Life Cycle Detectives at the Desert Arroyo

An Investigation at a Dry Desert Streambed

An arroyo is a streambed that is often dry. At a desert arroyo research trailer, Imani's class investigates how living things change during their lives. The class uses scientists' dated photographs and notes collected over several years.

Step 1: Choose records for darkling beetles, kit foxes, and desert lupine plants. Step 2: Use the dates to arrange each set from earlier to later. Step 3: Record body changes, new offspring, and the end of individuals' lives. Compare the three sets. Students change no living conditions; this is an observation study.

Darkling beetle results: A larva hatches from an egg. The larva grows longer. Later, it becomes a pupa. Inside the pupa, its body develops into an adult beetle. Adults reproduce, and females lay eggs. One female is seen alive after laying eggs. A later record reports the end of her life.

Kit fox results: Pups are born alive. They are small, with their eyes closed. As they grow, their eyes open and they develop adult bodies. Adult foxes can reproduce and have pups. Records show one mother alive with her pups and later with those young as adults. Eventually, her life ends.

Desert lupine results: A seed sprouts. The seedling develops more leaves and grows into an adult plant. Flowers develop, followed by pods containing new seeds. Later, that plant dies. Some of its seeds sprout after rain.

For their models, students use birth for the beginning of a young animal's life and sprouting for the beginning of a new plant's growth. Growth includes getting bigger or developing body parts. Reproduction means producing offspring. Death means an individual's life has ended.