In-Depth Guide
www.BioInteractive.org Page 6 of 9
IN-DEPTH FILM GUIDE
TEACHER MATERIALS
The Making of the Fittest:
Evolving Bodies, Evolving Switches
Demonstrates how stickleback fossils are collected and used to study evolution. It also shows the students who
attended the 2005 Holiday Lectures taking part in a fossil-collecting activity.
Stickleback Environment (http://www.hhmi.org/biointeractive/evolution/stickleback_environment.html
)
Dr. David Kingsley explains how Earth has changed in the 10,000 years since the last ice age and how these changes
have impacted the evolution of stickleback fish. This video shows stickleback fish in their natural environment and
some of the predators they may run into.
Stratigraphic Principles (http://www.hhmi.org/biointeractive/evolution/stratigraphy.html
)
Dr. John Shea uses a clever demonstration to illustrate the principle that younger rocks are farther up in a
stratigraphic rock layer than older rocks and that fossils found in the same layer are of the same relative age.
USING THE QUIZ
The quiz is designed as a summative assessment that probes student understanding of the key concepts addressed in the
film. However, some teachers use the quiz before and during the film to asses students’ prior knowledge and to guide
students as they watch the film Teachers are encouraged to choose the use that best fits their learning objectives and
their students’ needs. Moreover, because the vocabulary and concepts are complex, teachers are encouraged to modify
the quiz (e.g. only ask some of the questions, explain complicated vocabulary for ELL students) as needed. The last two
questions are intended for students with prior knowledge about mutations, genes expression, and development.
QUIZ QUESTIONS AND ANSWERS
1) (Key Concept B) Evaluate the following two statements as true or false.. Justify your answer in one or two sentences.
a) “Having pelvic spines is always advantageous to a stickleback.”
FALSE. Pelvic spines provide a selective advantage in some environments but not others. One factor that
appears to favor stickleback fish with pelvic spines is the presence of large-mouthed predatory fish, such as
trout. Pelvic spines provide stickleback fish with a defense against such predators; however, pelvic spines
appear to be a disadvantage in habitats without large-mouthed predatory fish and/or habitats with insects
that can grab the spines, so that they can eat the fish. Students may mention other factors in the
environment that could influence the presence or absence of pelvic spines.
b) “All mutations are bad.”
FALSE. Whether a mutation is advantageous (favored), disadvantageous (not favored), or neutral (neither
favored or not favored) depends first on whether the mutation affects a trait in the organism and next on
whether that particular trait is selected for or against. The nature of the selective pressure depends on the
environment the organism lives in. Some mutations that alter a trait, such as the loss of pelvic spines in
freshwater stickleback fish, are advantageous in some freshwater environments but not all.
2) (Key Concept B) What specific features of the environment in Bear Paw Lake, Alaska, may have favored the survival and
reproduction of stickleback fish with reduced pelvises? Answer in two or three sentences.
The lack of large-mouthed predatory fish in Bear Paw Lake meant that stickleback fish both with and without
pelvic spines could survive. Insects that live in Bear Paw Lake can grab stickleback spines to catch the fish and eat
them, which may have favored the survival of stickleback fish with reduced or no pelvic spines. Although this is
not mentioned in the film, students may note that more vegetation in freshwater lakes could also favor fish with
less armor, as they could more easily dart into hiding places.
3) (Key Concept G) In the film, Dr. Bell notes that in multiple freshwater populations and at multiple times in history, the
frequency of stickleback fish with pelvic spines decreased and the frequency of stickleback fish with reduced pelvises increased.
This demonstrates that:
a) only fish with smaller pelvises migrate to freshwater.
b) similar environments select for similar genetic changes.
c) the pelvis of the marine fish is destroyed by freshwater.