8.7 Disruptions to Ecosystems
Keywords
| English Term | 中文翻译 | Definition & Explanation |
|---|---|---|
| Adaptation | 适应 | A genetic variation that is favored by selection and provides an advantage to an organism in a particular environment. |
| Mutation | 突变 | A random change in the DNA sequence; the ultimate source of genetic variation. |
| Invasive Species | 入侵物种 | A non-native species introduced into a new area that spreads rapidly and harms native ecosystems, usually due to a lack of natural predators. |
| Biogeography | 生物地理学 | The study of the past and present geographic distribution of species and ecosystems. |
| Meteorological Event | 气象事件 | Short-term or long-term weather-related events (e.g., hurricanes, El Niño) that can dramatically alter habitats. |
1. The Evolutionary Foundation: Mutations and Adaptations
Ecosystems are constantly changing. To survive these disruptions, organisms rely on genetic diversity.
An adaptation is a genetic variation that is favored by natural selection. It manifests as a physical or behavioral trait that provides a distinct survival or reproductive advantage to an organism in a particular environment.
AP Exam Trap: The Nature of Mutations
A very common misconception is that animals mutate in order to survive a changing environment. This is completely false! Mutations are completely RANDOM and are NOT directed by specific environmental pressures.
The environment does not cause the right mutation to appear; it simply acts as a filter. It selects for random mutations that already exist in the population and happen to be advantageous in the new conditions.
2. Biological Disruptions: Invasive Species and Diseases
Sometimes the disruption comes in the form of a new biological organism entering the ecosystem.
Invasive Species
The intentional or unintentional introduction of an invasive species can devastate an ecosystem. When a non-native species is introduced to a new environment, it often exploits a new niche that is completely free of its natural predators or competitors.
Because nothing is hunting them or keeping their population in check, this sudden abundance of resource availability results in uncontrolled, exponential population growth and severe ecological changes, as they rapidly outcompete native organisms for food and space.
- Example 1: Kudzu: A fast-growing vine intentionally introduced to the US to prevent soil erosion. Without native herbivores to eat it, it grew uncontrollably, smothering entire forests in the American South.
- Example 2: Zebra Mussels: Unintentionally transported in the ballast water of ships, they quickly took over the Great Lakes, outcompeting native mussels and clogging water treatment pipes.
New Diseases
Human impact accelerates the introduction of new diseases, which can rapidly devastate native species that have zero natural immunity.
- Example: Dutch elm disease (a fungus spread by bark beetles) and Potato blight (the pathogen responsible for the Irish Potato Famine) wiped out massive, vulnerable populations lacking genetic resistance.
3. Habitat Change: Human and Geological Impacts
The distribution of local and global ecosystems is not static; it changes constantly over time. These changes are driven by both human activities and immense natural forces.
Human Impacts (Accelerating Change)
Human activity accelerates ecological change at unprecedented local and global levels.
- Habitat Destruction: Activities like aggressive logging and urbanization destroy native habitats, forcing species into smaller, fragmented areas.
- Agriculture: Mono-cropping (growing a single crop year after year on the same land) destroys local biodiversity and strips the soil of nutrients, making the ecosystem highly vulnerable to pests and diseases.
- Global Climate Change: The rapid altering of temperature and weather patterns shifts the livable zones for countless species, forcing them to migrate or face extinction.
Geological and Meteorological Events
Natural, physical events also violently affect habitat change and ecosystem distribution. Biogeographical studies illustrate how these changes have shaped life on Earth over millions of years.
- Meteorological Events: The El Niño climate pattern temporarily shifts ocean temperatures and currents, devastating local marine food webs (like the anchovy fisheries off the coast of Peru).
- Geological Events: Continental drift slowly separated populations, leading to unique evolutionary pathways (e.g., marsupials flourishing in isolated Australia). On a more catastrophic scale, the meteor impact 65 million years ago rapidly altered the global climate, blotting out the sun and leading to the extinction of the non-avian dinosaurs, thereby opening up new niches for mammals to exploit.
Quiz
Click the link above to practice related multiple-choice questions (opens in a new tab).