Final answer:
Human activity affects populations through the introduction of non-native species, the use of fertilizers, and deforestation.
Step-by-step explanation:
Human activity can affect populations in several ways:
- Fertilizers get washed into bodies of water causing algae to grow quickly: The excessive nutrients from fertilizers can lead to an overgrowth of algae, which can disrupt the balance of the aquatic ecosystem.
- Purposeful or accidental introduction of non-native species into an area: When non-native species are introduced to an area, they can outcompete native species for resources and disrupt the natural balance of the ecosystem.
- Removing trees from a forested area for the purpose of farming, building, or recreation: Deforestation can lead to habitat loss for many species, causing population declines and even extinction.