Bioaccumulation and Biomagnification - AP Environmental Science

1. DDT was sprayed near wetlands decades ago. Today, a heron that eats fish has 9 ppm DDT in its fat tissue, while the fish it eats average 2 ppm. Which term best describes why the heron's concentration is higher than the fish's?
   Answer: Biomagnification, because DDT concentration increases at higher trophic levels. Bioaccumulation is the process of toxins accumulating in an organism over time, while biomagnification is the increase in toxin concentration from one trophic level to the next. Here, the heron (9 ppm DDT) has more than its fish prey (2 ppm) due to biomagnification, as it consumes multiple fish, amplifying the persistent DDT. Top predators like herons have the highest levels because toxins are transferred and concentrated through the food chain without significant breakdown. Choice A swaps the terms; choice C errs by saying DDT is quickly metabolized; and choice D claims tissues prevent storage, which is false.
2. A single largemouth bass in a reservoir is tested for mercury (methylmercury) each year. Its mercury concentration rises from 0.3 ppm at age 1 to 0.7 ppm at age 3 to 1.2 ppm at age 6, even though the water concentration stays very low and stable. Which process is best illustrated?
   Answer: Bioaccumulation within the bass over time as mercury is retained faster than it is eliminated. Bioaccumulation is the gradual accumulation of a substance like mercury in an individual organism's tissues over its lifetime, where the rate of intake exceeds elimination. Biomagnification involves the amplification of toxin concentrations across trophic levels in a food web, as higher-level consumers eat many lower-level organisms. This scenario shows a single bass with increasing mercury levels over years (0.3 ppm to 1.2 ppm) despite stable water concentrations, which exemplifies bioaccumulation as the fish retains mercury from its diet over time. Top predators often have high concentrations due to both processes, but here the focus is on one organism's buildup, not chain-wide amplification. Choice B misapplies biomagnification to a single organism over time rather than across levels. Choice C incorrectly states mercury decreases at higher levels, and choice D wrongly claims mercury is rapidly excreted, preventing buildup.
3. A marine scientist finds that mercury concentration in a seal is higher than in the fish it eats, and also finds that older seals have higher mercury than younger seals. Which choice correctly matches each observation to the appropriate process?
   Answer: Higher mercury in seals than fish = biomagnification; higher mercury in older seals than younger seals = bioaccumulation. Bioaccumulation is time-based buildup in one organism, like higher mercury in older seals, while biomagnification is trophic increase, like seals higher than fish. This matches the observations correctly. Top predators like seals have high via biomagnification, plus bioaccumulation over life. Choice A reverses terms; choice C equates both to biomagnification; and choice D to bioaccumulation.
4. Why do persistent organic pollutants like PCBs often biomagnify in food webs?
   Answer: They are lipophilic and resistant to degradation, so they accumulate in tissues and are passed to predators through consumption. Bioaccumulation leads to toxin storage in individuals, and biomagnification amplifies this up chains. Persistent organic pollutants like PCBs biomagnify because they are lipophilic and resistant to degradation, accumulating in fat tissues and passing to predators via consumption. Top predators have highest from cumulative transfer. Choice A says metabolized into more toxic, not typical; choice C claims dilution; and choice D mislabels as energy source.
5. A lake is contaminated with mercury from an upstream mine. Over time, mercury is converted to methylmercury and enters the food web. Measurements show: water = $0.02\ \mu g/L$, zooplankton = $0.2\ \mu g/g$, small fish = $1.5\ \mu g/g$, and largemouth bass = $6.0\ \mu g/g$. Which statement best describes what is happening and which organism is expected to have the highest concentration?
   Answer: Biomagnification; the largemouth bass has the highest concentration because it is at the highest trophic level. Bioaccumulation is the buildup of substances within an individual organism over time, while biomagnification is the increase in concentration of substances as they move up trophic levels in a food chain. The data shows mercury concentration increasing from water (0.02 μg/L) to zooplankton (0.2 μg/g) to small fish (1.5 μg/g) to largemouth bass (6.0 μg/g), with each trophic level having higher concentrations than the one below it. This pattern clearly demonstrates biomagnification, where predators accumulate higher concentrations than their prey because they consume many contaminated organisms over their lifetime. The largemouth bass, as the top predator in this chain, has the highest concentration at 6.0 μg/g. Choice A incorrectly identifies this as bioaccumulation and wrongly states water has the highest concentration. Choice C correctly identifies the bass as having the highest concentration but incorrectly calls the process bioaccumulation. Choice D incorrectly states zooplankton has the highest concentration when the data clearly shows the bass does.
6. PCBs are fat-soluble and resistant to breakdown. Which scenario best illustrates biomagnification rather than bioaccumulation?
   Answer: PCB concentration is higher in eagles than in the fish they eat. Bioaccumulation is toxin buildup in one organism over time, while biomagnification is the amplification across trophic levels. The scenario of higher PCBs in eagles than fish illustrates biomagnification, as eagles consume many fish, concentrating the persistent, fat-soluble PCBs. Top predators have highest levels due to this trophic transfer. Choice A shows bioaccumulation in one trout; choice C depicts environmental change, not either process; and choice D shows toxin removal, opposite of accumulation.
7. A pesticide containing DDT enters a marsh. Over several months, a single heron continues eating contaminated fish. Measurements show the DDT concentration in the heron's fat tissue rises from $2\ ppm$ to $9\ ppm$ even though the average DDT concentration in its fish prey stays about $1\ ppm$ during that time. Which choice best describes the process shown and the most likely reason the concentration increases?
   Answer: Bioaccumulation; DDT concentration increases within the heron over time because it is persistent and lipophilic, so intake exceeds elimination. Bioaccumulation is the gradual buildup of a toxin within an individual organism over its lifetime, typically from repeated exposure through diet or environment, where intake exceeds the rate of metabolism or excretion. Biomagnification differs by describing the amplification of toxin concentrations across successive trophic levels in a food chain, as predators ingest contaminated prey. In this case, the heron's DDT concentration in fat tissue increases from 2 ppm to 9 ppm over months while feeding on fish with a stable 1 ppm, illustrating bioaccumulation because the persistent, lipophilic nature of DDT causes it to accumulate in the heron's body faster than it is eliminated. Top predators often have the highest concentrations in biomagnification scenarios due to consuming many lower-level organisms, but here the focus is on temporal buildup within one organism, not across levels. Choice A wrongly labels it biomagnification while describing bioaccumulation mechanics. Choice C incorrectly assumes rising water concentrations drive biomagnification, despite constant fish levels, and choice D misapplies bioaccumulation to trophic level shifts that aren't occurring. Therefore, choice B correctly identifies bioaccumulation and explains the intake-elimination imbalance.
8. A lab study exposes two groups of mussels to the same low PCB concentration in seawater. Group 1 is sampled after 1 week; Group 2 is sampled after 6 months. Group 2 has much higher PCB levels in its tissues. Which best explains the difference?
   Answer: Bioaccumulation, because PCBs persist and build up in an organism's tissues with continued exposure. Bioaccumulation occurs when an organism absorbs a toxin faster than it can eliminate it, leading to higher internal concentrations over time. Biomagnification is the escalation of toxin levels across trophic levels as predators consume contaminated prey. In this lab, Group 2 mussels exposed longer (6 months) have higher PCB levels than Group 1 (1 week), showing bioaccumulation as PCBs persist and accumulate in tissues with prolonged exposure. Top predators in natural settings have the highest concentrations due to biomagnification, but here the focus is on time-based buildup in one species. Choice A misidentifies it as biomagnification without trophic shifts; choice C errs on PCB solubility; and choice D incorrectly states PCBs break down rapidly.
9. A contaminated stream supports this chain: algae → snails → crayfish → raccoons. If algae contain 0.01 ppm PCBs and crayfish contain 0.5 ppm PCBs, which is the best prediction for raccoons that eat crayfish regularly?
   Answer: Raccoons will likely have PCB concentrations higher than 0.5 ppm due to biomagnification. Bioaccumulation is within organisms, biomagnification across levels. Raccoons, eating crayfish (0.5 ppm PCBs), would likely exceed 0.5 ppm due to biomagnification amplifying in predators. Top predators have highest from chain concentration. Choice B claims dilution; choice C assumes same as algae; and choice D says fully metabolized, false.
10. A researcher is deciding whether a chemical is more likely to show biomagnification like DDT or not. Which property would most strongly suggest it will biomagnify?
    Answer: High persistence and high fat solubility (lipophilicity). Bioaccumulation and biomagnification are favored by persistence and lipophilicity, allowing storage and transfer up chains like DDT. This property suggests biomagnification potential. Top predators have highest due to amplification. Choice B favors non-accumulation; choice C rapid breakdown; and choice D mislabels as nutrient.
11. A scientist studies mercury in a river food web. If aquatic insect larvae contain $0.8\ \mu g/g$ methylmercury and small fish that eat them contain $3.2\ \mu g/g$, what methylmercury concentration is most likely in a predatory fish that eats many small fish over its lifetime?
    Answer: Greater than $3.2\ \mu g/g$, because biomagnification increases concentration at higher trophic levels. Biomagnification causes toxin concentrations to increase at each trophic level because predators consume many contaminated prey items and retain the toxins in their tissues. The data shows methylmercury increasing from 0.8 μg/g in insect larvae to 3.2 μg/g in small fish - a 4-fold increase. Following this pattern of biomagnification, the predatory fish that feeds on many small fish would be expected to have an even higher concentration than 3.2 μg/g. Mercury biomagnifies particularly well because it binds to proteins and is not easily eliminated from organisms. Choice A incorrectly suggests dilution at higher levels, which contradicts biomagnification. Choice B wrongly states concentrations are cut in half at each transfer. Choice C incorrectly assumes concentrations stay constant across trophic levels. Only choice D correctly recognizes that biomagnification will cause the predatory fish to have a concentration greater than its prey.
12. Two observations are made in the same ecosystem containing mercury: 1) An individual catfish sampled each month shows increasing mercury concentration in its muscle tissue over a year. 2) Across species, mercury concentration is lowest in algae and highest in birds that eat fish. Which pairing correctly identifies observation (1) and observation (2)?
    Answer: (1) Bioaccumulation; (2) Biomagnification Bioaccumulation and biomagnification are distinct but related processes involving toxin buildup in organisms. Observation 1 describes an individual catfish showing increasing mercury concentration over time - this is bioaccumulation, where a substance builds up within a single organism because absorption exceeds elimination. Observation 2 describes a pattern across different species at different trophic levels, with mercury lowest in algae (producers) and highest in fish-eating birds (top predators) - this is biomagnification, where concentrations increase at successive trophic levels. The correct pairing recognizes that observation 1 tracks changes within one organism (bioaccumulation) while observation 2 compares concentrations across trophic levels (biomagnification). Choices A and D incorrectly identify one or both processes. Choice C incorrectly identifies both as bioaccumulation, missing that the second observation involves multiple trophic levels.
13. A pesticide similar to DDT is found at 0.000002 ppm in water. In a nearby ecosystem, measured concentrations are: insects 0.02 ppm, frogs 0.2 ppm, snakes 1.0 ppm, hawks 5.0 ppm. Which statement is most accurate?
    Answer: This pattern indicates biomagnification, and hawks are expected to have the highest concentrations as apex predators. Bioaccumulation is individual buildup, biomagnification is trophic amplification. The increasing pesticide from water (0.000002 ppm) to hawks (5.0 ppm) indicates biomagnification, with hawks as apex having highest from consuming concentrated prey. Choice B wrongly expects highest in water; choice C denies food web movement; and choice D misdefines as within-organism.
14. A food web contains phytoplankton → anchovies → tuna → shark. If mercury concentration in anchovies averages 0.05 ppm and tuna average 0.4 ppm, which is the most reasonable expected mercury concentration in sharks, assuming typical biomagnification and similar diets over time?
    Answer: Much higher than 0.4 ppm, because mercury biomagnifies toward top trophic levels. Bioaccumulation is the net buildup of a toxin in an organism over its lifetime, while biomagnification amplifies concentrations up the food chain as higher predators consume many lower ones. Given anchovies at 0.05 ppm and tuna at 0.4 ppm, sharks as top predators would likely exceed 0.4 ppm due to biomagnification of mercury through diet. Top predators have the highest levels because they integrate toxins from numerous prey, and mercury's persistence prevents easy elimination. Choice B wrongly suggests levels return to baseline; choice C claims faster excretion in sharks, which is false; and choice D denies mercury enters food webs, which it does.
15. PCBs are hydrophobic and stored in fatty tissues. A seal eats contaminated fish daily. Over several years, PCB levels in the seal's blubber rise steadily, even when short-term water concentrations fluctuate. This increase in PCB concentration within the seal over time is best described as:
    Answer: Bioaccumulation, because the pollutant builds up in an individual organism faster than it is eliminated. Bioaccumulation is the process where a substance builds up within an individual organism over time because it is absorbed faster than it can be eliminated or metabolized. The scenario describes PCB levels rising steadily in a single seal's blubber over several years, which is a classic example of bioaccumulation. PCBs are hydrophobic (water-repelling) and lipophilic (fat-loving), so they accumulate in fatty tissues like blubber. The seal absorbs PCBs from its contaminated fish diet, and because PCBs are persistent and not easily broken down, they accumulate in the seal's body over its lifetime. Choice B incorrectly identifies this as biomagnification, which would involve comparing concentrations across different trophic levels, not tracking one individual. Choice C wrongly suggests apex predators cannot store toxins. Choice D incorrectly defines bioaccumulation as requiring increases at every trophic level, which actually describes biomagnification.
16. A researcher claims: "Because mercury levels increased in an osprey compared with the fish it eats, the osprey is experiencing bioaccumulation." Which revision best corrects the claim?
    Answer: Replace bioaccumulation with biomagnification, because the comparison is across trophic levels. Bioaccumulation refers to the buildup of substances within an individual organism over time, while biomagnification describes the increase in concentration across different trophic levels in a food chain. The researcher's claim compares mercury levels between an osprey (predator) and the fish it eats (prey), which represents a comparison across trophic levels, not tracking changes within a single organism. This is biomagnification, not bioaccumulation - the osprey has higher mercury levels than its prey because it consumes many contaminated fish over its lifetime, accumulating mercury from all of them. The correct revision is to replace 'bioaccumulation' with 'biomagnification' to accurately describe this cross-trophic level comparison. Choice B incorrectly suggests only gases biomagnify, when heavy metals like mercury are classic examples of biomagnifying substances. Choice C incorrectly maintains the term bioaccumulation. Choice D incorrectly states toxins always decrease at higher levels, which contradicts the fundamental principle of biomagnification.
17. A pesticide similar to DDT is found in a terrestrial food chain: grass → grasshopper → frog → snake → hawk. If the grass contains 0.005 ppm of the pesticide and each consumer retains much of the pesticide in fatty tissue, which outcome is most likely?
    Answer: The hawk will have the highest concentration due to biomagnification across trophic levels. Biomagnification causes toxin concentrations to increase at each successive trophic level because predators consume many contaminated prey items and retain the toxins in their tissues. In this terrestrial food chain, if the grass contains 0.005 ppm of a DDT-like pesticide that is retained in fatty tissue, each subsequent trophic level will accumulate higher concentrations. The grasshopper eats many grass plants, the frog eats many grasshoppers, the snake eats many frogs, and the hawk eats many snakes - at each step, the predator accumulates all the pesticide from its many prey items. Since the pesticide is similar to DDT (fat-soluble and persistent), the hawk at the top of the food chain will have the highest concentration. Choice A incorrectly suggests dilution occurs at higher levels. Choice B wrongly states all levels will have identical concentrations. Choice D incorrectly claims only grass will contain the pesticide and that consumers can fully metabolize it.
18. A lake food web contains DDT. Concentrations are found to be: phytoplankton 0.01 ppm, zooplankton 0.08 ppm, smelt 0.6 ppm, and lake trout 4.8 ppm. Which process explains the increase from phytoplankton to lake trout, and why?
    Answer: Biomagnification, because predators consume many contaminated prey and DDT is not readily metabolized. Biomagnification is the process where toxin concentrations increase at each successive trophic level in a food chain, occurring when predators consume many contaminated prey items and cannot readily eliminate the toxin. The data shows DDT concentrations increasing dramatically: phytoplankton (0.01 ppm) → zooplankton (0.08 ppm) → smelt (0.6 ppm) → lake trout (4.8 ppm). This pattern clearly demonstrates biomagnification, with each trophic level showing higher concentrations than the one below it. DDT biomagnifies effectively because it is fat-soluble, persistent in the environment, and not readily metabolized by organisms, so it accumulates in fatty tissues. Choice A incorrectly states DDT becomes less concentrated at higher levels. Choice C wrongly identifies this as bioaccumulation and makes an irrelevant statement about producers. Choice D correctly identifies biomagnification but gives the wrong reason, stating DDT is rapidly broken down when actually it persists.
19. A river has a low but constant methylmercury concentration. Over several months, the mercury level inside mayfly larvae steadily increases even though the larvae remain at the same trophic level and eat the same type of algae. What process is this?
    Answer: Bioaccumulation, because mercury builds up within an organism over time. Bioaccumulation refers to the increasing concentration of a toxin in an individual organism over time due to ongoing exposure. Biomagnification describes toxin amplification across trophic levels. The mayfly larvae show steadily increasing mercury despite stable diet and trophic level, illustrating bioaccumulation from continuous intake exceeding elimination. In broader contexts, top predators have high concentrations via biomagnification, but this focuses on time within one level. Choice A misapplies biomagnification to non-predators; choice C wrongly states highest in producers; and choice D denies food-based entry, which occurs.
20. A student says: "Because mercury biomagnifies, the concentration in each organism must increase every day." Which choice best evaluates this claim?
    Answer: Incorrect; daily increases within an individual describe bioaccumulation, while biomagnification refers to higher concentrations at higher trophic levels. Bioaccumulation describes toxin buildup within an individual over time, like daily increases, while biomagnification is across trophic levels, not time-based in one organism. The student's claim is incorrect; daily increases are bioaccumulation, and biomagnification involves higher concentrations in predators. Top predators have high levels from chain amplification. Choice A misdefines biomagnification; choice C swaps with bioaccumulation; and choice D denies accumulation, which occurs.

Start this quiz