Chapter 25 HW/Quiz

Which of the following is true of secondary endosymbiosis?

An organism containing an endosymbiont is engulfed by another organism and becomes an endosymbiont.

Which of the following is a correct statement about cellular slime molds?

Cellular slime molds form masses when food is scarce, but their cells remain separated. almost like multicellular organisms when food is depleted. They form a multicellular mass that forms fruiting bodies.

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 genome of modern chloroplasts is roughly 50% of the size of the genome of the cyanobacterium from which it is thought to have been derived. In comparison, the genome of P. chromatophora's cyanelle is only slightly reduced relative to the size of the genome of the cyanobacterium from which it is thought to have been derived. What is a valid hypothesis that can be drawn from this comparison?

P. chromatophora's cyanelle is the result of an evolutionarily recent endosymbiosis.

Select the correct statement about photosynthesis by primary producers. Cyanobacteria carry out more of the world's photosynthesis than protists do. Photosynthetic protists and prokaryotes carry out the majority of the photosynthesis in aquatic communities. Land plants carry out over 80% of the world's photosynthesis.

Photosynthetic protists and prokaryotes carry out the majority of the photosynthesis in aquatic communities.,Scientists estimate that 30% of the world's photosynthesis is performed by aquatic protists. Photosynthetic prokaryotes contribute another 20%, and land plants are responsible for the remaining 50%. Read about the key roles that protists play in ecological communities.

Why do some scientists believe that RNA, rather than DNA, was the first genetic material?

RNA has both information storage and catalytic properties,catalyze certain reactions (as part of ribosomes, rRNA participates in the catalysis of the peptide bonds that form proteins). It can also store information and perform some self-replication.

Why has the kingdom Protista been abandoned?

Recognizing that the kingdom Protista as originally defined was polyphyletic and that some protists are more closely related to other eukaryotes than to each other, scientists have abandoned the kingdom Protista and reorganized the entire domain Eukarya.

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?

This finding indicates that there is a second evolutionary lineage of photosynthetic eukaryotes.

The oldest fossil eukaryote that can be resolved taxonomically is of

a red alga that lived 1.2 billion years ago.

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

all eukaryotes have mitochondria (or their remnants), whereas many eukaryotes do not have plastids.

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, which join the cells together. Inside each of these identical cells are mitochondria and chloroplasts. Such an organism would most likely be classified as a

colonial photosynthetic eukaryote

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

cyanobacteria → green algae → land plants

Archaeplastids, which include red and green algae and land plants, are thought to have descended from a heterotrophic protist that engulfed a(n) _____.

cyanobacterium endosymbiotic cyanobacteria gave rise to the chloroplasts found in red and green algae and land plants.

A sign on the beach states, "Beach Closed. Red Tide." The organisms interfering with your use of this beach are probably ___

dinoflagellates, Dinoflagellate blooms, episodes of explosive population growth, cause red tides in coastal waters.

Which of the following statements supports the hypothesis of an endosymbiotic origin of mitochondria?

each mitochondrion has its own DNA molecule.

The chloroplasts of all of the following are thought to be derived from ancestral red algae, except those of

green algae

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

horizontal gene transfer from bacterium to eukaryotes.

Which of the features below are found in all protist lineages?

mitochondria

The evolution of complex multicellularity in eukaryotes

occurred independently in several different eukaryotic lineages.

The evolution of multicellularity in animals has primarily occurred by the

remodeling of old genes

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

secondary emboss