Evolution Chapter 9

Snakes first evolved:

60 million years ago.

In humans, how many genes have been identified with olfactory receptors?

855, but 465 of these are pseudogens.

In what way is gene duplication involved in the evolution of aerobic citrate metabolism in E. coli?

A 2933 bp segment including the citT gene and the rnk promoter was duplicated and inserted next to the original segment.

What circumstances might give rise to a novel trait?

A deletion mutation alters the timing of the activation of a regulatory network.

In what way is gene recruitment involved in the evolution of aerobic citrate metabolism in E. coli?

A duplicated citT gene came under the control of new promoter, rnk.

What is a paralog?

A gene that has taken on a new function through gene duplication.

What is opsin?

A molecule that sits on the surface of photoreceptor cells and gathers light.

How does limb development differ between flies and mice?

A mouse builds proximal structures first then distal structures.

Which novel trait evolved in Lenski's E. coli experiments?

Aerobic citrate metabolism.

Which of the following is NOT true regarding the expression of Hoxd13 in zebrafish and mouse embryos?

After being silent, Hoxd13 becomes expressed again in fish and guides the development of ray fins.

Which of the following is an example of a complex adaptation?

All of the above. Venom delivery in snakes. Aerobic citrate metabolism in E. Coli. The vertebrate eye.

Which of the following statements is true regarding venom evolution in snakes?

All of the above. Venom genes have been recruited from genes expressed in many organs in snakes. Venom evolved before snakes evolved. The venom delivery system is a complex adaptation.

Venom delivery in snakes requires:

All of the above: Muscles around venom glands. Venom glands. Hollow teeth called fangs.

What evidence supports the hypothesis that organs for vision evolved independently across lineages?

All vertebrates have the light receptor protein c-opsin, which is the same shape across species. In contrast, invertebrates have r-opsin, which is shaped differently than c-opsin. Humans have eyes with a lens that focus light on the retina, whereas flatworms have light-sensitive eyespots that allow the organisms to detect differences in amount of light.

Arrange the steps for Fry's hypothesis of the evolution of snake venom from the ancestors of modern snakes to modern snakes?

Ancestors of modern snakes -Duplication of genes coding non-venomous compounds allows diversity of function. -A regulatory mutation in duplicated genes affects the location of their production. -Mutations in duplicated genes alter protein shape and function, creating venom. -Duplication of venom genes promotes diversification of the venom gene family.

A single nerve cord likely evolved:

At least three independent times.

Which of the following would Darwin disagree are homologous characteristics?

Bat wings and fly legs.

In a developing mouse, cells express ____ along the ventral side.

Bmp4

Which of the following processes did not lead to the evolution of snake venom?

Broad-sense heritability.

Which of the following extant animal groups does NOT have a single nerve cord?

Cnidarians.

The roles of Hox genes in development are to:

Direct head-to-toe patterning of body parts in animals with bilateral symmetry. Determine the timing of the development of body parts in animals with bilateral symmetry.

In a developing fly, cells express ____ along the dorsal side.

Dpp

Which of the following happened first in the evolution of snake venom?

Duplication of the defensin gene.

In Näsvall's experiments, the mutant gene hisA in Salmonella:

Encodes an enzyme that produces both histadine and tryptophan.

In Salmonella, the gene hisA:

Encodes an enzyme that produces histadine.

Role of both crystallin and opsin.

Evolved from duplicated genes with different functions. Differs substantially between vertebrate and invertebrate lineages.

How are Dpp and Bmp4 homologous?

Expression of these genes leads to the development of the digestive system.

How are Sog and Chordin homologous?

Expression of these genes leads to the development of the nervous system.

What do you predict would happen if you inserted a Pax-6 gene from a mouse into the genome of an octopus?

Extra eyes would develop, but with octopus crystallins.

What does the following evolutionary history of animals suggest?

Eyes are not present in the common ancestor of animals.

A diverse group of animals uses hemoglobins to transport oxygen to tissues throughout the body. In adult humans, hemoglobin A is made up of a tetramer of two alpha chains and two beta chains. A clustered set of five beta-globin genes exist in humans and other jawed vertebrates, but no extant species uses all five to produce the polypeptide chains expressed at the various stages of development.

Gene duplication.

Crystallins evolved through:

Gene recruitment.

The genes coding for crystallins are expressed in many tissues and produce enzymes that protect the integrity of other proteins. A mutation in the ancestral gene's regulatory region caused the expression of the transparent proteins in the eye, leading to further selection and evolution of the eye in a changing visual environment.

Gene recruitment.

The insect Hox gene Antennapedia contributes to the animal body plan during embryonic development. Novel expression of the gene in the post-embryonic wing discs of butterflies results in specific patterns of wing eyespots.

Gene recruitment.

What is not an example of antagonistic pleiotropy?

Genes that create insect breathing tubes cause decreased production of growth hormones.

Which of the following pieces of evidence suggests that changes to the timing and location of expression of Hox genes may be a clue to how tetrapod limbs evolved?

In tetrapod limb development, there is a reactivation of Hoxd13 that leads to development of wrist and digit bones.

What would be expected if a mutation successfully switched a protein to a new function, while removing the old function?

Increased fitness if the old function is not essential.

What role does Bmp2 play in the expression of bat wing phenotypes?

It is a regulatory gene that turns on many other genes.

Which of the following is NOT true about Bacillus anthracis?

It reproduces with spores.

All bilaterians have:

Left and right symmetry.

The nervous system of the ancestor of bilaterians:

Likely had a nervous system arranged in a diffuse net.

Role of Crystallin

Maintains protein configuration under stress. Bends light to focus an image on the retina. Forms the lens of the eye.

Which of the following is true of opsin evolution?

Opsins evolved through duplication of a G-protein-coupled receptor - GPCR gene.

Hh and Shh are:

Orthologs.

Which of the following is true regarding the evolution of flowering plant morphology?

Radial symmetry is more ancestral than bilateral symmetry.

Which organism does not use crystallins in its eyes to focus light?

Ragworms.

Which type of organism does NOT have a camera eye?

Silverfish.

Examples of parallel evolution:

Stickleback fish have reduced armor in each separate population that has low predator pressure. Each cave fish population independently evolved paler skin than its relatives in nearby surface lakes.

Role of Opsin.

Stimulated by light to emit an electrical signal to the brain.

What does the figure show?

The ability to feed on citrate did not evolve immediately, and once it appeared the bacteria performance improved gradually.

How do the laws of physics constrain insect size?

The amount of atmospheric O2 concentration.

Examples of Homology.

The bones in bat wings look like elongated versions of the finger bones in human hands. Hox genes control development in insects and mice.

Identify the examples in which a protein is co-opted.

The citT gene in E. coli produces a protein that allows the bacteria to feed on citrate only in the absence of oxygen. A duplication of he gene places the second copy under the control of a different promoter that allows the bacteria to feed on citrate even in the presence of oxygen. The hisA gene in Salmonella encodes for a histidine-producing enzyme. The gene mutates an enzyme that produces both histidine and tryptophan.

Based on the homology of Hox genes in mice and flies, what can we deduce?

The common ancestor of flies and mammals already had a set of Hox genes that controlled development.

What do you predict would happen to the hind legs of a fly if the gene Dpp were artificially overexpressed?

The legs would grow longer.

What happens when the Hox gene Shh is blocked in mice?

The limb-patterning is truncated, and limbs do not develop past a stump.

How can antagonistic pleiotropy limit the spread of a mutation?

The mutation may cause a negative effect that outweighs a simultaneous benefit.

How does the dorsal-ventral axis of invertebrates and vertebrates compare?

The nerve cord develops on the dorsal side of vertebrate embryos.

Why do giraffes have a recurrent laryngeal nerve that is 19 feet longer than the shortest route possible?

The route of that nerve was inherited from their ancestors.

Examples of convergent evolution:

The streamlined body forms of whales and fish reduce the energy needed to move through water. The broad, flat shape of bird wings and insect wings enables flight.

Which came first, the venom or the fang?

The venom, which probably evolved before the snake.

How do bat forelimbs differ from their mammalian counterparts?

They have elongated digits

How do novel traits arise?

Through mutations leading to new phenotypes.

Identify the challenges in comparing convergent evolution and parallel evolution.

Traits that appear to result from convergent evolution may be composed of other structures or traits that share a common ancestry and have independently evolved in parallel. Convergent evolution may actually be parallel evolution if distantly related species have a common ancestor from which they inherited a regulatory gene controlling their similar traits.

What is an ortholog?

Two genes in two different species that serve the same function and were inherited from a common ancestor.

Gene control regions are:

Upstream sections of DNA that include the promoter region as well as other regulatory sequences that influence the transcription of DNA.

Which of the following correctly differentiates c-opsin and r-opsin?

c-opsins are stored in stacks of disks that grows out of hairlike extension of the retina called a cilium.