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Since the introduction of the poisonous cane toad to Australia in 1935, there has been an increase in the ratio of body length to head size in two species of snakes, the Red-bellied Black Snake and the Green Tree Snake - VCE - SSCE Biology - Question 25 - 2008 - Paper 1
Question 25
Since the introduction of the poisonous cane toad to Australia in 1935, there has been an increase in the ratio of body length to head size in two species of snakes,... show full transcript
Worked Solution & Example Answer:Since the introduction of the poisonous cane toad to Australia in 1935, there has been an increase in the ratio of body length to head size in two species of snakes, the Red-bellied Black Snake and the Green Tree Snake - VCE - SSCE Biology - Question 25 - 2008 - Paper 1
Step 1
larger headed snakes were killed by the levels of toxin ingested when they ate a large cane toad.
Answer
The introduction of the cane toad has had significant ecological impacts on native species, including snakes. Snakes with larger heads, likely due to their greater size, could consume larger prey. However, when they attempted to swallow large cane toads, the high levels of toxin present in these toads could lead to fatal consequences. This evolutionary pressure may have resulted in smaller-headed snakes having a survival advantage because they might be less likely to ingest fatal doses of toxin from smaller prey items. Thus, the rapid evolution of body size in these snakes can be attributed to the negative effects of the cane toad toxin on larger-headed snakes.