Algae

Alga Palla Verde - Codium Bursa

Alga Palla Verde - Codium Bursa

Alga Palla Verde Codium Bursa Codiaceae intotheblue.it ....
Caulerpa a grappoli - Caulerpa racemosa

Caulerpa a grappoli - Caulerpa racemosa

Caulerpa racemosa J. Agardh 1873 è un'alga verde della famiglia Caulerpaceae. È originaria del mar Rosso, ma è una specie alloctona del mar Mediterraneo, in cui è penetrata attraverso il Canale di Suez fin dal 1926. ...
Halimeda Tuna

Halimeda Tuna

Halimeda tuna alga marina verde famiglia Halimedacae intotheblue.it, mar mediterraneo, mediterranean sea, algae, alghe, alghe verdi ....
Pavonia - Padina pavonica

Pavonia - Padina pavonica

Pavonia coda di pavone Padina pavonica Dictyotaceae intotheblue.it La Pavonia o coda di pavone, Padina pavonica, (L. Thivy 1960) è un'alga bruna della famiglia delle Dictyotaceae.....
Sphaerococcus coronopifolius

Sphaerococcus coronopifolius

Sphaerococcus coronopifolius alga algae alghe rosse intotheblue ....
Udotea

Udotea

Udotea alga marina verde Udoteaceae intotheblue.it ...

Algae (/ˈæliˈælɡi/; singular alga /ˈælɡə/) is an informal term for a large, diverse group of photosynthetic eukaryotic organisms that are not necessarily closely related, and is thus polyphyletic. Including organisms ranging from unicellular microalgae genera, such as Chlorella and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 m in length. Most are aquatic and autotrophic and lack many of the distinct cell and tissue types, such as stomataxylem, and phloem, which are found in land plants. The largest and most complex marine algae are called seaweeds, while the most complex freshwater forms are the Charophyta, a division of green algae which includes, for example, Spirogyra and the stoneworts.

Halimeda tuna - intotheblue.it

Halimeda tuna – intotheblue.it

 

No definition of algae is generally accepted. One definition is that algae “have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around their reproductive cells”. Although cyanobacteria are often referred to as “blue-green algae”, most authorities exclude all prokaryotes from the definition of algae.

Algae constitute a polyphyletic group since they do not include a common ancestor, and although their plastids seem to have a single origin, from cyanobacteria, they were acquired in different ways. Green algae are examples of algae that have primary chloroplasts derived from endosymbiotic cyanobacteria. Diatoms and brown algae are examples of algae with secondary chloroplasts derived from an endosymbiotic red alga.

 

Padina pavonica intotheblue.it

Padina pavonica intotheblue.it

 

Algae exhibit a wide range of reproductive strategies, from simple asexual cell division to complex forms of sexual reproduction.

Algae lack the various structures that characterize land plants, such as the phyllids (leaf-like structures) of bryophytesrhizoids in nonvascular plants, and the rootsleaves, and other organs found in tracheophytes (vascular plants). Most are phototrophic, although some are mixotrophic, deriving energy both from photosynthesis and uptake of organic carbon either by osmotrophymyzotrophy, or phagotrophy. Some unicellular species of green algae, many golden algaeeuglenidsdinoflagellates, and other algae have become heterotrophs (also called colorless or apochlorotic algae), sometimes parasitic, relying entirely on external energy sources and have limited or no photosynthetic apparatus. Some other heterotrophic organisms, such as the apicomplexans, are also derived from cells whose ancestors possessed plastids, but are not traditionally considered as algae. Algae have photosynthetic machinery ultimately derived from cyanobacteria that produce oxygen as a by-product of photosynthesis, unlike other photosynthetic bacteria such as purple and green sulfur bacteria. Fossilized filamentous algae from the Vindhya basin have been dated back to 1.6 to 1.7 billion years ago.

alga palla verde - seaweed green ball - codium bursa - intotheblue.it

alga palla verde – seaweed green ball – codium bursa – intotheblue.it

 

Traditional classification

Algae are common in all seas and in freshwater places. Before the appearance of phylogenetic classifications, they were divided into nine Divisions (suffix -phyta) according to the conformation and type of photosynthetic pigment used:

Classification

The algae contain chloroplasts that are similar in structure to cyanobacteria. Chloroplasts contain circular DNA like that in cyanobacteria and are interpreted as representing reduced endosymbiotic cyanobacteria. However, the exact origin of the chloroplasts is different among separate lineages of algae, reflecting their acquisition during different endosymbiotic events. The table below describes the composition of the three major groups of algae. Their lineage relationships are shown in the figure in the upper right. Many of these groups contain some members that are no longer photosynthetic. Some retain plastids, but not chloroplasts, while others have lost plastids entirely.

Phylogeny based on plastid not nucleocytoplasmic genealogy:

  Cyanobacteria
 
 
  Glaucophytes
 
 
rhodoplasts
  Rhodophytes
 
  Heterokonts
 
 
  Cryptophytes
 
  Haptophytes
 
 
 
chloroplasts
  Euglenophytes
 
 
 
  Chlorophytes
 
 
  Charophytes
 
  Land plants (Embryophyta)
 
 
 
  Chlorarachniophytes
 
 
 
 
 

https://it.wikipedia.org/wiki/Alga

https://en.wikipedia.org/wiki/Algae

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