Ch 25: The Origin and Diversification of Eukaryotes Flashcards
How old are the oldest widely accepted fossils of eukaryotic organisms?
- 8 billion years old
p. 507
Focusing on three stages documented by the fossil record: an initial diversification (1.8 - 1.3 billion years ago), the origin of multicellularity and other novel features (1.3 billion - 635 million), and the emergence of large eukaryotes (635-535 million years ago).
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Which two organelles are thought to be former small bacteria that began living as endosymbionts?
mitochondria and plastids
The serial endosymbiosis hypothesis supposes that ______ evolved before ______ through a sequence of endosymbiotic events.
mitochondria
plastids
What evidence supports the idea that red and green algae originated from a cyanobacterial endosymbiont?
Cyanobacteria are gram negative and have 2 cell membranes, just like plastids in red and green algae. Transport proteins in these membranes are homologous to proteins in the inner and outer membranes of cyanobacteria.
p. 510
How do diatoms affect global atmospheric CO2 levels?
CO2 absorbed by diatoms is “pumped” to the ocean floor when they die, lowering CO2 levels.
p. 523
The SAR supergroup includes 3 large and diverse clades:
- Stramenopiles (includes diatoms and brown algae)
- Alveolates (includes dinoflagellates, ciliates, and apicomplexans
- Rhizarians (includes forams and cercozoans)
The supergroup archaeplastida includes…
….red and green algae, along with plants. Many of these are informally known as “seaweed”. The green algae are grouped into chlorophytes and charophytes.
Image: Volvox is a multicellular freshwater green alga.
p. 515
The group Excavata includes…
Diplomonads
Parabasalids
Euglenozoans
p. 541
These clades of protists shown on p. 514 were all formerly classified as belonging to Kingdom ________
Protista
p. 514
What is one infamous genus of the Euglenozoan clade?
Trypanosoma, which is a kinetoplastid that causes sleeping sickness.
p. 516
The supergroup Unikonta includes….
….Tubulinds and slime molds (amoebozoans)
Nucleariids, fungi, choanoflagellates, and animals.
The last 4 are placed in a category known as Opisthokonts.
The green algae are believed to share a common ancestor with plants because….
…. Their chloroplasts are similar in structure and pigment composition to those of plants.
p. 520
Trypanosomes are effective parasites of humans because they evade the immune system by….
….sequentially changing surface proteins.
Dinoflagellates are responsible for the phenomenon called ___ ____. Periods of explosive population growth, or blooms, in dinoflagellates make coastal waters appear brownish red or pink because of the presence of ___________, the most common pigments in dinoflagellate plastids. Toxins produced by certain dinoflagellates have caused massive kills of invertebrates and fishes. Humans who eat mollusks that have accumulated the toxins are affected as well, sometimes fatally.
“red tide”
carotenoids
Diatoms, dinoflagellates, multicellular algae, and other aquatic protists perform __% of the world’s photosynthesis.
30%
The diplomonads and parabasalids lack ________ and have highly _______ mitochondria
plastids
reduced
p. 516
The protist genus __________ is responsible for malaria.
Plasmodium
Dinoflagellates posses _ flagella.
2
The term mixotroph refers to an organism that can be both….
….autotrophic and heterotrophic.
In other words, they combine photosynthesis and heterotrophic nutrition.
p. 518
Amoebas are motile protists that move by __________.
pseudopodia.
The contractile vacuole or Paramecium functions in what role?
water regulation
p. 518
The diplomonads and parabasalids are unique among eukaryotes in that…
….they have highly reduced mitochondria and obtain energy anaerobically
The name derives from the fact that some members of this diverse group feature an “excavated” _______ _______ on one side of the cell body.
feeding groove
Which if the following is NOT true of seaweeds?
a. ). They are found in the red, green, and brown algal groups.
b. ). They may be a source of food and commercial products.
c. ) They are multicellular photoautotrophs.
d. ) Most are classified as charophytes, the closest living relatives of land plants.
e. ) They have true roots that anchor them tightly to withstand the turbulence of waves.
e.
Plasmodium belongs to a group of _________, the apicomplexans, that includes other protists that cause serious human diseases. Nearly all apicomplexans are _________ of animals.
alveolates
parasites
_______ is the genus of mosquitoes that transmit Plasmodium.
Anopheles
What is true of all protists?
They are eukaryotes.
What statement is true of all algae?
They are photosynthetic.
A shared characteristic of eukaryotes and prokaryotes is….
…a cell membrane.
Which of the following is evidence that the transition to multicellularity did not require the origin of large numbers of novel genes?
Genomic studies indicate that multicellular Volvox has few novel genes compared with unicellular Chlamydomonas, and the ________ proteins of animals, which are involved in animal cell adherence to each other, contain only one novel domain not found in the cadherin proteins of unicellular choanoflagellates.
cadherin
