In her Belmont, MA classroom, Bonnie Chen's students participate in a hands-on simulation that illustrates the correlation between beak size and feeding success among a population of wading birds to learn about mutation and natural selection.
Bonnie Chen teaches ninth grade honors biology at Belmont High School in Belmont, Massachusetts. Located just outside of Boston and Cambridge, Belmont High School draws students from a range of communities in the Boston area. Roughly 25 percent of the students come from homes where at least one parent is a scientist, doctor, or researcher. Close to half of the students at Belmont High School take two science classes in a given year. Advanced Placement courses are offered in physics, chemistry, biology, and environmental science. Massachusetts' frameworks for teaching science direct curriculum topics, but teachers are free to set the order, plan how they will teach, and choose labs.
Ms. Chen began the year with an introduction to scientific understanding and an overview of evolution as a unifying theme in biology. In an evolution discovery lab students practiced putting skull and skeleton collections in chronological order and looking for similarities in vertebrates.
By the time Ms. Chen's students began the bird beak experiment, they'd covered several units in biology: the scientific method, inorganic and organic chemistry, and cell biology. Just prior to the lesson, students learned general information about DNA, chromosomes, transcription and translation, and types of gene mutations and chromosomal mutations. Students need this basic information about genetics in order to complete the lab. The lab asks students to carry out a gene/chromosomal mutation and then transcribe and translate the nucleotide sequence in order to discover the type of beak the offspring will possess.
The Bird Beak Lesson Ms. Chen's bird beak experiment falls within a unit on genetics. In this simulation, students gather data to see how beak mutations can influence natural selection.
After the Lesson After the lesson, students completed an individual performance task that reinforced their knowledge of concepts covered in the lesson and showed their understanding of those concepts.
The performance task asked students to pretend that they were doctoral students doing research on a particular, randomly assigned species of wading bird. Their research was intended to help them discover how this species of wading bird evolved from an ancestral bird with a beak much like the tongue-depressor beaks used in the lab. Students needed to incorporate real-life facts about their species of bird and use their knowledge learned from the lab in order to write their explanation. Each student submitted an abstract, similar to ones sent to scientific conferences, and presented their information in an oral presentation. As an introduction to the performance task, Ms. Chen showed pictures on an overhead different wading birds gave students a few facts about the birds to pique their interest.
After completing the Performance Task, the class went on to discuss other topics in genetics including karyotypes and genetic counselors, autosomal dominant and recessive disorders, sex-linked disorders, and mitosis and meiosis. The genetics unit was followed by plant structures, photosynthesis, cell respiration, animal structures, organ systems, and comparative anatomy to end the year.