ome populations of these frogs have been studied for decades. Below is a graph f
ID: 140819 • Letter: O
Question
ome populations of these frogs have been studied for decades. Below is a graph for one such u population depicting the distribution of ages at which eggs hatched in 1918 and the distribution of ages at which eggs hatched in 2018. 1918 - 2018 Age at hatching (days)-- 1. (1 point) What type of natural selection discussed in lecture does this graph depict? b n seleten beedr medicete rm a tat in An arganism s selected. 2. (3 points) Given the information above about the selective pressures acting on age of hatching in red-eyed tree frogs, provide a hypothesis to explain the change in the distribution of hatch ages over the last 100 years. Be sure that your hypothesis clearly explains your proposed links between the selective pressures in 1918, the selective pressures in 2018, and the observed change in the distribution of hatch ages.Explanation / Answer
ANSWER 2)
The above graph shows a comparison of the number of days taken for eggs to hatch vs number of eggs hached for a span of 100 years and compares the two inverted parabolas in the year 1918 and 2018.
Studying the graph, we can make out that the number of days being taken by an egg to hatch has increased in 100 years. For example, this might mean that if 1 egg hatched in 1 day in 1918, it takes 4 days for it to hatch in 2018.
Hypothesis- The most probable explanation for this phenomenon is the fact that since the egg hatching duration is affected by the external conditions like drying up of the eggs or presence of predation such as the cat eyed snake on the leaf or spiders in the pond, there is obviously a drastic change in their presence over a 100 years which has caused the shift in the graph. This can be linked as follows
In the year 1918, the population of the cat eyed snakes could have been high. According to this evolutionary mechanism, the frog eggs can detect the dangers of the snake, which loves feeding on them.Thus as the number of snakes grew, the eggs kept on hatching and escaped in the pond to protect themselves from the snakes. Also the population of spiders and fish was present , since some tadpoles kept on delaying the date of hatching to avoid their contact with them.
But in 2018, the population and the behavior of the snakes has varied. Their number has decreased and instead of attacking the eggs gradually, the attack is all of a sudden which immediately forces the eggs to hatch and the number of eggs hatching per day increases exponentially. Also the population of other dangers like fish and apiders in the pond is less, so the tadpoles decrease their duration of hatching.
Thus we can conclude, that in the span of 100 years, the total number of days taken by the tadpoles to hatch from their eggs has decreased with the change in the population and behavious of their external predators.
The above mentioned activity of the frogs, show an evolutionary Biology concept which is generally called phenotypic plasticity, a phenomenon where the genes can express into a physical outcome in response to external environmental pressure, even during the embryonic stage.
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