Search results
Results from the WOW.Com Content Network
Diagram of cospeciation, where parasites or endosymbionts speciate or branch alongside their hosts. This process is more common in hosts with primary endosymbionts. Scientists classify insect endosymbionts as Primary or Secondary.
Secondary endosymbiosis has occurred several times and has given rise to extremely diverse groups of algae and other eukaryotes. Some organisms can take opportunistic advantage of a similar process, where they engulf an alga and use the products of its photosynthesis, but once the prey item dies (or is lost) the host returns to a free living state.
The theory of endosymbiosis, as known as symbiogenesis, provides an explanation for the evolution of eukaryotic organisms. According to the theory of endosymbiosis for the origin of eukaryotic cells, scientists believe that eukaryotes originated from the relationship between two or more prokaryotic cells approximately 2.7 billion years ago.
Diagram of a four membraned chloroplast containing a nucleomorph. Such a layout results from secondary endosymbiosis. Nucleomorphs are small, vestigial eukaryotic nuclei found between the inner and outer pairs of membranes in certain plastids .
A symbiosome is formed as a result of a complex and coordinated interaction between the symbiont host and the endosymbiont. [5] At the point of entry into a symbiont host cell, part of the cell's membrane envelops the endosymbiont and breaks off into the cytoplasm as a discrete unit, an organelle-like vacuole called the symbiosome.
Secondary endosymbiosis results in the engulfment of an organism that has already performed primary endosymbiosis. Thus, four plasma membranes are formed. The first originating from the cyanobacteria, the second from the eukaryote that engulfed the cyanobacteria, and the third from the eukaryote who engulfed the primary endosymbiotic eukaryote. [11]
The nuclear envelope surrounds the nucleus, separating its contents from the cytoplasm.It has two membranes, each a lipid bilayer with associated proteins. [21] The outer nuclear membrane is continuous with the rough endoplasmic reticulum membrane, and like that structure, features ribosomes attached to the surface.
Euglenids or euglenoids are one of the best-known groups of eukaryotic flagellates: single-celled organisms with flagella, or whip-like tails.They are classified in the phylum Euglenophyta, class Euglenida or Euglenoidea.