Angiosperm Reproduction

Objectives:

Introduction:

This lab is a continuation of the previous lab in which you studied some of the basic aspects of plant evolution. Click here to briefly review the evolution of land plants. Next, review the generalized life cycle at the beginning of Part II of lab 7.

Finally, review the evolution of the gametophyte generation, starting as a free-living, multicellular, photosynthetic organism in ferns. In gymnosperms like pine, the microgametophyte was reduced to a small, wind-blown structure called "pollen". The megagametophyte was maintained within the sporophyte cone, and surrounded by the sporophyte layer called the integument (later to become the seed coat). The megagametophyte was still large enough to provide the nutrients for the young embryo in the mature seed. This trend of reducing the gametophyte generation is continued in angiosperms. These and other trends in plant evolution are diagrammed on the next page.

In this laboratory, you will observe several of the structures associated with the reproductive portion of the plant life cycle. You will start by observing the development of the megagametophyte ("embryo sac") as well as that of the microgametophyte ("pollen"). You will then study the subsequent development of the seed and fruit.

You will also examine examples of the different types of fruits to see how they have evolved different structures for protection and dispersion.

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