Students explore the relationships between genetics, biodiversity, and evolution through a simple activity involving hypothetical wild mouse populations. First, students toss coins to determine what traits a set of mouse parents possesses, such as fur color, body size, heat tolerance, and running speed. Next they use coin tossing to determine the traits a mouse pup born to these parents possesses. These physical features are then compared to features that would be most adaptive in several different environmental conditions. Finally, students consider what would happen to the mouse offspring if those environmental conditions were to change: which mice would be most likely to survive and produce the next generation?

Probability and statistics are just a few of the tools used in engineering. This lesson explores concepts studied by genetic scientists as well as biomedical and environmental engineers. genetics biodiversity adaptation natural selection evolution dominant gene recessive gene biomes Understanding of simple Mendelian inheritance, including concepts of dominant and recessive genes Understanding of the concept of adaptation would be helpful but is not essential Students will be able to explain what is meant by "biodiversity." Students will be able to explain how adaptive features are maintained in a population of organisms. Ask your students what they think of when they hear the word "diversity." After allowing a few minutes for them to share their ideas, point out that there are many contexts in which the word is used. Then ask them what they think is meant by the term "biodiversity." They shouldn't have any trouble realizing that it refers to diversity in a biological context. Point out that there are two ways to think about biodiversity. One way is the many diverse types of organisms. For example, mushrooms, vegetables, giraffes, whales, spiders, mosses, and bacteria all vary tremendously in their structures, body functions, and behavior. No one knows how many different species of organisms exist on earth, but the number is in the millions. Moreover, there were millions more that lived in the past and became extinct. Presently there are over 21,000 different species just of fish, and over 800,000 species of insects. The other way to think about biodiversity is the diversity that occurs within a species. As an example, ask students how many different breeds of dogs they can name. You can also ask how many humans they know that look and behave exactly alike. Even identical twins can usually be distinguished one from the other by their parents and close friends. Next ask where human babies come from -- that should get their attention! In the unlikely event that they are unclear about this, point out that babies are the result of sexual reproduction. This means that a sperm cell from the father and an egg cell inside the mother combine into one cell, an embryo, in the process of fertilization. Point out that not only humans, but most other animals and plants reproduce sexually. (In plants it is pollen that takes the place of sperm.) Finally, ask students why the girls in the class do not all look exactly like their mothers, and the boys do not look exactly like their fathers. They should already be aware that they each obtained half of their genes from the mothers and half of their genes from the fathers. Thus, they share characteristics of each of their parents, whose own characteristics are a mixing of their parents' characteristics, etc. By now, students should be able to explain why there is so much diversity among humans. Point out that similar amounts of diversity exist among plant species and other species of animals, even if to our eyes they may look very similar to each other. This lesson and the associated activity are designed to help students understand the theory of evolution by natural selection, as put forward by Charles Darwin. Below is an outline of this theory, modified from a similar outline developed by ecologist Robert Ricklefs. The left column states the theory in the general terms a biologist would use, and the right column gives a specific example that is easily understood by laypersons. Evolution by natural selection would not be possible if there was no variation among individuals in a population, because without variation, there would be no varieties from which to choose. Thus, environmental conditions, which can include climatic factors, food availability, the presence of predators, etc., favor those individuals with adaptive combinations of genes. Those individuals survive to adulthood and reproduce, passing some of their favorable genes on to their offspring. Meanwhile, those individuals with undesirable, i.e., non-adaptive combinations of genes, are selected out of the population before they are able to reproduce. The associated activity is called The Benefits of Biodiversity because it is intended to let students make the connection between genetic variability and long-term survival of a population. If environmental conditions change, many individuals that were previously well-adapted may no longer be well-adapted. However, if variation exists within the population, others will be. These will be the individuals that leave offspring to the next generation. This idea lays the foundation for understanding how a new species can evolve from an old one. At this point, change the subject of the lesson to mice. Tell students that rats and mice are examples of mammals known as rodents, along with hamsters, guinea pigs, squirrels, prairie dogs, beavers, and porcupines. Of the rodents, mice and rats represent the largest number of the species. They live in all types of habitats -- forests, fields, swamps, tundras, and even deserts. Explain that like humans, mice use sexual reproduction, but mice are very efficient at it. A single pair can mate every few weeks and give birth to 5-6 pups at a time. Ask the students, "Why, then, isn't the world covered with mice?" Or more specifically, ask them what reasons they can think of that would cause a young mouse to not survive. Students should be able to respond that some might get eaten by predators, such as owls, snakes, or cats. Others might not be able to get enough food, or die from disease, or freeze during the winter if they couldn't find a sheltered place to live. Point out that those that survived had good combinations of physical features that helped them survive to adulthood. We call these features adaptations. Then ask students how these surviving mice got the adaptations they have. The desired response is that the surviving mice inherited their adaptations from their parents, through the genes that were passed on from parents to offspring. a genetically inherited characteristic that enhances the ability of an organism to survive in its environment The Benefits of Biodiversity Ask students to think about what might happen if the environment a mouse pup was born in suddenly changed. For example, what might happen if a prolonged drought struck an area that was normally wet and lush with vegetation? Would all the mice die? Could they move to a new area several hundred miles away and out of the drought? Let students think about these questions, and some may want to share their ideas. However, instead of commenting on their responses, tell students that they will conduct an activity that will let them see for themselves what might happen in such a scenario. define biodiversity define adaptation Ricklefs, Robert E., 1979. Ecology, 2nd Edition, Chiron Press