Males of many marsupial species have forked penises that are incompatible with the anatomy of female placental mammals. What type of isolating mechanism does this represent?

Question

A.  ecological isolation
B.  temporal isolation
C.  mechanical incompatibility
D.  hybrid sterility
E.  prevention of gamete fusion

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?

  Gather Content
· What do you already know about reproductive isolation?

  Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

  Reflect on Process · Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

C.  mechanical incompatibility

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses reproductive isolation.
· What type of thinking is required?
        o This question is asking you to take what you already know and apply it to this unfamiliar situation.

  Gather Content
· What do you already know about reproductive isolation?
        o Populations are considered to be different species when the members are reproductively isolated from each other.
        o Reproductive isolating mechanisms prevent genetic exchange between species. Some prevent the formation of zygotes – prezygotic isolating mechanisms. Others prevent the proper functioning of zygotes after they form – postzygotic isolating mechanisms.
        o Prezygotic isolating mechanisms include ecological isolation, behavioral isolation, temporal isolation, mechanical isolation, and prevention of gamete fusion.
        o Ecological isolation happens when two species occur in the same area, but use different portions of the environment and thus do not hybridize.
        o Behavioral isolation is when related species differ in their courtship rituals, keeping these species distinct.
        o Temporal isolation is when species reproduce in different seasons.
        o Mechanical isolation is when the morphology of two species prevents mating.
        o Sometimes gametes cannot fuse properly even when they meet.
        o Postzygotic isolation occurs when hybrids between species are either inviable (poor at surviving) or infertile (unable to reproduce themselves).

  Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o In this example, it is the morphology that prevents mating – this is an example of mechanical isolation.

  Reflect on Process · Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that when two groups have incompatible genitalia, we call it mechanical isolation?