Objective
Students will learn a population sampling technique.
Students will practice counting, estimating, addition, multiplication, and percents.

Materials
As many loaves of raisin bread as you need for each student to have one slice (average loaf has 12 slices). Don't use the end pieces.
Class chart that has enough spaces for each student to enter their totals
Student recording sheet for each student
A paper towel for each student

Background Information
This activity is based on the "Raisin Reasoning - Cetacean Population Sampling" from Dolphin Quest. It can be used as an extension of that activity or on its own. In this version the raisins in the loaf are healthy marine mammals, while raisins in the crust are stranded marine mammals. This activity can be organized in a couple of ways depending on the time you have available and grade level or ability of the students. You can divide your class up into groups of three and give each group a loaf of bread. Or give each student a slice of bread and do it as a whole group activity. Students will calculate: How many marine mammals stranded along the coast? What is the population of marine mammals in the entire ocean? What percentage of the population stranded?

The Marine Mammal Center rescues and rehabilitates marine mammals from Mendocino to San Luis Obispo Counties. These stranded marine mammals represent a portion of all marine mammals along our coast. During the rehabilitation process we gather data and study these stranded animals. Not only can we learn about the individual but also about the health of their populations and the constantly changing conditions of their environment, the ocean.

Procedure
1. Ask the students why it is impossible to count the exact number of a marine mammal species? (Because we cannot see into the water and animals move from place to place). Population surveys are done by sampling methods. Observers on land, in boats and in airplanes count animals actually seen in the area. Based on that sampling information, they estimate (extrapolate) the entire stock or population. We will simulate this sampling procedure by trying to determine how many raisins are in a loaf of raisin bread. Have students imagine that the loaf of raisin bread is the ocean and the raisins are marine mammals. Raisins in the loaf are healthy marine mammals, while raisins in the crust are stranded marine mammals.

2. Supply each group with a recording sheet (see attached). Have the students guess how many raisins are in the whole loaf and record their guess. Explain that the principal researcher in a population study establishes counting guidelines that all data collectors must follow so that the count can be as consistent as possible. Set some sampling perimeters for your class, for example a raisin that is cut still counts as one in each slice, or if doing this in small groups and your expectation involves the students being detailed and thorough then cut raisins must be paired and count as one. Add any other guidelines that are relevant for the outcome of your lesson.

3. Have the students wash their hands. Record the number of slices in each loaf. Each student should then take one slice of bread and count and record the number of raisins on the crust. Then count and record the number of raisins in the entire slice (both sides including the crust). Then based on the count of their individual slice have the students estimate the total number of stranded animals (A on the recording sheet), healthy animals and total marine mammals (B on the recording sheet). Researchers must often determine a population size based on this same estimation process. However, in this activity the students can actually test how close their estimates are to reality. Continue counting all the raisins in the loaf or if done as a large group activity, compile all the slice data from each student. See how many raisins are actually in the loaf of bread. Compile all the data and results on a class chart. What do students conclude about population data based on estimates?

For Further Discussion
What problems could wildlife managers confront if a population estimate is actually too high or too low? What could future scientists such as yourselves do/learn/invent to improve marine mammal population sampling techniques.

Stranded Marine Mammal Population Recording Sheet
Initial guesses: # of raisins on the outside______ # of raisins in the loaf_______

A/B X 100 = % of stranded marine mammals in ocean

Your answer:_________________ %