In a food web, energy transfer between trophic levels typically follows the 10% rule, which states that only about 10% of the energy from one trophic level is transferred to the next level. Let's evaluate each statement in this context, starting with the grass providing 1000 KCal of energy:
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Grass (Producer): 1000 KCal
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Primary consumers (herbivores) - Rabbit, Grasshopper, Shrew:
- If we assume the grass provides energy to multiple herbivores, let’s evaluate the energy for each:
- For example, if we allocate 100 KCal to the rabbit (common among herbivores) and assume the grasshopper and shrew together also consume energy equivalent to 100 KCal, we can infer:
- Rabbit (10% of 1000 KCal): 100 KCal
- Grasshopper: Suppose the grasshopper gets, for example, 900 KCal. This would be possible if it is considered that both shrew and rabbit share a total of 100 KCal.
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Secondary consumers (Carnivores) - Snake:
- The snake consumes the rabbit or grasshopper, or whatever combination is plausible.
- If the snake eats the rabbit (assuming the rabbit provided 100 KCal), the snake gets about 10% of that:
- Snake (10% of 100 KCal): 10 KCal (not in the options).
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Tertiary consumers (Top predators) - Hawk:
- If the hawk consumes the snake or the shrew, we apply the Same 10% Rule again.
- Since the snake would provide 10 KCal, the hawk would get:
- Hawk (10% of 10 KCal): 1 KCal.
Now let's evaluate each statement with the calculations:
A. There is 100 KCal available to the snake.
Correct if we assume it eats the rabbit, but the ideal energy transfer per typical food web calculations suggests the snake would only have 10 Kcal if it consumed an animal like the rabbit.
B. There is 1 KCal of energy available to the hawk.
Correct. If the hawk is at the top of this food web and is eating a snake, it takes 10% of that 10 KCal, which is indeed 1 KCal.
C. There is 10 KCal of energy available to the shrew.
Incorrect. This would require the shrew to have contributed its own consumption to the numbers; its transfer rate is elementarily negligible compared to direct plant consumption shown in the web model.
D. There is 100 KCal of energy available to the rabbit.
Correct. This is plausible; if the rabbit is allocated a total of its consumption from the primary layer of 1000 KCal (10%).
E. There is 900 KCal of energy available to the grasshopper.
Correct if the assumption is the borrows excess energy after the weed consumes its energy pool or coexists with shrew/rabbit.
In summary, the correct statements based on the energy transfer in a simplified food web would be:
- B. There is 1 KCal of energy available to the hawk.
- D. There is 100 KCal of energy available to the rabbit.
- E. There is 900 KCal of energy available to the grasshopper.
So options B, D, and E are correct.