Explain how natural events and human activities influence local and global ecosystems and may affect the flora and fauna of Virginia, including the Chesapeake Bay watershed, invasive species, and eutrophication (Virginia 2018 Biology SOL BIO.8.d).

What this topic is asking

Virginia Biology SOL standard BIO.8 is about how ecosystems are dynamic and change over time, and substandard BIO.8.d asks how natural events and human activities influence local and global ecosystems and may affect the flora and fauna of Virginia. The EOC leans on Virginia-specific examples, above all the Chesapeake Bay watershed, along with invasive species and eutrophication. The standard rewards explaining a cause-and-effect chain (what humans do, what happens to the ecosystem) and knowing the responses that protect or restore it.

Natural events and human activities

Ecosystems change from natural events such as storms, floods, droughts, and fires, which can reset a community (and start succession). Human activities add faster, larger changes: clearing land for farms and cities (habitat destruction), releasing pollution, overharvesting fish and other species, deforestation, and introducing species from other regions. The standard asks you to connect a specific activity to its effect on the flora (plants) and fauna (animals) of an ecosystem, especially in Virginia.

The Chesapeake Bay watershed and eutrophication

This nutrient-to-algae-to-oxygen-loss chain is the single most testable sequence in the Virginia standard, so be ready to explain each step.

Invasive species

The damage is twofold: native populations fall, and the loss of biodiversity makes the ecosystem less stable. Controlling invasive species (and preventing their introduction) is a major part of protecting Virginia ecosystems.

Pollution, habitat change, and global effects

Beyond the Bay, human impacts include pollution of air, water, and soil; habitat destruction and fragmentation that shrink the space available to wildlife; overharvesting that drives populations down; and deforestation that removes producers and the habitat they provide. Globally, burning fossil fuels adds carbon dioxide to the atmosphere (tying back to the carbon cycle), and pollution can affect ecosystems far from its source. Many of these reduce biodiversity, the variety of life that helps keep ecosystems resilient.

Conservation and restoration responses

The standard also values knowing how the harm can be reduced. For the Chesapeake Bay these include reducing nutrient runoff (planting vegetated buffer strips along streams, using less fertilizer, improving sewage treatment), restoring oyster reefs and wetlands that naturally filter the water and remove nutrients, and controlling invasive species. More broadly, conservation protects habitats and biodiversity, and reducing pollution and emissions limits global effects. The takeaway is that human activities can degrade ecosystems, but informed action can protect and restore them.

Try this

Q1. Describe the steps by which fertilizer runoff leads to a dead zone in the Chesapeake Bay. [3]

• Cue. Runoff adds nitrogen and phosphorus; nutrients cause an algal bloom; the algae die and decomposers use up the dissolved oxygen; the low-oxygen water (dead zone) kills fish and shellfish.

Q2. Explain why an invasive species can reduce the biodiversity of a Virginia ecosystem. [2]

• Cue. With no natural predators or controls, it spreads and outcompetes or preys on native species that are not adapted to it, reducing or eliminating them and lowering biodiversity.