Biology Chapter 24

Rank the following in order from most general to most specific: 1. gametic isolation 2. reproductive isolating mechanism 3. sperm-egg incompatibility in sea urchins 4. prezygotic isolating mechanism

2, 4, 1, 3

Humans are diploid and have 46 chromosomes. How many chromosomes are found in each human gamete?

23

Prezygotic Barriers

Behavioral Isolation, Mechanical Isolation, Habitat Isolation, Temporal Isolation, Gametic Isolation

Which concept(s) for identifying species cannot be applied to asexual or fossil species?

Biological Species Concept

Which of the following is a correct comparison between the speciation of the trumpeters of the Amazon and the ongoing divergence of the maggot flies of North America?

Both events resulted from barriers to gene flow that arose between populations as well as mutations, natural selection, and genetic drift that occurred in those populations.

Mutant tetraploid plants _____.

are unable to interbreed with a diploid plant

Biological, morphological, and phylogenetic species concepts allow biologists to identify evolutionarily independent groups because they all rely on criteria indicative of _____.

no gene flow between populations

Which of these terms applies to an organism with extra sets of chromosomes?

polyploid

Mechanical Isolation

reproductive structure incompatibility; differently shaped snail shells prevent alignment of genital openings

Gametic Isolation

sperm and egg are incompatible; different coral species release gametes into the water, but only gametes of conspecifics can fuse

The origin of a new plant species by hybridizing two existing species, coupled with accidents during cell division, is an example of _____.

sympatric speciation and allopolyploidy

In a hypothetical situation, a certain species of flea feeds only on pronghorn antelopes. In the western United States, pronghorns and cattle often associate with one another in the same open rangeland. Some of these fleas develop a strong preference for cattle blood and mate only with other fleas that prefer cattle blood. The host mammal can be considered as the fleas' habitat. If this situation persists, and new species evolve, this would be an example of _____.

sympatric speciation and habitat isolation

Among known plant species, which of these have been the two most commonly occurring phenomena that have led to the origin of new species?

sympatric speciation and polyploidy

Beetle pollinators of a particular plant are attracted to its flowers' bright orange color. The beetles not only pollinate the flowers but mate while inside of the flowers. A mutant version of the plant with red flowers becomes more common with the passage of time. A particular variant of the beetle prefers the red flowers to the orange flowers. Over time, these two beetle variants diverge from each other to such an extent that interbreeding is no longer possible. What kind of speciation has occurred in this example, and what has driven it?

sympatric speciation; habitat isolation

Which term is used to describe populations that live close enough to interbreed?

sympatry

What would be the ploidy of the viable gametes produced by a tetraploid individual if nondisjunction of all chromosomes occurred in meiosis I?

Tetraploid

Which of the following statements explains why animals are less likely than plants to speciate by polyploidy?

Animals self-fertilize less often than plants, so diploid gametes are less likely to fuse.

Humans are diploid and have 46 chromosomes (or two sets). How many sets of chromosomes are found in each human gamete?

1

A particular diploid plant species has 48 chromosomes, or two sets. A mutation occurs and gametes with 48 chromosomes are produced. If self-fertilization occurs, the zygote will have _____ set(s) of chromosomes.

4

Three populations of crickets look very similar, but the males have courtship songs that sound different. What function would this difference in song likely serve if the populations came in contact?

A behavioral reproductive isolating mechanism

How might the timing of when fruit ripens be important in the sympatric speciation of fruit maggot flies?

Apple fruit ripens earlier than hawthorn fruit, reducing the interaction of the fly species in time

In which habitat should one find snapping shrimp most closely related to shrimp that live in habitat A4?

B4

Phylogenetic Species Concept

Based on evolutionary history , accommodates asexual reproduction, species acceptance criteria can be subjective, used by scientists in classification

How do autopolyploidy and allopolyploidy differ?

The chromosomes of an autopolyploid individual come from the same species, while an allopolyploid individual has sets of chromosomes from different species.

If autopolyploidy is responsible for the formation of a tetraploid grape (with extra-large fruit) from a diploid population (with smaller fruit), which of the following events must have occurred?

Doubling of chromosome number in the diploid population

True or false? A mating between a tetraploid individual and a diploid individual produces biologically fit offspring.

False

True or false? Speciation is a slow process.

False. Speciation is sometimes a slow process, but can occur rapidly, such as the formation of a new species of Tragopogon by allopolyploidy in a single generation.

What prevents speciation from occurring in sympatric populations?

Gene flow

Which of the following does not tend to promote speciation?

Gene flow

Two populations of birds with somewhat different coloration live on opposite sides of a peninsula. The habitat between the populations is not suitable for these birds. When birds from the two populations are brought together, they produce young whose appearance is intermediate between the two parents. These offspring will breed with each other or with birds from either parent population, and all offspring of these pairings appear intermediate to various degrees. What keeps the two population separate?

Habitat Isolation

How many chromosomes would be found in an allopolyploid plant if its parents had diploid numbers of 2 and 10, respectively?

Haploid number of 6

Hybrid zone formation

Hybridization occurs in a well-defined geographic area. This area may move over time or be stable; The hybrid zone between hermit and Townsends warblers appears to have moved over time.

Which of the following statements about species, as defined by the biological species concept, is (are) correct? I. Biological species are defined by reproductive isolation. II. Biological species are the model used for grouping extinct forms of life. III. All members of a species can potentially interbreed.

I and III

Fly species W, found in a certain part of the island, produces fertile offspring with species Y. Species W does not produce fertile offspring with species X or Z. If no other species can hybridize, then which of the following statements about species W and Y is/are TRUE? I. Species W and Y have genomes that are still similar enough for successful meiosis to occur in hybrid flies. II. Species W and Y have more genetic similarity with each other than either did with the other two species. III. Species W and Y may fuse into a single species if their hybrids remain fertile over the course of many generations.

I, II, III

Reinforcement of divergence

If hybrid offspring have low fitness, natural selection favors the evolution of traits that prevent interbreeding between the populations; Appears to be common for distinct populations of fruit fly species that occupy the same geographic areas.

Extinction of one population

If one population or species is a better competitor for shared resources, then the poorer competitor may be driven to extinction; Townsends warblers may be driving hermit warblers to extinction.

Formation of new species

If the combination of genes in hybrid offspring allows them to occupy distinct habitats or use novel resources, they may form a new species; Hybridization between sunflowers gave rise to a new species with unique characteristics.

What distinguishes a morphospecies ?

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

How is a hybrid zone most likely to change over time if hybrid offspring have higher fitness than both parental populations?

It should expand into the ranges of both parental populations.

How does the discovery of a past geological event that divided a once-continuous salt marsh in Florida support the tree depicted?

It supports the concept of allopatric speciation via vicariance.

The biological species concept can be applied only to which of the following groups?

Lizard species living today

Imagine that the human genome project has shown that individuals from a light-skinned population can exhibit greater similarity in DNA sequence with individuals from a dark-skinned population than they do with other individuals in the light-skinned population. Should these light- and dark-skinned human populations be considered separate species under the phylogenetic species concept? Why or why not?

No. The DNA sequence data do not suppose the conclusion that they represent different clades.

How can an allopolyploid plant become a biologically fit new species?

Nondisjunction event during mitosis

Biological Species Concept

Not applicable for extinct species, used by scientists in classification

Most causes of speciation are relatively slow, in that they may take many generations to see changes, with the exception of _____.

Polyploidy

Two species of tree frogs that live sympatrically in the northeastern United States differ in ploidy: Hyla chrysoscelis is diploid, and Hyla versicolor is tetraploid. The frogs are identical in appearance, but their mating calls, which females use to find mates, differ. Which likely evolved first?

Polyploidy

The common edible frog of Europe is a hybrid between two species, Rana lessonae and Rana ridibunda. The hybrids were first described in 1758 and have a wide distribution, from France across central Europe to Russia. Both male and female hybrids exist, but when the hybrids mate with other hybrids or with adults of either species, they are rarely successful in producing offspring. What can you infer from this information?

Post zygotic isolation exists between the two frog species

Postzygotic Barriers

Reduced Hybrid Fertility, Reduced Hybrid Viability

Morphological Species Concept

Relies on similarities in structure, accommodates asexual reproduction, species acceptance criteria can be subjective, used by scientists in classification

Which of the following could be a vicariance event?

The level of water in a lake recedes, creating two lakes where there used to be one.

Which species concept would be most useful to a team of biologists conducting a biodiversity survey?

The morhospecies moncept

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification?

The two forms interbreed often in nature, ad their offspring have good survival and reproduction

Fusion of the populations

The two populations freely interbreed; Occurs whenever populations of the same species come into contact.

Many songbirds breed in North America in the spring and summer and then migrate to Central and South America in the fall. They spend the winter in these warmer areas, where they feed and prepare for the spring migration north and another breeding season. Two hypothetical species of sparrow, A and B, overwinter together in mixed flocks in Costa Rica. In spring, species A goes to the east coast of North America, and species B goes to the west coast. What can you say about the isolating mechanisms of these two species?

Their winter habitat has no bearing on their degree of reproductive isolation

Which of the following statements about autopolyploid individuals is true?

They contain more than two haploid sets of chromosomes.

Why should deepwater shrimp on different sides of the isthmus have diverged from each other earlier than shallow-water shrimp?

They have been geographically isolated from each other for a longer time.

There is an island in the middle of a large river that houses a large population of ants. Damming of the river causes the island to flood and only the highest points of the island are now above water. The ants cannot swim, so are now in multiple isolated populations. Which of the following best describes this event?

This situation represents isolation by vicariance.

The largest unit within which gene flow can readily occur is _____.

a species

How are two different species most likely to evolve from one ancestral species?

allopatrically, after the ancestral species has split into two populations

A hybrid zone is properly defined as _____.

an area where mating occurs between members of two closely related species, producing viable offspring

On the Bahamian island of Andros, mosquitofish populations live in various, now-isolated, freshwater ponds that were once united. Currently, some predator-rich ponds have mosquitofish that can swim in short, fast bursts; other predator-poor ponds have mosquitofish that can swim continuously for a long time. When placed together in the same body of water, the two kinds of female mosquitofish exhibit exclusive breeding preferences. Which type of reproductive isolation operates to keep the mosquitofish isolated, even when fish from different ponds are reunited in the same body of water?

behavioral isolation

Habitat Isolation

differences in habitat occupied; different ticks live on different host species

Behavioral Isolation

differences in mating rituals or displays; different bird species display feathers of different colors during mating display

Temporal Isolation

differences in the timing of mating; one plant species flowers before dawn, a related species flowers in the late afternoon

_____ is the process by which haploid gametes form a diploid zygote.

fertilization

Rocky Mountain juniper (Juniperus scopulorum) and one-seeded juniper (J. monosperma) have overlapping ranges. Pollen grains (which contain sperm nuclei) from one species are unable to germinate and make pollen tubes to bring the sperm nuclei to the female ovules (which contain egg cells) of the other species. These two juniper species are kept separate by ________.

gametic isolation

In hybrid zones where reinforcement is occurring, you should see a decline in ________.

gene flow between distinct gene pools

Which of the following describes the most likely order of events in allopatric speciation?

genetic isolation, genetic drift, divergence

Reduced Hybrid Viability

hybrid offspring are produced but are feeble or unable to compete for mates; two species of fish successfully interbreed, but their offspring don't live to maturity

Reduced Hybrid Fertility

hybrid offspring are produced but are sterile, horses can be mated with zebras, but their offspring are sterile

On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila yakuba inhabits the island's lowlands, and is also found on the African mainland, located about 200 miles away. The very closely related species Drosophila santomea is found at higher elevations and only on Sao Tomé. The two species can hybridize, though male hybrids are sterile. A hybrid zone exists at middle elevations, where hybrids are greatly outnumbered by D. santomea. Studies of the two species' nuclear genomes reveal that D. yakuba on the island is more closely related to mainland D. yakuba than to D. santomea (2n = 4 in both species). Sao Tomé rose from the Atlantic Ocean about 14 million years ago. Which of the following reduces gene flow between the gene pools of the two species on Sao Tomé, despite the existence of hybrids?

hybrid sterility

Which mechanism causes postzygotic reproductive isolation?

hybrid sterility

Most polyploid plants arise as a result of _____.

hybridization

Reinforcement is most likely to occur when _____.

hybrids have lower fitness than either parent population

About 3 million years ago, the Isthmus of Panama (a narrow strip of land connecting North and South America) formed, dividing marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sides of the isthmus. Based on the morphological species concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated by the isthmus were indeed each other's closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. (N. Knowlton, L. A. Weigt, L. A. Solorzano, D. K. Mills, and E. Bermingham. 1993. Divergence in proteins, mitochondrial DNA, and reproductive incompatibility across the Isthmus of Panama. Science 260:1629-32.) Refer to the paragraph about the formation of the Isthmus of Panama. The sister populations on opposite sides of the isthmus are true species under which species concept?

the morphological species, biological species, and phylogenetic species concepts

There are two clusters of Amazonian trumpeter species on the phylogenic tree because _________.

the population of the common ancestral species was split into two isolated populations from whom all the other species evolved