It\'s a review sheet for my exam on monday. I need to study these. Distinguish b

Question

It's a review sheet for my exam on monday. I need to study these.

Distinguish between pre- and post-zygotic isolating mechanisms . List and describe the prezygotic isolating mechanisms List and describe the postzygotic isolating mechanisms o o Distinguish between allopatric and sympatric speciation o Describe the methods of allopatric speciation o Describe the methods of sympatric speciation Distinguish between autopolyploidy and allopolyploidy Describe what can happen when two separated populations come back into contact

Explanation / Answer

Pre-zygotic reproductive isolation post zygotic reproductive isolation It refers to the mechanisms used by various species to prevent breeding between different species before zygote formation. It includes mechanisms such as: Different mating calls and behaviour in different species. Difference in size/shape of reproductive organs, so that mating is not possible. Gamete inviability- gamete of different species cannot fertilise gamete of other species due to specific receptor/recognition molecules. Difference in chromosome number. It includes those mechanisms, which prevent the formation of fertile offspring after zygote formation has taken place. It includes following mechanism: Zygote inviability: zygote forms, but does not develop into embryo. Embryonic inviability: embryo fails to grow/implant. Hybrid inviability: The hybrid offspring does not survive beyond birth. Hybrid sterility: If the hybrid gets born, mechanism such as sterility (eg. hybrid of donkey & horse) do not allow hybrids to reproduce.

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