Pre-class assignment 3

A) C is more closely related to A than A is to B B) A and B have a more recent common ancestor than do A and C C) A is more closely related to C than B is to A D) A and C have a more recent common ancestor than do A and B B Reason: Because similar species are grouped into genera and similar genera are grouped into families, the classification of A and B in the same family indicates a closer relationship between them than either would have with C.

If species A and species B are in the same family, and species C is in a different family, and if the classification accurately reflects phylogeny, then you can infer that __________.

A) gradualist B) allopatric C) punctuated equilibrium D) adaptive radiation C Reason: This describes the punctuated equilibrium model.

According to the _____ model, evolution occurs in spurts: Species evolve relatively rapidly and then remain unchanged for long periods.

A) a founder effect B) coevolution C) convergent evolution D) homology C Reason: Species from different evolutionary backgrounds may come to resemble one another when they adapt to similar ecological conditions (in this case, deserts). This phenomenon is termed convergent evolution.

Cacti are native to deserts in the Americas, whereas cactus-like euphorbs are native to African deserts. The two plant groups are not closely related, and the euphorbs have normal broad-leaved plants such as the Christmas poinsettia in their ancestry. The most likely explanation for the similarity of some euphorbs to cacti is __________.

A) fossil bacteria, which are known to have reproduced asexually B) oaks and other sexually reproducing, extant (currently living) trees C) fossil dinosaurs, which are known to have reproduced sexually D) asexually reproducing plant and animal species that live in the present B Reason: The biological species concept can be applied to extant, sexual organisms.

For which of the following groups would the biological definition of species be useful?

A) extended hops B) gliding C) flight D) courtship E) all of these E Reason: All of these are, or may have been, functions of feathers.

Feathers either play a role, or may have played a role, in _____.

A) A species with inflexible morphological traits finds itself in a species-rich, highly competitive environment. B) The dominant organisms in an area become extinct. C) A new island chain forms far from shore and is reached by a few groups of long-distance colonists. D) A species has flexible morphological structures that lend themselves to specialization. A Reason: These conditions would reduce the likelihood of adaptive radiation.

In which of the following situations is adaptive radiation least likely to occur?

A) adaptive radiation B) hybrid breakdown C) allopatric speciation D) gradualism A Reason: Cichlids may be prone to adaptive radiation due to their unusual mouth structure and mate recognition mechanisms.

Lake Victoria, in the African Rift Valley, is home to hundreds of species of cichlid fishes, each with slightly different diets and habits. All these fishes probably evolved from one or a few ancestors within the past 100,000 years, making them an example of _____.

A) adaptive radiation B) genetic drift C) microevolution D) gene flow E) paedomorphosis A Reason: Mass extinctions reduce competition and allow for periods of rapid speciation.

Mass extinctions create conditions that promote _____.

A) changes in the gene pool of a population from one generation to the next B) evolution on a molecular level C) speciation D) dramatic changes that take place over long periods of time A Reason: Microevolution involves a process of adaptation of a population to its environment.

Microevolution is _____.

A) adaptive radiation B) artificial selection C) mass extinction D) paedomorphosis E) gene flow A Reason: The finches that initially immigrated to the Galápagos Islands experienced little competition, the result of which was the promotion of speciation.

The different finch species found on the Galápagos Islands probably arose as a result of _____.

A) the allopatric population is small and is isolated from the parent population by a formidable barrier to dispersal B) there is a lot of gene flow between the two populations C) both populations are large and exhibit a sufficient diversity of alleles D) it is in a similar environment to the "parent" population A Reason: This promotes rapid microevolution in the small splinter population and prevents gene flow between the groups, which makes it more likely that a reproductive barrier will arise.

Speciation is likely to occur between a parent population and a population that has become allopatric if _____.

A) the rapid emergence of many ecologically diverse species from a single ancestor B) the appearance of a new species in the same area as its parent species C) most common in animals D) initiated by the appearance of a geographic barrier B Reason: Sympatric speciation is often associated with polyploidy in plants. It is less common in animals, where it is associated with ecological specialization and sexual selection.

Sympatric speciation is _____.

A) mass extinction B) adaptive radiation C) mutation D) paedomorphosis E) gene flow B Reason: The appearance of an evolutionary novelty may allow for the exploitation of previously unexploited niches.

The appearance of an evolutionary novelty promotes _____.

A) postzygotic ... hybrid breakdown B) postzygotic ... behavioral isolation C) prezygotic ... behavioral isolation D) prezygotic ... temporal isolation C Reason: It occurs before formation of a zygote and is due to different behaviors.

Three species of frogs—Lithobates pipiens, Lithobates clamitans, and Lithobates sylvatica—all mate in the same ponds, but they pair off correctly because they have different calls. This is a specific example of a _____ barrier, called _____.

A) The most parsimonious tree has the fewest number of branch tips (twigs) on it. B) The most parsimonious tree always arranges species from simpler to more complex over time. C) The most parsimonious tree produces the observed traits in the organisms with the lowest number of evolutionary changes. D) The most parsimonious tree can be found by matching the phylogeny to known evolutionary trends. C Reason: This tree is less complicated than others, because it indicates how observed traits could have arisen by relatively few evolutionary events.

When analyzing relationships among a particular group of taxa, how does a biologist decide which trees are the most parsimonious?

A) Molecular data is easier to obtain for fossil organisms. B) Molecular systematics uses the principle of parsimony, which is not used to build trees using morphological data. C) Molecular data is often more helpful in discovering relationships among very closely or very distantly related species. D) Molecular data are cheap and easy to obtain, whereas morphological studies require expensive laboratory equipment. C Reason: Deep relatedness is evident in slowly evolving genes such as rRNA; patterns of relatedness among close relatives can be seen in fast-changing genes such as mtDNA.

Which comparison accurately states why phylogenetic trees based on molecular data can be more informative than those based on morphology?

A) Limited interbreeding occurs between two closely related species. This always leads to fusion, because any level of gene flow will remove reproductive barriers between species. B) Distantly related species come into contact and become similar due to extensive interbreeding. C) The absolute effectiveness of reproductive barriers between species is evident. D) Limited interbreeding occurs between two closely related species. Over time, evolution of a strong reproductive barrier may fully separate the species or the species may continue to hybridize, or the two species may fuse into a single species. D Reason: The hybrid zone provides a glimpse of the process of speciation (or its reversal) in progress.

Which statement is true of hybrid zones?

A) animals, particularly those with highly selective females that select mates based on exaggerated traits B) plant species that are incapable of asexual reproduction and do not self-pollinate C) animal species with poor dispersal abilities whose populations exist in widely separated, small patches of habitat D) plant species that are capable of self-pollination and some degree of asexual reproduction D Reason: Sympatric speciation by polyploidy is common in plants, and the capacity to reproduce asexually and through self-pollination enhances the likelihood that polyploid speciation will be completed.

Which type of organism is most likely to undergo sympatric speciation by polyploidy?

A) Paedomorphosis B) Microevolution C) Gene flow D) Genetic drift E) Adaptive radiation E Reason: Adaptive radiation is rapid speciation under conditions in which there is little competition.

_____ is rapid speciation under conditions in which there is little competition.