What is the definition of algae

Algae is typically an aquatic plant of a large group that includes the seaweeds and many single-celled forms. Algae is also non-flowering and fairly simple. Algae contain chlorophyll but lack true stems, roots, leaves, and vascular tissue.

a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.