Bio 202 Exam 1 (Chp. 24)

What is the fundamental functional difference between prezygotic and postzygotic reproductive barriers?

Prezygotic barriers block fertilization from occurring, whereas postzygotic barriers prevent hybrid zygotes from developing into viable, fertile adults.

What are populations connected by in order to form a new species?

Gene flow, typically three populations

How are gene flows shown to be established during the process of forming a new species?

A reproductive barrier

During the formation of a new species, what occurs to the following population after a barrier is established that prevents gene flow?

The population begins to diverge genetically

What occurs as a result of a population diverging genetically that leads to the formation of a new species?

Reproductive isolation

What is Reproductive isolation a result of?

Biological barriers impeding members of two species from interbreeding and producing viable, fertile offspring

What do barriers that result in Reproductive Isolation limit the formation of?

Hybrids, offspring that result from interspecific mating

What can Reproductive isolation be classified by?

Whether factors act before or after fertilization

How do prezygotic barriers block fertilization from occurring?

Impeding different species from mating, preventing successful completion of acting, hindering fertilization if mating is done

What can Habitat Isolation be defined as?

Two species that occupy different habitats within the same area may encounter each other rarely, if at all, even though not isolated by obvious physical barriers

Apple maggot flies and blueberry maggot flies feed and lay eggs on different fruits in the same geographic area, encountering each other rarely. What type of reproductive barrier does this represent?

Habitat isolation

What is Temporal Isolation defined as?

Species that breed at different times of the day, in different seasons, or different years cannot mix their gametes

Western spotted skunks mate in summer, whereas eastern spotted skunks mate in winter. What reproductive barrier prevents them from mixing gametes?

 Temporal isolation

How is Behavioral isolation defined?

Courtship rituals and other behaviors unique to a species as effective barriers to mating

Blue-footed boobies mate only after a unique courtship display where the male high-steps to show off his blue feet. What type of prezygotic barrier is this?

Behavioral isolation

How is Mechanical Isolation defined?

Mating is attempted, but morphological difference prevent its successful completion

Two species of terrestrial snails cannot mate because one shell spirals clockwise while the other spirals counterclockwise, preventing genital alignment. What barrier is operating?

Mechanical isolation

Red and purple sea urchins release gametes into the ocean simultaneously, but surface proteins on the sperm and eggs bind poorly, preventing fertilization. What type of barrier is this?

Gametic Isolation

In Reduced Hybrid Fertility, what is the result of a different number of chromosomes or structures in the parent species?

Meiosis may fail to produce normal gametes, resulting in sterility and the inability to produce offspring/gene flow when mating with either parent species

A male donkey and a female horse produce a mule, which is a robust individual but completely sterile because meiosis fails to produce normal gametes. What postzygotic barrier does this represent?

Reduced hybrid fertility

In reduced hybrid viability, how do the genes of different parent species affect a hybrid’s development?

They may interact in ways that impair the hybrids development or survival in its environment

The hybrid offspring of different subspecies of salamanders of the genus Ensatina are a result of which post-zygotic barrier and how is it affected?

Reduced Hybrid Viability, in which development is usually not complete and those that do are frail

Through hybrid breakdown, what is the difference between first-generation hybrids and offspring in the next generation?

Hybrids are viable and fertile, offspring in next generation are feeble or sterile

Which of the following represents a recognized limitation of the biological species concept?

It cannot be applied to fossils or asexual organisms, including all prokaryotes.

How does the morphological species concept distinguish species compared to the ecological species concept?

The morphological concept defines species by structural features, whereas the ecological concept defines species by ecological niche.

What does the morphological species concept usually apply to in regard to species and gene flow?

Sexual and asexual species, which does not require information on the extent of gene flow

Two species of oak trees might differ in their size or in their ability to tolerate dry conditions, yet still occasionally interbreed. Which species concept is this an example of?

Ecological species concept

What does the ecological species concept usually apply to in regard to species and are said to emphasize?

It applies to sexual and asexual species, emphasizing the role of disruptive selection

Allopatric speciation

Populations are geographically isolated

Sympatric speciation

Populations are not geographically isolated

What is the fundamental difference between allopatric speciation and sympatric speciation?

Allopatric speciation occurs in populations that are geographically isolated, whereas sympatric speciation occurs in populations in the same geographic area.

What outcome occurs in a hybrid zone when hybrids are less fit than their parent species, leading natural selection to strengthen prezygotic barriers?

Reinforcement

In the fossil record, what pattern is described by punctuated equilibria?

Long periods of apparent stasis punctuated by sudden morphological change.

What do postzygpotic barriers prevent?

Hybrid zygotes from developing into viable, fertile adults