Excavates + SAR

key terms + more

protist

• term used for Eukarya that are not land plants, fungi, or animals

• NOT a monophyletic group

characteristics of excavates

• unicellular

• most have flagellum

• many found in digestive track of animals (including species that aid digestion of cellulose in insects)

• bodies typically supported by internal rod consisting of microtubules or strips of proteins under plasma membrane

• undergo phagocytosis

two types of excavata?

• Giardia Lamblia

• Euglena species

characteristics of Giargia Lamblia

common intenstinal parasite of mammals (also in dogs and humans)

characteristics of Euglena species

• one of best studied group of excavates

• mixotrophic

mixotrophic

organism that can obtain nutrition by autotrophic or heterotrophic means, usually facultatively

what is a derived trait of excavates?

excavated feeding groove

characteristics of stramenopila

• unicellular and multicellular forms

• includes diatoms, brown algae, water molds

characteristics of diatoms

• major component of plankton

• most important primary producers in freshwater and marine ecosystems

• wide variety of shapes with glassy cell walls

plankton

diverse group of mostly microscopic organisms that drift in marine and freshwater systems and serve as a food source for larger aquatic organisms

characteristics of brown algae

• multicellular

• includes many “seaweeds” and kelp

• some have specialized tissues that resemble plants

  • holdfasts (roots), stipes (stems), blades (leaves)

• Kelp “forests” (foundation species, support diverse communities, important producers)

characteristics of alveolata

• unicellular

• alveolus

• includes dinoflagellates and ciliates

alveolus

flattened, membrane-bound vesicles packed into a continuous layer supporting the cell plasma membrane; provides support for the cell

characteristics of dinoflagellates

• unicellular

• more species in marine than freshwater

• another important component of plankton

• bioluminescence (light up when disturbed)

• a few species are responsible for harmful algal blooms (“red tide”)

characteristics of ciliates

• unicellular

• covered in cilia that “swim”

• 2 distinct nucleo

  • micronucleus: sexual reproduction

  • macronucleus: asexual reproduction

• has contractile vacuoles

contractile vacuole

vesicle that fills with water (as it enters the cell by osmosis) and then contracts to squeeze water from the cell; an osmoregulatory vesicle

characteristics of rhizaria

• single-celled

• lack cell walls

• vary widely in form but most are amoeba-like

• move by amoeboid motion with long slender pseudopodia

characteristics of foraminierans

• best studied of Rhizaria

• foramin = “hole”

• has tests

• abundant marine plankton, found at deep benthic zones

tests

porous shell of a foram that is built from various organic materials and typically hardened with calcium carbonate; holes thorugh which the pseudopodia protrude

stramenopila contains which organisms?

• diatoms

• brown algae

alveolata includes which organisms?

• dinoflagellates

• cillitates

rhizaria includes which organisms?

foraminiferans

biological carbon pump

process by which inorganic carbon is fixed by photosynthetic species that then die and fall to the sea floor where they cannot be reached by saprobes and their carbon dioxide consumption cannot be returned to the atmosphere

bioluminescence

generation and emission of light by an organism, as in dinoflagellates

cytoplasmic streaming

movement of cytoplasm into an extended pseudopod such that the entire cell is transported to the site of the pseudopod

endosymbiosis

engulfment of one cell within another such that the engulfed cell survives, and both cells benefit; the process responsible for the evolution of mitochondria and chloroplasts in eukaryotes

mitosome

nonfunctional organelle carried int he cells of diplomonads (excavata) that likely evolved from a mitochondrion

main traits that eukarya share

1. membrane-bound chromosomes

2. nuclei with nuclear envelope

3. linear chromosomes

4. sexual reproduction

Lynn Margulis

suggested that the endosymbiotic theory described the origin of the mitochondria

secondary endosymbiosis

• engulfment of on cell within another, and then the engulfment of that cell within a new cell

• this creates four membranes

• the theory that explains the origin of eukaryotic chloroplasts (a protist engulfed a cyanobacterium)

amoeboid motion

• the extending of part of a cell, pushing down on something, and dragging the rest of the cell behind it (movement without cilia)

• seen in rhizaria

• uses pseudopodia, which are long and hair-like

ecosystem service

benefits that humans derive, directly or indirectly, from ecosystem functions