Isolation can be due to behavioral, geographical, or temporal barriers. <span>Speciation can take place in two general ways. A single species may change over time into a new form that is different enough to be considered a new species. This process is known as anagenesis. More commonly, a species may become split into two groups that no longer share the same gene pool. This process is known as cladogenesis. There are several ways in which anagenesis and cladogenesis may take place. In all cases, reproductive isolation occurs. Hope this helps! </span>
The two serous membranes of pericardium are :visceral pericardium,parietal pericardium.
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Biennial plants</h2>
Explanation:
This plant is a biennial, which means it will just take longer than a season to mature enough to produce flowers.
Since the Sweet William plant did not flower last year when it was planted and this year also it did not bud till the spring. So, we can assume that these plant will need atleast two seasons to mature hence they are biennials.
Depending on the life span, plants are classified as annuals (one season), biennials(two season) and perennials (more than two years).