Materials

■ live and preserved specimens representing four plant phyla

■ stereomicroscope or hand lens

■ compound light microscope

■ prepared slides of male and female gametophytes of mosses and ferns

Background

1. How do plants you commonly see compare with their ancestors, the green algae?

2. What are the differences between nonvascular plants and vascular plants? How do these differences relate to the size of a plant?

3. What is alternation of generations? Is it found in all plants?

4. Do all plants produce spores? Do all plants produce seeds? What are the advantages of producing seeds?

5. What do you think was the evolutionary pressure that resulted in colorful flowers?

Procedure

CAUTION Put on protective gloves. Keep your hands away from your face while handling plants. You will travel to four stations to observe plants from four phyla. Record the answers to the questions in your lab report.

STATION 1 Mosses

2. Use a stereomicroscope or a hand lens to examine the samples of mosses, which are bryophytes. Which part of the moss is the gametophyte? Which part of the moss is the sporophyte? Make a sketch of your observations in your lab report. In your drawing, label the gametophyte and sporophyte portions of the moss plant and indicate whether each is haploid or diploid.

3. Use a compound microscope to look at the prepared slides of male and female gametophytes. What kinds of reproductive cells are produced in each of these structures? Draw the cells in your lab report.

4. Do mosses have roots? How do mosses obtain water and nutrients from the soil?

STATION 2 Ferns

5. Look at the examples of ferns at this station. The fern leaf is called a frond. Use the hand lens to examine the fronds.

a. How does water travel throughout a fern? List observations supporting your answer.

b. Make a drawing of the fern plant in your lab report.

c. Indicate whether the leafy green frond in your drawing is haploid or diploid.

d. Search the underside of the fern fronds for evidence of reproductive structures. Make a drawing of your findings in your lab report. What kind of reproductive cells are produced by these structures?

6. Examine the examples of fern gametophytes.

a. Locate and identify the reproductive organs found on the gametophytes. In your lab report, sketch and label these organs and identify the reproductive cells produced by each.

b. Are the gametophytes haploid or diploid?

7. In what ways are ferns like bryophytes? In what ways are they different?

STATION 3 Conifers

8. The gymnosperms most familiar to us are conifers.

Look at the samples of conifers at this station.

a. When you look at the limb of a pine tree, which portion (gametophyte or sporophyte) of the plant life cycle are you seeing?

b. In what part of the conifer would you find reproductive structures?

9. Name an evolutionary advancement found in gym-

nosperms but lacking in ferns.

STATION 4 Angiosperms

10. Draw one of the representative angiosperms at this station in your lab report. Label the representative angiosperm as a monocot or a dicot, and list at least two characteristics you used to identify it.

11. Name an evolutionary development that is present in both gymnosperms and angiosperms but absent in bryophytes and ferns.

12. How do the seeds of angiosperms differ from those of gymnosperms?

13. Examine the fruits found at this station. How have fruits benefited angiosperms?

14. Jlt^ JL Clean up your materials and wash your ^^ ^r hands before leaving the lab.

Analysis and Conclusions

1. In bryophytes, how do the sperm travel from the male gametophyte to the female gametophyte?

2. In angiosperms, how do the sperm get to the part of the flower containing the egg?

3. Which portion of the plant life cycle is dominant in bryophytes? Which portion is dominant in ferns, gym-nosperms, and angiosperms?

4. What is a seed? Why is the seed a helpful adaptation for terrestrial plants?

5. Why are gymnosperms referred to as naked seed plants?

6. Which group of plants is the most successful and diverse today? What are some adaptations found among members of this group?

Further Inquiry

1. Find out how the geographic distribution of the phyla of living plants relates to their structures.

2. Research the deforestation of tropical rain forests. How are the different groups of plants affected by deforestation?

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