Lecture 3: Protists

Protists

-group composed of eukaryotes that are not classified as plants, animals, or fungi

-most diverse in structural & function diversity of of any group of eukaryotes

-most nutritionally diverse out of all eukaryotes

Eukaryotes

-large genome

-large cell size

-numerous membranes w/n cell membrane

-lots of complex organelles

Prokaryotes

-small genome

-has complex organelles

-small cell size

- usually no membrane other than cell membrane, which may be infolded

-few organelles (ribosome)

What are the different modes of locomotion for protists?

pseudopodal, flagellar, cilia

photoautotrophs

contains chloroplasts

chemoheterotrophs

absorb organic molecules or ingest larger food particles

mixotrophs

mixture of photoautotrophs & chemoheterotrophs

What is most likely the origin of eukaryotes?

Prokaryote Ancestor; Archaean

Where does the mitochondria come from?

1) Ancestral prokaryote goes through invagination (plasma membrane infolds to form nuclear membrane & endoplasmic reticulum (ER)

2) Then it engulfs an aerobic heterotrophic prokaryote (this becomes the mitochondria)

Where does chloroplasts/plasmids come from?

1) Ancestral prokaryote goes through invagination (plasma membrane infolds to form nuclear membrane & endoplasmic reticulum (ER)

2) Then it engulfs an aerobic heterotrophic prokaryote (this becomes the mitochondria)

3) then it engulfs a photosynthetic prokaryote (becomes plasmid [membrane-bound organelle; e.g. chloroplast])

plasmid

a small, circular, double-stranded DNA molecule that exists separately from a cell's main chromosomal DNA and can replicate independently, often carrying genes for beneficial traits like antibiotic resistance

What are the four clades of eukaryotes?

Excavata, SAR, Archaeplastida, Unikonta

secondary endosymbiosis

eukaryote engulfing another eukaryote; leads to development of organelles

primary endosymbiosis

primitive prokaryote engulfs another prokaryote

What are the characters of the Clade Excavata?

-whip-like flagellum (allows for swimming movement through liquids)

-organelles: eyespots, chloroplasts

Eyespots

photoreceptors that acts as taxis; light stimuli -> movement

What are the characteristics of the clade stramenopila, alveolata, & rhizaria (SAR)

-locomotion by cilia (short, hair-like protrusions)

cilia

-ALL go in one direction

-occurs in large #'s; bands

-cillary beating is coordinated (do NOT work against each other)

What does SAR include?

diatoms, cilates, dinoflagellates, brown algae, apicomplexans, radiolarian

Apicomplexans

-parasite of animals

-have complex life cycles

-requires TWO organisms to complete its life cycle

Malaria

requires two organisms to complete its life cycle: humans & mosquitoes

What do both radiolarian and diatoms have in common?

they construct tests ("shell that surrounds"; shells made out of silica)

How does the clade SAR move (locomotion & capture food?

filamentous pseudopods (thin, thread-like temporary cellular extensions made of actin)

Which eukaryote is the source of photosyntheis in the ocean?

SAR

What does the clade Archaeplastida include?

red algae, green algae, & land plants

What are the characteristics of the clade Archaeplastida?

-uni to multicellular

-photosynthetic

-forms base of food webs (goes to omnivores or herbivores)

What does the clade Unikonta include?

amoebozoans, choanoflagellats, fungi, animals

What is the sister taxa to animals?

choanoflagellates

the clade Unikonta are

similar at the genetic level

What does the group Amoebozoans include?

Entamoebae*, Slime molds, Tublinids

What are the characteristics of Entamobas?

-may be free-living or parasitic

-lack tests, cilia, flagella

-uses pseudopod for movement/crawling & capturing food

-must have a food vacuole & contractile vacuole

What are the parasitic pathogenic entamobas?

naeglaeria, amoebc dysentery

pseudopod

large extensions of cytoplasm shaped by microtubles & microfilaments

What do vacuoles do?

stores water, nutrients, & waste

What do contractile vacuoles do?

pump excess water out of cells, which helps maintains ionic balance