28.1 Most eukaryotes are single-celled organisms

Question 1

1) Protists are alike in that all are
A) unicellular.
B) eukaryotic.
C) symbionts.
D) monophyletic.
E) autotrophic.

Answer 1

B) eukaryotic.

Question 2

2) Biologists have long been aware that the defunct kingdom Protista is paraphyletic. Which
of these statements is both true and consistent with this conclusion?
A) Many species within this kingdom were once classified as monerans.
B) Animals, plants, and fungi arose from different protist ancestors.
C) The eukaryotic condition has evolved only once among the protists, and all
eukaryotes are descendants of that first eukaryotic cell.
D) Chloroplasts among various protists are similar to those found in prokaryotes.
E) Some protists, all animals, and all fungi share a protist common ancestor, but these protists, animals, and fungi are currently assigned to three different kingdoms.

Answer 2

E) Some protists, all animals, and all fungi share a protist common ancestor, but these protists, animals, and fungi are currently assigned to three different kingdoms.

Question 3

3) The strongest evidence for the endosymbiotic origin of eukaryotic organelles is the
similarity between extant prokaryotes and which of the following?
A) nuclei and chloroplasts
B) mitochondria and chloroplasts
C) cilia and mitochondria
D) mitochondria and nuclei
E) mitochondria and cilia

Answer 3

B) mitochondria and chloroplasts

Question 4

4) According to the endosymbiotic theory of the origin of eukaryotic cells, how did
mitochondria originate?
A) from infoldings of the plasma membrane, coupled with mutations of genes for proteins in energy-transfer reactions
B) from engulfed, originally free-living prokaryotes
C) by secondary endosymbiosis
D) from the nuclear envelope folding outward and forming mitochondrial membranes
E) when a protoeukaryote engaged in a symbiotic relationship with a protobiont

Answer 4

B) from engulfed, originally free-living prokaryotes

Question 5

5) Which of these statements is false and therefore does not support the hypothesis that
certain eukaryotic organelles originated as bacterial endosymbionts? Such organelles
A) are roughly the same size as bacteria.
B) can be cultured on agar, because they make all their own proteins.
C) contain circular DNA molecules.
D) have ribosomes that are similar to those of bacteria.
E) have internal membranes that contain proteins homologous to those of bacterial plasma membranes.

Answer 5

B) can be cultured on agar, because they make all their own proteins.

Question 6

6) Which process allowed the nucleomorphs of chlorarachniophytes to be first reduced, and
then (in a few species) lost altogether, without the loss of any genetic information?
A) conjugation
B) horizontal gene transfer
C) binary fission
D) phagocytosis
E) meiosis

Answer 6

B) horizontal gene transfer

Question 7

7) Which organisms represent the common ancestor of all photosynthetic plastids found in
eukaryotes?
A) autotrophic euglenids
B) diatoms
C) dinoflagellates
D) red algae
E) cyanobacteria

Answer 7

E) cyanobacteria

Question 8

8) An individual mixotroph loses its plastids, yet continues to survive. Which of the following
most likely accounts for its continued survival?
A) It relies on photosystems that float freely in its cytosol.
B) It must have gained extra mitochondria when it lost its plastids.
C) It engulfs organic material by phagocytosis or by absorption.
D) It has an endospore.
E) It is protected by a siliceous case.

Answer 8

C) It engulfs organic material by phagocytosis or by absorption.