In Australia, when red-bellied black snakes first encountered cane toads, most o
ID: 91078 • Letter: I
Question
In Australia, when red-bellied black snakes first encountered cane toads, most of the snakes were highly susceptible to the cane toad toxin, and died soon after eating them. The graph shown below compares susceptibility to toad toxin of individual snakes, from two populations, one never exposed to cane toads (TOAD NAIVE), the other having been exposed to cane toads for 50 years (TOAD EXPOSED). Each point on the graph represents data for a single snake. You suspect that natural selection has caused the changes shown in the graph. We know that snakes reproduce, meeting the first condition for evolution by natural selection to occur. What are the additional 3 key conditions that must be met in the snake population in order for natural selection to have occurred? Based on the information in this graph, is there evidence that each of these conditions is met? If so, how is each met? If not, what kind of evidence would convince you?Explanation / Answer
Natural selection is a mechanism of evolution that acts to promote traits and behaviors which increase an organisms chance of survival, and eliminates those traits and behaviors that are detrimental. Reproduction is the first condition for evolution by natural selection to occur.
The additional three key conditions that must be met in the snake population in order for natural selection to have
occured are
*Heredity
*Variation in fitness of snakes
*Variation in individual characters among the members of snake population
Based on the information in this graph, there is no evidence that each of these conditions are met.
The evidence from molecular genetics and biochemistry would convince about heredity. The study of relative fitness measures provides evidence for variation in fitness of snakes. The study of genetic diversity , levels of biodiversity within a habitat,genetic constitution(genotypes , phenotypes) would convince about variation in individual characters among the members of snake population.