Chapter 19, Problem 21A

Summary Introduction

To determine:

The match of the given definition with the correct vocabulary term.

Introduction:

Algae are a large and diverse group of organisms. Usually they are aquatic and have ability to perform photosynthesis. Based on the number of diploid and haploid organisms’ algae have five different types kinds of life cycles. These five life cycles in algae are haplontic, diplontic, haplobiontic, haplodiplontic, and haplo-diplobiontic.

Explanation of Solution

The life cycle of algae that requires two generations of the individuals, one is haploid generation and the second is diploid generation, is known as the alternation of generation. Alternation of generation (metagenesis) is the life cycle that takes place in the algae that have different diploid asexual and haploid sexual stages. In these algal groups, the haploid gametophyte is found with the haploid (n) number of chromosomes. This multicellular gametophyte alternates with the multicellular diploid sporophyte that have diploid (2n) number of chromosomes. In this life cycle, the mature sporophyte (2n) of the alga produces haploid spores (n) by the process of meiosis. These haploid spores then germinate and develop into the haploid gametophyte. The mature gametophyte then produces gametes (n) by the process of mitosis. After that two gametes fuse and produce a diploid zygote (2n). The diploid zygote then grows into a diploid sporophyte. This cycle from sporophyte to gametophyte or from gametophyte to sporophyte goes on and called as alternate of generation.

Conclusion

A life cycle of algae that requires two generations is matches with the termAlternation of generation.