define the term alternation of generation

Alternation of generations is a type of life cycle found in terrestrial plants and some algae in which subsequent generations of individuals alternate between two modes of reproduction: sexual and asexual.

Here are the steps to understand this concept:

1. The cycle begins with a mature individual in the sporophyte stage. The sporophyte is diploid, meaning it has two sets of chromosomes.

2. The sporophyte produces spores by meiosis, a process which reduces the number of chromosomes in each spore to one set (haploid).

3. These haploid spores grow into multicellular individuals without fusing with another cell. This stage of the life cycle is called the gametophyte stage.

4. The gametophyte produces gametes (sex cells) by mitosis, which does not alter the number of chromosomes.

5. Two gametes fuse to form a diploid zygote, which grows into a new sporophyte. This completes the cycle.

In summary, alternation of generations is the process where a plant or algae alternates between a sexual phase (the gametophyte) and an asexual phase (the sporophyte).