Biology: Invasive Species and Their Effects on Ecosystems
How non-native species change food webs, habitats, and biodiversity
Biology: Invasive Species and Their Effects on Ecosystems
How non-native species change food webs, habitats, and biodiversity
Biology - Grade 6-8
- 1
Define an invasive species in your own words. Include both where it comes from and what effect it has on an ecosystem.
Include the ideas of non-native, spreading, and harm.
An invasive species is a non-native organism that spreads in a new area and causes harm to the ecosystem, the economy, or human health. - 2
A plant from another continent is brought to a park. It grows quickly, blocks sunlight from native plants, and reduces the number of insects that feed on native plants. Is this plant invasive? Explain your answer.
Yes, this plant is invasive because it is non-native, spreads quickly, and harms native plants and insects in the ecosystem. - 3
List three ways invasive species can be introduced to a new ecosystem by humans.
Think about travel, trade, pets, and transported materials.
Invasive species can be introduced through ships carrying organisms in ballast water, people releasing pets into the wild, and plants or insects being transported on goods, vehicles, or firewood. - 4
Zebra mussels are invasive in many freshwater lakes. They attach to surfaces, filter large amounts of plankton, and compete with native mussels. Describe two possible effects zebra mussels could have on a lake ecosystem.
Zebra mussels could reduce plankton that small fish and other organisms need for food. They could also outcompete native mussels for space and resources, causing native mussel populations to decline. - 5
A native bird eats a native insect. An invasive lizard arrives and eats many of the same insects. Predict what might happen to the native bird population over time and explain why.
Focus on competition for a limited resource.
The native bird population might decrease because the invasive lizard competes with the bird for the same insect food source, leaving less food for the birds. - 6
In one forest, an invasive beetle kills many ash trees. Explain how losing many ash trees could affect other organisms in the forest.
Losing many ash trees could reduce food and habitat for animals that use the trees. It could also change the amount of sunlight reaching the forest floor, which may affect smaller plants and the animals that depend on them. - 7
A pond food web includes algae, small insects, frogs, fish, and herons. An invasive fish eats many frogs and small insects. Describe one direct effect and one indirect effect of the invasive fish.
A direct effect happens right away between two species. An indirect effect happens through another species in the food web.
A direct effect is that frog and small insect populations may decrease because the invasive fish eats them. An indirect effect is that herons may have less food if frog populations drop. - 8
A student says, "All non-native species are invasive." Explain why this statement is not correct.
The statement is not correct because some non-native species do not spread quickly or cause harm. A species is considered invasive when it is non-native and causes ecological, economic, or health problems. - 9
Kudzu is a fast-growing vine that can cover trees and shrubs. Explain how kudzu can reduce biodiversity in an ecosystem.
Biodiversity means the variety of living things in an area.
Kudzu can reduce biodiversity by covering native plants and blocking their sunlight. When native plants die or decline, the animals that depend on them may also decline. - 10
A lake has 200 native snails before an invasive crayfish arrives. After one year, there are 120 native snails. After two years, there are 60 native snails. What trend is shown, and what is one possible explanation?
Look at how the number changes from year to year.
The native snail population is decreasing over time. One possible explanation is that the invasive crayfish is eating the snails or competing with them for food or habitat. - 11
Scientists often recommend cleaning mud and plant material off boats, boots, and fishing gear before moving to another lake or stream. Explain how this helps prevent invasive species.
Cleaning boats, boots, and fishing gear helps prevent invasive species because seeds, eggs, larvae, or small organisms can be carried in mud or plant material and moved to a new habitat. - 12
Study this data: In 2020, a wetland had 80 native plant patches and 5 invasive plant patches. In 2024, it had 45 native plant patches and 40 invasive plant patches. What happened to each plant group, and what concern might scientists have?
Compare the starting and ending numbers for each group.
The number of native plant patches decreased from 80 to 45, while invasive plant patches increased from 5 to 40. Scientists might be concerned that the invasive plant is spreading and replacing native plants. - 13
Explain why invasive species often spread quickly when they have few natural predators in a new ecosystem.
Invasive species can spread quickly when they have few natural predators because fewer organisms are eating them or keeping their population under control. This allows them to survive, reproduce, and take over resources. - 14
A community wants to control an invasive plant near a river. They are choosing between pulling it by hand, using herbicide, and releasing an insect that eats the plant. Choose one method and describe one benefit and one possible risk.
Every control method can have trade-offs.
One method is releasing an insect that eats the plant. A benefit is that the insect may reduce the invasive plant population naturally, but a possible risk is that the insect could also harm native plants if it is not carefully studied first. - 15
Write a short explanation of why invasive species are a problem for ecosystem balance. Include at least two effects they can have.
Invasive species are a problem for ecosystem balance because they can compete with native species for food, space, and sunlight. They can also change habitats, reduce biodiversity, and disrupt food webs.