When a male duck of one species performed a courtship display to a female of ano

Question

When a male duck of one species performed a courtship display to a female of another species, she interpreted his behavior as aggressive rather than amorous. What type of reproductive isolating mechanism does this seenario illustrate? 1) How many chromosomes would you be likely to find in the allopolyploid hybrid offspring of parents that had 2n-8 and 2n-12, respectively? 2) 3) What is the difference between a phylogenetic tree and a classification? 4) What is the difference between a monophyletic taxon, a polyphyletic taxon and a paraphyletic taxon? Give examples

Explanation / Answer

1) The given scenario illustrates the behavioral isolating mechanism as it involves display behavior.

2) Parent with 2n=8 will produce 4 chromosomes in haploid cell while parent with 2n=12 will produce 6 chromosomes in its haploid cell. Both the haploid cells will hybridize to form an interspecific hybrid cell containing 10 chromosomes. A spontaneous doubling of chromosomes in the interspecific hybrid results in 20 chromosomes after mitosis. Next, the cell containing 20 chromosomes will undergo meiosis to produce diploid gametes (n=10). Finally, two diploid gametes (each containing 10 chromosomes) undergo self-fertilization to produce tetraploid zygote offsprings (2n = 20). Therefore the correct answer to the question will be 20 chromosomes.

3) Classification refers to the naming and organizing species into a hierarchy of increasingly inclusive groups of organisms that share similar traits. Phylogenetic tree represents the classification in a form of tree that is exclusively based on the evolutionary relationship of species/organisms.

4) Monophyletic taxa comprise of a single clade that is an ancestral species and all of its descendants. Example includes mammalia and aves.

Polyphyletic taxa include organisms from different clade (they do not show common ancestor). Example includes a taxon with birds and bats. Birds and bat's are two clades of vertebrates capable of flying. They are polyphyletic as the taxon do not include their last common ancestor (four legged creature that lived before birds and bats).

Paraphyletic taxa include an ancestor and some but not all of its descendants. Example includes pisces and reptilia.

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