Alternation of Generations in Plants

Alternation of Generations in Plants

• Alternation of generations is a unique life cycle found in plants, where they alternate between two different stages of life: diploid (sporophyte) and haploid (gametophyte).
• Each generation of the plant looks like its grandparent, not its parent.

Diploid and Haploid Stages

• Diploid (sporophyte) stage: 2n, has two sets of chromosomes, one from each parent.
• Haploid (gametophyte) stage: n, has one set of chromosomes.
• Diploid sporophyte cells contain one set of chromosomes from each parent.
• Haploid gametophyte cells contain only one set of chromosomes.

Alternation of Generation Life Cycle

• The life cycle starts with a diploid sporophyte, which produces spores through meiosis.
• The spores develop into a haploid gametophyte, which produces gametes (sex cells).
• Two gametes of opposite sex unite in fertilization, forming a diploid zygote.
• The zygote grows into a diploid sporophyte, and the cycle begins again.

Gametophyte Stage

• The gametophyte stage is the haploid stage, which produces gametes (sex cells).
• It begins as a spore, which grows into a multi-celled organism through mitosis.
• The gametophyte stage can be independent and survive outside the plant.

Sporophyte Stage

• The sporophyte stage is the diploid stage, which grows from the fusion of male and female sex cells.
• It produces spores through meiosis, which contain one set of chromosomes.
• The sporophyte stage can be dominant in some plants, such as ferns and angiosperms.

Evolution of Alternation of Generation

• In bryophytes, the gametophyte stage is dominant, and the sporophyte stage is temporary.
• In more complex plants, such as ferns and angiosperms, the sporophyte stage is dominant, and the gametophyte stage is small and temporary.
• As plants evolved, the gametophyte stage became smaller and less long-lived, and the diploid sporophyte stage became the dominant life stage.

Explore the unique life cycle of plants, where each generation alternates between two distinct stages. Understand the fascinating process of Alternation of Generations in plant life cycles.