading to population collapse: $H > R$. Examples include overfishing and illegal wildlife trade.

Invasive Species: Non-native species introduced to a new environment that cause ecological or economic harm. They often lack natural predators, allowing their population ($N$) to grow exponentially, outcompeting native species for resources ($Food, Space, Sunlight$).

Sustainability: The practice of using resources in a way that meets current needs without compromising the ability of future generations to meet theirs. This is often measured by the Ecological Footprint.