Thursday, November 29, 2007

Concept 28.1

Question:
I. Cite at least 4 examples of structural & functional diversity among protists

Answer:
a) Protists are more diverse than all other eukaryotes and are no longer classified in a single Kingdom. Most protists are unicellular, some are colonial or multicellular. Protists include photoautotrophs, heterotrophs, & mixotrophs. Most species are aquatic, but others are found in moist terrestrial habitats. Some species are exclusively asexual; others reproduce asexually.

Question:
II. Immediately after a eukaryotic cell ingests a gramnegative cyanobacterum dirung primary endosymboisis, how many membranes separate the cytoplasm of the bacterium from the fluid outside the eukaryotic cell? Identify each membrane.

Answer:
a) Some biologists hypothesize that mitochondria and plastids are descendans of alpha proteobacteria and cyanobacteria, respectively, that were engulfed bt itger cekks abd became endosymbionts. The plastid-bearing lineage enventually evolved into red algae and green algae. Other protist groups evolved form secondary endosymbiotic events in which red algae or green algae were themselves engulfed.