chapter22

Allopatric

A fish species in different lakes. A bird species on different islands. A squirrel species separated by a mountain range.

Sympatric

A plant species within a location that has areas of wet and dry soils. An insect species that can feed on different parts of a plant. A plant producing polypoid offspring.

Promote Speciation

A small population of humans establishes a colony on Mars and no more spaceships arrive. Nuclear warfare destroys 99% of the human population, leaving only small pockets of survivors

In which population would the rate of genetic drift be the greatest?

A small population that is geographically isolated from its parent population

In which environment(s) is a population of seed-eating birds likely to undergo adaptive radiation? Check all that apply.

A volcanic island with many different types of plants but is relatively new. A large island has high plant diversity, and few existing species of animals.

Which statements about gradualism and punctuated equilibrium are true? Check all that apply.

According to the theory of punctuated equilibrium, evolutionary change occurs only during brief periods of speciation. Gradualism suggests that evolutionary change is not linked to speciation.

Scientists found that different beak shapes correlate with different mating songs in Darwin's finches. Which hypothesis does this support?

Adaptation to different food sources led to behavioral isolation in Darwin's finches.

Would the following organisms be considered separate species according to the biological species concept? 2. Black bears in the United States can have coat colors ranging from blonde to jet black, but bears with different coat colors occupy the same habitat and interbreed successfully.

False

Indicate true or false, whether the following statements are consistent with the idea of punctuated equilibrium. a. Each new species evolves continuously over long spans of time. b. Species mainly stay unchanged for large spans of time. c. New species can evolve rapidly over a short period of time. d. Large phenotypic differences that produce new species are due to the accumulation of many small changes in phenotype. e. Punctuated equilibrium and gradualism are mutually exclusive.

False True True False False

Which of the following could occur if two partially reproductively isolated populations become sympatric? Check all that apply.

Gene flow between the populations will occur The populations may eventually become separate species through reinforcement The populations may eventually lose their genetic distinctiveness

Choose the evidence that supports that the polyploidy sunflower species, Helianthus anomalus, is a true biological species formed sympatrically by hybridization of the parental polyploidy sunflower species, H. petiolaris and H. annuus. Check all that apply.

H. anomalus contains genetic material from H. petiolaris and H. annuus. The ranges of H. anomalus, H. petiolaris, and H. annuus overlap.

Habitat fragmentation is a big concern to conservation biologists. How would habitat fragmentation affect evolution by genetic drift?

Habitat fragmentation would increase genetic drift, and decrease variation.

Which scenario would be most likely to promote the evolution of prezygotic isolating mechanisms between two similar species in a hybrid zone?

Hybrid offspring have low fitness relative to the parental species.

Supports Punctuated Equilibrium/Stasis

Marine bryozoan fossils lack intermediate forms. Leaves from living Ginkgo trees look the same as 40-million-year-old fossils of the same species. Single genetic mutations can lead to large phenotypic changes. Mass extinctions are often followed by adaptive radiations.

A few scarlet flycatchers colonize an island from another nearby island. Research has shown that the parent island is hotter and drier than the new island. Over many generations, the flycatchers diverge between the two islands and become reproductively isolated. Which of the following likely contributed to this divergence? Check all that apply.

Natural selection Genetic drift

Prevent Speciation

Plane tickets are subsidized by the United Nations, leading to essentially free international travel. World peace makes it safe to travel anywhere in the world.

Supports Gradualism

The horse fossil record has many intermediate forms. Trilobite fossils show a regular increase in number of ribs over time.

In general, how has the number of species changed over time?

The number of species has increased.

A ship was caught in a storm and landed on a small island in the middle of the South Pacific. For generations, no one encountered this small colony who, despite the odds, made a thriving settlement on their island. After many years, what characteristics would be unique about this island population?

The people would look very similar to each other, and may exhibit abnormally high occurrences of genetic diseases that are rare in the general human population.

Why do the Galápagos Islands and the Hawaiian Islands have so many endemic species of flies and birds? Check all that apply.

There are numerous islands in each archipelago. There is adequate distance between islands to allow divergence. The founder effect was common when islands were colonized.

Would the following organisms be considered separate species according to the biological species concept? 1. Lions and tigers can interbreed to produce viable, fertile offspring, but lions live in open grasslands and tigers live in dense forests.

True

Would the following organisms be considered separate species according to the biological species concept? 4. Many of Darwin's finches can interbreed in captivity to produce viable, fertile offspring, but they differ in their mating songs.

True

Would the following organisms be considered separate species according to the biological species concept? Many leopard frogs in the eastern United States look the same and can mate to produce a fertilized egg, but the embryo does not develop past the early stages.

True

Which is an example of ecological isolation?

Two plant species live on the same mountainside, but one lives on rocky outcrops and the other in open meadows.

Lake Victoria is famous for its variety of cichlid fishes. In fact, they offer the most diverse assembly of vertebrates presently known to science. One trait that scientists have focused on as one possible reason for their adaptability is

a second set of jaws in their throats.

The phenomenon where one species diverges into many by occupying a different habitats within a region is called ___________________.

adaptive radiation

A single seed landed on an archipelago. Several million years later, its descendants have evolved into a number of new species on the different islands, representing a variety of growth forms. This is an example of

adaptive radiation.

The sunflower species Helianthus anomalus is thought to have been formed by hybridization between the sunflower species H. petiolaris and H. annuus because it contains a set of chromosomes from both parental species. H. anomalus is most likely an example of instantaneous speciation through

allopolyploidy.

Which of the following are causes of mass extinctions?

asteroids global climate change human activities

How many mass extinctions have been identified during the history of life on Earth?

five

Once species have formed, they keep their identity by

isolating mechanisms.

Which is an example of temporal isolation?

one plant species blooms in June-July and a second plant species blooms in August-September.

The most common mechanism for sympatric speciation in plants is

polyploidy.

Evolution acts at the level of the

population.

A type of isolating mechanism that leads to reproductive isolation after a hybrid zygote has formed is called a _____________ isolating mechanism.

postzygotic

Very rapid speciation occurred when cichlid fishes were isolated in Lake Victoria. Widespread extinction was dramatically seen when

predatory fish were added.

When species are kept separate by preventing the formation of hybrid zygotes, the mechanism that keeps the species separate is known as a _____________ isolating mechanism.

prezygotic

Reinforcement is most likely to drive the evolution of

prezygotic isolating mechanisms, because selection favors alleles that prevent hybridization.

Many male songbirds have very distinctive songs that are used to attract females. These songs are an example of a ________ isolating mechanism.

prezygotic, behavioral

Several species of sea urchins may inhabit the same tide pool and their reproductive periods overlap. Although they practice external fertilization, they seldom interbreed because eggs produce chemicals that are only attractive to sperm of their own species. This is an example of a _________ barrier that _______________.

prezygotic; prevents gamete fusion Correct

In 1938, scientists found a population of coelacanths in the Indian Ocean. This fish species is considered a "living fossil" and appears not to have changed morphologically for 80 million years. This discovery supports the ___________ model of evolution.

punctuated equilibrium

The __________ __________ model assumes that evolution occurs in spurts, between which there are long periods of stasis with little evolutionary change.

punctuated equilibrium

Genetic drift

reduces genetic variation in a population.

Imagine two species of birds with similar beak sizes and diets. Where the two species are allopatric, we would expect that their beak sizes

should be more similar than when sympatric.

The effect of genetic drift is much more significant in ________ populations.

small

According to the biological species concept, two groups of organisms that are unable to form fertile, viable hybrids are considered to be different

species.

Which form of speciation is most rapid?

sympatric speciation via polyploidy

If two species are able to mate and produce an offspring which can mate with itself, but is unable to mate with either parent's species, it is an example of

sympatric speciation via polyploidy.

If populations within the same area split into species, the process is known as

sympatric speciation.

Several new tetraploid species of a plant called salsify (Tragopogon) known as salsify have arisen in western North America. These new species each arose from a diploid species that went through the process of allopolyploidy. This mode of speciation is a type of ________ and it occurs _______.

sympatric speciation; almost instantaneously

If a new species is produced by the interbreeding of two members of distinct species, this would be __________ speciation achieved via _________.

sympatric; allopolyploidy