This comprehensive middle school science reading passage examines how introduced species disrupt ecosystems and reduce biodiversity. Aligned with NGSS standard MS-ESS3-4, the passage describes how invasive species introduced by human activity outcompete native species and trigger cascading effects across food webs. Students explore specific examples including Burmese pythons in the Florida Everglades and zebra mussels in the Great Lakes. The passage explains key ecological concepts including competition, predation, and ecosystem balance. Audio-integrated content supports diverse learners, while differentiated versions ensure accessibility for all reading levels. Activities include comprehension questions, writing prompts, and graphic organizers that help students analyze cause-and-effect relationships and compare native versus invasive species. This resource provides engaging, standards-aligned instruction on human impacts on ecosystems and the importance of biodiversity conservation.
Written by Workybooks TeamPublished by Workybooks
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Sample passage and quiz content
Zebra mussels filter enormous amounts of water as they feed, removing microscopic plants and animals called plankton. Native fish and other organisms that depend on plankton for food face starvation. Zebra Mussels (Dreissena polymorpha) (52117258744) by USFWS Mountain Prairie / Wikimedia Commons
An introduced species is an organism that humans move from its natural habitat to a new location where it did not previously exist. When an introduced species spreads rapidly and harms its new environment, it becomes an invasive species. These organisms disrupt ecosystems by outcompeting native species, which are the plants and animals that naturally live in an area. Human activities such as international trade, travel, and the pet industry frequently transport species across continents and oceans, often with devastating ecological consequences.
Invasive species succeed in their new environments because they lack natural predators and competitors. In their original habitats, these organisms face many challenges that keep their populations in check. However, when humans introduce them to new locations, they often find abundant resources and few threats. This allows invasive species to reproduce quickly and spread throughout the ecosystem. They consume food that native species need, occupy critical habitats, and sometimes directly prey upon or infect native organisms. This intense competition often results in declining populations of native species.
The Burmese python provides a clear example of how an invasive species disrupts an ecosystem. These large snakes, native to Southeast Asia, were brought to Florida as pets. When owners released them into the wild, the pythons thrived in the warm, wet conditions of the Everglades. With no natural predators in Florida, python populations exploded. Scientists have documented dramatic declines in native mammal populations, including raccoons, opossums, and rabbits. Some species have decreased by more than 90 percent in areas with high python populations. This demonstrates how a single invasive species can devastate multiple native populations.
Invasive species also trigger cascading effects throughout food webs. A food web shows how energy and nutrients flow through an ecosystem as organisms eat and are eaten by other organisms. When an invasive species removes or reduces one population, the effects ripple through the entire web. In the Everglades, as pythons consume native mammals, predators that depend on those mammals for food also suffer. Birds of prey like hawks and owls have fewer prey animals to hunt. This chain reaction affects organisms at multiple levels of the food web, fundamentally changing the ecosystem's structure.
Zebra mussels illustrate another way invasive species harm ecosystems. These small shellfish, native to Eastern Europe, arrived in North American waters through ballast water discharged from ships. Zebra mussels filter enormous amounts of water as they feed, removing microscopic plants and animals called plankton. Native fish and other organisms that depend on plankton for food face starvation. The mussels also attach to surfaces in huge numbers, clogging water pipes and covering native mussels until they cannot feed or breathe. This demonstrates how invasive species reduce biodiversity, which is the variety of different species living in an ecosystem.
The loss of biodiversity weakens ecosystems and makes them less resilient to environmental changes. Each species plays a specific role in its ecosystem, contributing to processes like nutrient cycling, pollination, and pest control. When invasive species eliminate native species, these important functions may be lost or disrupted. Ecosystems with high biodiversity can better withstand disturbances like droughts, diseases, or climate changes because multiple species can perform similar roles. However, when invasive species reduce the number of native species, the entire ecosystem becomes more vulnerable to collapse.
Preventing and controlling invasive species requires human action and awareness. People can help by never releasing pets or aquarium plants into the wild, cleaning boats and equipment when moving between water bodies, and reporting sightings of invasive species to local authorities. Scientists and resource managers work to remove invasive species and restore native populations, but prevention remains the most effective strategy. Understanding how introduced species disrupt ecosystems helps us recognize our responsibility to protect biodiversity and maintain healthy, balanced ecosystems.
Interesting Fact: A single zebra mussel can filter one liter of water per day, and a large colony can filter all the water in a small lake in just a few weeks, removing the plankton base of the entire food web.
What is an invasive species?
Any animal that lives in waterAn introduced species that spreads rapidly and harms its new environmentA species that only eats plantsAn animal that migrates seasonally
Why do invasive species succeed in new environments?
They are larger than native speciesThey can survive without waterThey lack natural predators and competitorsThey only eat non-living things
According to the passage, what does the term 'competition' mean in an ecosystem?
Animals racing to see who is fastestThe struggle between organisms for limited resourcesPlants growing taller than each otherPredators hunting prey
What does 'biodiversity' refer to?
The number of trees in a forestThe amount of water in an ecosystemThe variety of different species living in an ecosystemThe size of animal populations
How did Burmese pythons arrive in the Florida Everglades?
They migrated naturally from AsiaThey were brought as pets and released by ownersThey swam across the oceanThey evolved in Florida
What effect have Burmese pythons had on native mammal populations in the Everglades?
Mammal populations have increasedNo change has occurredSome species have decreased by more than 90 percentMammals have learned to avoid pythons
How do zebra mussels harm aquatic ecosystems?
They produce toxic chemicalsThey filter out plankton that native species need for foodThey eat only large fishThey make the water too warm
What are cascading effects in a food web?
When water flows through an ecosystemWhen animals migrate to new areasA series of changes that spread through an ecosystem when one part is disruptedWhen plants grow in a specific pattern
True or False: Ecosystems with high biodiversity are more resilient to environmental changes.
TrueFalse
True or False: Invasive species always have natural predators in their new environments.
