PART 3: Directions: Classify each of the following situations as A) either a pre
ID: 211111 • Letter: P
Question
PART 3: Directions: Classify each of the following situations as A) either a pre- or postzygotic isolating mechanism and B) the specific type of pre or post zygotic isolating mechanism. 1. In flowering plants, the pollen is often transferred from the pistil (male part) of one plant to the stigma (female part) of another by some type of animal vector (e.g. bee, hummingbird). As a result, there are times when the pollen of one species ends up on the stigma of another. But for fertilization to occur, a pollen tube must form that allows the pollen to reach and fertilize the ovum (egg). In most cases, this will not occur when the wrong pollen reaches the stigma due to differences in the structures of the pollen. b. A short hike through the Sandia Mountains from early spring to late summer will often reveal several different species of penstemom (a plant). The Rocky Mountain penstemon blooms in the spring while the very similar inflated penstemon blooms in late summer. As a result, hybrids are rarely encountered. 2. b. Ligers are the result of a cross between a male lion and a female liger. Almost all known male offspring of these crosses have been infertile. 3. a. b. Norway rats and black rats are very similar. Attempts to cross the two species (why?) have led to pups being born, but they die within hors. 4. a. b. When male fruit flies of one species (Drosophila melanogaster) attempt to mate with females of another (D pseudoobscura), the act generally leads to severe injury or even death to both flies. 5. b.Explanation / Answer
Part 3:-
1:- A-Prezygotic isolating mechanism
B- gametic isolation
3:- A-Postzygotic (after mating)
B- Hybrid infertility
4:- A- Postzygotic ( after mating)
B- Hybrid inviability
5:- A-Prezygotic ( before matting)
B- Mechanical barriers
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