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Human Impacts: Overexploitation — Reading Comprehension

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MS-LS2-4
MS-LS2-5

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This middle school science passage aligns with NGSS standards MS-LS2-4 and MS-LS2-5, focusing on human impacts through overexploitation of wild species. Students will learn how practices such as overfishing and overhunting have led to population declines, species extinctions, and disrupted ecosystems. Real-world examples like the collapse of the Atlantic cod fishery, the extinction of the passenger pigeon, and threats to elephants and rhinos from illegal trade are explored. The passage also covers the concept of bycatch, bushmeat hunting, and introduces sustainable harvesting principles and fisheries management as solutions. Activities include a glossary, reading comprehension questions, writing prompts, and graphic organizers. Audio integration is available for accessibility. This comprehensive resource builds scientific literacy and supports key Next Generation Science Standards. Keywords: overexploitation, overfishing, biodiversity, wildlife trade, sustainable harvesting, ecosystem management.

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Close-up of fresh sardines on ice at a seafood market, highlighting freshness and quality. — One of the clearest examples of overexploitation is overfishing. Image by energepic.com / Pexels.

Overexploitation is a major threat to global biodiversity, affecting ecosystems and the species within them. Overexploitation happens when humans remove wild plants or animals from their environments faster than those populations can naturally recover. This causes population declines, disrupts food webs, and can even lead to extinction. Scientists have documented many cases where unsustainable harvesting has changed entire ecosystems and reduced species diversity.

Mechanisms and Examples of Overexploitation

One of the clearest examples of overexploitation is overfishing. When fish are caught faster than they can reproduce, their populations shrink dramatically. For instance, in the northwest Atlantic Ocean, commercial fishing led to a 99% drop in Atlantic cod populations by the early 1990s, causing the fishery to collapse. This not only affected the cod but also disrupted the entire marine ecosystem, as cod are top predators. Overhunting has also caused major losses. The passenger pigeon, once the most numerous bird in North America, was driven to extinction by hunting and habitat loss by 1914. Similarly, the dodo, a bird native to Mauritius, was wiped out in less than a century after humans arrived.

Illegal Wildlife Trade and Bycatch

Illegal wildlife trade is another form of overexploitation. Poaching for ivory and rhino horn has pushed species like African elephants and rhinos toward extinction. The illegal trade in exotic pets and animal parts threatens hundreds of species worldwide. Additionally, bycatch—when non-target species like turtles, dolphins, or seabirds are caught unintentionally—causes millions of animal deaths each year. In some regions, bushmeat hunting for wild animal meat has severely reduced populations of primates and other mammals, disturbing ecological balance and endangering species.

Sustainable Harvesting and Solutions

Scientists and resource managers use the principle of sustainable harvesting to combat overexploitation. This means taking fewer individuals than the population can naturally replace each year. Fisheries managers may set catch limits, protect breeding areas, and monitor fish populations using data such as catch rates and population models. In some areas, community-based management and international agreements help enforce laws and reduce illegal trade. These efforts aim to balance human needs with the health of wild populations and ecosystems. Success depends on scientific research, government regulation, and cooperation among countries and communities.

Overexploitation shows how human activities can disrupt natural systems and reduce biodiversity. By understanding the causes and effects of overexploitation, people can make choices that support conservation, sustainable use, and the long-term health of our planet.

Interesting Fact:
The last wild passenger pigeon was seen in 1901, and the very last individual, named Martha, died in captivity in 1914.

What is overexploitation?

Removing wild plants or animals faster than they can recoverProtecting wild species using lawsBreeding animals in captivityPlanting more trees in forests

Which animal experienced a 99% population drop due to overfishing?

Atlantic codPassenger pigeonAfrican elephantDodo

What does the term 'bycatch' mean in the passage?

Catching only target fish speciesAnimals caught unintentionally while fishingFish caught illegallyAnimals bred in captivity

What is an example of an animal that went extinct because of overhunting?

RhinoAtlantic codPassenger pigeonSea turtle

What is the main purpose of sustainable harvesting?

To increase the variety of fish caughtTo take fewer individuals than the population can replaceTo catch as many animals as possibleTo introduce new species to an ecosystem

What is one effect of illegal wildlife trade?

Increased animal populationsThreats to species like elephants and rhinosMore biodiversity in forestsRestoration of extinct animals

Why is overfishing harmful to ecosystems?

It only affects one speciesIt disrupts food webs and harms other speciesIt helps fish reproduce fasterIt increases the number of predators

If a country wants to reduce overexploitation, which action would help most?

Setting catch limits and protecting breeding areasAllowing unlimited huntingIgnoring illegal tradeRemoving all laws about fishing

True or False: Bycatch only affects fish populations.

TrueFalse

True or False: The last wild passenger pigeon was seen in 1901.

TrueFalse