Bryopsidales is an
order
Order, ORDER or Orders may refer to:
* A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
...
of
green algae
The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...
, in the
class
Class, Classes, or The Class may refer to:
Common uses not otherwise categorized
* Class (biology), a taxonomic rank
* Class (knowledge representation), a collection of individuals or objects
* Class (philosophy), an analytical concept used d ...
Ulvophyceae
The Ulvophyceae or ulvophytes are a class of green algae, distinguished mainly on the basis of Ultrastructure, ultrastructural morphology, Biological life cycle, life cycle and molecular phylogenetics, molecular phylogenetic data. The sea lettu ...
.
It is a diverse group of mostly
marine macroalgae
Seaweed, or macroalgae, refers to thousands of species of Macroscopic scale, macroscopic, Multicellular organism, multicellular, ocean, marine algae. The term includes some types of ''Rhodophyta'' (red), ''Brown algae, Phaeophyta'' (brown) and ...
.
[
]
Characteristics
The thallus
Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...
is filamentous, highly branched, and may be packed into a mass. It is coenocytic, having multi-nucleate cells consisting of cytoplasm
The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...
contained within a cylindrical cell wall
A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...
. There are no septae, and the many discoid chloroplasts, nuclei and other organelle
In cell biology, an organelle is a specialized subunit, usually within a cell (biology), cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as Organ (anatomy), organs are to th ...
s are free to move through the organism. The whole organism may consist of a single cell; in the genus '' Caulerpa'', this single cell may be several metres across. In the genus ''Halimeda
''Halimeda'' is a genus of green macroalgae. The algal body (thallus) is composed of calcified green segments. Calcium carbonate is deposited in its tissues, making it inedible to most herbivores. However one species, ''Halimeda tuna'', was desc ...
'', whole seabed meadows may consist of an individual, single-celled organism connected by filamentous threads running through the substrate.
Reproduction
Propagation is normally vegetative from small fragments which grow into new individuals. Under certain conditions, sexual reproduction occurs in a process called ''holocarpy''. Almost all of the cytoplasm in the thallus
Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...
is converted into biflagellate gamete
A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as s ...
s, which are discharged into the sea through papillae. After fertilisation, the zygote
A zygote (; , ) is a eukaryote, eukaryotic cell (biology), cell formed by a fertilization event between two gametes.
The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individ ...
becomes a protonema and this, in turn, develops into a new thallus.[Overview of the Genus ''Caulerpa'']
Proceedings of the International ''Caulerpa taxifolia'' Conference, 2002.
Phylogeny
Molecular phylogenetic studies suggest the following relationships between extant taxa (Chaetosiphonaceae not included):
References
{{Taxonbar, from=Q6452523
Chlorophyta orders