Protists

protist

all eukaryotes except land plants, fungi, and animals

what defining characteristics do protists share?

none- paraphyletic group

medical impacts of protists

disease causing in humans (malaria, giardia, chogas disease) and parasitize crops

what ecological impacts do protists have

harmful algae blooms, base of the food chain, carbon cycle

symbiosis

individuals of two different species live in physical contact

endosymbiosis

organism of one species lives inside the cells of an organism of another species

endosymbiotic theory for mitochondria

originated when bacterial cell took up residence inside another cell; bacterial cell gives ATP, host cell gives carbon source and oxygen

mitochondrial evidence

1) similar in size to bacteria 2) use binary fission to reproduce like bacteria 3) have two membranes 4) have own genomes 5) have ribosomes

primary endosymbiosis

cell with mitochondria and nucleus engulfed a cyanobacteria; host cell gets sugar and oxygen and cyanobacteria gets sunlight and protection

secondary symbiosis

host with nucleus engulfed a protist that could photosynthesize (has chloroplast and nucleus), nucleus of protist degrades; tradeoffs same as primary endosymbiosis

chloroplast evidence

1) bacterial-like characteristics 2) genetics like cyanobacteria 3) later of peptidoglycan in outer covering 4) cyanobacteria can live inside animals and protists 5) multiple membranes

what did primary endosymbiosis mainly create

occurred before common ancestor to plantae; land plants, red and green algae

what did secondary endosymbiosis mainly create

diatoms brown algae, dinoflagellates, and euglenids

support structures of protists

cell wall, protein covering, silica plates, cellulose plates, and calcium carbonate shell

ingestive feeding

flexible membrane and dynamic cytoskeleton allow them to surround and “swallow” prey with pseudopodia

phagocytosis

takes in packets of food much larger than individual molecules

ciliary feeding

sweeping food particles into mouth with cilia

absorptive feeding

nutrients taken up across plasma membrane, directly from the environment; done by decomposers or parasites

amoeboid

pseudopodia stream forward

flagella

filament used for swimming

cilia

numerous hair-like projections used for swimming

asexual reproduction

cell undergoes mitosis and produces an identical cell

sexual reproduction

cell undergoes meiosis and produces four genetically unique cells

alternation of generations

gametophyte —> (mitosis) eggs and sperm —> (fertilization) zygote —> (mitosis) sporophyte —> (meiosis) spores —> (mitosis) gametophyte

gametophyte

multicellular stage, 1N

eggs and sperm

1N, unicellular

zygote

2N, unicellular

sporophyte

multicellular, 2N

spores

1N, unicellular