Toxins in Food Chains and Organisms Changing Habitats · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
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Pollutants and Habitat Change

Science · Ecosystems & Habitats · ages 12-13
Name ______________________   Date ____________

  1. Which action changes water flow and can create wetland habitat?

    • A beaver builds a dam, slowing the stream and flooding nearby land
    • A rabbit crosses a field beside a stream
    • A bird flies over a stream while the water keeps following its usual path

  2. What does bioaccumulation mean?

    • A substance breaks down within an organism faster than any new amount can enter it
    • A substance spreads evenly between organisms until all have the same concentration
    • A substance builds up within an organism because intake is faster than removal

  3. A pollutant that biomagnifies can reach a higher concentration in top predators than in their prey.

    Circle one:   True   False

  4. How did DDT use contribute to peregrine falcon population declines?

    • Contaminated prey reduced the falcons' food supply but did not affect their eggshells
    • Contaminated prey exposed falcons to DDT; DDE thinned shells, so more eggs broke
    • Contaminated prey made shells thicker, so chicks could no longer break out of their eggs when hatching

  5. A large fish contains more toxin in total than a small fish. Does this alone prove that the large fish has a higher toxin concentration?

    • Yes. More toxin in total means a higher concentration
    • No. Concentration compares toxin per gram of tissue, not total amount alone
    • Yes. Knowing which fish is larger removes the need to compare toxin per gram of tissue

  6. In a model, a big fish starts with zero toxin units. It eats 5 small fish containing 10 units each and retains all their toxin without losing any. How many toxin units does it then contain?

    Answer: ______________

  7. A beaver dam floods part of a valley and creates a wetland. Which is a possible effect on other species?

    • Some wetland species gain habitat while some land species lose habitat
    • Only wetland species can gain or lose habitat
    • All species using the flooded land gain habitat because the dam provides more water nearby

  8. Mia says every pollutant builds up in top predators, which must suffer most harm. One pollutant breaks down quickly and leaves bodies faster than it enters. Which explanation challenges both parts of her claim?

    • Many meals guarantee build-up; a predator's feeding position also determines the harm it suffers
    • Rapid removal prevents exposure; sensitivity matters only if a pollutant never enters the body
    • Removal can prevent build-up, and sensitivity affects how much harm a pollutant causes
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Pollutants and Habitat Change W1-mt_YvCgDM0Scg-s1

  1. A beaver builds a dam, slowing the stream and flooding nearby land · A dam can slow water and flood nearby land. This changes habitat rather than only changing an animal's location.
  2. A substance builds up within an organism because intake is faster than removal · Bioaccumulation happens within an organism over time. Its stored amount can grow when intake is faster than removal.
  3. True · Biomagnification is an increase in concentration across feeding levels. Persistent pollutants retained from prey can reach high concentrations in predators.
  4. Contaminated prey exposed falcons to DDT; DDE thinned shells, so more eggs broke · Falcons ate contaminated birds. DDT and DDE could build up, and DDE disrupted eggshell formation. More eggs broke during nesting, reducing successful hatching.
  5. No. Concentration compares toxin per gram of tissue, not total amount alone · Total amount does not account for body size. Concentration compares the amount per gram of tissue, so a greater total alone does not prove a higher concentration.
  6. 50 · The initial amount is zero, and five doses of 10 units are retained. 5 × 10 = 50 units. This is a total amount, not a concentration.
  7. Some wetland species gain habitat while some land species lose habitat · Wetland species may gain suitable habitat. Species needing the unflooded land may lose habitat. A change does not have the same effect on every species.
  8. Removal can prevent build-up, and sensitivity affects how much harm a pollutant causes · The pollutant's rapid breakdown and removal mean build-up is not inevitable. Harm also depends on sensitivity, so feeding position alone does not tell us which organism suffers most.
Worksheet · LightMySky