Detailed Summary of Chlorophyceae
Chlorophyceae, commonly known as green algae, encompasses a diverse group of chlorophyll-bearing organisms that primarily inhabit aquatic environments, including freshwater and marine ecosystems. These organisms can exhibit various growth forms such as unicellular, colonial, or filamentous structures.
Key Characteristics:
- Pigments: The organisms are predominantly green due to chlorophyll a and b, found in distinct chloroplasts that can vary in shape (discoid, plate-like, spiral, etc.).
- Cell Structure: Their rigid cell walls consist of an inner layer of cellulose and an outer layer of pectose.
- Reproduction:
- Vegetative Reproduction: Often occurs through fragmentation, where pieces of the algal body develop into new thalli.
- Asexual Reproduction: Primarily via flagellated zoospores produced in specialized structures called zoosporangia, which can swim and germinate into new individuals.
- Sexual Reproduction: Varies in gamete formation which can be isogamous, anisogamous, or oogamous.
- Storage Bodies: Many species contain pyrenoids in their chloroplasts that store starch and proteins; others may accumulate lipids as a food reserve.
Green algae are ecologically significant, contributing to half of Earth's photosynthesis and thereby increasing oxygen levels in aquatic environments. They also form the base of food chains in aquatic ecosystems. Familiar examples include Chlamydomonas, Volvox, Ulothrix, Spirogyra, and Chara.