Chapter 25 quiz and practice problems

Question 1

Which of the following is the correct sequence of events in the origin of life?

I. Formation of protocells

II. Synthesis of organic monomers

III. Synthesis of organic polymers

IV. Formation of DNA-based genetic systems

Answer 1

II,

III,

I,

IV.

Question 2

The first genetic material on Earth was probably ________.

A. DNA produced by reverse transcriptase from abiotically produced RNA

B. DNA molecules whose information was transcribed to RNA and later translated in polypeptides

C. self-replicating RNA molecules

D. oligopeptides located within protocells

Answer 2

C

Question 3

Which of the following organisms would be most likely to form a fossil?

Question 3 options:

A. a common worm

B. a rare worm

C. a common squirrel

D. a rare squirrel

Answer 3

A

Question 4

You are the lucky student of a wacky professor who develops a time machine. He asks if you will test it with him. You get in, and there is an immediate glitch—the date readout fails so that when you land, you are not sure what era you are in. As your time machine lands, you see an unusual landscape before you. As you open the door, you realize you cannot breathe. You quickly shut the door, realizing you are in the ________.

A. Cenozoic era

B. Archaean eon

C. Cambrian period

D. Mesozoic era

Answer 4

B

Question 5

What is true of the Cambrian explosion?

A. There are fossils of animals in geological strata that are older than the Cambrian explosion.

B. Only the fossils of microorganisms are found in geological strata older than the Cambrian explosion.

C. The Cambrian explosion marks the appearance of filter-feeding animals in the fossil record.

D. The Cambrian explosion is evidence for the instantaneous creation of life on Earth.

Answer 5

A

Question 6

Which factor most likely caused animals and plants in India to differ greatly from species in nearby southeast Asia?

A. The climates of the two regions are similar.

B. India is in the process of separating from the rest of Asia.

C. India was a separate continent until 45 million years ago.

D. Life in India was wiped out by ancient volcanic eruptions.

Answer 6

C

Question 7

What concept explains the evolution of complex eyes?

A. Mollusc eye’s evolution was dependent on vertebrate eye evolution.

B. Through evolutionary history, eyes lose function of vision.

C. Mollusc eyes evolved from a different ancestor than vertebrate eyes.

D. Complex eyes evolved through a series of steps that benefited the eyes.

Answer 7

D

Question 8

Bagworm moth caterpillars feed on evergreens and carry a silken case or bag around with them in which they eventually pupate. Adult female bagworm moths are larval in appearance; they lack the wings and other structures of the adult male and instead retain the appearance of a caterpillar even though they are sexually mature and can lay eggs within the bag. This is a good example of ________.

A. allometric growth

B. paedomorphosis

C. sympatric speciation

D. adaptive radiation

Answer 8

B

Question 9

The loss of ventral spines by modern freshwater sticklebacks is due to natural selection operating on the phenotypic effects of Pitx1 gene ________.

A. elimination (loss)

B. duplication (gain in number)

C. mutation (change)

D. silencing (loss of expression)

Answer 9

D

Question 10

The duplication of homeotic (Hox) genes has been significant in the evolution of animals because it ________.

A. caused the extinction of major groups

B. allowed animals to survive on significantly fewer calories

C. reduced morphological diversity into simpler forms of life

D. permitted the evolution of novel forms

Answer 10

D

Question 11

What hypothesis did Miller and Urey (1953) test? What did their results show?

Answer 11

They tested whether the environment of early Earth could allow for the synthesis of organic molecules from abiotic or inorganic ingredients. They were successful!

Question 12

How would the appearance of protocells have represented a key step in the origin of life?

Answer 12

Protocells are membranes that maintain a stable environment as the outside environment changes, which in a lot of ways resembles the homeostatic patterns of organisms and their body systems.

Additionally, separating these newly formed organic molecules via membrane will assist in biochemical reactions

Question 13

In changing from an “RNA world” to today’s “DNA world”, genetic information must have flowed from RNA to DNA. After reviewing figures 17.4 and 19.9, suggest how this could have occurred. Does such a flow occur today?

Answer 13

Today’s pattern is more transition from DNA to RNA, as DNA is used as a genetic template to synthesize mRNA to encode a particular protein.

However, in the life cycle of retroviruses like HIV, we see the flow from RNA to DNA as RNA is used as a genetic template by the enzyme reverse transcriptase.

It is thought that a similar enzyme was used in early earth, as it is largely assumed that RNA was developed before DNA.

Question 14

Describe an example from the fossil record that shows how life changes over time.

Answer 14

The Cambrian explosion is a good example of how the fossil record can show the diversity and relative life cycles of species (when they emerged and became extinct). Due to a catastrophic event, there were many animals with skeletons/cytoskeletons and hard shells that are found around this time, suggesting that this catastrophic event led to the collapse of many animal species.

The fossil record shows which organisms dominated at different times of Earth’s history as well. It can also indicate how new organisms can arise via gradual modification from previous organisms too.

Question 15

What evidence supports the hypothesis that mitochondria preceded plastids in the evolution of eukaryotic cells?

Answer 15

All Eukaryotes have mitochondria (or remnants of these organelles) but not all Eukaryotes have plastids

Question 16

Explain the consequences of plate tectonics for life of Earth

Answer 16

Plate tectonics describes continental drift, which can alter the physical geography and climate of their environments, as well as which organisms are isolated and which are not.

This has profound affects on the organisms that reside on these continents, as many become extinct, proliferate, migrate, etc due to these changes. They are also a source of allopatric speciation after landmasses separate

Question 17

What factors promote adaptive radiation?

Answer 17

1. Mass Extinctions
2. Major evolutionary innovations
3. The diversification of another group of organisms
4. migration to a new location where few competitors exist

Question 18

Suppose that an invertebrate species was lost in a mass extinction caused by a sudden catastrophic event. Would the last appearance of this species in the fossil record necessarily be close to when
the extinction occurred? Would the answer to this question differ depending on whether the species was common (abundant and widespread) or rare? Explain.

Answer 18

In theory, both rare and common species would be present in the fossil record up until the extinction event, and then disappear.

The fossil record is not perfect, however, and does not give an all-encompassing picture of life of earth. This muddies the water of when common and rare species may appear in the fossil record, with rare species being even less likely to make an appearance right before extinction (even if they were alive the entire time).

Question 19

Explain how new body forms originate from heterochrony.

Answer 19

Heterochrony can lead to many morphological changes, such as paedomorphosis (which is the retention of juvenile characteristics in mature organism). These changes (and others, like jaw size in a human vs a chimpanzee) can arise in very small genetic changes.

Question 20

Why is it likely the Hox genes have played a major role in the evolution of novel morphological forms?

Answer 20

In animal embryos, Hox genes influence the development of structures such as limbs and feeding appendages. As a result, changes in these genes - or the regulation of these genes - are likely to have major effects on morphology

Question 21

Given that changes in morphology are often caused by changes in the regulation of gene expression, predict whether noncoding DNA is likely to be affected by natural selection. See concept 18.3 to review noncoding DNA and regulation of gene expression if needed

Answer 21

Genetics tells us that gene regulation is altered by how well transcription factors bind to noncoding DNA sequences called control elements.

So if gene regulation causes major changes to morphology, portions of non-coding DNA that contain control elements which dictate morphological changes would be definitely be impacted by natural selection.

Question 22

How can the Darwinian concept of descent with modification explain the evolution of such complex structures as the vertebrate eye?

Answer 22

Complex structures do not evolve all at once, but in small incremental changes, and these changes are due to natural selection that selects for advantageous/adaptive variants of older structures.

Question 23

The myxoma virus kills up to 99.8% if infected European rabbits in populations with no previous exposure to the virus. The virus is transmitted between living rabbits by mosquitoes. Describe an
evolutionary trend (in either the rabbit or virus) that might occur after a rabbit population first encounters the virus

Answer 23

The myxoma virus is lethal (with a 99.8% mortality rate among rabbits) but roughly 0.2% of rabbits survive and have innate resistance to the virus. We can expect that more rabbits will then possess this resistance trait given the virus being a strong selective pressure.

The virus will also become less lethal over time, given that if it kills the host, the virus also dies, so less lethal strains will be selectively favored.

Question 24

Darwin’s comments about eyes are often used as evidence against evolution by natural selection, but only because his quotes are taken out of context. Darwin did not think that the possibility that eyes evolved through natural selection was actually “absurd in the highest degree.” What was the basis of his logical argument and what evidence do we have to support it?

Answer 24

Darwin believed that complex structures like eyes underwent a series of small, incremental, evolutionary changes in which natural selection was selected for more adaptive and favorable characteristics until a novel, simplistic structure became complex. We can observe this in the different complexities of eyes (from eye spots to complex eyes) in mollusks.

Question 25

We see an enormous diversity of eyes in Kingdom Animalia. Until recently it was postulated that eyes must have evolved at least 40 times independently. Explain how the discovery of Pax6 (and its homologs such as eyeless ) has overturned this idea in favor of genes for eye development being present in an ancestor to all bilateral organisms.

Answer 25

The discovery of the Pax6 gene has overturned this idea that eyes must have evolved independently because Pax6 is a transcription factor that controls the expression of developmental genes that form the eye in an organism, and it was found that Pax6 is present in many different organisms (and is utilized the same way) to express developmental genes for very different eye structures in a diverse range of organisms. The example of the transfer of the mouse Pax6 gene to the fruit fly (and the fruit fly still successfully developing a normal fruit fly eye) suggests that Pax6 is universally utilized across many different organisms.

Question 26

How should Madison explain to Aiden the meaning of “homologous” in evolutionary theory? Textbooks typically introduce the term with anatomical structures, but the term is more broadly applicable. How might the term apply to DNA sequences?

Answer 26

“Homologous” is a term that is often used in evolutionary theory because it equates physical (and genetic characteristics) that all species have inherited by a common ancestor they were derived from in the evolutionary process. This can be seen in homologous structures – anatomical structures found in many animal species that exhibit the same (or remarkably similar) construction. This can also be equated to DNA sequences found in diverse animal species – although there are notable differences between genomic sequences, DNA among animal species is generally very similar and thus can be equated to a common ancestor as a homologous inherited trait.

Question 27

If Pax6 is so important, predict how similar homologous sequences would be in humans, mice, squid, fruit flies, and sharks. Would you expect the amino acid sequences in the proteins expressed from the Pax6 genes to follow a similar pattern? Explain.

Answer 27

Although Pax6 is important and found in many animal species and is the gene that helps other genes be expressed/not expressed (thus stimulating the formation of the eye in many organisms), this does not necessarily mean that the Pax6 gene will influence/express the same genes in all species, and thus the form of each eye will be different depending on which genes are influenced by the Pax6 gene in each organism. I would therefore not expect the amino acid sequences in the proteins expressed from the Pax6 genes to follow a similar pattern of structure formation.

Question 28

There is variation in nucleotide sequences, but the amino acid sequences for the partial sequence presented in this case are identical between the five species. Explain why natural selection might have favored the conservation of the amino acid sequence.

Answer 28

Natural selection may have favored the conservation of the amino acid sequence between the five species because of eye functionality amongst all 5 organisms. If the amino acid sequence varied between these animals, the formation of the eye would also vary, making it more likely for some of the organisms to experience poor or absent eyesight, etc. Because of this, natural selection would favor the organisms (through natural selective pressure) that possessed Pax6 genes that encode these same amino acid sequences that form a functional eye.

Question 29

In the mouse/fly experiment that Madison referred to, the mouse Pax6 gene is used in place of the fly eyeless gene (a copy of the homolog to Pax6 ; fruit flies have two homologs). The gene codes for a transcription factor, a protein that controls the expression of other genes. Explain how a mammalian gene can successfully induce
development of a compound eye in fruit flies.

Answer 29

Since Pax6 utilizes a similar function to the eyeless gene due to their homologous relationship (2), the replacement of the mouse Pax6 gene in fruit flies is successful in that the mouse Pax6 gene controls the expression of the necessary amino acid sequences to result in a functional eye.

Question 30

If covered earlier in your course, how could different nucleotide sequences result in the same amino acid sequences?

Answer 30

Different nucleotide sequences can result in the same amino acid sequence because there are multiple codons that can code for the same amino acid sequence (1). This means that although nucleotide sequences may vary in these organisms, these combinations will still code for the same amino acid sequence, forming a functional eye in each.