Prokaryotes were the first cells; bacteria-like organisms
• Descendants belong in two groups: Archaea and Eubacteria Symbiogenesis: process whereby cells of one prokaryotic lineage engulfed, but did not digest cells from another prokaryotic lineage. The engulfed cell was eventually reduced to an organelle inside the host cell. Eukaryotic products of symbiogenesis include mitochondria and plastids Primary endosymbiosis: development of organelle by prokaryote engulfed and modified the bacteria Secondary endosymbiosis: ie. When eukaryote obtains plastids from another eukaryote Protozoa: assemblage of eukaryotic unicellular organisms
“-zoa” refers to the absence of cell wall and presence of at least one motile stage in life cycle unicellular eukaryotes= protozoans, found wherever life exist, highly adaptable and easily moved from place to place mutualistic: both partners benefit
commensalistic: one partner benefits, no effect on the other parasitic: one partner benefits at the expense of the other, cause of most important diseases of humans and domestic animals metazoans: multi-cellular animals
protist: a.k.a. protozoan; general term acknowledging the futility of placing unicellular forms within the plant or animal kingdoms plant-like & animal-like: refer in part to the way that food is gathered plants are typically autotrophic (synthesize their own organic constituents from inorganic substrates, ie. Via photosynthesis) animals are typically heterotrophic (obtain organic molecules synthesized by other organisms, in soluble form or particulate form) Particulate food (visible particles) is acquired by phagocytosis (infolding or invagination of the cell membrane to surround a visible food particle); these heterotrophs are phagotrophs or holozoic feeders Those who ingest soluble food are osmotrophs or saprozoic feeders Autotrophic protozoa = phototroph; use light energy to synthesize their organic molecules, but often practice phagotrophy and osmotrophy...
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