Answer: Layer a is 500 million years old.
Explanation:
Trilobite is a member of the group of extinct arthropods found as fossils and they can be identified by the three-lobed as well as three segmented forms. These were the marine animals. These were appeared initially in the Cambrian Period. They used to live 542 million years ago so the fossils can be estimated to be aged of 500 above years old. These animals used to dominate in the sea area.
Crossing over<span> occurs </span>between<span> prophase 1 and metaphase 1 and is the process where </span>homologous chromosomes<span> pair up with each other and </span>exchange<span> different segments of their genetic material to form recombinant </span>chromosomes<span>. It can also happen </span>during<span> mitotic division, which may </span>result<span> in loss of heterozygosity. </span>
Answer:
You could generate cDNA libraries and compare the transcribed regions of the genome
