Michael Herring

Reproductive Structures and Functions Lesson

Grade Level: 9

Source Of The Lesson: BSCS

TEKS:

 Introduction.

In Biology, students laboratory investigations. Students in Biology study genetics, biological evolution, and plants and their development.

Knowledge and skills.

Students will demonstrate safe practices during laboratory investigations.

Scientific processes. The student uses scientific methods during laboratory investigations. The student is expected to:

Collect data and communicate valid conclusions.

Science concepts. The student knows how an organism grows and how specialized cells, tissues, and organs develop. The student is expected to:

Compare cells from different parts of plants.

Science concepts. The student knows the theory of biological evolution. The student is expected to:

illustrate the results of natural selection in speciation, diversity, phylogeny, adaptation, behavior, and extinction.

I. Overview

This lesson allows the students to explore the structure/function relationships in the reproductive cycle of moss. Students will dissect the moss and directly observe reproductive parts. The students will also discuss the evolution of plants from water to land.

II. Objectives

The students will be able to:

• · Identify the spore, sperm, and egg of a moss plant
• · Relate the structures of the moss plant to their functions for reproduction
• · Discuss alternation of generations in terms of diploid and haploid life forms, sexual and asexual reproduction, and meiosis and mitosis.
• · Diagram the reproductive life cycle for moss
• · Discuss the evolution of plants from water to land

III. Materials (per team of 2)

• · 2 microscope slides
• · 2 cover slips
• · dissecting needle
• · scalpel
• · forceps
• · compound microscope
• · moss plant with sporophyte

IV. Safety Considerations

The students are expected to handle all of the dissecting tools with caution. The needles are sharp and should be handled with care. A cork should be given to each group to store the dissecting needles when not in use.

V. Handout

The students will be given a handout to guide them through the investigation. The handout is attached.

Teacher Does Student Does

Engage:

Explore: Learning Experience: Discuss the safety concerns with the students. Split the class up into groups of two. Pass out the materials to each group. Give each group a worksheet that will act as a guide for the investigation. Have each group hold up their piece of moss and identify the sporophyte and gametophyte. The students begin by dissecting the sporophyte and observing spores under the microscope. Next, the students will dissect and observe the leafy shoot of the gametophyte. Finally, the students will dissect the male and female parts of the gametophyte and observe the sperm and egg under the microscope. The students will answer questions after each observation. Questions: Does everyone have the necessary materials? Has everyone located the gametophyte and sporophyte?

Hoped For Student Response: Students will split up into groups and organize the materials. Expected Student response: Before the investigation begins, the students will hold up their moss and point to the gametophyte and sporophyte.

Evaluate

Circulate the classroom and monitor the students. Ask each group to discuss what they are doing and why.

Explain: The students will be asked to discuss the investigation. Groups will be called on to answers various questions about the structure/function relationships of the moss reproductive life cycle. As the students discuss the various structures/functions, a diagram of the moss life cycle will be drawn on the board. Questions: What was inside the sporophyte? How are these structures distributed in nature? How are they adapted for life on land? How many N is the sporophyte? Through what process is the spore made? Are mosses vascular plants? How is water delivered throughout the plant? How many N is the gametophyte? How does the moss produce gametes? How is this different from animal gamete production? How does the sperm reach the egg? Where would you expect moss to grow? Why? Where is the zygote formed? What is the result of the zygote?

Hoped For Student Response: Students will be attentive and engaged in class discussion. Expected Student Response: Spores are located inside the sporophyte. The spores are distributed by wind. The spores have thick, waterproof walls that allow them to live on land without drying out. Mosses are nonvascular plants adapted to life on land through spore, embryo, and gametangia. The sperm reaches the egg by swimming through water. Therefore, moss is found in damp environments because fertilization requires water for sperm to reach the egg. The zygote grows to become the sporophyte.

Evaluate

Have the students make a concept map including the major structures of the moss reproduction cycle and their functions. For a 50 min. class, this should be given as homework.

Extend/Elaborate: Discuss evolutionary adaptations required to make the transition from land to water. Questions: What structures did you see in the moss that help with the transition from water to land? What adaptations are necessary for plants to move completely out of water?

Expected Student Response: Spores help the moss live on land. In order for plants to move completely out of the water, they will need better support and a better system for delivering water and nutrients.

Evaluate

Have the students draw a sketch of the reproductive cycle of moss. The students should label important structures and describe their function.

Handout:

Name_____________________

Date______________________

Moss Reproductive Structures and Functions

1. 1. Examine the moss plant with sporophyte attached. The sporophyte consists of a smooth stalk terminated by a little capsule. Separate the two generations by pulling the sporophyte stalk out of the leafy shoot of the gametophyte.
2. 2. Using a dissecting needle, break open the capsule of the sporophyte into a drop of water on a slide. Add a cover slip and examine under the low power of a compound microscope.
1. A. What are the structures you observe?

B. How are these structures distributed in nature?

C. How are they adapted for life on land?

3. Most moss spores germinate on damp soil and produce a filamentous stage that looks like a branching green alga. Examine a prepared slide of this stage.

4. The filamentous stage gives rise to the leafy shoot of the gametophyte. Using forceps, carefully remove a leafy shoot from the fresh moss.

A. How does this shoot obtain water and nutrients for growth?

5. The reproductive organs of the gametophyte are at the upper end of the leafy shoot. Examine a prepared slide of these organs under the low power of a compound microscope. The male sex organs are saclike structures that produce large numbers of sperm cells. The female sex organs are flask-shaped and have long, twisted necks. An egg is formed within the base of the female organ.

A. How does a sperm reach the egg?

B. Where would you expect moss plants to grow? Explain.

C. The union of the egg and sperm results in a cell called the zygote. Where is the zygote formed and what eventually grows from the zygote?