Lesson: Natural selection, adaptations and lizard camouflage
DO NOW: How does an species get the adaptations that enable its survival?
Note: I don’t get into too much detail about natural selection in my class. I simply discuss the implications that natural selection has on ecology, especially when discussing species as a category of an ecosystem. It is important to have a solid foundation of these ideas, however, so I have included a refresher below.
Teacher Refresher: (Refer to the link about natural selection for more info) I have tried to summarize the basic information that can be gleaned from the link.
Address misconceptions about natural selection and adaptations right away! Most students will have the misconceptions that organisms are able to choose what they will look like or that all organisms are seeking perfection—this is not true! Natural selection determines what organisms will survive, based on which ones are suited for their environment at that particular time. The “survival of the fittest” idea can be misleading, too. Fitness is not necessarily referring to strength or physique; it is referring to the species that has characteristics which enable it to survive. No species or individual within that species is perfect. There is a range of “fitness” that is adequate for survival. For example, humans have many genetic diseases, yet they are able to survive and reproduce, despite having the genetic disposition for the illnesses. As a result, they can survive, reproduce and spread their genes into a population. Over time, as environments change and requirements for survival are influenced, those organisms that still have the range of fitness required to survive usually will. It’s important to note that evolution occurs over millions of years. This is not something that happens over night.
1) There is no such thing as a perfect species
2) Natural selection is the process of “fit” organisms surviving and reproducing. Since offspring look like their parents, species look very similar. Remember: species can’t pick and choose what adaptations to have—they either have the genes for those adaptations or they don’t.
3) Nature isn’t selecting at random—organisms that are fit will survive, those who are not will die off. Selection itself is a misleading term! It’s not like nature is determining at random that this species will survive and another one won’t.
Activity 1: To teach the idea of natural selection, I use camouflage to get the point across. I give students an outline of a lizard (See lizard worksheet) and ask them to color the lizard in a way that would make it blend in with the classroom environment. Explain that the lizards will be hidden and students will try to find them later.
Rationale for activity: Students will search for lizards. Those that are not found will survive and reproduce. As a result, this models natural selection in nature. Remember: It’s only a model and realistically natural selection and evolution will occur over millions of years. This activity simply models the process, but does have its flaws. Depending of the age group of kids and their abilities, you could discuss genetics, etc.
Activity 1, part 2: Have a few students attempt to prey upon lizards in the room. Give each student 5-10 seconds to find as many lizards as possible. The lizards that are found are not able to reproduce. After a few students go, have the students get their lizards, if they survived, and bring them to the front of the room. Discuss how their camouflage enabled them to survive.
Review Adaptations and the role that they play in natural selection.
Reflection: Students love this activity. You can use any organism that you'd like--I've used butterflies before, too.
|Understanding Evolution and Natural Selection||