The Venn diagram shows that there are some characteristics that are unique to each group of algae. For example, only red algae have the photosynthetic pigment phycoerythrin, and only brown algae have the photosynthetic pigment fucoxanthin.
The Venn diagram you provided shows the following relationships between the characteristics of red, brown, and green algae:
Red algae:
- Unicellular or multicellular
- No flagellated stages
- Cell wall composition: cellulose and galactans
- Photosynthetic pigments: chlorophyll a, phycoerythrin, phycocyanin
- Found in both marine and freshwater environments
- Show biphasic or triphasic life cycle patterns
- Multicellular, filamentous, or blade-like structure
- Stored food in the form of starch and polymers of galactan sulfate
Brown algae:
- Multicellular
- No flagellated stages
- Cell wall composition: cellulose, alginates, and fucoidan
- Photosynthetic pigments: chlorophyll a, c, fucoxanthin
- Found primarily in marine environments
- Show haplontic life cycle patterns
- Multicellular, thallus-like structure
- Stored food in the form of laminarin
Green algae:
- Unicellular or multicellular
- Flagellated stages in many species
- Cell wall composition: cellulose and hemicelluloses
- Photosynthetic pigments: chlorophyll a, b
- Found in both marine and freshwater environments
- Show a variety of life cycle patterns
- Multicellular, filamentous, thallus-like, or colonial structure
- Stored food in the form of starch
Characteristics shared by all three groups:
- Autotrophs (meaning they produce their own food)
- Photosynthetic (meaning they use sunlight to convert carbon dioxide and water into oxygen and glucose)
- Eukaryotes (meaning their cells have a nucleus and other organelles)
Characteristics shared by red and green algae:
- Unicellular or multicellular
- No flagellated stages in many species
- Cell wall composition contains cellulose
- Found in both marine and freshwater environments
- Show a variety of life cycle patterns
Characteristics shared by brown and green algae:
- Flagellated stages in many species
- Photosynthetic pigments include chlorophyll a and c
- Found primarily in marine environments