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Human Impacts: Invasive Species — Reading Comprehension

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MS-LS2-4
MS-LS2-5

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This passage explores the science behind invasive species—non-native organisms that harm native ecosystems. Aligned to NGSS standards MS-LS2-4 and MS-LS2-5, it explains how invasive species are introduced (both intentionally and accidentally), why they often succeed in new environments, and the ecological and economic impacts they cause. Real-world examples like kudzu, zebra mussels, and Burmese pythons illustrate the mechanisms and consequences of biological invasions. The passage includes a glossary, simplified version, Spanish translation, graphic organizers, and comprehension activities. Audio integration supports diverse learners. This resource helps students understand systems, interactions, and human impacts on biodiversity, providing critical thinking and real-world application opportunities.

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The springtime yellow blooms along this Clatsop County hillside, and thousands like it along the northern Pacific Coast, are lovely but detested locally. They are highly invasive Scotch broom shrubs, native to the British Isles and Europe, that spread aggressively and soon crowd out native plants — Invasive species like Scotch broom shrubs spread aggressively and crowd out native plants. Image by Highsmith, Carol M., 1946- / Library of Congress.

Invasive species are a major challenge for ecosystems around the world. These are non-native organisms that enter a new habitat and cause harm to the environment, economy, or even human health. In recent decades, the spread of invasive species has increased, affecting biodiversity and ecosystem stability. Scientists study how these species spread and why they often outcompete native organisms, leading to complex changes in the environment.

How Species Become Invasive

Species can become invasive through both intentional introduction and accidental means. Humans may bring in new plants or animals for crops, landscaping, or as pets. Sometimes, species are introduced by accident, such as through ballast water discharged by ships or organisms hitchhiking on cargo. Once in a new environment, some of these species thrive because they have no natural predators or diseases to keep their populations in check. For example, zebra mussels arrived in North America in the 1980s via ballast water from ships. They quickly spread throughout waterways, clogging pipes and outcompeting native mussels.

Why Invasive Species Succeed

Invasive species often succeed because of several interacting factors. Without natural predators, their populations can grow rapidly. Some have short reproduction cycles or produce many offspring, allowing them to spread quickly. Invasive plants like kudzu in the southern United States can grow up to 30 centimeters per day, smothering native vegetation. In Australia, the cane toad was introduced to control pests but became invasive, poisoning native animals that tried to eat it. In Florida, the Burmese python now preys on mammals and birds, reducing native wildlife populations by more than 90% in some areas.

Impacts and Control Strategies

The effects of invasive species are far-reaching. They can reduce biodiversity by outcompeting or preying on native species, disrupt food webs, and cause economic damage. For instance, zebra mussels cost the U.S. billions of dollars each year in maintenance and control. The brown tree snake in Guam has caused the extinction of several bird species. To address these problems, scientists and governments use different control strategies, such as physical removal, biological control (using natural enemies), and stricter regulations on species transport. Prevention—stopping invasives from entering new areas in the first place—is usually the most effective approach.

Understanding the mechanisms behind invasive species helps scientists and communities protect ecosystems and maintain biodiversity. Studying these complex interactions deepens our knowledge of how human actions impact natural systems and highlights the importance of responsible environmental management.

Interesting Fact: Some invasive species, like the Asian carp, can jump up to 3 meters out of the water when startled, posing a danger to boaters as well as ecosystems!

What is an invasive species?

A non-native organism that causes harm in a new environmentA native species that helps the ecosystemA plant or animal only found in one placeA species that is going extinct

Which of the following is NOT a way species become invasive?

Intentional introduction as petsArriving by accident in ballast waterStaying in their natural habitatHitchhiking on cargo

What is one reason invasive species can outcompete native species?

They have more natural predatorsThey often reproduce quicklyThey are always smallerThey need less water

According to the passage, what is a control strategy for invasive species?

Physical removalAllowing them to spread freelyFeeding them more foodIntroducing more invasive species

In the passage, what does the term 'ballast water' mean?

Water carried in ships that can transport organismsWater found only in riversA special drink for zebra musselsA type of natural predator

What does 'biodiversity' mean in the context of the passage?

The number and variety of living things in an areaA way to control zebra musselsThe economic cost of invasivesThe process of moving species

Why was the cane toad originally introduced in Australia?

To control pestsFor scientific studyAs a petTo increase biodiversity

Which of the following is an example of economic damage caused by invasive species?

Zebra mussels clogging pipes and costing billionsBurmese pythons eating native animalsKudzu growing over treesBrown tree snake causing bird extinctions

True or False: Prevention is usually the most effective approach to managing invasive species.

TrueFalse

True or False: All invasive species are brought in on purpose by humans.

TrueFalse