B replaced because it takes place when water dissolves the original hard parts and replaces them with mineral matter.
Answer:
The number of genes partially explains how an organism has evolved and how it gained complexity.
Explanation:
The number of genes of a bacteria versus an eucaryotic organism is quite distinct and so is their complexity. A prokaryotic organism like a bacteria has a set of genes necessary to exert their basic functions and the number of genes compared to a eucaryotic cell is 3-30 times smaller, which defines a direct correlation of number of genes and complexity. However if we consider only eucaryote organisms and their complexity there is no such direct correlation between number of genes and their complexity when, for example, we compare the number of genes of humans (approximately 18000) and the number of genes of the <em>Trichomonas vaginalis, </em>an anaerobic, flagellated protozoan parasite and the causative agent of trichomoniasis. The number of genes of <em>T. vaginalis</em> is far bigger than the human cell, however the human complexity is far more advanced than the parasite organism.
Crossing over at prophase I results in the linked genes (those on the same chromosome) becoming unlinked and separated. Prophase I is this first stage of meiosis, the chromosomes condense, form tetrads<span>, and exchange DNA. The nucleolus and nuclear envelope disappear.</span>
The data are not found here, but evolution means 'descendence with modification', which may occur due to natural selection and mutations.
<h3>What is evolution?</h3>
Evolution is descendence with modification, which generally is caused by a process called natural selection.
Natural selection 'selects' the most adaptive variants in the population, which occurs due to the emergence of mutations.
A mutation is any genetic change in the nucleotide sequence of the genome of an individual.
Learn more about evolution here:
brainly.com/question/4207376
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The third one made the most sense
