What distinguishes a morphospecies?

a. It has distinctive characteristics, such as size, shape, or coloration.

b. It represents a distinct branch in a phylogeny of populations.

c. It is reproductively isolated from other species.

d. It is a fossil from a distinct time in Earth history.

Which of the following describes vicariance?

a. Small populations coalesce into one large population.

b. A population is fragmented into isolated subpopulations.

c. Individuals colonize a novel habitat.

d. Individuals disperse and found a new population.

Select True or False to indicate which of the following groups could be identified using the biological species concept.

T/F lizard species living today

T/F sunflower species living today

T/F extinct dinosaurs

T/F bacteria living today

Evaluate this statement: Gene flow increases the genetic divergence of populations.

When the ranges of two different species meet, a stable 'hybrid zone' occupied by hybrid individuals may form. How is this possible?

a. Two diverged populations are capable of mating and producing viable and fertile offspring.

b. Hybrid individuals are always allopolyploid and are thus unable to mate with either of the original species.

c. Hybrid individuals may have reduced fitness and thus be strongly selected against.

d. One species has a selective advantage, so as hybridization continues, the other species will go extinct.

Sexual selection favors individuals with traits that increase their ability to obtain mates, such as mating calls in crickets. Using this example, propose a scenario where sexual selection could contribute to divergence in sympatric speciation.

If one species (2n = 10) crosses with another species (2n = 18), producing an allopolyploid offspring, what is the ploidy of the offspring?

a. 2n = 10

b. 2n = 18

c. 2n = 10 + 18 = 28

d. 4n = 36 +20 = 56

True or false? Speciation is a slow process. Justify your answer.

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.

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?

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.

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?

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 as

a. Species living in sympatry following allopatric speciation

b. Species living in sympatry following sympatric speciation

c. Species living in allopatry following allopatric speciation

d. Species living in allopatry following sympatric speciation

Svante Pääbo and colleagues were the first to sequence the Neanderthal genome from fossils and compare the sequences to modern humans. According to the data shown here, did the two species interbreed when they overlapped in Europe? Explain.

In a follow-up study in 2020, Joshua Akey and colleagues discovered that the genomes of modern Africans contain a small amount of Neanderthal DNA due to migration of some Europeans back to Africa after interbreeding with Neanderthals. Given the large amount of variation within human populations, how would you know whether there is a significant difference in percentage of Neanderthal DNA between modern Europeans and modern Africans?