Bio 121 Ch 22 Exam

A bacteriologist is studying two asexually reproducing strains of E. coli. The two require different amounts of trace minerals for survival; on these grounds, the bacteriologist determines that they are separate species. In making his determination, he is using which species concept or concepts?

A bacteriologist is studying two asexually reproducing strains of E. coli. The two require different amounts of trace minerals for survival; on these grounds, the bacteriologist determines that they are separate species. In making his determination, he is using which species concept or concepts?

ecological species concept

Horses and donkeys can interbreed, but their offspring (mules) are infertile. This is an example of what kind of reproductive isolating mechanism?

post-zygotic, genetic incompatibility

Gus and Ida are two polar bears (Ursus maritimus) that live at the Central Park Zoo in New York City. They are first-generation zoo polar bears (meaning they were caught in the wild and brought to the zoo). They have lived at the zoo since 1985 and are kept in their own area so that they are reproductively isolated from all other polar bears in the zoo.

1. Consider the possibility that Gus and Ida were released back into the wild in 2011, in an area that already has a population of polar bears. You observe them for many years and note that Gus and Ida only breed with each other. Does this prove that they are members of a different species than the wild polar bears?

2. The zoo decides to keep all of Gus and Ida's descendants under zoo conditions for the next 30,000 years. They breed only with each other. You visit the zoo in 30,000 years and see their offspring. Do you expect their offspring, which are alive in 30,000 years, to be identical in genotype and phenotype to Gus and Ida? Keep in mind, polar bears start reproducing when they are between 5 and 10 years old, and adult females give birth to two cubs every 2-3 years.

3.Are Gus and Ida a different species from all other polar bears, based on the biological species concept?

1. no

2. no

3. no

Different species of fruit flies occupy each of the islands in the Hawaiian island chain, a group of volcanic islands that formed one after the other. One hypothesis for how the different fruit fly species formed is that, after each new island was formed, fruit flies from existing islands colonized it and subsequently diverged. If this hypothesis is correct, it would be an example of:

allopatric speciation by dispersal.

You begin an experiment with two populations of E. coli that are each composed of 100 cells. The cells are all genetically identical (i.e., they are clones). You grow them up in flasks on a lab bench under identical conditions with unlimited resources. After 10,000 generations, you analyze the genome of each population. Do you expect the genomes of each population to be identical after 10,000 generations?

No, because mutation and natural selection (once genetic variation is present) were factors in this experiment.

Disruptive selection is a key component of sympatric speciation because it acts against the homogenizing effect of gene flow between the diverging populations. Imagine a case in which a bird population is undergoing disruptive selection on bill size in response to the availability of seeds to eat. The birds' environment contains two seed types, large and small, and lacks medium-sized seeds. Assume that a bird's ability to eat a seed is a direct function of its bill size (large bills are good for large seeds, and so on). Disruptive selection acts against birds with:

intermediate (medium-sized) bills.

A drawback of the biological species concept is that it CANNOT be applied to:

extinct and asexual organisms.

Several species of fireflies are active on the same summer nights in the same fields. Males and females recognize one another by their distinctive flashing patterns. This is an example of what kind of reproductive isolation?

pre-zygotic, behavioral isolation