23. Speciation

Based on what you know of the peptide bonds that link together amino acid residues, why would proline's side chain reduce the flexibility of the backbone?

When analyzing a sample of cells from a patient, you find the lysosomes are filled with undigested material. This observation makes you think that the lysosomes are not functioning properly. What are three different defects that could be responsible for malfunctioning lysosomes?

Three-spine sticklebacks are small fish that originated in the ocean and continue to exist there, but then some took up residence in hundreds of streams and freshwater lakes in the Northern Hemisphere. Predict whether you would expect to find different species in lakes today.

In the field of nanotechnology, DNA is used like Velcro to assemble tiny particles into structures that are < 0.0001 mm in size. Draw a model to illustrate how two particles (a circle and a square) could be brought together by linking them to short single-stranded DNA molecules. If the DNA sequence linked to the circle is GGATC, then provide the sequence linked to the square and identify the 5′ and 3′ ends of each strand.

Make a concept map (see BioSkills 12) that relates the four levels of protein structure and shows how they can contribute to the formation of hemoglobin. Your map should include the following boxed terms: Primary structure, Secondary structure, Tertiary structure, Quaternary structure, Amino acid sequence, R-groups, αα-helices, and ββ-pleated sheets.

What prevents horses and donkeys from hybridizing to form a new species?a. limited hybrid fertilityb. limited hybrid viabilityc. hybrid breakdownd. gametic isolation

All over the world, natural habitats are being fragmented into tiny islands by suburbs, ranches, farms, and roads. If asked to join a science panel to speak to Congress, could you explain how this fragmentation process could lead to extinction? How it could lead to speciation?

When hybrids produced in a hybrid zone can breed with each other and with both parent species, and they survive and reproduce as well as members of the parent species, one would predict thata. the hybrid zone would be stable.b. sympatric speciation would occur.c. reinforcement of reproductive barriers would keep the parent species separate.d. reproductive barriers would lessen and the two parent species would fuse.

Distinguish between microevolution and macroevolution.

A revolution in the study of human evolution is under way thanks to the invention of techniques that enable DNA sequencing of not only modern humans, but also ancient humans.Human populations today are not considered separate species under the biological species, morphospecies, and phylogenetic concepts. Explain what kind of evidence supports this statement.

Which of the following factors would not contribute to allopatric speciation?a. A population becomes geographically isolated from the parent population.b. The separated population is small, and genetic drift occurs.c. The isolated population is exposed to different selection pressures than the parent population.d. Gene flow between the two populations continues to occur.

A revolution in the study of human evolution is under way thanks to the invention of techniques that enable DNA sequencing of not only modern humans, but also ancient humans.Before the application of DNA sequencing to fossils, which species concept was most useful for distinguishing human fossils? What is one disadvantage of this approach?

Explain how each of the following makes it difficult to clearly define a species: variation within a species, geographically isolated populations, asexual species, fossil organisms.

A revolution in the study of human evolution is under way thanks to the invention of techniques that enable DNA sequencing of not only modern humans, but also ancient humans.Modern humans (Homo sapiens) and archaic humans called Neanderthals (H. neanderthalensis) shared a common ancestor in Africa but diverged in different geographic areas. When modern humans migrated out of Africa and dispersed around the world starting about 100,000 years ago, they overlapped with Neanderthals in Europe. This scenario is best described asa. species living in sympatry following allopatric speciationb. species living in sympatry following sympatric speciationc. species living in allopatry following allopatric speciationd. species living in allopatry following sympatric speciation

Explain why allopatric speciation would be less likely on an island close to a mainland than on a more isolated island.