Which statement below best describes the ways that energy and pesticides are transferred between levels in food chains ?

Options

A. Available energy increases and pesticide concentrations increase as you move up a food chain.
B. Available energy decreases and pesticide concentrations increase as you move up a food chain.
C. Available energy decreases and pesticide concentrations decrease as you move up a food chain.
D. Available energy increases and pesticide concentrations decrease as you move up a food chain.

Answer

To answer the question regarding how energy and pesticides are transferred between levels in food chains, we can break down the concepts involved:

### Step 1: Understand Energy Transfer in Food Chains
Energy transfer in food chains follows the 10% energy law. This law states that only about 10% of the energy from one trophic level is transferred to the next level. For example:
- If producers (first trophic level) produce 10,000 joules of energy, only about 1,000 joules will be available to herbivores (second trophic level).
- From herbivores to primary carnivores (third trophic level), only about 100 joules will be transferred.
- This pattern continues, with only 10 joules going to secondary carnivores (fourth trophic level) and 1 joule reaching top carnivores (fifth trophic level).

### Step 2: Understand Pesticide Transfer in Food Chains
Pesticides, particularly non-biodegradable ones, undergo a process known as bio-magnification. This means that as you move up the food chain, the concentration of these pesticides increases. For example:
- A small amount of pesticide may be present in producers, but when herbivores consume these producers, they accumulate the pesticide in their bodies.
- As carnivores consume herbivores, they accumulate even higher concentrations of the pesticide.
- This results in top predators having the highest levels of pesticides in their bodies.

### Step 3: Compare Energy and Pesticide Transfer
- Energy decreases at each trophic level due to the 10% energy law.
- Pesticide concentration increases at each trophic level due to bio-magnification.

### Conclusion
The best statement that describes the transfer of energy and pesticides in food chains is that energy decreases while pesticide concentration increases as you move up the trophic levels.

### Final Answer
The correct option is that energy decreases at each trophic level (following the 10% rule), while pesticide concentration increases (due to bio-magnification).

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