protists 2

Eukaryotes

organisms with membrane-bound organelles

Eukaryote group type

monophyletic

Protists group type

paraphyletic

Protists

eukaryotes that are not plants animals or fungi and usually live in aquatic/wet environments

Characteristics of eukaryotes

membrane-bound organelles larger cell size cytoskeleton sexual or asexual reproduction and ability for multicellularity

Nuclear envelope origin

formed from infoldings of the plasma membrane

Mitochondria origin

formed by endosymbiosis with an alpha-proteobacterium

Evidence for endosymbiosis (mitochondria)

own circular DNA double membrane replicate by fission have their own ribosomes

Chloroplast origin

endosymbiosis with a cyanobacterium (primary then secondary events)

Evidence for endosymbiosis (chloroplasts)

circular DNA peptidoglycan layer in glaucophytes bacteria-like traits

Seven monophyletic eukaryote groups

amoebozoa opisthokonta excavata plantae rhizaria alveolata stramenopila

Protists found in

all seven major eukaryotic groups (five groups only protists)

Support/protection structures examples

diatoms silica walls; dinoflagellates cellulose plates; forams CaCO3 shells; euglenids protein pellicle

Feeding: photosynthesis

protists produce their own organic compounds using light

Feeding: absorptive

nutrients taken directly across membrane using transport proteins

Feeding: ingestive

engulf prey using pseudopodia or sweep in particles with cilia

Movement: flagella

long and few used for swimming

Movement: cilia

short and many used for swimming

Movement: pseudopodia

sliding/amoeboid motion

Ecological role: carbon cycle

photosynthetic protists use CO2 and sinking shells store carbon

Ecological role: decomposers

some protists break down organic material

Ecological role: phytoplankton

base of aquatic food webs including diatoms dinoflagellates algae

Ecological role: habitat formation

brown algae (kelp) and sargassum create habitat

Human health: malaria

caused by Plasmodium (apicomplexan)

Human health: sleeping sickness/Chagas

caused by Trypanosoma (kinetoplastid)

Human uses: diatomaceous earth

used in filtration and abrasives

Human uses: algae foods

nori seaweed salad carrageenan thickener

Human uses: algin

polysaccharide from brown algae used in many products

Human uses: agarose

polysaccharide from red algae used for gels

Dinoflagellates characteristics

alveolates mostly unicellular biflagellates often photosynthetic some with cellulose plates

Zooxanthellae

symbiotic dinoflagellates living in coral doing photosynthesis

Dinoflagellate toxins

produce saxitoxin that blocks nerve function

Harmful algal blooms

toxic dinoflagellate blooms poison shellfish and animals

Saxitoxin accumulation

clams and filter feeders accumulate toxins from eating dinoflagellates

Biomagnification

saxitoxin moves up food chains to predators

Paralytic shellfish poisoning

illness in humans from eating shellfish with saxitoxin

Coral–dinoflagellate interaction

zooxanthellae give carbon to coral and receive nutrients from coral waste

Coral bleaching

loss of zooxanthellae leading to reduced energy for coral

Bleaching causes

higher and more frequent thermal stress

Bleaching trend

bleaching occurred at higher temperatures recently suggesting adaptation or loss of sensitive genotypes