Lesson 04: Embryo Growth

Sturgeon Lesson Plan #4

Background:

Lake Sturgeon embryo traits at the time of hatch are associated with environmental conditions (temperature) at the time of spawning and when eggs are incubating. Below are data showing mean body length of Lake Sturgeon at hatch after incubation in water temperatures associated with different river temperatures during early, and late portions of the spawning season corresponding to increasing water temperatures. Heritability of body size at hatch is attributed to family.  In other words, who mom and dad are, greatly influences how big their offspring are.

Embryos grow rapidly during the period immediately following hatch.  Embryos feed on yolk reserves for a period of several days to weeks and nearly double in size from hatch until the time of emergence from stream substrate and dispersal.  The rate of change in body size over time is similar for free embryos from each family.  However, body size varies significantly by family over this period.  Embryos from females spawning earlier in the season remain larger in size than embryos from females spawning later in the season.  Data on larval Lake Sturgeon growth (Total Length (mm) and Yolk-Sac Area (mm²) from the time of hatch (week 0) and weekly through 3 consecutive weeks was collected.  Larvae were raised in 3 liter aquaria in the Black River stream-side rearing facility.  Offspring use yolk-sac to develop body mass and sensory abilities (mouth, eyes, Sense of smell) before they are able to feed themselves.

Procedure:

1. Discuss the process of science with students as a review.  Also, provide a short lecture of the life history periods that encompass this curriculum (Egg/developing embryo, embryo, larvae).
2. Provide students the “Embryo and Larval Growth by Family” Excel spreadsheet and provide a short summary of what is contained the file.
3. Divide the class into 5 groups.  Assign one of the 5 groups to each of the 5 crosses (e.g., Group 1 = “Early Cross 1”) listed at the bottom of the Excel spreadsheet.
4. Allow students to look over their assigned data set and to follow the process of science to formulate a hypothesis from the data and information provided.
5. Instruct the students on how to calculate Mean (or Average), Min (or Minimum), and Max (or Maximum) for an example set of data.
6. Give students a limited amount of time (30 minutes or less) to analyze the data and record questions they have on their process of science worksheet.  Start by asking student to calculate the average Total Length, Yolk-Sac Area, and Temperature for each week period (0(Hatch), 1, 2, 3).
7. Then Compile a list of questions on the whiteboard and give the students a few minutes to choose the question they’d like to pursue, while the teacher eliminates questions that time or the data will not support.
   1. Example questions:
      1.  How does temperature during incubation effect size at hatch?
      2. Is there a size at hatch difference between families that are hatched during the same time periods (early vs. late).
8. Assign questions from the list to be answered by pairs of students or allow students to choose their own question and groups.
9. Allow time for students to analyze and compile data for their hypothesis.
10. Students present their initial question, hypothesis, data, additional questions that arose and conclusion for peer review and discussion.
11. The teacher should keep a running list of the additional question that arose during the analysis.  This is a good reminder of the circular nature of science.

Extended Learning Opportunities:

The process of science exercise can and should be repeated multiple times using different data sets or other phenomenon (video).

Assessment and Evaluation: