Algae Types and Life Cycles

Algae are composed of members that have prokaryotic (e.g. Chlamydomonas) and eukaryotic type (e.g. Chroococcus) of cells.

Microalgae (e.g. Chlorella) can only be observed under a microscope while macroalgae (e.g. Sargassum) can be seen with the naked eye.

Filamentous algae (e.g. Chlorococcum) are composed of cells that are in the form of a chain while a colonial algae (e.g. Volvox) are composed of cells that can appear as organized mass.

Chlorophyll a absorbs the red and blue wavelengths while reflecting the green wavelenght of visible light.

The blue-green (e.g. Gloeocapsa), red (e.g. Caulerpa) and brown (e.g. Macrocystis) color of some algae are due to the masking of the green Chlorophyll a by different accessory pigments.

In the diplontic life cyle, the only free-living multicellular stage is the diploid stage which assigns specific cells to undergo meiosis to produce sex cells or gametes.

In a diplo-haplontic biphasic life cycle, the zygote undergoes mitotis to produce a multicellular diploid generation called a gametophyte which in turn undergoes meiosis to produce haploid spores that will germinate to produce a multicellular haploid generation called a sporophyte.

In a diplo-haplontic triphasic life cycle, the alternating multicellular stages are the diploid carposporophyte stage, diploid tetrasporophyte stage and the haploid gametophyte stage.

Thallus-bodied algae (e.g. Laminaria) have plant-like parts (root-like stipe, stem-like holdfast and leaf-like blade) that are not considered as true organs because of the absence of vascular tissues.

The blue-green algae are classified under Division Cyanophyta and Kingdom Eubacteria while red algae are classified under Division Rhodophyta and Kingdom Plantae.

The euglenoids are classified under Division Euglenophyta and Kingdom Plantae while the dinoflagellates are classified under Division Dinophyta and Kingdom Chromista.

The red algae are a product of the primary endosymbiosis between a heterotrophic eukaryote and a cyanobacteria which later became its chloroplast.

The euglenoids are a product of the secondary endosymbiosis between a heterotrophic eukaryote and a eukaryotic red algae which later became its chloroplast.