Red algae
Red algae, or Rhodophyta ( , ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority of species (6,793) are found in the Florideophyceae (class), and mostly consist of multicellular, marine algae, including many notable seaweeds. Red algae are abundant in marine habitats but are relatively rare in freshwaters. Approximately 5% of the red algae occur in freshwater environments with greater concentrations found in warmer areas. Except for two coastal cave dwelling species in the asexual class Cyanidiophyceae, there are no terrestrial species, which may be due to an evolutionary bottleneck where the last common ancestor lost about 25% of its core genes and much of its evolutionary plasticity.

The red algae form a distinct group characterized by having eukaryotic cells without flagella and centrioles, chloroplasts that lack external endoplasmic reticulum and contain unstacked (stroma) thylakoids, and use phycobiliproteins as accessory pigments, which give them their red color. Red algae store sugars as floridean starch, which is a type of starch that consists of highly branched amylopectin without amylose, as food reserves outside their plastids. Most red algae are also multicellular, macroscopic, marine, and reproduce sexually. The red algal life history is typically an alternation of generations that may have three generations rather than two.
The coralline algae, which secrete calcium carbonate and play a major role in building coral reefs, belong here. Red algae such as dulse "(Palmaria palmata)" and laver (nori/gim) are a traditional part of European and Asian cuisines and are used to make other products such as agar, carrageenans and other food additives.
Q19088
eukaryotic
Concept
Q37868
algae
Concept
Q1002125
Florideophyceae
Concept
Q37517
class
Concept
Q36458
multicellular
Concept
Q9430
marine
Concept
Q237169
seaweed
Concept
Q1319026
Cyanidiophyceae
Concept
Q189998
flagella
Concept
Q178355
centriole
Concept
Q47263
chloroplast
Concept
Q79927
endoplasmic reticulum
Concept
Q337889
thylakoid
Concept
Q3234015
phycobiliprotein
Concept
Q3737836
accessory pigment
UNK
Q24900734
floridean starch
Concept
Q271643
amylopectin
Concept
Q207466
amylose
Concept
Q36458
multicellular
Concept
Q182353
reproduce sexually
Concept
Q725951
alternation of generations
Concept
Q2524330
coralline algae
Concept
Q23767
calcium carbonate
Concept
Q11292
coral reef
Concept
Q864648
dulse
Concept
Q60483094
laver
UNK
Q201565
nori
Concept
Q582328
gim
Concept
Q579316
European
Concept
Q728206
Asian cuisine
Concept
Q177998
agar
Concept
Q421991
carrageenan
Concept
Q189567
food additives
Concept
Q103169
Red algae
Concept
Q103169
Red algae
Concept
Q103169
Red algae
Concept
Q103169
Red algae
Concept
+6.793^^http://www.w3.org/2001/XMLSchema#decimal
6,793
NUMBER
+5^^http://www.w3.org/2001/XMLSchema#decimal
5
NUMBER
+25^^http://www.w3.org/2001/XMLSchema#decimal
25
NUMBER
subclass of
taxon rank
use