Algae Diversity and Characteristics

Study Notes

Algae are organisms that are neither plants nor animals, belonging to the Kingdom Protista or Prototista.
They can be found in terrestrial and aquatic habitats, including freshwater and marine environments.
Algae come in many different forms, shapes, sizes, and colors, and can exist on their own or grow on the surfaces of other organisms.

Small free-floating algae are known as phytoplanktons.
They can be found in aquatic habitats, including semi-permanent pools, ponds, lakes, streams, and ocean shorelines.
In terrestrial habitats, algae can be found on rock, wood surfaces, and in symbiotic association with fungal species, known as lichens.

Algae are grouped into three divisions based on their pigmentation:
- Rhodophyta (Red Algae)
- Phaeophyta (Brown Algae)
- Chlorophyta (Green Algae)

Chlorophyta (Green Algae):
- Made up of unicellular, colonial, and multicellular forms
- Mostly found in freshwater, with some marine forms
- Reproduce asexually and sexually, with biflagellated gametes
Rhodophyta (Red Algae):
- Multicellular, mostly marine groups
- Cells are non-flagellated
- Alternation of generation is common
- Chlorophyll is masked by red pigments
Phaeophyta (Brown Algae):
- Multicellular, mostly marine groups
- Found in intertidal zones
- Chlorophyll is masked by brown pigments
- Alternation of generation is common

Algae reproduce via three different modes:
- Vegetatively (e.g., fragmentation, fission)
- Asexually (e.g., by different spores)
- Sexually (e.g., by gametes)
Green algae reproduce asexually and sexually
Sexual reproduction involves biflagellated gametes
Alternation of generation is common in Brown and Red algae

Algae are capable of synthesizing their own food from inorganic substances using light or chemical energy
They are autotrophic organisms, using light as the source of energy to prepare their food
They are photoautotrophs, meaning they use light to synthesize their own food

Algae are a link in the food chain, providing energy for other organisms
They are useful in fish culture, serving as a source of feed for fish
Algae can be harmful in large quantities, causing harmful algal blooms that can have negative impacts on humans, marine and freshwater environments, and coastal economies
They are used in sewage treatment plants to provide oxygen for bacterial decomposition
They are used in the petroleum and gas industry, with some varieties having high lipid content serving as a source of bio-fuel
Algae form extensive deposits of limestone, accumulating calcium carbonate in their cell walls
They are used as food, providing carbohydrates, vitamins, and inorganic substances
Algae are used as fodder, with some species being used as stock feed
They are used as fertilizer, with some species having nitrogen-fixing capabilities
Algae are used in medicine, with some species being used to treat goitre and other glandular problems
They are used in industrial applications, such as the production of agar, kelp, and algin.