Invasive Species - IELTS Listening Answers & Explanations
From Cambridge IELTS 21 Academic Listening Test 3 · Part 4 · Questions 31–40
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Questions 31–40 Note Completion
Complete the notes below.
Write ONE WORD ONLY for each answer.
Invasive species
Definition: an animal or plant that causes harm to an environment after being introduced by humans
An invasive species can be a problem when it:
- eats native species.
- introduces a new 31.
- takes food from native species.
- threatens an entire 32.
How invasive species spread
- accidentally e.g. via people returning from their 33 or on cargo ships
- intentionally e.g. for pest control, or as 34.
Examples of invasive species
- Rhinella marina (toads)
- were introduced to Australia from Hawaii in 1935 to eat a type of insect that was damaging the 35 plantations.
- failed to solve the problem and became widespread in the north of Australia.
- are poisonous for any species that eats them and reduce the food available for native frogs.
- Japanese knotweed plants were popular among 19th-century gardeners in the UK.
- Rhododendron plants prevent 36 from reaching native plants.
- Grey squirrels from N. America reduce sources of food for the UK's native red squirrels and spread a 37 that kills red squirrels.
Tackling invasive species
- Monitoring helps us to understand the 38 of invasive species and the impact they have.
- Setting up a national 39 makes it easier to track them.
- Asking the public to 40 and report them helps with monitoring.
Answers & Explanations Summary
| # | Answer | Evidence | Explanation |
|---|---|---|---|
| Q31 | disease | First of all, invasive species may eat native species, or sometimes they may bring a disease with them, which native species have never faced before and therefore have no defences against | Excerpt/Transcript Explanation: The transcript explains that invasive species are dangerous because they can kill local animals by eating them or by carrying a sickness (disease) that the local animals cannot stop. Answer Explanation: The answer is an illness or sickness that makes animals or plants unhealthy. Reason For Correctness: The correct answer is 'disease' because the speaker lists it as one of the specific ways invasive species cause problems. When a new species arrives, it often carries germs or sicknesses that the local, native animals have never seen before. Because these native animals have no way to fight the sickness, it causes them great harm. This matches the point in the notes about introducing something new and harmful. |
| Q32 | ecosystem | Species invasions are one of the biggest causes of damage in an ecosystem, actually putting its survival at risk | Excerpt/Transcript Explanation: The transcript explains that when new species come into a place where they don't belong, they cause a lot of damage and can make it dangerous for the whole natural community to survive. Answer Explanation: The answer is a word for a biological community of interacting organisms and their physical environment. Reason For Correctness: The correct answer is 'ecosystem' because the transcript states that invasive species are a major cause of damage within these biological communities. It specifically mentions that species invasions can put the survival of an ecosystem at risk. In the context of the notes, 'putting its survival at risk' is synonymous with 'threatens'. |
| Q33 | holidays / holiday | This could be intentional, or it could be accidental, such as when people who've been on holiday in another country come back with, say, the seeds of plants on their clothes or shoes | Excerpt/Transcript Explanation: The transcript says that people who go on a vacation (holiday) might carry seeds back home on their clothing by mistake. Answer Explanation: The answer refers to a trip or vacation that someone takes in another country for fun. Reason For Correctness: The correct answer is holiday because the speaker explains that human activity is the biggest reason invasive species spread. This can happen by accident when people return from a trip (holiday) and unknowingly bring seeds on their clothes or shoes. The transcript specifically uses the phrase "been on holiday" to describe this accidental spread. |
| Q34 | pets | But sometimes humans deliberately move animals and plants around the world, for example to use them to control pests on farms, or to be pets | Excerpt/Transcript Explanation: The transcript explains that people sometimes move plants and animals to different parts of the world on purpose. They do this for specific reasons, such as helping farmers manage insects or because they want to keep the animals in their homes. Answer Explanation: The answer "pets" refers to animals that people keep at home for pleasure and companionship, rather than for work or food. Reason For Correctness: The correct answer is located in the section of the transcript discussing how humans intentionally move species to new places. It lists "pest control" as one reason and then mentions "pets" as another reason humans choose to bring animals into a new environment. Since the notes ask for a word describing why species are spread intentionally, "pets" fits perfectly. |
| Q35 | sugar | It was hoped that the toads would eat the grey-backed beetles responsible for destroying crops of sugar on many of the plantations | Excerpt/Transcript Explanation: The transcript explains that experts hoped the toads would eat the beetles that were causing damage to the sugar plants on many farms. Answer Explanation: The answer 'sugar' refers to a plant that is grown on large farms to make the sweet white or brown substance we use in food and drinks. Reason For Correctness: The correct answer is sugar because the speaker talks about why people brought certain toads to Australia in 1935. They wanted these toads to eat a type of beetle. These beetles were ruining the sugar crops being grown on large farms, which are called plantations. |
| Q36 | light | Another invasive plant is rhododendrons, which can be found in UK parks and woodlands. Their introduction dates back to 1763, but they're now seen as harmful because they block out so much light that native wild flowers can't grow beneath them | Excerpt/Transcript Explanation: The transcript describes rhododendrons as plants that were brought to the UK long ago. They are a problem now because they are so big or thick that they cover everything under them. This stops the sun's brightness from reaching the small, local flowers on the forest floor, so those flowers die. Answer Explanation: The answer is the natural brightness from the sun that plants need to live and grow. Reason For Correctness: The correct answer is light because the transcript explains that rhododendrons are harmful plants. This is because they grow in a way that stops sunshine from getting to the smaller flowers on the ground. In the text, the phrase 'block out' means the same as 'prevent from reaching', and 'native wild flowers' are a type of 'native plant'. |
| Q37 | virus | Grey squirrels have outcompeted the smaller, native red squirrels. They both eat the same food, and the grey squirrels carry a type of virus that is deadly to the red squirrels | Excerpt/Transcript Explanation: The transcript explains that grey squirrels and red squirrels are in a competition, but grey squirrels also have a germ (virus) that is dangerous and causes the red squirrels to die. Answer Explanation: The answer 'virus' refers to a tiny germ that makes people or animals sick. In this case, it is a sickness that grey squirrels carry which causes red squirrels to die. Reason For Correctness: The correct answer is found in the section about squirrels in the UK. The speaker explain that grey squirrels carry a 'virus'. They describe this virus as 'deadly' to the red squirrels. To be 'deadly' means it has the power to kill. Therefore, a virus is the thing they spread that kills the native squirrels. |
| Q38 | behaviour / behavior | The first step in controlling invasive species is learning about the behaviour of new species coming into the country. Monitoring is an important part of this, so that we can know if the new species begins to have a negative impact in its new environment | Excerpt/Transcript Explanation: The transcript states that watching these species closely (monitoring) helps experts understand how they act (behaviour) and if they are hurting the world around them. Answer Explanation: The answer "behaviour" (also spelled "behavior") means the way an animal or plant acts or lives in its environment. Reason For Correctness: The correct answer is "behaviour" because the speaker identifies it as the first thing we must learn to manage invasive species. The text explains that monitoring is a key tool used to study these actions and understand how the species affects its new home. Finding out how a species acts helps ecologists decide how to stop it. |
| Q39 | database | One effective way to keep track of invasive species is to create a database for the whole country | Excerpt/Transcript Explanation: The transcript states that making a database for the entire country is a good way to follow where invasive species are and what they are doing. Answer Explanation: The answer is a database, which is a computer system that stores and organizes a large amount of information to make it easy to find. Reason For Correctness: The correct answer is database because the speaker identifies it as a useful tool for monitoring invasive species across an entire nation. By having a central place for information, different groups can share their findings and decide how to act. Important words to notice are track, which means to follow or monitor, and database. |
| Q40 | photograph | They should be encouraged to photograph harmful species – because this helps with identification – and then to report when and where these were observed | Excerpt/Transcript Explanation: The transcript explains that regular people are very important for tracking these species. It says we should ask people to take photos of harmful species and then tell the authorities where they found them. Answer Explanation: The answer "photograph" means taking a picture of something using a camera or a phone. Reason For Correctness: The correct answer is found in the final section about how common people can help experts. The speaker suggests that the public should be encouraged to take pictures of harmful plants or animals. This helps scientists identify them. After taking a picture, people should then report where and when they saw the species to help with monitoring. |
Transcript
Today I'm going to talk about invasive species. Let me start by saying what an invasive species is and what it's not. Invasive species are any animal or plant that is introduced into an environment by humans, and which is then harmful to that environment. It's important to be clear that not all introduced species are invasive. Many introduced – or non-native – species thrive in new areas without posing any threat.
In some cases, invasive species have changed the natural world beyond recognition, so let's look at the different ways they can be problematic. First of all, invasive species may eat native species, or sometimes they may bring a disease with them, which native species have never faced before and therefore have no defences against. Often the invasive species breed very quickly – which further adds to the problem of native species losing their sources of food. Species invasions are one of the biggest causes of damage in an ecosystem, actually putting its survival at risk.
So, how do invasive species spread? Without a doubt, the biggest cause is human activity. This could be intentional, or it could be accidental, such as when people who've been on holiday in another country come back with, say, the seeds of plants on their clothes or shoes. Plants and animals, especially insects, arrive in or on the cargo of ships, and then escape into their new 'home'. But sometimes humans deliberately move animals and plants around the world, for example to use them to control pests on farms, or to be pets. This can go very wrong if those animals and plants move into wild settings and start breeding or begin growing in ways that weren't predicted.
Let's now look at an example of an invasive species here in Australia: Rhinella marina is a species of toad that was deliberately introduced from Hawaii in 1935 as a form of biological control. It was hoped that the toads would eat the grey-backed beetles responsible for destroying crops of sugar on many of the plantations. At first, just a handful of toads were released by scientists into Queensland, but this number soon grew as other states followed suit. Within two years, 62,000 young toads had been released into the wild. The toads did nothing to protect the plantations, but they did reproduce rapidly and could soon be found all over the northern half of the country. The toads are poisonous at every stage of their life cycle, and anything that eats them will die.
My second example regarding invasive species is the United Kingdom. Actually, there are more than three-thousand invasive species there, including some that are extremely common. Some invasive plants, such as Japanese knotweed, have had a devastating impact on parts of the UK. Gardeners in the nineteenth century considered it a beautiful ornamental plant – which it is, when it's kept under control – but it soon spread into the countryside and remains a problem even to this day as it's so hard to eradicate. Another invasive plant is rhododendrons, which can be found in UK parks and woodlands. Their introduction dates back to 1763, but they're now seen as harmful because they block out so much light that native wild flowers can't grow beneath them.
And then there are grey squirrels, which are one invasive species almost everyone in the UK will have come across. They were brought to the UK from North America and introduced to private estates around the 1870s but are now found everywhere, from forests to city squares. Grey squirrels have outcompeted the smaller, native red squirrels. They both eat the same food, and the grey squirrels carry a type of virus that is deadly to the red squirrels. Red squirrel populations have collapsed, and there are only a handful of sites left in the UK where they're found.
An important question for ecologists worldwide is, what can we do to tackle the problem of invasive species? The first step in controlling invasive species is learning about the behaviour of new species coming into the country. Monitoring is an important part of this, so that we can know if the new species begins to have a negative impact in its new environment. One effective way to keep track of invasive species is to create a database for the whole country. That way, all relevant authorities and agencies can share important information and take whatever action's needed. But the public also have a vital role to play in this process. They should be encouraged to photograph harmful species – because this helps with identification – and then to report when and where these were observed. But it's important to tell people not to destroy or even touch what they've found.
Now, I'm going to move on to ...