Unit 05 - A Pretty Little Leech

Investigating a mini beast

The following tools are specifically focused on supporting an investigation about leeches. They can be adapted to investigate other wet tropics animals:
KWL
Brainstorm
Discussion
Questions
Debate
Question and Answer Session
Before and After
Draw and Label
Construct a Leech Home
Observe
Compare Invertebrates
Compare Leeches

KWL
The KWL chart can be used to provide a knowledge base and questions for the investigation:

• What do we Know?
• What do we Want to know? (This should generate a series of questions, and should answer the question, “How can we find out?”)
• What have we Learned?

Brainstorm
Brainstorming is a strategy that is useful for drawing out students’ prior knowledge. This provides an information base for further exploration and a starting point for the formulation of questions to direct the investigation.

Discussion
Students discuss what they know about leeches. As there are a lot of misconceptions regarding leeches it is essential that students categorise information as to what is plausible and implausible. It is important to record this information so that students can re-categorise it at a later stage of their investigation. List all ideas for later reference.

Questions
You may find these questions useful to scaffold your investigation:

• What is a leech?
• Where do they live?
• What do they eat?
• How do they move?
• How do they breathe?
• How do they breed?
• What do they need to survive?
• How can we look after them?
• Who can we ask to find more information?
• Do they co-exist with other species?
• Are they important to the rainforest?
• What would happen if there were no leeches?
• Why do most people dislike them?
• Why do some people like them?
• Are they useful to people?

Debate
A debate format provides a lively arena for sustained conversation and deeper understanding. Debatable questions or information will emerge from class discussions. They can be used to form the basis for a formal student debate. It is important to scaffold students as they learn the skills of debating (i.e. formulating supporting statements and being able to justify opinions with evidence).

Question and Answer Session
Invite parents to ask the students questions about leeches. Organise the students into ‘expert’ panels to answer questions on particular topics. (For example one panel of students are ‘experts’ regarding feeding behaviour, size or reproduction.)

Before and After
Students record their concept of a leech by drawing them before and after accessing information on them. Students compare the two pictures. Below are some questions that you may use to focus their comparisons:

• Have the drawings changed?
• What is different?
• Describe how they are different.
• Why do you think the drawings are different?
• What is the same?

Draw and Label a Leech
Draw a leech and label its anatomy. There are several websites listed in Resources with anatomical drawings of leeches.

Construct a Leech Home
Environment. A tank with a secure lid is important; leeches can elongate their bodies and loop through very small openings. The tank needs to be out of direct sunlight. A constant temperature needs to be maintained as leeches are susceptible to sudden changes in temperature. Provide rocks, plants, soil and sand to simulate a natural habitat.

Leech diet. Provide a source of water (rain or spring NOT chlorinated or distilled). Feed leeches on insect larvae every day, earthworms every two to three weeks, and some raw mincemeat every six months.

The leeches. Leeches can be found in back gardens under rocks where the soil is moist. They can also be collected from streams with a small dipping net or from plants gently using tweezers. For safety reasons keep leeches in the tank for observation only. Please note that leeches are protected in Queensland and should be returned to the wild.

Observe
As leeches are very common in rainforests they are easy to collect. They should be kept moist and in a glass container (or in the leech habitat see above). Have students observe leeches (or a video of leeches, if unable to find any). Possible observations include how they move, what they feel like and what they look like under a magnifying glass.

Compare Invertebrates
Students compare and contrast leeches with other invertebrates. Where possible repeat the ‘observe’ activity with another invertebrate, such as an earthworm, a beetle, centipede or millipede. Use a retrieval chart to record similarities and differences.

Compare Leeches
Using the focus question ‘Are all leeches the same?” Compare and contrast the different types of leeches. Discuss with the students reasons for the similarities/differences.