BIOL 215 Multicellularity Flashcards
Why does most picture of evolution show a bias ?
Because they show evolution as a linear process but it is not, it is multidirectional.
How many times did multicellular life forms appear ?
At least 13 different times.
Why did it take so long for unicellular organisms to become multiellular ?
The transition to unicellular life to multicellular is a hard transition.
What are the currently studied animals to understand their primary origin and why?
Sponges (they are not included in eumetasoa though) because they have a basic multicellular structure sharing common characteristics with the colonial form of choanoflagellates and DNA sequences. (see diagram in the notes to see how closely related are sponges to animals and sponges to choanoflagellates)
How did fungi evolved to becoome multicellular ?
With networks like those we see with the coprinus mushroom. Spores are signe cells that creates networks to connect together (anastamose) and share nutrients to create the mushroom.
How did algae develop to become multicellular ?
Algae evolved in at least to different ways. The first exemple we see is with the lettuce Ulva where single cells failed to divide completely and this mutation was then transmitted. In the case of green algae, it’s a phenomenon called volvox that is observed, where single cells combined to form a larger cell.
How did diatom develop to become multicellular ?
The most known example is the colonial diatom where diatoms form colonies surrounded by a siliceous structure (“wall”) and are gaining advantages doing so.
How did ciliate develop to become multicellular ?
The best example is the zoothamnium: colonial ciliates linked together by a muscle thread that can contract.
How did cellular slime molds develop to become multicellular ?
At the first stage of their life, they are unicellular beings, but when food start missing, they aggregate to form a fruiting body.
What is the general feature of multicellularity observed on aquatic individuals ?
A failure to separate.
What is the general feature of multicellularity observed on terristrial individuals ?
Aggregation (motile) or aggregation of nuclei
What are the advantages of multicellularity for aquatic organisms ?
Prevent to be eaten by filtrer feeder, faster swimming and internal cellular environment.
What are the advantages of multicellularity for terrestrial organisms ?
Propagation of spores, feeding and internal cellular environment.
