Organizational level

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In biology, an organizational level is a group of living beings that is characterized by common morphological characteristics and often a common way of life. The term organizational level is used regardless of whether the group is a natural kinship group, i.e. is monophyletic .

An example of an organizational level are flagellates or green algae .

In the past, before DNA sequence comparisons were used in phylogenetic research, organizational levels were also used in taxonomy when the morphological, anatomical and biochemical characteristics were insufficient to identify natural kin groups.

The following organizational levels are distinguished for algae :

  • Amoeboid stage: unicellular naked algae with pseudopodia.
  • Monadal stage: unicellular, flagellated algae, after cell division they can form colonies
  • Capsal or tetrasporal stage: vegetative cells are immobile, often have remnants of flagella; after division, the daughter cells remain embedded in a common gelatinous shell. The cell wall is thin or absent. Flagged stages are limited to the germ cells.
  • Coccal stage: vegetative cells are not flagellated and surrounded by a cell wall. They are single cells, coenobia or cell aggregates.
  • Trichal stage: The algae form branched or unbranched threads from mononuclear cells. The growth occurs intercalary or through parietal cells .
  • Siphonocladal level: like trichal, only the cells contain several cell nuclei and are therefore polyenergid .
  • Siphonal stage: The entire thallus consists of a single, multinucleated, macroscopically visible cell.
  • Felt or braided thallus : The individual threads are matted or intertwined, often also glued together.
  • Tissue thallus: The cells dividing in more than one level remain connected to one another in a real tissue .