Biology - HOT Science Lab

Student
Natural Selection
(Adapted from: District Adopted – Prentice Hall Laboratory Manual)
NGSSS:
SC.912.L.15.13 Describe the conditions required for natural selection, including: overproduction
of offspring, inherited variation, and the struggle to survive, which result in differential
reproductive success. (AA)
Background Information:
To start your investigation you will learn about a population of birds called medium ground
finches on Daphne Major, one of the Galápagos Islands. Then you and your classmates will
simulate the fitness of birds of a fictional species called Saccharae utensilus. This bird species
has three possible variations in beak phenotype. Each ―bird‘s‖ ability to acquire food will
determine whether it dies, or whether it survives and reproduces. The number of offspring
produced depends on the amount of food each bird acquires, which can vary greatly under
changing environmental conditions. After simulating changes in the bird population for six
generations, you will analyze data to discover how the frequency of each beak phenotype in the
population changed over the generations.
Medium ground finches typically feed on small, soft fruit and seeds. The birds prefer soft seeds
because they are easier to crack. However, during periods of drought, food becomes scarce.
The birds are forced to eat more hard seeds that are difficult to break open. Scientists Peter and
Rosemary Grant and their team studied the island‘s population of medium ground finches and
discovered that there are significant variations in the beak depths of individual birds. Birds with
deeper beaks are better able to crack open hard seeds than birds with shallower beaks. These
variations in beak depth made it possible for some of the medium ground finches to get enough
food to survive and reproduce during long droughts.
Problem Statement:
Can natural selection change the frequency of traits in a population in only a few generations
Safety:
Be sure to inform your teacher of allergies to nuts or other foods if they are going be
using that particular food item.
Take care that you do not injure yourselves or others while moving around or using their
utensil ―beaks‖.
Do not consume any food items being used in activity.
Vocabulary:
Evolution, natural selection, adaptation, decent with modification, phenotype
Materials (per group):
Plastic spoon, knife, or fork
Self-sealing plastic sandwich bag
Food pieces (candies, unshelled nuts, beans, etc.)
Plastic container for nest (optional)
Biology HSL Page 77
Curriculum and Instruction