module six: "protists"

Explain why modern scientists do not recognize a protist "kingdom"

members of the “protista kingdom” do not share a single EXCLUSIVE COMMON ANCESTOR (paraphyletic group)

List the unifying characteristics of eukaryotes

• nuclei, nuclear envelope, nuclear pores

• mitochondria

• cytoskeleton, microtubules, microfilaments

• flagella, cilia

• chromosomes (organized by histones)

• mitosis, sexual reproduction

• cell walls

Describe what scientists know about the origins of eukaryotes based on the last common ancestor

extant eukaryotes are likely the descendants of a chimera-like organism that was a combination of a host cell and the cells of an alpha-proteobacterium that underwent endosymbiosis.

Explain the endosymbiotic theory

result of one cell engulfing another, living within the cell, then coevolving into a single cell and sharing genetic control to a mutual metabolic pathway to create ATP

Describe the role that protists play in the ecosystem

• provide food and nutrients to other organisms

• provide essential symbiotic relationships

Describe important pathogenic species of protists

• plasmodium: causes malaria

• trypanosomes: flagellate protozoa that lives in blood and tissues of vertebrate hosts

• plant parasites: agents that destroy food crops

• saprobes (protist decomposers): absorbs nutrients from non-living organisms