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1. four / 4

Question: Focused on a total of 1…………. different age groups of ants,

Keywords:

– Focused on

– different age groups = age ranges

– of ants = on ants

Explain: In paragraph 3, it is stated that “Giraldo focused on ants at four age ranges”, so the answer must be “four/4”.

2. young

Question: how well ants looked after their 2…………..

Keywords:

– how well ants = how well the ants

– looked after = took care of

Explain: The first sentence of paragraph 4 states that “Giraldo watched how well the ants took care of the young of the colony”

3. food

Question: their ability to locate 3…………… using a scent trail

Keywords:

– Locate = mark a trail to

– using a scent trail = followed the telltale scent

Explain: In the second sentence of paragraph 4, the author mentions how ants “followed the telltale scent that the insects usually leave to mark a trail to food”. This means that she studied ants‟ ability to locate food using a scent trail.

4. light

Question: the effect that 4……………. had on them

Keywords: The effect = responded to

Explain: In the same paragraph, we are told that “she tested how ants responded to light”, meaning that she tested the effect of “light” on ants

5. aggressively

Question: how 5…………….. they attacked prey

Keywords: Attacked, prey = the poor fruit fly

Explain: Still in paragraph 4, Giraldo compared the way old and young ants attacked their prey and found that the old ones attacked “just as aggressively” as the young ones did. In other words, she studied how aggressively they attacked the prey.

6. location

Question: comparison between age and the 6……………… of dying cells in the brains of ants

Keywords: comparison between = no major difference age of dying cells

Explain: In paragraph 5, we know that Giraldo didn’t find any major difference in age and the location of dying brain cells between 20-day-old and 95-day-old ants. This suggests that she compared between the age and location of dying cells.

7. neurons

Question: condition of synaptic complexes (areas in which 7…………… meet) in the brain’s ‘mushroom bodies’

Keywords:

– in the brain’s ‘mushroom bodies’ = in their brains called mushroom bodies,

– areas in which = where

– Meet = come together.

– synaptic complexes

Explain: In paragraph 5, it is stated that synaptic complexes are “regions where neurons come together”

8. chemicals

Question: level of two 8………….. in the brain associated with ageing

Keywords:

– Level of two = levels of either serotonin or dopamine-brain

– associated with ageing = coincides with aging

Explain: Still in paragraph 5, we are told that Giraldo studied the level of serotonin and dopamine, which are two “brain chemicals whose decline often coincides with aging”. This implies that they are associated with aging. Thus, the answer is “chemicals”.

9. FALSE

Question: Pheidole dentata ants are the only known animals which remain active for almost their whole lives.

Keywords:

– Remain active = doesn’t seem to show any signs of aging = stay fit

– or almost their whole lives = for nearly their entire lives.

Explain: In paragraph 2, the author mentions naked mole rats as an age-defying animal: they stay fit for nearly their entire lives and they can reproduce even when old. It can be said that they remain active for almost their whole life. Thus, Pheidole dentata ants are not the only animal with this feature.

10. TRUE

Question: Ysabel Giraldo was the first person to study Pheidole dentata ants using precise data about the insects’ ages.

Keywords: precise data about the insects’ ages = their exact ages.

Explain: It is stated in paragraph 3: “Unlike all previous studies, which only estimated how old the ants were…she knew their exact ages”. This means that she was the first person to use the ants’ exact ages in her studies.

11. FALSE

Question: The ants in Giraldo’s experiments behaved as she had predicted that they would.

Keywords:

Behaved = perform

Predicted = expected

Explain:  It is stated in paragraph 4 that “Giraldo expected the older ants to perform poorly…but the elderly ants were all good caretakers and trail-followers”. This implies that the elderly ants behaved differently from what she expected (predicted). She thought that they would perform badly, but they performed well.

12. NOT GIVEN

Question: The recent studies of bees used different methods of measuring age-related decline.

Keywords:

– age-related decline.

– The recent studies of bees = the results of recent bee studies

Explain: With regard to recent studies of bees, the author only mentions in paragraph 6 that the results about age-related decline were mixed: some showed it while some didn’t. However, there is nothing said about the methods used, so this statement is NOT GIVEN.

13. TRUE

Question: Pheidole dentata ants kept in laboratory conditions tend to live longer lives.

Keywords: Pheidole dentata laboratory, live, longer

Explain: The first sentence of paragraph 3 reveals that in the lab, Pheidole dentata ants typically live for around 140 days. Later, in paragraph 7, it is said that “out in the wild, the ants probably don’t live for a full 140 days”. This clearly means that the ants tend to live longer in laboratory conditions. The statement is therefore TRUE.

Passage 1

The secret of staying young

Pheidole dentata, a native ant of the south-eastern U.S., isn’t immortal. But scientists have found that it doesn’t seem to show any signs of aging (Q9). Old workers ants can do everything just as well as the youngsters, and their brains appear just as sharp. ‘We get a picture that these ants really don’t decline,’ says Ysabel Giraldo, who studies the ants for her doctoral thesis at Boston University.

Such age-defying feats are rare in the animal kingdom. Naked mole rats can live for almost 30 years and stay fit for nearly their entire lives (Q9). They can still reproduce even when old, and they never get cancer. But the vast majority of animals deteriorate with age just like people do. Like the naked mole rat, ants are social creatures that usually live in highly organised colonies. ‘It’s this social complexity that makes P. dentata useful for studying aging in people,’ says Giraldo, now at the California Institute of Technology. Humans are also highly social, a trait that has been connected to healthier aging. By contrast, most animal studies of aging use mice, worms or fruit flies, which all lead much more isolated lives.

In the lab, P. dentata worker ants typically live for around 140 days. Giraldo focused on ants at four age ranges: 20 to 22 days, 45 to 47 days, 95 to 97 days and 120 to 122 days (Q1). Unlike all previous studies, which only estimated how old the ants were, her work tracked the ants from the time the pupae became adults, so she knew their exact ages (Q10). Then she put them through a range of tests.

Giraldo watched how well the ants took care of the young of the colony, recording how often each ant attended to, carried and fed them (Q2). She compared how well 20-day-old and 95-day-old ants followed the telltale scent that the insects usually leave to mark a trail to food (Q3). She tested how ants responded to light and also measured how active they were by counting how often ants in a small dish walked across a line. And she experimented with how ants react to live prey: a tethered fruit fly. Giraldo expected the older ants to perform poorly in all these tasks. But the elderly insects were all good caretakers and trail-followers – the 95-day-old ants could track the scent even longer than their younger counterparts (Q11). They all responded do light well, and the older ants were more active (Q4). And when it came to reacting to prey, the older ants attacked the poor fruit fly just as aggressively as the young ones did, flaring their mandibles or pulling at the fly’s legs (Q5).

Then Giraldo compared the brains of 20-day-old and 95-day-ole ants, identifying any cells that were close to death. She saw no major differences with age, nor was there any difference in the location of the dying cells, showing that age didn’t seem to affect specific brain functions (Q6). Ants and other insects have structures in their brains called mushroom bodies, which are important for processing information, learning and memory. She also wanted to see if aging affects the density of synaptic complexes within these structures – regions where neurons come together (Q7). Again, the answer was no. What was more, he old ants didn’t experience any drop in the levels of either serotonin or dopamine – brain chemicals whose decline often coincides with aging (Q8). In humans, for example, a decrease in serotonin has been linked to Alzheimer’s disease.

‘This is the first time anyone has looked at both behavioral and neural changes in these ants so thoroughly,’ says Giraldo, who recently published the findings in the Proceeding of the Royal Society B. Scientists have looked at some similar aspects in bees, but the results of recent bee studies were mixed – some studies showed age-related declines, which biologists call senescence, and others didn’t (Q12). ‘For now, the study raises more questions than it answers,’ Giraldo says, ‘including how P. dentata stays in such good shape.’

Also, if the ants don’t deteriorate with age, why do they die at all? Out in the wild, the ants probably don’t live for a full 140 days thanks to predators, disease and just being in an environment that’s much harsher than the comforts of the lab (Q13). ‘The lucky ants that do live into old age may suffer a steep decline just before dying,’ Giraldo says, but she can’t say for sure because her study wasn’t designed to follow an ant’s final moments.

‘It will be important to extend these findings to other species of social insects,’ says Gene E. Robinson, an entomologist at the University of Illinois at Urbana-Champaign. This ant might be unique, or it might represent a broader pattern among other social bugs with possible clues to the science of aging in larger animals. Either way, it seems that for these ants, age really doesn’t matter.

14. B

Question: a reference to how quickly animal species can die out

Keywords:

– die out = are becoming extinct

– how quickly = Colossal numbers of species + are increasingly threatened

Explain: It is mentioned in paragraph B that “some of these collapses have been sudden, dramatic and unexpected”, with “these collapses” referring to the extinction of animals. The word “sudden” is a synonym for quickly, so the sentence suggests that some animals may become extinct, or die out, quickly.

15. E

Question: reasons why it is preferable to study animals in captivity rather than in the wild

Keywords:

– Reasons: less risk + fewer variables

– study animals in captivity =undertake research on animals in zoos

Explain: The term “animals in captivity” is another way of saying “animals in zoos”. The role of zoos in animal research is mentioned in paragraph E: “Being able to undertake research on animals in zoos where there is less risk and fewer variables means real changes can be effected on wild populations”. So, zoos have many advantages for studying how animals live, act and react. Thus, – The answer is paragraph E.

16. C

Question: mention of two ways of learning about animals other than visiting them in zoos

Keywords:

– two ways of learning about animals: television documentaries + natural history specimens

– visiting them in zoos = seeing a living creature

– in the flesh, hearing it, smelling it, watching what it does

Explain: Several ways of learning about animals are mentioned in paragraph C: zoos, television documentaries, and museums. Thus, this paragraph shows two ways of learning about animals other than visiting them in zoos.

17. A

Question: reasons why animals in zoos may be healthier than those in the wild

Keywords: Reasons: get a varied and high-quality diet with all the supplements required + any illnesses they might have will be treated

Explain: The first sentence of the passage is: “it is perfectly possible for many species of animals living in zoos or wildlife parks to have a quality of life as high as, or higher than, in the wild”. Higher quality of life implies that zoo animals may be healthier than those in the wild. The author then goes on to discuss various reasons why zoos are healthy places for animals, including a good diet, treatment of illnesses and a safe environment from predators.

18. TRUE

Question: An animal is likely to live longer in a zoo than in the wild.

Keywords: live longer = have a greater life expectancy

Explain: As we know from question 17, the comparison between animals living in zoos and in the wild is in paragraph A. “The average captive animal will have a greater life expectancy compared with its wild counterpart”. The captive animal refers to animals in zoos. Its wild counterpart refers to animals of the same species in the wild.

19. TRUE

Question: There are some species in zoos which can no longer be found in the wild.

Keywords:

– can no longer be found in the wild = only exist in captivity

– some species in zoos = many of these living in zoos

Explain: It is stated in paragraph B that “A good number of species only exist in captivity”, implying that these species cannot be found in the wild. The statement is TRUE.

20. NOT GIVEN

Question: Improvements in the quality of TV wildlife documentaries have resulted in increased numbers of zoo visitors.

Keywords: improvements, TV, wildlife, documentaries, increased, numbers, zoo visitors

Explain: With regard to TV documentaries, the author only mentions (in paragraph C) that “television documentaries are becoming ever more detailed and impressive” but there is no relation between this and zoo visitor numbers. This information is NOT GIVEN.

21. FALSE

Question: Zoos have always excelled at transmitting information about animals to the public.

Keywords: transmitting information about animals to the public = communication and outreach work

Explain: Paragraph D states that zoos can “communicate information to visitors about the animals they are seeing and their place in the world”. In other words, zoos can transmit information about animals to the public. It is mentioned, however, that “this was an area where zoos used to be lacking”, implying that zoos were not good at this in the past. The statement is therefore FALSE.

22. NOT GIVEN

Question: Studying animals in zoos is less stressful for the animals than studying them in the wild.

Keywords: Studying animals in zoos = undertake research on animals in zoos

Explain: In comparison with studying animals in the wild, studying them in zoos is less risky and involves fewer variables. We only know that there is less risk for both the animals and the scientists themselves, but we do not know if studying animals in zoos is less stressful. There is no information regarding this.

23-24. B, D

Question: Which TWO of the following are stated about zoo staff in the text?

B   Some travel to overseas locations to join teams in zoos.

D   Some teach people who are involved with conservation projects

Keywords:

– travel to overseas locations = send their animal keepers abroad

– join teams in zoos = contribute their knowledge and skills to those working in zoos and reserves…

– Teach = educate

– people who are involved with conservation projects = conservation workers

Explain:

– It is stated in paragraph D that: “Many zoos also work directly to educate conservation workers in other countries” -> zoo staff can teach conservation workers, or people involved with conservation projects. So D is correct.

– “…or send their animal keepers abroad to contribute their knowledge and skills to those working in zoos and reserves”. This means that some animal keepers (a type of zoo staff) travel to overseas to help other zoo staff. So B is correct

25-26. B, E

Question: Which TWO of these beliefs about zoos does the winter mention in the text?

B   They can increase public awareness of environmental issues.

E   They can raise animals which can later be released into the wild.

Keywords:

– Raise public awareness of environmental issues = he need to be more environmentally conscious

– Increase = more

– public awareness of environmental issues.

– raise animals = can be bred up to

Explain:

– In paragraph B, it is stated that some animals have been reintroduced into the wild from zoos, or that wild populations have been increased by the introduction of captive bred animals. The term “reintroduce” means that animals will be raised in zoos before being released into the wild. So E is correct.

– Thus, the sentence can be paraphrased into: zoos can increase public awareness of environmental issues. B is correct.

Passage 2

Why zoos are good

Scientist David Hone makes the case for zoos

A

In my view, it is perfectly possible for many species of animals living in zoos or wildlife parks to have a quality of life as high as, or higher than, in the wild. Animals in good zoos get a varied and high-quality diet with all the supplements required, and any illnesses they might have will be treated (Q17). Their movement might be somewhat restricted, but they have a safe environment in which to live, and they are spared bullying and social ostracism by others of their kind. They do not suffer from the threat or stress of predators, or the irritation and pain of parasites or injuries. The average captive animal will have a greater life expectancy compared with its wild counterpart, and will not die of drought, of starvation or in the jaws of a predator (Q18). A lot of very nasty things happen to truly ‘wild’ animals that simply don’t happen in good zoos, and to view a life that is ‘free’ as one that is automatically ‘good’ is, I think, an error. Furthermore, zoos serve several key purposes.

B

Firstly, zoos aid conservation. Colossal numbers of species are becoming extinct across the world, and many more are increasingly threatened and therefore risk extinction (Q14). Moreover, some of these collapses have been sudden, dramatic and unexpected, or were simply discovered very late in the day. A species protected in captivity can be bred up to provide a reservoir population against a population crash or extinction in the wild (Q25 Q26). A good number of species only exist in captivity, with many of these living in zoos (Q19). Still more only exist in the wild because they have been reintroduced from zoos, or have wild populations that have been boosted by captive bred animals. Without these efforts there would be fewer species alive today. Although reintroduction successes are few and far between, the numbers are increasing, and the very fact that species have been saved or reintroduced as a result of captive breeding proves the value of such initiatives.

C

Zoos also provide education. Many children and adults, especially those in cities, will never see a wild animal beyond a fox or pigeon. While it is true that television documentaries are becoming ever more detailed and impressive (Q20), and many natural history specimens are on display in museums, there really is nothing to compare with seeing a living creature in the flesh, hearing it, smelling it, watching what it does and having the time to absorb details (Q16). That alone will bring a greater understanding and perspective to many, and hopefully give them a greater appreciation for wildlife, conservation efforts and how they can contribute.

D

In addition to this, there is also the education that can take place in zoos through signs, talks and presentations which directly communicate information to visitors about the animals they are seeing and their place in the world. This was an area where zoos used to be lacking, but they are now increasingly sophisticated in their communication and outreach work (Q21). Many zoos also work directly to educate conservation workers in other countries, or send their animal keepers abroad to contribute their knowledge and skills to those working in zoos and reserves (Q23 Q24), thereby helping to improve conditions and reintroductions all over the world.

E

Zoos also play a key role in research. If we are to save wild species and restore and repair ecosystems we need to know about how key species live, act and react. Being able to undertake research on animals in zoos where there is less risk and fewer variables means real changes can be effected on wild populations (Q15 Q22). Finding out about, for example, the oestrus cycle of an animal of its breeding rate helps us manage wild populations. Procedures such as capturing and moving at-risk or dangerous individuals are bolstered by knowledge gained in zoos about doses for anaesthetics, and by experience in handling and transporting animals. This can make a real difference to conservation efforts and to the reduction of human-animal conflicts, and can provide a knowledge base for helping with the increasing threats of habitat destruction and other problems.

F

In conclusion, considering the many ongoing global threats to the environment, it is hard for me to see zoos as anything other than essential to the long-term survival of numerous species. They are vital not just in terms of protecting animals, but as a means of learning about them to aid those still in the wild, as well as educating and informing the general population about these animals and their world so that they can assist or at least accept the need to be more environmentally conscious (Q25 Q26). Without them, the world would be, and would increasingly become, a much poorer place.

27. FALSE

Question: Rochman and her colleagues were the first people to research the problem of marine debris.

Keywords:

– Rochman and her colleagues

– the problem of marine debris = the state of marine debris

Explain: Paragraph 2 mentions that “plenty of studies have sounded alarm bells about the state of marine debris” and that “Rochman and her colleagues set out to determine how many of those perceived risks are real”. This implies that there has been other research on marine debris before Rochman and her colleagues, and they want to examine these previous studies. Thus, the statement is FALSE.

28. NOT GIVEN

Question: The creatures most in danger from ocean trash are certain seabirds.

Keywords: certain seabirds

Explain: Paragraph 3 only mentions that “certain seabirds eat plastic bags” but we do not find any information about them being the most in danger. Scientists have only “speculated” about wider effects: “There wasn’t a lot of information”. Thus it is NOT GIVEN.

29. FALSE

Question: Combining work with play may be the best way for children to learn.

Keywords:

– Combining work with play = this mid-point between play and work

– be the best way for children to learn = create robust opportunities for playful learning.

Explain: Joan Goodman (paragraph 7) suggested that “hybrid forms of work and play can provide optimal contexts for learning”. This means that such hybrid, or combination, could be the best way for children to learn.

30. TRUE

Question: Rochman analysed papers on the different kinds of danger caused by ocean trash.

Keywords:

– different kinds of danger = 366 perceived threats

– analysed = examined

– ocean trash = marine debris

Explain: Paragraph 4 states that “Rochman and her colleagues examined more than a hundred papers on the impacts of marine debris” and found 366 perceived threats. It can be understood that these papers focused on various kinds of danger (threat) caused by ocean trash (marine debris).

31. FALSE

Question: Most of the research analysed by Rochman and her colleagues was badly designed.

Keywords:

– was badly designed = weaknesses in design

– research = studies

Explain: In paragraph 5, the author states that “In 83 percent of cases, the perceived dangers of ocean trash were proven true”. So, there is obviously no reason to think that this research was badly designed if the findings were proven true, “In the remaining cases, the working group found the studies had weaknesses in design”. Therefore, only 17 percent of the cases analysed were badly designed. So, most of the cases were well designed. The statement is FALSE.

32. TRUE

Question: One study examined by Rochman was expecting to find that mussels were harmed by eating plastic.

Keywords:

– One study = only one well-designed study

– was expecting to find = failed to find

Explain: The information about mussels (a type of shellfish) can be found in paragraph 6 The study examined mussels that eat plastic, “but it didn’t seem to stress out the shellfish”. This means that the plastic didn’t seem to have any harmful effect on the mussels. Rochman said this study “failed to find the effect it was looking for”, so clearly it was looking for some effect of the plastic on the mussels.

33. NOT GIVEN

Question: Some mussels choose to eat plastic in preference to their natural diet.

Keywords: some, mussels, choose, eat, plastic, preference, natural, diet

Explain: Paragraph 7 only states that the “mussels may be fine eating trash”. It does not mean they prefer trash to their natural diet. The statement is NOT GIVEN.

34. large

Question: bits of debris that were 34…………… (harmful to animals)

Keywords:

– bits of debris = pieces of debris

– harmful to animals = injuring themselves.

Explain: Rochman found (paragraph 8) that “most of the dangers also involved large pieces of debris” that can cause severe injuries to animals. So the answer is “large”.

35. microplastic

Question: There was little research into 35…………… e.g. from synthetic fibres

Keywords:

– There was little research into = found little research on

– From synthetic fibres = fibers shed by synthetic clothing

Explain: Paragraph 9 mentions that “Rochman’s group found little research on the effects of these tiny bits”, with “tiny bits” referring to microplastic. So the answer is “microplastic”.

36. populations

Question: most of them focused on individual animals, not entire 36…………….

Keywords:

– focused on = have looked at

– individual animals = individual animal

– entire = whole

– Not = rather than

Explain: The remaining questions refer to the drawbacks of the studies. According to paragraph 10: “Many studies have looked at how plastic affects an individual animal… rather than the whole populations”.

37. concentrations

Question: the 37……………. of plastic used in the lab did not always reflect those in the ocean

Keywords: in the lab, plastic, those in the ocean = what’s really in the ocean.

Explain: It is mentioned in paragraph 10 that “in the lab, scientists often use higher concentrations of plastic than what’s really in the ocean”. This means that the concentrations of plastic used in the lab was different from, and thus did not always correctly reflect, those in the ocean.

38. predators

Question: there was insufficient information on numbers of animals which could be affected the impact of a reduction in numbers on the 38…………… of that species The impact on the ecosystem

Keywords:

– there was insufficient information = None of that tells us

– numbers of animals which could be affected = how many birds or fish or sea turtles could die from plastic pollution

– the impact … on the = affects

– reduction in numbers = deaths in one species

– Of that species = that animal’s

Explain: Rochman said in paragraph 10 that no one can tell us “how deaths in one species could affect that animal’s predators”. Deaths in one species can be understood as a reduction in numbers of that species. Thus, there is insufficient information on how a reduction in numbers of a species can impact on their predators. The blank should be filled with “predators”.

39. disasters

Question: Rochman says more information is needed on the possible impact of future 39…………… (e.g. involving oil).

Keywords:

– more information is needed = need to be asking more ecologically relevant questions/ scientists don’t know exactly

– (e.g. involving oil) = such as a tanker accidentally spilling its whole cargo of oil

Explain: According to Rochman in paragraph11, we need to ask more “ecologically relevant questions”, such as how disasters will affect the environment before they actually happen. This means that more information related to disasters is needed. She also mentioned an oil spill as an example of the impact of future disasters which we need to know more about, by asking the right questions earlier. Hence, the answer is “disasters”.

40. A

Question: What would be the best title for this passage?

A   Assessing the threat of marine debris

Explain:

– The passage does not focus on who is to blame for marine debris, nor does it focus on any new solutions or international action, which are only briefly referred to in paragraph 12. In the final paragraph, Rochman refers to the importance of “clearing up…misconceptions” in order to know how serious the threat of marine debris really is. Therefore, it is important to interrogate “the existing scientific literature” to help ecologists to figure out “which problems really need addressing”.

– The entire passage concerns Rochman and her study on other prior research on marine debris. She assessed these studies to answer the question of whether the situation is as bad as they suggested. In other words, Rochman assessed the threat of marine debris mentioned by other researchers. A is the correct answer.

Passage 3

Chelsea Rochman, an ecologist at the University of California, Davis, has been trying to answer a dismal question: Is everything terrible, or are things just very, very bad?

Rochman is a member of the National Center for Ecological Analysis and Synthesis’s marine-debris working group, a collection of scientists who study, among other things, the growing problem of marine debris, also known as ocean trash. Plenty of studies have sounded alarm bells about the state of marine debris; in a recent paper published in the journal Ecology, Rochman and her colleagues set out to determine how many of those perceived risks are real (Q27).

Often, Rochman says, scientists will end a paper by speculating about the broader impacts of what they’ve found. For example, a study could show that certain seabirds eat plastic bags, and go on to warn that whole bird populations are at risk of dying out (Q28). ‘But the truth was that nobody had yet tested those perceived threats,’ Rochman says. ‘There wasn’t a lot of information.’ (Q29)

Rochman and her colleagues examined more than a hundred papers on the impacts of marine debris that were published through 2013. Within each paper, they asked what threats scientists had studied – 366 perceived threats in all – and what they’d actually found (Q30).

In 83 percent of cases, the perceived dangers of ocean trash were proven true. In the remaining cases, the working group found the studies had weaknesses in design and content which affected the validity of their conclusions – they lacked a control group, for example, or used faulty statistics (Q31).

Strikingly, Rochman says, only one well-designed study failed to find the effect it was looking for, an investigation of mussels ingesting microscopic bits. The plastic moved from the mussels’ stomachs to their bloodstreams, scientists found, and stayed there for weeks – but didn’t seem to stress out the shellfish (Q32).

While mussels may be fine eating trash, though, the analysis also gave a clearer picture of the many ways that ocean debris is bothersome.

Within the studies they looked at, most of the proven threats came from plastic debris, rather than other materials like metal or wood. Most of the dangers also involved large pieces of debris – animals getting entangled in trash, for example, or eating it and severely injuring themselves (Q34).

But a lot of ocean debris is ‘microplastic’, or pieces smaller than five millimeters. These may be ingredients used in cosmetics and toiletries, fibers shed by synthetic clothing in the wash, or eroded remnants of larger debris. Compared to the number of studies investigating large-scale debris, Rochman’s group found little research on the effects of these tiny bits (Q35). ‘There are a lot of open questions still for microplastic,’ Rochman says, though she notes that more papers on the subject have been published since 2013, the cutoff point for the group’s analysis.

There are also, she adds, a lot of open questions about the ways that ocean debris can lead to sea-creature death. Many studies have looked at how plastic affects an individual animal, or that animal’s tissues or cells, rather than whole populations (Q36). And in the lab, scientists often use higher concentrations of plastic than what’s really in the ocean (Q37). None of that tells us how many birds or fish or sea turtles could die from plastic pollution – or how deaths in one species could affect that animal’s predators, or the rest of the ecosystem (Q38).

‘We need to be asking more ecologically relevant questions,’ Rochman says. Usually, scientists don’t know exactly how disasters such as a tanker accidentally spilling its whole cargo of oil and polluting huge areas of the ocean will affect the environment until after they’ve happened (Q39). ‘We don’t ask the right questions early enough,’ she says. But if ecologists can understand how the slow-moving effect of ocean trash is damaging ecosystems, they might be able to prevent things from getting worse.

Asking the right questions can help policy makers, and the public, figure out where to focus their attention. The problems that look or sound most dramatic may not be the best places to start. For example, the name of the ‘Great Pacific Garbage Patch’ – a collection of marine debris in the northern Pacific Ocean – might conjure up a vast, floating trash island. In reality though, much of the debris is tiny or below the surface; a person could sail through the area without seeing any trash at all. A Dutch group called ‘The Ocean Cleanup’ is currently working on plans to put mechanical devices in the Pacific Garbage Patch and similar areas to suck up plastic. But a recent paper used simulations to show that strategically positioning the cleanup devices closer to shore would more effectively reduce pollution over the long term.

‘I think clearing up some of these misperceptions is really important,’ Rochman says. Among scientists as well as in the media, she says, ‘A lot of the images about strandings and entanglement and all of that cause the perception that plastic debris is killing everything in the ocean.’ Interrogating the existing scientific literature can help ecologists figure out which problems really need addressing, and which ones they’d be better off – like the mussels – absorbing and ignoring.

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