BI158 - Quiz 3 study guide

Chapter 28 terms and some questions for understanding

Protists

informal name of the group of mostly unicellular eukaryotes

eukaryotic cells

have organelles and are more complex than prokaryotic cells

• have a cytoskeleton that provides structural support and allows for diversity in shape

single-celled protists

Can be complex, as their biological functions are carried out by organelles in each individual cell

Photoautotrophs

protists that contain chloroplasts

Heterotrophs

protists that absorb organic molecules or ingest large food particles

Mixotrops

Protists that combine photosynthesis and heterotrophic nutrition

Amitochondriates

used to be considered the oldest lineage of eukaryotes

1. excavates

2. SAR clade

3. archaeplastida

4. uniknots

What are the 4 supergroups of protists?

Endosymbiosis

A relationship between 2 species in which one organism lives inside the cell or cells of the other organism (hosts)

• Skews the evolution of eukaryotes

Prokaryotes that were engulfed by the ancestor of early eukaryotic cells

What are mitochondria and plastids derived from?

Lynn Margulis in 1967

Who proposed the idea that mitochondria and plastids were engulfed by ancestor of eukaryotic cells?

Support came from the comparison of mtDNA (mitochondrial DNA) with those of bacteria and archaea

What supported Margulis’s hypothesis?

Red and green algae

What groups of photosynthetic protists did the plastid-bearing lineage evolve to?

Secondary endosymbiosis

when red and green algae were ingested by a heterotrophic eukaryote

Chlorarachniophytes

Likely evolved when a heterotrophic eukaryote engulfed a green algae

Nucleomorph

a vestigial nucleus that is located in engulfed cells which have similar genes to green algae

Excavata

Originally categorized by its cytoskeleton

• some members have an excavated feeding groove

• these protists have modified mitochondria

Diplomonads

• no plastids

• mitochondria are reduced to mitosomes

• live in anaerobic environments

• have 2 equal-sized nuclei and multiple flagella

• often parasitic

  • Ex: Glardia

Parabasalids

• no plastids

• mitochondria are reduced by hydrogenosomes

• Generate some energy anaerobically

• produce H₂ gas

  • Ex: Trichomonas vaginalis

Trichomonas vaginalis

A pathogen that causes yeast infections in females

• 5 million per year

Euglenozoans

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

They have a spiral or crystalline road inside their flagella

What is the main feature that distinguishes euglenozoans?

Kinetoplastids

Have a single mitochondrion with an organized DNA

Kinetoplast

The organized DNA found in the single mitochondrion of a kinetoplastid

Trypanosoma

Parasitic kinetoplastids that cause sleeping sickness in humans or Chagas’ disease

Trypanosoma could switch the surface proteins and a cell would produce copies of a different protein, allowing the trypanosoma to invade the immune system and prevent the host from developing immunity

How does the Trypanosoma affect our cells?

Euglenids

Have one or two flagella that emerge from a pocket at one end of the cell

• some can be autotrophic, heterotrophic, mixotrophs, depending on the available light

SAR Clade

• Diverse monophyletic supergroup

• Grouping is based mostly on similarities of whole genome DNA sequences

• Most controversial of the 4 supergroups because of the presence of chloroplasts

Stramenopiles and Alveolates

Which clades of SAR show evidence of 2nd endosymbiosis from red algae

Stramenopiles

Include some of the most important photosynthetic organisms

• Has a “hairy” flagellum paired with a shorter “smooth” flagellum

  • Include diatoms, golden algae, and brown algae

Diatoms

Unicellular algae with a unique two-part glass-like silicon wall

• Can withstand pressures up to 1.4 million kg/m²

• 100K living species, common in some surface plankton communities

• Major component of phytoplankton and highly diverse

Diatomaceous earth

Composes the wall of the fossilized diatom

Many dead diatoms sink to the ocean floor undecomposed, which removes carbon dioxide from the atmosphere and “pumps” it to the ocean floor

What happens after a diatom population blooms?

Golden Algae

• Yellow & brown carotenoids

• Mixotrophs

• Photosynthetic

Brown Algae

• Largest and most complex algae

• multicellular and most are marine

• include kelp & some seaweeds

Holdfast

Anchors the dalga of a brown algae

• rootlike

Stemlike stipe

supports the blade

Blade

leaflike top of a brown algae

They are analogous

What is the structural similarities between algae and plants?

Alternations of generations

Alternation of multicellular algae

Alveolates

Has membrane-enclosed sacs (alveoli) just under the plasma membrane

• includes dinoflagellates, apicomplexan, and ciliates

Dinoflagellates

• have 2 flagella

• each cell is reinforced by cellulose plates

• abundant components of marine and freshwater phytoplankton

• Diverse groups of aquatic phototrophs, mixotrophs, and heterotrophs

• Toxic “red tides” are caused by dinoflagellate blooms

Apicomplexans

Parasites of animals and some cause serious human diseases

• the apex end contains a complex of organelles specialized for penetrating host cells and tissue

• most have sexual & asexual stages that require different host species for completion

Sporozites

When the apicomplexans spread through host as infectious cells

• apex end has complex organelles for penetrating host cells and tissues

• most have sexual and asexual stages that require different host species for completion

Plasmodium

Parasite that causes malaria

• needs mosquitos and humans to complete their life cycles

• Approx. 900,000 die each year from this disease

Ciliates

large varied groups of protists named for their use of cilia to move and feed

• have large macronuclei and small micronuclei

Conjugation

Sexual process and is separate from reproduction which generally occurs by binary fission

Rhizarians

Amoebas that move and fee by threadlike pseudopodia

Radiolarians

Have delicate, symmetrical internal skeletons that are made of silica

• Pseudopodia is used to engulf microorganisms through phagocytosis and radiates from the central body

Phagocytosis

When a cell engulfs another cell

• also known as “cell eating”

Foraminiferans / Forams

Named for porous, generally multi chambered shells called tests

• Pseudopodia extend through the pores in the tests

foram tests in marine sediments

Form extensive fossil records to estimate changes in ocean temperature over time

cercozoans

Include amoeboid and flagellated protists with threadlike pseudopodia

• common in marine, freshwater, and soil ecosystems

• heterotrophic including parasites

Paulinella Chromatophora

Autotroph with a unique photosynthetic structure that evolved from a cyanobacteria

Chromatophore

The photosynthetic structure found in the Paulinella Chromatophora

Red and green algae

What are the closest relatives to land plants?

Archaeplastida

• Plastids that arose when a heterotrophic protist acquired a cyanobacterial endosymbiont

• Land plants are descendants of green algae

• First group of eukaryotes where chloroplasts appeared due to endosymbiosis

Red algae

• Reddish in color due to an accessory pigment that masks the green.

• Varies in color from greenish-red to almost black

• Usually multicellular

• most abundant large algae in coastal waters

  • Ex: Nori, Bonnemaisonia hamifera

Phycoerythrin

The pigment found in red algae that masks the green chlorophyll

Green algae

• named for their grass-green chloroplasts

• Plants are descended from green algae

• Paraphyletic group of chlorophytes and charophytes

Charophytes

Green algae that is more related to land plants

Chlorophytes

• simplest ones are unicellular resemble gametes of the complex ones

• Have complex life cycles with sexual & asexual reproductive stages

• live in freshwater and marine environments

• live in damp soil as symbionts to lichens

• live in environments exposed to intense visible and UV radiation

  • Have compounds that block the effects of radiation

• Ex: Sea lettuce

1. Formation of colonies from individual cells

2. Formation of true multicellular bodies by cell division and differentiation

3. The repeated division of nuclei with no cytoplasmic divisions

   1. Ex: Caulerpa

How did larger and greater complexity evolve in chlorophytes?

Uniknota

• includes animals, fungi, and some protists

• Includes the Amoebozoans and opisthoknots

• have flagella, generally one

• Root of their life is controversial

Amoebozoans

Amoeba that have lobe or tube shaped pseudopodia rather than threadlike

• Include slime molds, tubulinids, and entamoebas

slime molds

• AKA mycetozoans, which were fungi

• DNA sequence indicate that the resemblance to fungi is from convergent evolution

• Includes the plasmodial and cellular lineages

Plasmodial slime mold

• Brightly pigmented yellow or orange

• Plasmodium is a giant single cell (mass of cytoplasm) that do not increase in a cell number but nuclei

• Extends pseudopodia through decomposing material and engulf food by phagocytosis

Cellular slime mold

form multicellular aggregates in which cells are separated by their membranes

• cells feed individually but can aggregate and form a fruiting body

  • Ex: Dictyostelium discoideum

Tubulinids

• Unicellular protists in soil, freshwater, and marine environments

• Most are heterotrophic and consume bacteria and other protists

Entamoebas

Parasites of vertebrates and some invertebrates

• could cause amebic dysentry

Opisthokonts

Fungi, Choanoflagellates, and animals

Diverse aquatic and moist terrestrial environments

Where are protists found?

Symbiont and producer

What are the two key roles of protists in ecological communities?

• Dinoflagellates nourish coral polyps that build reefs

  • Zooxanthellae in their tissues that allow for efficient extraction of calcium carbonate

• Wood-digesting protists inhabit the gut of termites

What are the symbiont benefits?

• Aquatic-photosynthetic protists and prokaryotes are the main producers and limited by nutrients

• Biomass of photosynthetic protists has declines as sea surface temperature has increased

  • Growth of phytoplankton relies on nutrients delivered from ocean bottom through process of upwelling which is limited by warm surface water

What are the produce benefits?

Plasmodium

Causes Malaria

Pfiesteria shumwayae

A dinoflagellate that causes fish kills

Phytophthora ramorum

causes sudden oak death