Unit B: Ecosystems
1. Get Set to Explore
- algae: Plantlike organisms that live in water.
- polyp: A small water animal whose body is tube-shaped; its mouth is at one end of the tube, surrounded by tentacles for drawing in food; the other end of its body often connects to other polyps, allowing the polyps to form colonies.
- reef: A ridge of coral or other materials at or near the surface of the water.
- subtropical: Related to something that borders the tropics.
- tropical: Related to something in or from the region close to the equator.
- Explain that the topic of this simulation is a coral reef and how it grows. If possible, bring in a large picture or a poster that shows a coral reef. Let students point out organisms that they recognize in the picture.
- Guide students to understand that a coral reef is an underwater ecosystem that forms in warm parts of the ocean. The main organisms are corals, which are tiny, soft animals that build their skeletons around themselves. Each skeleton is a tube with a hole at the top; the coral, called a polyp, lives in this tube and pokes its mouth out of the hole to feed. As you go over this information, present the definitions of the vocabulary words, using them in context.
- Pose the Discover! question: Elicit predictions from the class. Have students give reasons for their predictions. Ask the class to vote on the maximum age of coral reefs. Tally votes on the board.
2. Guide the Exploration
- Direct students to launch the Discover! Simulation. When they begin playing the simulation, students should use the cursor to look at close-up views of the different coral reef organisms. They should listen to the descriptions of these organisms and jot down notes about each one. They should also move the cursor over various nonliving parts of the ecosystem to learn how each contributes to the growth of the reef. Eleven important organisms and ecosystem elements are featured.
- Suggest that students make a chart to compare the different kinds of corals. They should compare coral shape, size, color, rate and manner of growth, and function in the coral reef.
- After they have learned about all eleven featured organisms or elements, tell students to run the animation. It shows the rate of growth of the coral reef. The bar at the bottom of the screen indicates how much time has passed, in years.
- Review Step 3's Wrap-Up text, and let volunteers summarize it in their own words.
- You may wish to return to students' predictions about how old a coral reef can be. Students should realize that coral reefs generally grow very, very slowly. Large reefs such as the Great Barrier Reef of Australia have parts that are 2 million years old. The bulk of the base of the reef is about 500,000 years old. The living part of the reef has been growing steadily for the past 8,000 years.
- Present the Extension questions to the class. Students should return to the simulation to formulate answers to these questions.
- Many different human actions and environmental factors can affect the growth of coral reefs. These could include:
- nything that increases the cloudiness of the water or of the air, such as increased pollution or volcanic eruptions
- anything that increases or decreases the temperature of the water significantly, including thermal pollution or severe global warming
- anything that increases the depth of the water
- anything that increases the populations of bioeroders of the reef
- anything that increases the wave action near the reef
If time permits, present students with the following activity:
- Critical Thinking Apply Draw a three-link food chain for some coral reef organisms. Answer: Food chains should start with a producer, for example, the algae in the coral's body; the middle link would be the coral, which get energy from using the extra sugars that the algae produce via photosynthesis; the third link might be the parrotfish, which eat the coral.
4. Reaching All Learners
On Level: Logical Learners
Direct students to study the interdependence of the different organisms in the coral reef, as they do the simulation. Then they can make a drawing or a flow chart to show how the different corals have different roles in forming the structure of the reef, as well as the contribution of the parrotfish in reef variety and formation. They should also explain how the coral and the algae that live inside them are interdependent.