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
A. cane toad toxin reduced the head size of the snakes.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
This option suggests that the toxin itself affects the physical dimensions of the snakes, which is not supported by evidence in the context provided.
Step 2
B. even small cane toads contain enough toxin to kill a long-bodied snake.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
While this statement may be true, it doesn’t explain the evolution of head size in the snake species.
Step 3
C. smaller headed snakes are better at catching cane toads than large headed snakes.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
This implies a behavioral adaptation but does not address the evolutionary trend discussed.
Step 4
D. larger headed snakes were killed by the levels of toxin ingested when they ate a large cane toad.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
This option directly addresses the situation wherein larger headed snakes, unable to cope with the toxin, would lead to a selection pressure that favors smaller headed snakes. Hence, this explains the observed evolution in the snake populations.
