Crossing over occurs at the four-strand stage when two homologous chromosomes, each consisting of a pair of sister chromatids, are paired. Each crossover involves just two of the four strands and generates two recombinant strands.
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Insects (Insecta) are the most diverse of all animal groups. There are more species of insects that there are species of all other animals combined. Their numbers are nothing less than remarkable, both in terms of how many individual insects, as well as many species of insects that are. In fact, there are many insects that is not very known how to count them all, the best thing we can do is to make calculations.
Approximate scientists who can be as many as 30 million species of insects alive today. To date, they have identified over 1 million. At any time, the number of live insects on our planet is amazingly, some scientists estimate that for every human being alive today, there are 200 million insects.
The success of insects as a group is also reflected in the diversity of habitats in which they live. Insects are more numerous in the land such as deserts, forests and grassland environments. They are also numerous fresh water such as ponds, lakes, streams and wetlands habitats. Insects are relatively scarce in habitats marine, but are more common in the waters brackish, like marshes and mangrove
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Diffusion -SKx is your answer. Hope this helps! ;D
