Question

a grassland ecosystem contains grasses, rabbits, snakes, and hawks. using the laws of thermodynamics, what prediction can be made about the energy transfer through this food chain? energy is not lost in the food chain, it cycles completely back to the grass. rabbits will receive the same amount of energy from the grass as the grass gained from sunlight. only a small portion of the grasses energy will be available to the rabbits, and even less will transfer to the snakes and hawks. all the energy from the grass will be passed to the rabbits, and the same amount of energy will be transferred to the hawks.

Explanation:

Step1: Recall 1st law of thermodynamics

Energy is conserved but can change forms. In a food - chain, energy is transferred from one trophic level to another.

Step2: Recall 2nd law of thermodynamics

There is always some energy loss as heat during energy transfer. Producers (grasses) convert solar energy into chemical energy. When primary consumers (rabbits) eat the grasses, only a small fraction (about 10 - 20%) of the grass - energy is transferred to the rabbits. When secondary consumers (snakes) eat the rabbits and tertiary consumers (hawks) eat the snakes, even less energy is transferred at each step.

Step3: Analyze each option

• Option 1: Energy is lost in the food - chain as heat and does not cycle completely back to the grass. So this is incorrect.
• Option 2: Rabbits receive only a fraction of the energy the grass gained from sunlight due to energy losses in the grass's metabolic processes and during the transfer to rabbits. So this is incorrect.
• Option 3: This is correct based on the principles of energy transfer in a food - chain.
• Option 4: Not all the energy from the grass is passed to the rabbits, and there are energy losses at each transfer step, so the amount of energy transferred to the hawks is much less than the energy in the grass. So this is incorrect.

Answer:

Only a small portion of the grasses' energy will be available to the rabbits, and even less will transfer to the snakes and hawks.