Crossing over happens in Meiosis 1 only. In Prophase 1 a cells chromatin (chromatin = chromosomes that have not condensed yet) condense and pair up forming homologous chromosomes (paired = XX (2 chromosomes together)). When this happens segments/ alleles of the chromosomes pairing up swap over. This creates genetic diversity as each chromosome is different, it has parts from its pair. This leaves every chromosome unique and individual.
I hope this helps, sorry some of the vocab is rather technical. By the way I would suggest watching the
'Crash Course: Meiosis' on YouTube, this really helped me when I was learning this topic. :D
Answer:
sounds hard have a good day
Explanation:
This family trait that skips a generation comes from an autosomal recessive trait or as Mendel called as hidden non-dominant trait. Offsprings have a dominant and recessive trait which comes from both parents. Recessive trait appears only when two offspring with same recessive trait blends. This happens in self-fertilization. In the human population, marriage is prohibited between offsprings, thus having recessive trait is only imminent when cousins are married.
The level most commonly meant by the term biodiversity is the species level.