Chapter 23: Protists

Last Eukaryote Common Ancestor (LECA)

suggested organism that all eukaryotes come from

LECA and eukarya are believed to have which shared characteristics?

cells with nuclei surrounded by nuclear envelope, mitochondria (exceptions), histone-organized chromosomes, sexual reproduction (exceptions), mitosis, and locomotion via flagella/cilia (exceptions)

the 3D model for eukaryotic emergence is traditional and depicts ___

3 domains (bacteria, archaea, and eukarya), suggesting that archaea and eukarya separated early on from the root

in the 3D model, the nodes suggest ___, which can’t be proven without ___, so scientists use ___

hypothetical common ancestor, fossils, DNA sequences and traits

the 2D model for eukaryotic emergence was developed in the 90s, is the most favored now, and depicts ___

2 domains (bacteria, and archaea and eukarya), suggesting that eukarya descended from archaea

the 2D model for eukaryotic emergence argues that ___

eukarya and archaea are much closer related than previously thought

endosymbiosis

one cell engulfs another cell, allowing the engulfed cell to survive

endosymbiont

organism living inside the host (necessary for its survival); some are harmful (parasites); some are beneficial

endosymbiotic theory

all eukaryotes descend from a prokaryotic cell (the endosymbiont) that took residence in side a proto-eukarote cell (ancestral/primative host)

2.4-2.5 mya, an ancient ___ (host) engulfed an ___ (endosymbiont)

anaerobic prokaryote, aerobic alpha-proteobacteria

during the 1st and 2nd steps of eukaryotic evolution, a proto-eukaryotic cell develops what three structures?

cell membrane, nucleus, endomembrane system

during the 3rd and 4th steps of eukaryotic evolution, ___ is engulfed by a proto-eukarotic cell

aerobic bacteria

during eukaryotic evolution, aerobic bacterium loses its ability to leave the cell because it becomes ___

assimilated (symbiont)

mitochondria and alpha-proteobacteria have similar shapes, such as the ___

folds of inner membrane

mitochondria inner membrane is similar to ___

bacterial plasma membrane

mitochondrial DNA, ribosomes, and tRNA are closely related to ___

alpha-proteobacteria

mitochondria divide similarly to ___

bacterial fission

endosymbiotic theory and ___ occurred at the same time

photosynthesis

chloroplasts of plants and some protists originate from a ___

Cyanobacteria symbiont (host cell engulfed mitochondria, and them photosynthetic prokaryote)

during chloroplast-containing eukaryotic evolution, photosynthetic prokaryotes evolved into ___ once they were engulfed by the host cell

chloroplast

chloroplast also have 2 membranes with similar compositions to ___, and their own ___

bacteria, DNA

protist

eukaryotes not belonging to Fungi, Plantae, or Animalia kingdoms

protist cell structure can be

microscopic and unicellular (diverse); or macroscopic and multicellular (simple)

protist protection can be

animal-like plasma membrane; plant-like cell wall

protist metabolism can be

aerobic, anaerobic, photoautotropic, heterotrophic, or ingestion via phagocytosis

phagocytosis is the process of ___

removing bacteria/unwanted substances via food vacuole and lysosome fusion

protist living/environment can be

free or parasitic; aquatic (nearly all)

protist reproduction can be

asexual (common; ancestor may have lost the ability to sexually reproduce); some have maintained sexual reproduction

protist movement can be

with cilia (simultaneous and cohesive), flagellum, or pseudopod (thick finger-like protections)

protists are the only eukaryotes that are polyphyletic, meaning they ___

developed from more than one ancestral lineage

eukaryotes can be classified into 4 ___ supergroups based solely on genetics because protists’ lineage is diverse

monophyletic (sharing one single common ancestor)

excavata

single celled organisms with a feeding groove “excavated” from one side (e.g., Giardia lamblia)

excavata’s metabolism can be ___

heterotrophic predators, photosynthetic species, and parasites

excavata orders are

diplomonads, parabasilids, and euglenazoans

SARS

3 major lineages varying in size, organization, and metabolism

stramenopiles are organisms within SARS that are ___

mostly photosynthetic/some autotrophs with one smooth and one hairy flagellum

diatoms are stramenopiles that have ___

additional protective later inside made of silicon dioxide

golden algae are unicellular stramemopiles that ___

form colonies, conduct photosynthesis, and obtain yellow color from carotene

brown algae are multicellular stramenopiles that are ___

very similar to plants (especially organs, when complex) and conduct photosynthesis

alveolates are organisms within SARS that have the ___

presence of an alveolus (membrane-enclosed sac under the plasma membrane [unknown function]; e.g., opicomplexans)

dinoflagellates are alveolates with ___

2 perpendicular flagella for limitied mobility, and interlocked cellulose plates for protection

ciliates are alveolates that have ___

rows, tufts, or spirals, of tiny cilia for coordinated direction and ingestion (e.g., paramecium and tetrahymena)

rhizarians are organisms within SARS that include ___

ceecozoans, formas, and radiolarians

archeaplastida are organisms within SARS closely related to plants that ___

have chloroplast; many do photosynthesis, have cells walls, and store food as starch

red algae are protist archeaplastida that are ___

primarily multicellular but can also be be unicellular, microscopic, or macroscopic

green algae are protist archeaplastida that make up ___

a large and diverse group and are most closely related to plants (e.g., chlorophytes and charophytes). they can be unicellular and multicellular

land plants are the only ___ archeaplastida

non-protists