Biology 2 Chapter 28: Protists

Heterotrophs

absorb organic molecules or ingest larger food particles

secondary endosymbiosis

red and green algae underwent this; in which they were ingested by a heterotrophic eukaryote

Excavates

protists with modified mitochondria and protists with unique flagella

Excavata

characterized by its cytoskeleton; some members have a feeding grove

Excavates

controversial group includes the diplomonads, parabasalids, and euglenozoans

Diplomonads and Parabasalids

lack plastids, have modified mitochondria, and most live in anaerobic environments

Diplomonads

have modified mitochondria called mitosomes; derive energy from anaerobic biochemical pathways; have two equal-sized nuclei and multiple flagella; are often parasites

Parabasalids

have reduced mitochondria called hydrogenosomes that generate some energy anaerobically; include Trichomonas vaginalis, the pathogen that causes yeast infections (vaginitis) in human females and urethritis in human males

Euglenozoa

diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, and parasites

Euglenozoa

main feature distinguishing them as a clade is a spiral or crystalline rod of unknown function inside their flagella

Euglenozoa

This clade includes the kinetoplastids and euglenids

Kinetoplastids

a single mitochondrion with an organized mass of DNA called a kinetoplast

Protist

the informal name of the group of mostly UNICELLULAR eukaryotes

Eukaryotic cells

have organelles and are more complex than prokaryotic cells

Photoautotrophs

contain chloroplasts

Mixotrophs

combine photosynthesis and heterotrophic nutrition

Endosymbiosisis

the process in which a unicellular organism engulfs another cell, which becomes an endosymbiont and then organelle in the host cell

Mitochondria

evolved by endosymbiosis of an aerobic prokaryote

Plastids

evolved by endosymbiosis of a photosynthetic cyanobacterium

red and green algae

The plastid-bearing lineage of protists evolved

Kinetoplastids

this group includes Trypanosoma, which causes sleeping sickness in humans

Euglenids

have one or two flagella that emerge from a pocket at one end of the cell; some species can be both autotrophic and heterotrophic

Chromalveolatais

monophyletic and originated by a secondary endosymbiosis event

Chromalveolatais

proposed endosymbiont is a red alga

Chromalveolatais

this clade is controversial and includes the alveolates and the stramenopiles

Alveolata

have membrane-bounded sacs (alveoli) just under the plasma membrane

alveolates in Alveolata

dinoflagellates, apicomplexans, ciliates

Dinoflagellates

have two flagella and each cell is reinforced by cellulose plates; are abundant components of both marine and freshwater phytoplankton; they are a diverse group of aquatic phototrophs, mixotrophs, and heterotrophs

"red tides"

caused by dinoflagellate blooms

Apicomplexans

are parasites of animals, and some cause serious human diseases

sporozoites

spread through their host as infectious cells

apex end of apicomplexans

contains a complex of organelles specialized for penetrating host cells and tissues

apicomplexan Plasmodium

the parasite that causes malaria

Plasmodium

requires both mosquitoes and humans to complete its life cycle

Ciliates

a large varied group of protists; named for their use of cilia to move and feed

Ciliates

have large macronuclei and small micronuclei

conjugation

which two individuals exchange haploid micronuclei

Stramenopila

includes important phototrophs as well as several clades of heterotrophs; most have a "hairy" flagellum paired with a "smooth" flagellum

Stramenopiles

include diatoms, golden algae, brown algae, and oomycetes

Diatoms

unicellular algae with a unique two-part, glass-like wall of hydrated silica

Diatoms

a major component of phytoplankton and are highly diverse

Fossilized diatom

walls compose much of the sediments known as diatomaceous earth

Golden algae

named for their color, which results from their yellow and brown carotenoids

Golden algae

are photosynthetic, and some are mixotrophs; most are unicellular, but some are colonial

Brown algae

the largest and most complex algae; multicellular, and most are marine; include many species commonly called "seaweeds"; have the most complex multicellular anatomy of all algae

kelps

giant seaweeds; live in deep parts of the ocean

thallus of kelp

algal body is plantlike but lacks true roots, stems, and leaves

kelps

rootlike holdfast anchors the stemlike stipe, which in turn supports the leaflike blades

diploid sporophyte

produces haploid flagellated spores called zoospores

zoospores

develop into haploid male and female gametophytes, which produce gametes

alternation of generations

the alternation of multicellular haploid and diploid forms

Heteromorphic (anisomorphic)

generations are structurally different

isomorphic

generations look similar

Oomycetes

include water molds, white rusts, and downy mildews; decomposers or parasites; have filaments (hyphae) that facilitate nutrient uptake

Rhizaria

a monophyletic clade; include radiolarians, foraminifera (forams), and cercozoans

Amoebas

move and feed by pseudopodia; some but not all belong to the clade Rhizaria

radiolarians

marine protists; have tests fused into one delicate piece, usually made of silica; use their pseudopodia to engulf microorganisms through phagocytosis

Foraminiferans or forams

named for porous, generally multichambered shells, called tests; endosymbiotic algae

Cercozoans

include most amoeboid and flagellated protists with threadlike pseudopodia

Cercozoans

common in marine, freshwater, and soil ecosystems; most are heteroptrophs, including parasites and predators

red and green algae

the closest relatives of land plants

Archaeplastida

the supergroup that includes red algae, green algae, and land plants

Red algae

reddish in color due to an accessory pigment called phycoerythrin, which masks the green of chlorophyll; multicellular

designation of seaweeds

the largest multicellular red alga are included in the

Red algae

most abundant large algae in coastal waters of the tropics

Green algae

named for their grass-green chloroplasts

Charophytes

most closely related to land plants

Charophytes and Chlorophytes

paraphyletic groups of green algae

Larger size and greater complexity evolved in chlorophytes by

the formation of colonies from individual cells; the formation of true multicellular bodies by cell division and differentiation; the repeated division of nuclei with no cytoplasmic division

Unikonta

supergroup includes animals, fungi, and some protists

Unikonta

the amoebozoans and the opisthokonts

Amoebozoans

are amoeba that have lobe-or tube-shaped, rather than threadlike, pseudopodia

Slime molds or mycetozoans

were once thought to be fungi; in the clade amoebozoa

plasmodial slime molds

are brightly pigmented, usually yellow or orange; form a mass called a plasmodium

plasmodium in plasmodial slime molds

not multicellular; undivided by plasma membranes and contains many diploid nuclei; extends pseudopodia through decomposing material, engulfing food by phagocytosis

Cellular slime molds

form multicellular aggregates in which cells are separated by their membranes

Dictyostelium discoideumis

an experimental model for studying the evolution of multicellularity

Gymnamoebas

common unicellular amoebozoans in soil as well as freshwater and marine environments; heterotrophic and actively seek and consume bacteria and other protists

Entamoebas

parasites of vertebrates and some invertebrates

Entamoeba histolytica

causes amebic dysentery, the third-leading cause of human death due to eukaryotic parasites

Protists

play the role of symbiontor producer

Dinoflagellates

nourish coral polyps that build reefs

Wood-digesting protists

digest cellulose in the gut of termites

Plasmodium

causes malaria

Pfiesteria shumwayae

a dinoflagellate that causes fish kills

Phytophthora ramorum

causes sudden oak death

aquatic environments

photosynthetic protists and prokaryotes are the main producers

declined; increased

Biomass of photosynthetic protists has ____ as sea surface temperature has ____