Chapter 25

Which of the statements is a hypothesis to explain the origin of the modern eukaryotic cell?

A cell evolved a nucleus first, then incorporated a proteobacterial cell that became a mitochondrion.

Chloroplasts are thought to have originated from a symbiotic relationship between an ancient eukaryotic cell and:

A cyanobacterium

What structure is found in all members of the superkingdom Stramenopila?

A flagellum with stiff hairs

Which of the answer choices is the best description of a protozoan?

A heterotrophic protist

Which of the answer choicesf is the best description of algae?

A photosynthetic protist

The majority of prokaryotic DNA is arrayed in:

A single circular chromosome

Photosynthetic protists are informally referred to as:

Algae

Which superkingdom contains members that are responsible for forming red tides?

Alveolata

To which superkingdom do corn and wheat belong?

Archaeplastida

Which of the seven superkingdoms contains all photosynthetic organisms?

Archaeplastida

You are in a lab studying a newly discovered cell type. You observe a rigid cytoskeleton in this cell, along with a nucleus and a compartmentalized interior. How would you classify this cell?

As a possible transitional cell changing from prokaryotic to eukaryotic

What components of eukaryotic cells leave a fossil record?

Cell walls

Which of the statements is evidence supporting the hypothesis that eukaryotic chloroplasts originated from Cyanobacteria?

Chloroplasts and Cyanobacteria have similar DNA sequences for shared genes.

Chloroplasts are thought to have evolved from:

Cyanobacteria

The diversity of shapes found in eukaryotic cells is made possible by the:

Cytoskeleton

Sexual fusion brings two haploid cells together to produce a ____ cell.

Diploid

Chloroplasts and mitochondria in eukaryotes are thought to have originated by ____, wherein on organism lives inside another

Endosymbiosis

Chloroplasts and mitochondria in eukaryotes are thought to have originated by ____, wherein one organism lives inside another.

Endosymbiosis

Which of the statements is a key advantage of eukaryotic cells over prokaryotic cells?

Eukaryotic cells have a flexible cytoskeleton, which allows them to change shape and gives them the ability to engulf other materials.

Chloroplasts originated from endosymbiotic Cyanobacteria once and only once

False

Eukaryotes have more ways to obtain energy than prokaryotes

False

The terms 'algae' and 'protozoa' have significant phylogenetic meaning.

False

A young paleontologist is extremely excited. I'm sedimentary rocks dating from 70 million years ago, she has found some new microfossils. The shells of which organisms likely contributed to the accumulation of sediments on the sea floor (and the formation of these sedimentary rocks)?

Foraminiferans, diatoms, radiolarians, and coccolithophorids

In which group of archaeplastids are the chloroplasts most similar to those of the ancestral Cyanobacterial endosymbiont?

Glaucocystophytes

In animals, the egg and sperm cells are:

Haploid

In eukaryotes that lack mitochondria, what structures are present to generate ATP for cellular use?

Hydrogenosomes

The current theory is that chloroplasts are descendants of symbiotic Cyanobacteria that lived within eukaryotic cells. If we look at the respective genomes, however, we see that the Cyanobacteria have many more genes than do chloroplasts. Where did the Cyanobacteria genes go?

Many of the genes were transported to the nucleus, and others were lost.

All of the membranes in the eukaryotic fell are in dynamic continuity except for membranes in the:

Mitochondria and chloroplasts

Which of the statements regarding diatoms is false?

Most diatoms are multicellular eukaryotes

To which of the superkingdom do jellyfish belong?

Opisthokonta

Which of the features is responsible for the evolutionary success of eukaryotes?

Possessing a dynamic cytoskeleton, having complex patterns of gene regulation, localizing where energy metabolism takes place, and possessing a dynamic endo membrane system

Which is the oldest group of eukaryotes to be recognized in the fossil record?

Red algae

Which of the statements describes characteristics of eukaryotic cells but not prokaryotic cells?

Relatively large genome, dynamic cytoskeleton, compartmentalized metabolic processes

You have learned that having linear DNA had consequences, the major one being that the DNA is shortened every time it replicated. This does not happen with the circular DNA found in prokaryotes. What, then, is the advantage of having linear DNA?

Replication can begin from multiple sites on the linear DNA, allowing rapid replication and relieving the evolutionary pressure for a streamlined genome.

Imagine that a researcher discovers a new type of organelle in single-celled eukaryotes. She suspects that this new organelle is the result of endosymbiosis. How could she support this theory?

She could determine whether this organelle has both an inner or outer membrane, she could use electron microscopy to determine if any structural similarities exist between this new organelle and prokaryotic cells (such as whether it is similar to proteobacteria or Cyanobacteria), or of this organelle has its own DNA, she could compare its genetic sequence to those certain prokaryotes.

The term protist lacks phylogenetic accuracy because it represents a paraphyletic group. Which of the statements reflects the paraphyly of protist taxa?

Some eukaryotic lineages evolved from protists, and they are not included in the group called protists.

Which statement correctly describes the relationship among species in a phylogenetic tree?

Species with only one branch point separating them are more closely related than species with more than one branch separating them

In plasmodia slime molds, what structure is responsible for producing the haploid cells that disperse into the environment?

Sporangium

To which of the super kingdoms do diatoms belong to?

Stramenopila

Organelles have their own genomes. When chloroplast DNA is sequences and compares to genomes from members of the Cyanobacteria, the chloroplast DNA sequence is nested within the genomes of Cyanobacteria. This is strong evidence for the hypothesis that:

The chloroplast originated as a symbiotic Cyanobacteria that became permanently incorporated into its host

Most eukaryotic cells contain mitochondria, but a few single-celled eukaryotic organisms found it oxygen-free environments do not. Which of the observations led biologists to reject the hypothesis that these mitochondria-free eukaryotes evolved before the endosymbiotic event that established mitochondria in other eukaryotes?

The nuclear genome of these mitochondria-free eukaryotes contains relics of mitochondrial genes.

Which of the statements is false regarding protists?

They are a monophyletic group of organisms

How do eukaryotic cells generate and maintain genetic diversity?

Through sexual reproduction

A symbiont is an organism that lives in close association with another species.

True

Choanoflagellates are the closest protistan relatives of animals

True

Diatoms appeared during the Mesozoic Era, and the skeletons of these organisms contributed to the accumulation of sediments of the deep sea floor.

True

Photosynthesis spread through eukaryotes by repeated endosymbiosis involving eukaryotic algae

True

The genes in chloroplasts more closely match the genes found in Cyanobacteria as compared to the genes found in the nuclei of photosynthetic eukaryotes.

True

The photosynthetic amoeba Paulinella is an example of a second chloroplast endosymbiotic event involving a Cyanobacterium.

True

There is no known synopsis between a heterotrophic host and a photosynthetic partner in mammals.

True

Many single-celled have evolved complex life cycles that include sexual reproduction. This means that:

Two cells, at some point, must fuse to become diploid

Which of the statements accounts for why eukaryotic cells are typically much larger than prokaryotic cells?

Using molecular motors, eukaryotic cells can transport materials throughout their cytoplasm much faster than prokaryotic cells can; prokaryotic cells have to rely on simple diffusion

How does current theory explain the origin of a nucleus in eukaryotic cells?

While there are some competing theories on the origin of the nucleus, neither theory discussed in the text really explains the origin of the nucleus.

Green algae are most closely related to:

land plants

A cell with chloroplasts that have four membranes (not counting the thylakoid membranes) likely arose by _____ endosymbiotic event(s).

two