Capillaries: <span>any of the fine branching blood vessels that form a network between the arterioles and venules.</span>
The spiders that survived the first pesticide spraying were resistant to the pesticide and when they reproduced most of their offsprings got the gene of pesticide resistance.
Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes (including single-celled organisms) that reproduce sexually. ... These resultant haploid cells can fuse with other haploid cells of the opposite sex or mating type during fertilization to create a new diploid cell, or zygote.
Lots of hand waving as is in the current field of much of molecular biology. Other than that experiments and observations. Basically the utilization of the scientific method and then trying to find the mechanism by which something occurs through even more research/experimentation.
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