Invasive Species
Introduced| English |
|---|
| native/ˈneɪtɪv/ |
| invasive species/ɪnˈveɪsɪv ˈspiːsiːz/ |
| no natural predators/nəʊ ˈnætʃərəl ˈpredətəz/ |
| outcompete/aʊtkəmˈpiːt/ |
Species in the wrong place
- A native 本地 species belongs naturally in its area.
- Sometimes a species is moved to a new place, by accident or on purpose.
- Most newcomers cannot survive, but a few thrive and spread.
- One that spreads and causes harm is an invasive species 入侵物种.
Why they take over
- In the new place, they often have no natural predators 天敌.
- Nothing hunts them, so their numbers explode.
- Many reproduce fast and spread quickly.
- They outcompete 排挤 the natives for food and space.
An invasive species is one that…
An invasive species is a non-native one that spreads aggressively and harms the ecosystem.
The harm they do
- Invasives can eat native species that cannot defend themselves.
- They crowd out native plants and animals.
- Some carry diseases the natives have never faced.
- They can drive native species all the way to extinction.
Native or invasive?
Sort each example into a native species or an invasive one.
Invasive species often take over because they…
With no natural predators to control them, invasives multiply and outcompete the natives.
A species that naturally belongs in an area is called a ____ species.
A native species evolved in the area and is part of its natural balance.
How they arrive and how to stop them
- Ships, planes, and trade carry species around the world.
- Released pets and dumped aquariums add more.
- Checking cargo and banning risky imports helps stop them.
- Once established, invasives are very hard to remove.
Invasive species can drive native species to extinction by outcompeting them.
By eating or outcompeting natives that cannot fight back, invasives can wipe them out.
Select all reasons invasive species spread so successfully.
No predators, fast breeding, and outcompeting natives all help them spread. Local diseases rarely stop them.
The key to why invasives are so destructive is what they left behind: their natural predators, parasites, and diseases. In their home range, those enemies kept them in check. In the new place, nothing does — so they multiply unchecked and outcompete the natives that do have local enemies. It's not that they're "stronger"; they've simply escaped the things that used to control them.
A fish in a new lake:
- Someone empties an aquarium into a lake, releasing a fish from another continent.
- In this lake it has no natural predators, so it breeds unchecked and outcompetes the native fish for food.
- Within a few years the native fish are gone, the food web is disrupted, and removing the invader is nearly impossible.
An invasive species is a non-native species that spreads and harms an ecosystem. They take over because they have no natural predators in the new place, often reproduce fast, and outcompete or eat the native species. They can drive natives to extinction, and once established are very hard to remove — so prevention matters most.