Old Man's Beard
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Fact file
Old Man's Beard is a noxious plant. It threatens garden shrubs and native forests. It is a fast growing vine, which forms a smothering mass over trees and shrubs.
A single plant is capable of covering an area measuring 180 m2 (e.g., 13 metres by 13 metres). It produces many seeds, which can stay alive in the ground for several years. A stem can grow up to 10 metres in one year.
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| Y8 (09/2005) | |||
| a) |
Special feature
Can cover a large area Produces many seeds Seeds stay alive for years Can grow up to 10m a year |
How this special feature helps the plant to survive
Gets wide exposure to sunlight, air and water, promoting healthy growth Increases its chances of survival by reproducing in great numbers Can wait out adverse conditions before seeds germinate Grows very quickly giving it height advantages over other plants to access sunlight |
Features 1 correct feature - very easy
2 correct features - moderate
At least 3 correct features - very difficult
Explanations
1 correct explanation - very easy
2 correct explanations - moderate
At least 3 correct explanations - very difficult
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| b) |
A general explanation of the effect Destroys plants by smothering them. A specific explanation of the effect Destroys other plants by smothering them so they can't get sunlight or grow. Or General explanation Grows widely very quickly. Specific explanation The special features that help it grow so quickly also make it a threat to other plants, so growing and spreading very quickly means other slower growing plants do not have a chance to survive. Or General explanation Many seeds are produced, which are able to stay alive in the ground for years and ensure survival of the plant. Specific explanation Ability to both grow and spread widely very quickly and also produce many seeds, which can stay alive in the ground for years, means that the plant is able to wait if necessary until conditions for growth are ideal. (Do not accept it's hard to get rid of as an answer by itself). |
General explanations - very easy
Specific explanations - difficult
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Trial number 152 students.
Pest plants have highly developed adaptations to ensure survival. Their ability to thrive puts other species at risk and this is why they are considered pests. These pest plants are all introduced plants.
For question a) common difficulties were:
- Confusion over the meaning of the word 'noxious', some students interpreting noxious as 'poisonous'.
- The lack of specific detail. See examples below of 2 different answers from students in the trial. The first shows a lack of detail - the second is an example of a detailed answer.
| Feature | How the feature helps | |
| Answer 1 | Seeds | Stay alive in the ground for years |
| Answer 2 | It produces many seeds that can survive in the ground for many years | Because there are many seeds there is more chance that one will grow and because they can stay alive in the ground for several years they are more likely to end up growing even if conditions aren't right when the seeds are dropped. |
An important part of a student's learning in science is the development of their knowledge of the vocabulary of science. Students need to develop the understanding that the word “feature” in science is used to refer to a characteristic or prominent trait. Students may be familiar with different meanings of the word in their every day worlds, e.g., a feature film, or a news feature, or an actor featuring in a film or someone having fine features. It is worthwhile drawing out these different meanings of words so that students develop the understanding that words can have different meanings in different situations. Further investigation into the use and correct meaning of the word 'noxious' may be needed too, depending on student responses to this resource.
Interdependence
Those plants that have special features that enable them to survive in a range of conditions are likely to become pests, especially when growing with less robust plants. This is especially likely when plants are introduced from a different ecosystem. When one species is very dominant it can lead to an imbalance in the ecosystem, affecting other plants and animals. A possible extension would be for students to investigate the specific impact of various pest plants on other species in the ecosystem.