--- title: "Toxins in Food Chains and Organisms Changing Habitats" description: "Explain how organisms affect and are affected by their environment, including the bioaccumulation of toxic materials (e.g. pesticides, heavy metals) through food chains" canonical: https://lightmysky.com/learn/science/toxins-in-food-chains-and-organisms-changing-habitats-mt_YvCgDM0Scg source: https://lightmysky.com/learn/science/toxins-in-food-chains-and-organisms-changing-habitats-mt_YvCgDM0Scg.md retrieved: 2026-09-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Toxins in Food Chains and Organisms Changing Habitats Explain how organisms affect and are affected by their environment, including the bioaccumulation of toxic materials (e.g. pesticides, heavy metals) through food chains Subject: Science · Area: Ecosystems & Habitats · Ages 12 to 13 Page: https://lightmysky.com/learn/science/toxins-in-food-chains-and-organisms-changing-habitats-mt_YvCgDM0Scg ## Ready when they can - Defines bioaccumulation and explains why toxins increase in concentration higher up the food chain - Gives a real example of bioaccumulation (e.g. DDT in peregrine falcons, mercury in tuna) - Explains how organisms can change their habitat (e.g. earthworms aerating soil, beavers creating wetlands) - Discusses why top predators are most at risk from bioaccumulation ## Lesson: How Toxins Build Up in Food Chains You already know that a food web connects every living thing to what it eats and what eats it. That connection goes both ways: living things change their surroundings, and their surroundings change them. One powerful example of being changed by the environment is bioaccumulation, when a toxin like a pesticide or heavy metal builds up inside a body faster than it can leave. Here is why bioaccumulation gets worse up a food chain. A small toxin dose lands on a plant or in the water. A tiny animal absorbs a bit of it. A bigger animal eats hundreds of those tiny animals, so it collects all of their toxin doses at once. An even bigger predator eats many of those animals, and collects even more. At each step, the toxin does not disappear, it just moves into a smaller number of bodies and piles up. *(drawing: Each step up the food chain, the toxin amount inside one body grows, even though no new toxin was added to the water.)* **Example.** In the 1950s, farmers sprayed the pesticide DDT on crops. Rain carried tiny traces into rivers, where fish absorbed it from the water and their food. Peregrine falcons ate contaminated fish and birds their whole lives, so DDT built up heavily in their bodies. It thinned their eggshells so much that many eggs cracked before hatching, and falcon numbers crashed. Falcons sit at the top of their food chain, so they carried the heaviest toxin load of any animal in it. Living things do not just absorb what is around them, they reshape it too. Earthworms tunnel through soil, letting air and water reach plant roots. Beavers cut down trees to build dams, turning a flowing stream into a still wetland that new plants, fish, and birds move into. Both toxins and habitat changes show the same idea: an organism and its environment are always shaping each other. **Recap.** Toxins build up more at each step of a food chain, so top predators carry the heaviest load, while organisms can also reshape the habitats they live in. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Food Webs & Interdependence](https://lightmysky.com/learn/science/food-webs-and-interdependence-mt_URTJbS3hhs) ## Opens up - [Biodiversity & Resilience](https://lightmysky.com/learn/science/biodiversity-and-resilience-mt_xSs0xAd6i1)