Ch 25: The Origin and Diversification of Eukaryotes

Question 1

How old are the oldest widely accepted fossils of eukaryotic organisms?

Answer 1

1. 8 billion years old

p. 507

Question 2

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).

Answer 2

**

Question 3

Which two organelles are thought to be former small bacteria that began living as endosymbionts?

Answer 3

mitochondria and plastids

Question 4

The serial endosymbiosis hypothesis supposes that ______ evolved before ______ through a sequence of endosymbiotic events.

Answer 4

mitochondria

plastids

Question 5

What evidence supports the idea that red and green algae originated from a cyanobacterial endosymbiont?

Answer 5

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

Question 6

How do diatoms affect global atmospheric CO2 levels?

Answer 6

CO2 absorbed by diatoms is “pumped” to the ocean floor when they die, lowering CO2 levels.

p. 523

Question 7

The SAR supergroup includes 3 large and diverse clades:

Answer 7

1. Stramenopiles (includes diatoms and brown algae)
2. Alveolates (includes dinoflagellates, ciliates, and apicomplexans
3. Rhizarians (includes forams and cercozoans)

Question 8

The supergroup archaeplastida includes…

Answer 8

….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

Question 9

The group Excavata includes…

Answer 9

Diplomonads
Parabasalids
Euglenozoans

p. 541

Question 10

These clades of protists shown on p. 514 were all formerly classified as belonging to Kingdom ________

Answer 10

Protista

p. 514

Question 11

What is one infamous genus of the Euglenozoan clade?

Answer 11

Trypanosoma, which is a kinetoplastid that causes sleeping sickness.

p. 516

Question 12

The supergroup Unikonta includes….

Answer 12

….Tubulinds and slime molds (amoebozoans)
Nucleariids, fungi, choanoflagellates, and animals.

The last 4 are placed in a category known as Opisthokonts.

Question 13

The green algae are believed to share a common ancestor with plants because….

Answer 13

…. Their chloroplasts are similar in structure and pigment composition to those of plants.

p. 520

Question 14

Trypanosomes are effective parasites of humans because they evade the immune system by….

Answer 14

….sequentially changing surface proteins.

Question 15

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.

Answer 15

“red tide”

carotenoids

Question 16

Diatoms, dinoflagellates, multicellular algae, and other aquatic protists perform __% of the world’s photosynthesis.

Answer 16

30%

Question 17

The diplomonads and parabasalids lack ________ and have highly _______ mitochondria

Answer 17

plastids
reduced

p. 516

Question 18

The protist genus __________ is responsible for malaria.

Answer 18

Plasmodium

Question 19

Dinoflagellates posses _ flagella.

Answer 19

2

Question 20

The term mixotroph refers to an organism that can be both….

Answer 20

….autotrophic and heterotrophic.
In other words, they combine photosynthesis and heterotrophic nutrition.

p. 518

Question 21

Amoebas are motile protists that move by __________.

Answer 21

pseudopodia.

Question 22

The contractile vacuole or Paramecium functions in what role?

Answer 22

water regulation

p. 518

Question 23

The diplomonads and parabasalids are unique among eukaryotes in that…

Answer 23

….they have highly reduced mitochondria and obtain energy anaerobically

Question 24

The name derives from the fact that some members of this diverse group feature an “excavated” _______ _______ on one side of the cell body.

Answer 24

feeding groove

Question 25

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.

Answer 25

e.

Question 26

Plasmodium belongs to a group of _________, the apicomplexans, that includes other protists that cause serious human diseases. Nearly all apicomplexans are _________ of animals.

Answer 26

alveolates

parasites

Question 27

_______ is the genus of mosquitoes that transmit Plasmodium.

Answer 27

Anopheles

Question 28

What is true of all protists?

Answer 28

They are eukaryotes.

Question 29

What statement is true of all algae?

Answer 29

They are photosynthetic.

Question 30

A shared characteristic of eukaryotes and prokaryotes is….

Answer 30

…a cell membrane.

Question 31

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.

Answer 31

cadherin