Water Striders: Survival Adaptations
OverviewHow do water striders skip across the surface of the water? What advantage does this give them over other insects that helps them survive in their environment? Your students will find out in this lesson as they build their own insects from pieces of wire, and see which ones sink and which ones float.
- Demonstrate how water striders can survive better than other insects on the surface of water
NGSS AlignmentThis lesson helps students prepare for these Next Generation Science Standards Performance Expectations:
- 3-LS4-3. Construct an argument with evidence that in a particular habitat some organisms can survive well, some survive less well, and some cannot survive at all.
Science & Engineering Practices
Constructing Explanations and Designing Solutions. Use evidence (e.g. observations, patterns) to construct an explanation.
Disciplinary Core Ideas
LS4.C: Adaptaion. For any particular environment, some kinds of organisms survive well, some survive less well, and some cannot survive at all.
Patterns. Patterns can be used as evidence to support an explanation.
Each group of students will need:
- Shallow plate or tray with water
- About 2 feet of 30 AWG magnet wire, available from Amazon.com
- Optional: double-sided foam tape and small googly eyes for decorating
- Optional: blue food coloring (makes the water easier to see)
Background Information for TeachersThis section contains a quick review for teachers of the science and concepts covered in this lesson.
Water striders are small insects that can walk on the surface of water without falling in or sinking (Figure 1). Their long, skinny legs spread out horizontally and are supported by the water's surface tension. This is in contrast to other insects with shorter (and sometimes thicker) legs that point downward, as shown in this slideshow that you can show your students.
Figure 1. Water striders on the surface of water (image credit: Wikimedia Commons user Cory).
As shown in the video here, this adaptation to walking on water gives water striders a survival advantage over other insects in their habitat. Other insects that fall into the water get stuck and are unable to escape. This allows water striders, which can easily move around on the water, to prey on them.
In this lesson, your students will build their own insects by twisting together pieces of wire. Depending on the size and shape of the insects' legs, they might float on top of the water like a water strider, or sink into the surface like a different insect (Figure 2).
Figure 2. A wire "insect" with long, skinny legs that point outward can float on top of the water like a water strider. The insect with shorter legs that point downward sinks—making it easy prey for the water strider!