According to the endosymbiotic theory of the origin of eukaryotic cells, how did mitochondria originate?

1. A) from infoldings of the plasma membrane, coupled with mutations of genes for proteins in energy-transfer reactions
2. B) from engulfed, originally free-living proteobacteria
3. C) by secondary endosymbiosis
4. D) from the nuclear envelope folding outward and forming mitochondrial membranes
5. E) when a protoeukaryote engaged in a symbiotic relationship with a protocell

B

An individual mixotroph loses its plastids, yet continues to survive. Which of the following most likely accounts for its continued survival?

1. A) It relies on photosystems that float freely in its cytosol.
2. B) It must have gained extra mitochondria when it lost its plastids.
3. C) It engulfs organic material by phagocytosis or by absorption.
4. D) It has an endospore.
5. E) It has multiple alveoli.

C

Which of the following was derived from an ancestral cyanobacterium?

1. A) chloroplast
2. B) mitochondrion
3. C) hydrogenosome
4. D) mitosome

A

Why can eukaryotes be considered "combination" organisms?

1. A) Some of their genes and cellular characteristics were derived from archaea, and others from bacteria.
2. B) They eventually developed flagella.
3. C) Their diversity outnumbers prokaryotes by over 1 million species.
4. D) They eventually developed cellulose plates.

A

In a sample of pond water, a new organism is identified with the following characteristics: It consists of 70 cells surrounded by rigid cell walls that join the cells together. Inside each of these identical cells are mitochondria and chloroplasts. Such an organism would most likely be classified as a

1. A) colonial photosynthetic eukaryote.
2. B) fungal photosynthetic eukaryote.
3. C) colonial photosynthetic prokaryote.
4. D) multicellular photosynthetic prokaryote.
5. E) colonial eukaryotic fungus.

A

Which of the following is the most likely sequence of events, from earliest to most recent, in the evolution of sponges (organisms with many cells that have different functions)?

1. single-celled eukaryote
2. single-celled prokaryote
3. multicellular eukaryote
4. colonial eukaryote

1. A) 2, 1, 4, 3
2. B) 2, 1, 3, 4
3. C) 1, 2, 3, 4
4. D) 1, 2, 4, 3

A

The evolution of multicellularity in animals required adaptations that promoted

1. A) cellular migration and intercellular communication.
2. B) cellular migration and cellular adhesion.
3. C) cellular adhesion and intercellular communication.
4. D) photosynthesis and cellular migration.
5. E) cellular fusion and regeneration.

C

The last common ancestor of fungi and animals was most likely a

1. A) multicellular photosynthetic eukaryote.
2. B) colonial photosynthetic prokaryote.
3. C) multicellular photosynthetic prokaryote.
4. D) single-celled eukaryote.

D

The evolution of multicellularity in animals has primarily occurred by

1. A) changing how existing genes are used.
2. B) deleting many old genes.
3. C) producing many new genes.
4. D) deleting many old chromosomes.

A

Multicellular colonies of plant cells adhere to each other primarily by ________, whereas multicellular colonies of animal cells are typically held together by ________.

1. A) fusion of cellular membranes; cell walls
2. B) cell walls; fused cellular membranes
3. C) cell walls; proteins
4. D) interlocking chloroplasts; interlocking mitochondria
5. E) interlocking cellular shapes; large, calcified capsules

C

Which of the following organism pairs is/are an example of secondary endosymbiosis?

1. red algae–heterotrophic eukaryote
2. green algae–heterotrophic eukaryote

III. E. coli bacteria–photosynthetic cyanobacterium

1. Chlamydomonas and Gonium

1. A) I only
2. B) III and IV
3. C) I and II
4. D) II and III

C

Which of the following pairs of protists and their characteristics are mismatched?

1. A) apicomplexans–internal parasites
2. B) mixotrophs–combine photosynthesis and heterotrophic nutrition
3. C) euglenozoans–unicellular flagellates
4. D) ciliates–red tide organisms

D

Which of the following statements about dinoflagellates is true?

1. A) They possess two flagella.
2. B) All known varieties are autotrophic.
3. C) Their walls are usually composed of silica plates.
4. D) Many types lack mitochondria.
5. E) Their dead cells accumulate on the seafloor and are mined to serve as a filtering material.

A

Why is the filamentous morphology of the slime molds considered a case of convergent evolution with fungi?

1. A) Water molds evolved from filamentous fungi.
2. B) Body shape reflects ancestor-descendant relationships among organisms.
3. C) DNA sequence analyses indicate that slime molds descended from different unicellular ancestors than did fungi.
4. D) Filamentous body shape is evolutionarily ancestral for all eukaryotes.

C

Diatoms are mostly asexual members of the phytoplankton. They obtain their nutrition from functional chloroplasts, and each diatom is encased within two porous, glasslike valves. Which question would be most important for one interested in the day-to-day survival of individual diatoms?

1. A) How does carbon dioxide get into these protists with their glasslike valves?
2. B) How do diatoms get transported from one location on the water's surface layers to another location on the surface?
3. C) How do diatoms with their glasslike valves keep from sinking into poorly lit waters?
4. D) How do diatoms with their glasslike valves avoid being shattered by the action of waves?
5. E) How do diatom sperm cells locate diatom egg cells?

C

A large seaweed that floats freely on the surface of deep bodies of water would be expected to lack which of the following?

1. A) alveoli
2. B) bladders
3. C) holdfasts
4. D) flagella

C

Rhizarians that feed using threadlike pseudopodia include which of the following group(s)?

1. forams
2. red algae

III. cercozoans

1. green algae

1. A) I and III
2. B) II and III
3. C) I and IV
4. D) II and IV

A

A snail-like, coiled, porous test (shell) of calcium carbonate is characteristic of which group?

1. A) diatoms
2. B) foraminiferans
3. C) red algae
4. D) cercozoans

B

The chloroplasts of land plants are thought to have been derived according to which evolutionary sequence?

1. A) cyanobacteria → green algae → land plants
2. B) cyanobacteria → green algae → fungi → land plants
3. C) red algae → brown algae → green algae → land plants
4. D) cyanobacteria → red algae → green algae → land plants

A

A biologist discovers an alga that is marine, multicellular, and can absorb both green and blue light. This alga probably belongs to which group?

1. A) red algae
2. B) brown algae
3. C) green algae
4. D) dinoflagellates

A

Green algae differ from land plants in that some green algae

1. A) are heterotrophs.
2. B) are unicellular.
3. C) have plastids.
4. D) have alternation of generations.
5. E) have cell walls containing cellulose.

B

Some scientists who study organismal classification believe that green algae should be in an expanded "plant" kingdom called Viridiplantae. If land plants are excluded from this kingdom, then what will be true of it?

1. A) It will be monophyletic.
2. B) It will more accurately depict evolutionary relationships than does the current taxonomy.
3. C) It will be paraphyletic.
4. D) It will be a true clade.

C

The best evidence for not classifying the slime molds as fungi comes from slime molds'

1. A) DNA sequences.
2. B) nutritional modes.
3. C) choice of habitats.
4. D) physical appearance.
5. E) reproductive methods.

A

Which pair of alternatives is highlighted by the life cycle of the cellular slime molds, such as Dictyostelium?

1. A) prokaryotic or eukaryotic
2. B) unicellular or multicellular
3. C) diploid or haploid
4. D) autotroph or heterotroph

B

Which of the following statements concerning protists is true?

1. A) All protists have mitochondria, although in some species they are much reduced and known by different names.
2. B) The primary organism that transmits malaria to humans by its bite is the tsetse fly.
3. C) All apicomplexans are autotrophic.
4. D) All slime molds have an amoeboid stage that may be followed by a stage during which spores are produced.
5. E) Euglenozoans that are mixotrophic lack functional chloroplasts.

A

Of the four supergroups of eukaryotes, which one contains red algae, green algae, and all land plants?

1. A) SAR
2. B) Archeplastida
3. C) Excavata
4. D) Unikonta

B

Why is there controversy surrounding the eukaryotic tree?

1. A) It suggests that the unikonts are evolutionarily derived from the archeplastids.
2. B) It suggests that amoebozoans are more closely related (evolutionarily) to red algae than green algae.
3. C) The tree lacks branches for species that have yet to be classified.
4. D) The root of the tree is uncertain such that it is unknown which supergroup was the first to diverge from all other eukaryotes.

D

Which of the following is correctly described as a primary producer?

1. A) foram
2. B) kinetoplastid
3. C) apicomplexan
4. D) diatom

D

You discover a new species of aerobic, mixotrophic protist that can perform photosynthesis in fairly deep water (for example, 250 m deep). It can also crawl about and engulf small particles. Which two characteristics does your protist have to have in order to successfully complete these tasks?

1. hydrogenosome
2. apicoplast
3. pseudopods
4. chloroplast from red alga
5. chloroplast from green alga

1. A) 1 and 2
2. B) 2 and 3
3. C) 2 and 4
4. D) 3 and 4
5. E) 4 and 5

D

In a synthetic biology experiment, you are given a task to design a new species of aquatic protist. Your design should account for the following characteristics:

1. The protist functions as a primary producer.
2. It cannot swim on its own.
3. It must stay in well-lit surface waters.
4. It must be resistant to physical damage from wave action.

Based on these criteria, you decide to model your creation after a(n)

1. A) diatom.
2. B) dinoflagellate.
3. C) apicomplexan.
4. D) red alga.
5. E) radiolarian.

A

Which of the following is (are) mutualistic partnerships between a protist and a host organism?

1. cellulose-digesting gut protists—wood-eating termites
2. dinoflagellates—reef-building coral animals

III. Trichomonas—humans

1. algae—certain foraminiferans

1. A) I only
2. B) II and IV
3. C) I, II, and III
4. D) I, II, and IV

D

Living diatoms contain brownish plastids. If global warming causes blooms of diatoms in the surface waters of Earth's oceans, how might this be harmful to the animals that build coral reefs?

1. A) The coral animals, which capture planktonic organisms, may be outcompeted by the diatoms.
2. B) The coral animals' endosymbiotic dinoflagellates may get "shaded out" by the diatoms.
3. C) The coral animals may die from overeating the plentiful diatoms.
4. D) The diatoms' photosynthetic output may over-oxygenate the water.

B

Which two genera have members that can evade the human immune system by frequently changing their surface proteins?

1. Plasmodium
2. Trichomonas
3. Paramecium
4. Trypanosoma

1. A) 1 and 2
2. B) 1 and 4
3. C) 2 and 3
4. D) 2 and 4

B

Judging from the table and given that water's density and, consequently, its buoyancy decrease at warmer temperatures, in which environment should diatoms (and other suspended particles) sink most slowly?

1. A) cold pure water
2. B) warm pure water
3. C) cold seawater
4. D) warm seawater

C

Using dead diatoms to "pump" CO2 to the seafloor is feasible only if dead diatoms sink quickly. Consequently, application of mineral fertilizers, such as iron, should be most effective at times when diatom valves

1. A) are thickest, and laminarin is being produced rather than oil.
2. B) are thickest, and oil is being produced rather than laminarin.
3. C) are thinnest, and laminarin is being produced rather than oil.
4. D) are thinnest, and oil is being produced rather than laminarin.

A

You are given four test tubes, each containing an unknown protist. Your task is to read the following description and match these four protists to the correct test tube.

When red and blue light are shone on the tubes, oxygen bubbles accumulate on the inside of test tubes 1 and 2. Chemical analysis of test tube 1 indicates the presence of a chemical that is toxic to fish and humans. Chemical analysis of test tube 2 indicates the presence of substantial amounts of silica. Microscopic analysis of organisms in test tube 3 reveals the presence of an apicoplast in each. Microscopic analysis of the contents in test tube 4 reveals thousands of cilia on the surface of the organism.

Test tube 4 contains

1. 1. A) Paramecium
   2. B) Navicula (diatom).
   3. C) Pfiesteria (dinoflagellate).
   4. D) Plasmodium.

A

You are given four test tubes, each containing an unknown protist. Your task is to read the following description and match these four protists to the correct test tube.

When red and blue light are shone on the tubes, oxygen bubbles accumulate on the inside of test tubes 1 and 2. Chemical analysis of test tube 1 indicates the presence of a chemical that is toxic to fish and humans. Chemical analysis of test tube 2 indicates the presence of substantial amounts of silica. Microscopic analysis of organisms in test tube 3 reveals the presence of an apicoplast in each. Microscopic analysis of the contents in test tube 4 reveals thousands of cilia on the surface of the organism.

Test tube 2 contains

1. A) Paramecium.
2. B) Navicula (diatom).
3. C) Pfiesteria (dinoflagellate).
4. D) Plasmodium.

B

You are given four test tubes, each containing an unknown protist. Your task is to read the following description and match these four protists to the correct test tube.

When red and blue light are shone on the tubes, oxygen bubbles accumulate on the inside of test tubes 1 and 2. Chemical analysis of test tube 1 indicates the presence of a chemical that is toxic to fish and humans. Chemical analysis of test tube 2 indicates the presence of substantial amounts of silica. Microscopic analysis of organisms in test tube 3 reveals the presence of an apicoplast in each. Microscopic analysis of the contents in test tube 4 reveals thousands of cilia on the surface of the organism.

Test tube 1 contains

1. A) Paramecium.
2. B) Navicula (diatom).
3. C) Pfiesteria (dinoflagellate).
4. D) Plasmodium.

C

You are given four test tubes, each containing an unknown protist. Your task is to read the following description and match these four protists to the correct test tube.

When red and blue light are shone on the tubes, oxygen bubbles accumulate on the inside of test tubes 1 and 2. Chemical analysis of test tube 1 indicates the presence of a chemical that is toxic to fish and humans. Chemical analysis of test tube 2 indicates the presence of substantial amounts of silica. Microscopic analysis of organisms in test tube 3 reveals the presence of an apicoplast in each. Microscopic analysis of the contents in test tube 4 reveals thousands of cilia on the surface of the organism.

Test tube 3 contains

1. A) Paramecium.
2. B) Navicula (diatom).
3. C) Pfiesteria (dinoflagellate).
4. D) Plasmodium.

D

Giardia intestinalis is an intestinal parasite of humans and other mammals that causes intestinal ailments in most people. It can infect people when they drink water contaminated with feces containing Giardia cysts. Upon ingestion, each cyst releases two motile cells, called trophozoites. These attach to the small intestine's lining via a ventral adhesive disk. The trophozoites anaerobically metabolize glucose from the host's intestinal contents to produce ATP. Reproduction is completely asexual, occurring by longitudinal binary fission of trophozoites, with each daughter cell receiving two haploid nuclei (n = 5). A trophozoite will often encyst as it passes into the large intestine by secreting around itself a case that is resistant to cold, heat, and dehydration.

Giardia's mitosome can be said to be "doubly degenerate," because it is a degenerate form of ________, an organelle that is itself a degenerate form of ________.

1. A) nucleus; archaean
2. B) nucleus; bacterium
3. C) mitochondrion; proteobacterium
4. D) mitochondrion; spirochete
5. E) chloroplast; cyanobacterium

C

Giardia intestinalis is an intestinal parasite of humans and other mammals that causes intestinal ailments in most people. It can infect people when they drink water contaminated with feces containing Giardia cysts. Upon ingestion, each cyst releases two motile cells, called trophozoites. These attach to the small intestine's lining via a ventral adhesive disk. The trophozoites anaerobically metabolize glucose from the host's intestinal contents to produce ATP. Reproduction is completely asexual, occurring by longitudinal binary fission of trophozoites, with each daughter cell receiving two haploid nuclei (n = 5). A trophozoite will often encyst as it passes into the large intestine by secreting around itself a case that is resistant to cold, heat, and dehydration.

Given its mode of reproduction and internal structures, which of the following should be expected to occur in Giardia at some stage of its life cycle?

1. separation (segregation) of daughter chromosomes
2. crossing over
3. meiosis

1. A) 1 only
2. B) 3 only
3. C) 1 and 2
4. D) 1 and 3
5. E) 2 and 3

A

Giardia intestinalis is an intestinal parasite of humans and other mammals that causes intestinal ailments in most people. It can infect people when they drink water contaminated with feces containing Giardia cysts. Upon ingestion, each cyst releases two motile cells, called trophozoites. These attach to the small intestine's lining via a ventral adhesive disk. The trophozoites anaerobically metabolize glucose from the host's intestinal contents to produce ATP. Reproduction is completely asexual, occurring by longitudinal binary fission of trophozoites, with each daughter cell receiving two haploid nuclei (n = 5). A trophozoite will often encyst as it passes into the large intestine by secreting around itself a case that is resistant to cold, heat, and dehydration.

Unlike most excavates, Giardia trophozoites have no oral groove and are unable to form food vacuoles. Thus, we should expect its nutrition (mostly glucose) to come from

1. A) its mitosomes.
2. B) endosymbiotic cyanobacteria.
3. C) the ventral disk by which it adheres to the intestinal lining.
4. D) osmosis involving aquaporins (proteins that transport water across cell membranes).
5. E) plasma membrane proteins that are transporters or pumps.

E

Giardia intestinalis is an intestinal parasite of humans and other mammals that causes intestinal ailments in most people. It can infect people when they drink water contaminated with feces containing Giardia cysts. Upon ingestion, each cyst releases two motile cells, called trophozoites. These attach to the small intestine's lining via a ventral adhesive disk. The trophozoites anaerobically metabolize glucose from the host's intestinal contents to produce ATP. Reproduction is completely asexual, occurring by longitudinal binary fission of trophozoites, with each daughter cell receiving two haploid nuclei (n = 5). A trophozoite will often encyst as it passes into the large intestine by secreting around itself a case that is resistant to cold, heat, and dehydration.

During passage through the large intestine, a trophozoite will often secrete a case around itself, forming a cyst. Cysts contain four haploid nuclei. When cysts "hatch" within a new host, two trophozoites are released. Thus, which of the following must happen within the cyst prior to hatching?

1. meiosis
2. nuclear division
3. S phase
4. binary fission

1. A) 1 only
2. B) 1 and 2
3. C) 2 and 3
4. D) 2 and 4
5. E) 2, 3, and 4

E

Giardia intestinalis is an intestinal parasite of humans and other mammals that causes intestinal ailments in most people. It can infect people when they drink water contaminated with feces containing Giardia cysts. Upon ingestion, each cyst releases two motile cells, called trophozoites. These attach to the small intestine's lining via a ventral adhesive disk. The trophozoites anaerobically metabolize glucose from the host's intestinal contents to produce ATP. Reproduction is completely asexual, occurring by longitudinal binary fission of trophozoites, with each daughter cell receiving two haploid nuclei (n = 5). A trophozoite will often encyst as it passes into the large intestine by secreting around itself a case that is resistant to cold, heat, and dehydration.

The cysts of Giardia are most analogous to the

1. A) mitochondria of ancestral diplomonads.
2. B) nuclei of archaeans.
3. C) endospores of bacteria.
4. D) capsids of viruses.

C

Giardia intestinalis is an intestinal parasite of humans and other mammals that causes intestinal ailments in most people. It can infect people when they drink water contaminated with feces containing Giardia cysts. Upon ingestion, each cyst releases two motile cells, called trophozoites. These attach to the small intestine's lining via a ventral adhesive disk. The trophozoites anaerobically metabolize glucose from the host's intestinal contents to produce ATP. Reproduction is completely asexual, occurring by longitudinal binary fission of trophozoites, with each daughter cell receiving two haploid nuclei (n = 5). A trophozoite will often encyst as it passes into the large intestine by secreting around itself a case that is resistant to cold, heat, and dehydration.

If the mitosomes of Giardia contain no DNA, yet are descendants of what were once free-living organisms, then where are we likely to find the genes that encode their structures, and what accounts for their current location there?

1. A) plasmids; conjugation
2. B) plasmids; transformation
3. C) nucleus; horizontal gene transfer
4. D) nucleus; S phase

C

The primary treatment for giardiasis (infection with Giardia), trichomoniasis (infection with Trichomonas vaginalis), and amoebic dysentery (infection with Entamoeba histolytica) is a drug marketed as Flagyl (generic name is metronidazole). The drug also kills anaerobic gut bacteria. Consequently, which of these are cues that Flagyl's mode of action has nothing to do with attacking or disabling flagella, as the drug's name might imply?

1. Flagyl would also harm the flagellated lining of the human intestine.
2. Entamoeba possesses pseudopods, not flagella, yet it is killed by Flagyl.
3. Not all anaerobic gut bacteria possess flagella, yet flagyl kills these bacteria.

1. A) 1 only
2. B) 2 only
3. C) 1 and 2
4. D) 2 and 3
5. E) 1 and 3

D

Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two elongated "cyanelles." The cyanelles are contained within vesicles of the host cell, and each is derived from a cyanobacterium, though not the same type of cyanobacterium that gave rise to the chloroplasts of algae and plants.

What must occur for asexual reproduction to be successful in P. chromatophora?

1. mitosis
2. S phase
3. meiosis
4. equal distribution of cyanelles during cytokinesis

1. A) 1 only
2. B) 1 and 2
3. C) 1, 2, and 3
4. D) 1, 2, and 4
5. E) 2, 3, and 4

D

Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two elongated "cyanelles." The cyanelles are contained within vesicles of the host cell, and each is derived from a cyanobacterium, though not the same type of cyanobacterium that gave rise to the chloroplasts of algae and plants.

The closest living relative of P. chromatophora is the heterotroph P. ovalis. What type of evidence permits biologists to make this claim about relatedness?

1. A) morphological
2. B) ecological
3. C) biochemical
4. D) genetic
5. E) fossil

D

Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two elongated "cyanelles." The cyanelles are contained within vesicles of the host cell, and each is derived from a cyanobacterium, though not the same type of cyanobacterium that gave rise to the chloroplasts of algae and plants.

The closest living relative of P. chromatophora is the heterotroph P. ovalis. P. ovalis uses threadlike pseudopods to capture its prey, which it digests internally. Which of the following, if observed, would be the best reason for relabeling P. chromatophora as a mixotroph?

1. A) a threadlike pseudopod
2. B) a vacuole with food inside
3. C) a secretory vesicle
4. D) a contractile vacuole

B

Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two elongated "cyanelles." The cyanelles are contained within vesicles of the host cell, and each is derived from a cyanobacterium, though not the same type of cyanobacterium that gave rise to the chloroplasts of algae and plants.

Which of the following represents the true significance of the finding that the cyanelles of P. chromatophora stem from a different type of cyanobacterium than gave rise to chloroplasts?

1. A) This finding indicates that there is a second evolutionary lineage of photosynthetic eukaryotes.
2. B) This finding represents the first time that primary endosymbiosis has been directly observed.
3. C) This finding is the strongest evidence yet for the theory of endosymbiosis.
4. D) This finding is an example of the phenomenon known as "serial endosymbiosis."
5. E) This finding is the first evidence that eukaryotic cells do not necessarily digest prokaryotic cells that manage to gain access to their cytoplasm.

A

Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two elongated "cyanelles." The cyanelles are contained within vesicles of the host cell, and each is derived from a cyanobacterium, though not the same type of cyanobacterium that gave rise to the chloroplasts of algae and plants.

If true, which of the following would be most important in determining whether P. chromatophora's cyanelle is still an endosymbiont or is an organelle, as the term cyanelle implies?

1. A) if chromatophora is less fit without its cyanelle than with it
2. B) if the cyanelle is less fit without the host cercozoan than with it
3. C) if there is ongoing metabolic cooperation between the cyanelle and the host cercozoan
4. D) if there has been movement of genes from the cyanelle genome to the nuclear genome, such that these genes are no longer present in the cyanelle genome

D

Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two elongated "cyanelles." The cyanelles are contained within vesicles of the host cell, and each is derived from a cyanobacterium, though not the same type of cyanobacterium that gave rise to the chloroplasts of algae and plants.

If true, which of the following is the best evidence that the cyanelles are providing nutrition (in other words, calories) to the surrounding cercozoan?

1. A) if the cyanelle performs aerobic photosynthesis
2. B) if the vesicle membrane that surrounds each cyanelle possesses glucose-transport proteins
3. C) if the cyanelle performs aerobic respiration
4. D) if radiolabeled 14CO2enters the cyanelle and if, subsequently, radiolabeled glucose is present in cercozoan cytosol

D

Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two elongated "cyanelles." The cyanelles are contained within vesicles of the host cell, and each is derived from a cyanobacterium, though not the same type of cyanobacterium that gave rise to the chloroplasts of algae and plants.

A crucial photosynthetic gene of the cyanobacterium that gave rise to the cyanelle is called psaE. This gene is present in the nuclear genome of the cercozoan, but is not in the genome of the cyanelle. This is evidence of

1. A) reciprocal mutations in the cyanelle and nuclear genomes.
2. B) horizontal gene transfer from bacterium to eukaryotes.
3. C) genetic recombination involving a protist and an archaean.
4. D) the origin of photosynthesis in protists.
5. E) transduction by a phage that infects both prokaryotes and eukaryotes.

B

Including the membrane of the surrounding vesicle, how many phospholipid (not lipopolysaccharide) bilayers should be found around each cyanelle, and which one of these bilayers should have photosystems embedded in it?

1. A) two; innermost
2. B) two; outermost
3. C) three; innermost
4. D) three; middle
5. E) three; outermost

A

Healthy individuals of Paramecium bursaria contain photosynthetic algal endosymbionts of the genus Chlorella. When within their hosts, the algae are referred to as zoochlorellae. In aquaria with light coming from only one side, P. bursaria gathers at the well-lit side, whereas other species of Paramecium gather at the opposite side. The zoochlorellae provide their hosts with glucose and oxygen, and P. bursaria provides its zoochlorellae with protection and motility. P. bursaria can lose its zoochlorellae in two ways: (1) if kept in darkness, the algae will die; and (2) if prey items (mostly bacteria) are absent from its habitat, P. bursaria will digest its zoochlorellae.

Which term best describes the symbiotic relationship of well-fed P. bursaria with their zoochlorellae?

1. A) mutualistic (each species benefits from the other)
2. B) photosynthetic
3. C) parasitic
4. D) predatory

A

Healthy individuals of Paramecium bursaria contain photosynthetic algal endosymbionts of the genus Chlorella. When within their hosts, the algae are referred to as zoochlorellae. In aquaria with light coming from only one side, P. bursaria gathers at the well-lit side, whereas other species of Paramecium gather at the opposite side. The zoochlorellae provide their hosts with glucose and oxygen, and P. bursaria provides its zoochlorellae with protection and motility. P. bursaria can lose its zoochlorellae in two ways: (1) if kept in darkness, the algae will die; and (2) if prey items (mostly bacteria) are absent from its habitat, P. bursaria will digest its zoochlorellae.

The motility that permits P. bursaria to move toward a light source is provided by

1. A) pseudopods.
2. B) a single flagellum composed of the protein flagellin.
3. C) many cilia.
4. D) contractile vacuoles.

C

Healthy individuals of Paramecium bursaria contain photosynthetic algal endosymbionts of the genus Chlorella. When within their hosts, the algae are referred to as zoochlorellae. In aquaria with light coming from only one side, P. bursaria gathers at the well-lit side, whereas other species of Paramecium gather at the opposite side. The zoochlorellae provide their hosts with glucose and oxygen, and P. bursaria provides its zoochlorellae with protection and motility. P. bursaria can lose its zoochlorellae in two ways: (1) if kept in darkness, the algae will die; and (2) if prey items (mostly bacteria) are absent from its habitat, P. bursaria will digest its zoochlorellae.

A P. bursaria cell that has lost its zoochlorellae is said to be aposymbiotic. It might be able to replenish its contingent of zoochlorellae by ingesting them without subsequently digesting them. Which of the following situations would be most favorable to the reestablishment of resident zoochlorellae, assuming that compatible Chlorella are present in P. bursaria's habitat?

1. A) abundant light, no bacterial prey
2. B) abundant light, abundant bacterial prey
3. C) no light, no bacterial prey
4. D) no light, abundant bacterial prey

B

Healthy individuals of Paramecium bursaria contain photosynthetic algal endosymbionts of the genus Chlorella. When within their hosts, the algae are referred to as zoochlorellae. In aquaria with light coming from only one side, P. bursaria gathers at the well-lit side, whereas other species of Paramecium gather at the opposite side. The zoochlorellae provide their hosts with glucose and oxygen, and P. bursaria provides its zoochlorellae with protection and motility. P. bursaria can lose its zoochlorellae in two ways: (1) if kept in darkness, the algae will die; and (2) if prey items (mostly bacteria) are absent from its habitat, P. bursaria will digest its zoochlorellae.

Theoretically, P. bursaria can obtain zoochlorella either vertically (via the asexual reproduction of its mother cell) or horizontally (by ingesting free-living Chlorella from its habitat). Consider a P. bursaria cell containing zoochlorellae, but whose habitat lacks free-living Chlorella. If this cell subsequently undergoes many generations of asexual reproduction, if all of its daughter cells contain roughly the same number of zoochlorellae as it had originally contained, and if the zoochlorellae are all haploid and identical in appearance, then what is true?

1. A) The zoochlorellae also reproduced asexually, at an increasing rate over time.
2. B) The zoochlorellae also reproduced asexually, at a decreasing rate over time.
3. C) The zoochlorellae also reproduced asexually, at a fairly constant rate over time.
4. D) The zoochlorellae reproduced sexually, undergoing mitosis and meiosis.

C

Healthy individuals of Paramecium bursaria contain photosynthetic algal endosymbionts of the genus Chlorella. When within their hosts, the algae are referred to as zoochlorellae. In aquaria with light coming from only one side, P. bursaria gathers at the well-lit side, whereas other species of Paramecium gather at the opposite side. The zoochlorellae provide their hosts with glucose and oxygen, and P. bursaria provides its zoochlorellae with protection and motility. P. bursaria can lose its zoochlorellae in two ways: (1) if kept in darkness, the algae will die; and (2) if prey items (mostly bacteria) are absent from its habitat, P. bursaria will digest its zoochlorellae.

Which term most accurately describes the nutritional mode of healthy P. bursaria?

1. A) photoautotroph
2. B) photoheterotroph
3. C) chemoheterotroph
4. D) chemoautotroph
5. E) mixotroph

E

When diatoms die, their shells fall to the floor of the ocean or lake that they inhabit and form sediments called diatomaceous earth (DE).

Diatoms can be identified by their shells. Different species of diatoms prefer different water temperatures. What information can be gained if scientists take samples of long-existing DE and identify the diatom species that created it?

1. A) Scientists can decipher evolutionary lineages between diatom species.
2. B) Scientists can predict future trends in greenhouse gas emissions.
3. C) Scientists can learn about past climates.
4. D) Scientists can better understand how wind currents affect water temperature.

C

The diatoms' porous shells are hard but often break and result in sharp edges. Crop farmers incorporate DE into their soil to help kill insect pests. When insects encounter DE, sharp shell edges cut through their exoskeletons and then softer, broken down DE absorbs insect body fluids, thereby causing the insects to die due to dehydration. Why might farmers who raise large livestock also use DE in the animals' feed?

1. A) The sharp shells can damage the tissue of intestinal parasites and eventually kill them.
2. B) DE helps to slow down the livestocks' digestion of food, thereby increasing nutrient absorption.
3. C) The porous nature of the shells in the DE helps keep livestock hydrated.
4. D) DE encourages growth of "healthy" intestinal bacteria.

A

The oldest fossil eukaryote that can be resolved taxonomically is of

1. A) a red alga that lived 1.2 billion years ago.
2. B) a red alga that lived 635 million years ago.
3. C) a fungus that lived 2 billion years ago.
4. D) an Ediacaran that lived 550 million years ago.

A

The evolution of complex multicellularity in eukaryotes

1. A) occurred only once, in the common ancestor of all eukaryotes.
2. B) occurred only once, in the common ancestor of all multicellular eukaryotes.
3. C) occurred only once, in the animal lineage.
4. D) occurred independently in several eukaryotic lineages.

D

Plastids that are surrounded by more than two membranes are evidence of

1. A) evolution from mitochondria.
2. B) fusion of plastids.
3. C) origin of the plastids from archaea.
4. D) secondary endosymbiosis.

D

Biologists think that endosymbiosis gave rise to mitochondria before plastids partly because

1. A) the products of photosynthesis could not be metabolized without mitochondrial enzymes.
2. B) all eukaryotes have mitochondria (or their remnants), whereas many eukaryotes do not have plastids.
3. C) mitochondrial DNA is less similar to prokaryotic DNA than is plastid DNA.
4. D) without mitochondrial CO2production, photosynthesis could not occur.

B

Which group is incorrectly paired with its description?

1. A) diatoms–important producers in aquatic communities
2. B) red algae–acquired plastids by secondary endosymbiosis
3. C) apicomplexans–parasites with intricate life cycles
4. D) diplomonads–protists with modified mitochondria

B

Based on the phylogenetic tree in the figure given below, which of the following statements is correct?

The most recent common ancestor of Excavata is older than that of SAR.

1. B) The most recent common ancestor of red algae and plants is older than that of nucleariids and fungi.
2. C) The most basal (first to diverge) eukaryotic supergroup cannot be determined.
3. D) Excavata is the most basal eukaryotic supergroup.

C