LESSON PLAN

Name: Katie Weber

Title of lesson: Sea Urchin Fertilization

Date of lesson: TBD

Length of lesson: 50 minutes

Description of class:

Name of course: Biology

Grade level: 9^th

Honors or regular: Either

Source of the lesson: UT BIO 206L lab manual

TEKS addressed:

(1) Scientific processes. The students, for at least 40% of instructional time, conducts field and laboratory investigations using safe, environmentally appropriate, and ethical practices. The student is expected to:

(A) demonstrate safe practices during field and laboratory investigations; and

(6) Science concepts. The student knows the structures and functions of nucleic acids in the mechanisms of genetics. The student is expected to:

(E) compare the processes of mitosis and meiosis and their significance to sexual and asexual reproduction

I. Overview

The students will prepare a mixture of sea urchin sperm and egg on a slide and watch fertilization of the egg occur.

II. Performance objectives

Students will be able to…

• Prepare a slide mount of sea urchin sperm and egg
• Observe fertilization, cleavage, and gastrulation in the sea urchin embryo
• Explain how fertilization occurs in sexual organisms
• Consider the consequences of polyspermy

III. Resources, supplies, and materials needed

• Live sea urchins
• Syringe
• .5 M Potassium chloride
• Beakers
• Pasteur pipettes and bulbs
• Depression slides
• Vaseline
• Toothpicks
• Fresh sea water
• Cover slips

IV. Supplementary handouts

• Lab Directions Sheet (1 per student)

V. Advanced teacher preparation

Shortly before the lab, the teacher should extract the sea urchin gametes using the following procedure:

• Inject both the male and female sea urchins with the .5 potassium chloride.
• Invert the male on a petri dish and collect the sperm “dry.”
• Invert the female on top of a beaker filled with seawater.
• Once the eggs settle, wash them by removing the supernatant seawater and replacing it with fresh seawater, therefore suspending the eggs.
• Store in a refrigerator until time for use.

Five-E Organization

Teacher Does Probing Questions Student Does

Engage: Encourage students to think about the idea of fertilization. “Today you are going to get to see the fertilization of a sea urchin egg. Let’s go through the directions together.” Have the students take turn reading the directions and pointing out which materials they will use with each step and where they will get the materials from.

How do you think the very first cell of a sexual organism is formed?

By the union of sperm and egg.

Explore: Ask the students to follow the directions sheet and perform the lab.

Where will you get your sperm and egg from? Should you leave the light on your microscope on the whole time? Can you see the fertilization membrane forming? What might be its purpose?

The petri dish and beaker in the front of the room. No, the light could damage egg and sperm mixture on the slide. Answers will vary.

Explain: Place one of the group’s slides on the light microscope that can be projected on the TV so they can see a bigger picture of the fertilization.

What do you think is the function of the fertilization membrane that forms when the egg is fertilized?

Protection; a block to polyspermy.

Extend / Elaborate: Encourage the students to consider the consequences of polyspermy.

What would happen if more than one sperm fertilized a single egg? Could that organism survive? What if it was a plant?

It would result in polypoloidy. This would not lead to a viable animal but sometimes plants can survive being aneuploid.

Evaluate:

Because this is mainly an observational lab, there would be no formal evaluation. Simply be sure that all students have had the opportunity to view the fertilization process under the microscope.