Variation & Adaptation
Grades 3-4 | 20 sessions
Students learn about biodiversity, relatedness among organisms, heredity, adaptations, and the fossil record. They also learn to make inferences, to use captions and illustrations as they read, and to write comparison paragraphs. They learn and use scientific vocabulary such as characteristic, extinct, evidence, and claim.» Download Unit Description
Students engage in hands-on activities, such as classifying a series of bird cards while listening to recordings of their calls. Students also watch video clips to observe animals’ adaptations.
Students are provided with many opportunities for small group discussions to help them make sense of science ideas. For example, students discuss what living things need in order to survive, and use evidence to make explanations.
Students read four science books, including Mystery Mouths, which guides students to make inferences about different animals’ adaptations for eating based on their mouth parts. Students use comprehension strategies and learn how to navigate informational text.
Students write comparisons, including a comparison of two organisms’ adaptations. Throughout the unit, students write to record observations and reflect on their learning.
Nature and Practices of Science
The Variation and Adaptation unit introduces students to some of the most important basic concepts in life science—including the diversity of living things, relatedness of species, heredity, adaptations, and the fossil record. Understanding these concepts will provide a foundation for success in life science classes in middle school, high school, and beyond.
Variation: There is enormous variation among species living on Earth. Students are exposed to many aspects of this diversity—the range in size of living things, their diversity of appearance and behaviors, the various ways they protect themselves, move, and more. Students also learn that there is variation within a species.
Relatedness among species: Different species are related to one another. Depending on the species, they may be fairly closely related (for example, foxes and wolves) or very distantly related (for example, polar bears and redwood trees). Students learn that shared characteristics can be evidence of how closely related two species are. In general, the more characteristics two species share, the more closely related they are likely to be. Students also learn that different species share some of the same genes, and that the number of shared genes is also evidence of how closely related two species are.
Heredity: Inherited characteristics are passed via genes from parent organisms to their offspring. This means that offspring generally resemble their parents, both in general characteristics of their entire species, and in the specific variations of the individuals. This unit does not teach more complex ideas of heredity (such as dominant and recessive genes) which are taught in later grades. Students learn that while many characteristics are inherited, others (such as scars, learned behaviors, etc.) are acquired, and that acquired characteristics cannot be passed on in genes.
Adaptations: Inherited characteristics that help a species survive are called adaptations. Organisms have adaptations that help them get food, maintain their temperature, avoid being eaten, reproduce, and more. Students learn that adaptations are often related to habitat. For example, organisms that live in the water and organisms that live in tree branches have very different adaptations for moving. Organisms that live in a habitat with many predators are likely to have adaptations for avoiding or keeping away from those predators. This unit does not teach the mechanisms by which adaptations arise in species.
The Fossil Record: A fossil is any preserved remains that are evidence of life from long ago. The vast majority of species that have ever lived are now extinct. Scientists know about these organisms only from fossils. Students learn about ways scientists make inferences about extinct species, their habitats, and their adaptations by observing fossils, and by comparing them to related living species.