16.3

Question 1

What is Morphology?

Answer 1

The internal and external structure and appearance of an organism.

Question 2

What was used ofr many years as the chief criteria for dissifying an organism?

Answer 2

Morphology

Question 3

Why is morphology convienant?

Answer 3

becasue it is easy to observe

Question 4

What are two limitations of morphology?

Answer 4

• phenotypic differences among individuals in a single population
• some organisms that appear different enough to belong to different species interbreed in the wild and produce fertile offspring

Question 5

What is the biological species concept?

Answer 5

A species is a population of organisms that can successfully interbreed but not breed with other groups.

Question 6

Who proposed the biological species concept?

Answer 6

Ernst Mayr

Question 7

What is the biological species concept useful for? What is it not useful for?

Answer 7

• Useful for living animals
• Does not provide a satisfactory definition for species of extinct organisms who reproductive compatibility cannot be tested
• Not useful for organisms that do not reproduce sexually

Question 8

What is geographical isolation? How may this happen?

Answer 8

The physical seperation of members of a population. Populations may be physically seperated when an original habitat becomes divided. For example, a deep canyon could develop, a river could change course, or a drying climate in a valley could force surviving gragments of an original population into seperate mountain ranges.

Question 9

What happens once the subpopulations become isolated in geographic isolation?

Answer 9

Gene flow between them stops. Natural selection and genetic drift cause the two subpopulations to diverge, eventually making them incompatible for mating.

Question 10

What is reproductive isolation?

Answer 10

Sometimes groups of organisms withing a a population become genetically isolated without being geographically isolated.

Question 11

What does reproductive isolation result from?

Answer 11

Results from barriers to successful breeding between population groups in the same area.

Question 12

What kind of natural selection may reproductive isolation arise from and why?

Answer 12

May arise from disruptive selection.

Question 13

What happens once successful mating is prevented between members of the two subpopulations in reproductive isolation?

Answer 13

The effect is the same as what would have occured if the two subpopulations had been geographically isolated. So genen flow stops and the two subpopulations diverge, eventually making them incompatible for mating.

Question 14

What is prezygotic isolation?

Answer 14

Type of reproductive isolation. Occures before fertilization.

Question 15

What is postzygotic Isolation?

Answer 15

Type of reproductive isolation. Occurs after fertilization.

Question 16

What can postzygotic isolation prevent?

Answer 16

The production of healthy, fully fertile, offspring.

Question 17

From an evolutionary standpoint, what happens if death or sterility of offspring occurs?

Answer 17

The parent organisms have wasted their gametes producing offspring that cannot, in turn, reproduce.

Question 18

Does the situation of the offspring not being able to produce favor poszygotic or prezygotic isolation? Why?

Answer 18

This situation favors prezygotic mechanisms, such as incompatible behavior, that reduce the chance of hybrid formation. For example, a mating call that is not recognized as such by a potential mate can contribute to isolation.

Question 19

Differences in mating times is a type of what isolation?

Answer 19

prezygotic isolation

Question 20

Discuss the frog example of prezygotic isolation.

Answer 20

Both mechanisms (differences inmating times and mating calls) are in effect for the frogs int he figure in the book. Their mating calls and peak mating times differ, reducing the chance of interbreeding. As a result, the wood frog and the leopard frog are reproductively isolated. Though these two frogs interbreed in captivity, they do not interbreed where their ranges overlap in the wild.

Question 21

What is the punctuated equilibrium?

Answer 21

Divergence of organisms and thus speciation may not occur smoothly or gradually. The fossil record suggests that rapid speciation may be the norm. Fossil record indicated that many species existed w ithout change for long periods of time. Periods of stability were seperated by an “instant” change in terms of geological time. A change occured in a few thousand rather than a few million years. The punctuated part refers to the sudden shift of form that is often seen in the fossil record.

Question 22

What are two shortcomings of the biological species concept?

Answer 22

• It does not provide a satisfactory definition for species of extinct organisms (reproductive compatibility cannot be tested).
• It is notuseful for organisms that do not produce sexually.

Question 23

How can geographical isolation lead to speciation? What is the principle cause of such speciation?

Answer 23

• Populations can become physically sseperated when an original habitat becomes divided. Once the subpopulations become divided, gene flow between them stops.
• The principle casue for this type of speciation is that natural selection and genetic drift cause the subpopulations to diverge, eventually making them incompatible for mating.

Question 24

What are two examples of postzygotic isolation mechanisms?

Answer 24

• The offspring of interbreeding species may be develope completely and may die early
• If the offspring of interbreeding species are born healthy, they may not be fertile

Question 25

What is less metabolically costly to an animal, prezygotic or postzygotic isolation? Why?

Answer 25

Prezygotic isolatoin is less metabolically costly to an animal because they don’t actually physically reproduce. In postzygotic isolation, the organisms actually do reproduce, but they die.