Study Guide: Plant Diversity and the Colonization of Land

Q9. Use Figure 26.6 to label this figure. Be sure to begin with number 1.

Background

Topic: Alternation of Generations in Plants

This question is testing your understanding of the plant life cycle, specifically the alternation of generations. You are asked to label the main stages and processes in the life cycle of a fern, which is a classic example of this concept.

Key Terms and Concepts:

• Gametophyte: The haploid (n) generation that produces gametes by mitosis.

• Sporophyte: The diploid (2n) generation that produces spores by meiosis.

• Spore: A haploid cell produced by meiosis in the sporophyte; grows into a gametophyte.

• Fertilization: The fusion of gametes to form a diploid zygote.

• Meiosis: Cell division that reduces chromosome number, producing spores.

• Mitosis: Cell division that maintains chromosome number, used for growth and gamete production in plants.

Step-by-Step Guidance

1. Start by identifying the two main plant generations in the diagram: the large leafy fern (sporophyte, 2n) and the small heart-shaped structure (gametophyte, n).

2. Locate the arrows that represent the transitions between generations. One arrow should indicate meiosis (sporophyte to spore), and another should indicate fertilization (fusion of gametes to form a zygote).

3. Label the structures that produce gametes (gametophyte) and spores (sporophyte). Remember, gametophytes produce gametes by mitosis, and sporophytes produce spores by meiosis.

4. Identify where mitosis occurs in the cycle (growth of gametophyte from spore, and growth of sporophyte from zygote).

Try solving on your own before revealing the answer!

Final Answer:

1. The large leafy plant is the sporophyte (2n). 2. The small heart-shaped structure is the gametophyte (n). 3. The arrows from the sporophyte to the small circles represent meiosis (production of spores). 4. The arrows from the gametophyte to the small circles represent gamete production (by mitosis). 5. The fusion of gametes (fertilization) leads to the formation of a zygote (2n), which grows into the sporophyte. 6. Mitosis occurs during the growth of both the gametophyte and sporophyte generations.

This diagram illustrates the alternation of generations, a key feature of the plant life cycle.