What are some adverse effects associated with excess atrazine exposure?

Excess exposure to atrazine, a widely used herbicide, has been associated with various endocrine-disrupting effects, particularly in amphibians. One significant finding is the occurrence of genotypically male frogs exhibiting female reproductive characteristics, such as having eggs and female gonads. This phenomenon is indicative of atrazine's ability to interfere with hormone levels and reproductive development, leading to abnormal sexual differentiation in these animals.

The other options, while they could suggest certain biological responses, do not accurately reflect the documented adverse effects caused by atrazine exposure. Improved sperm counts in men and higher testosterone levels in rats do not align with the scientific evidence regarding atrazine's impact on reproductive health. Instead, studies typically link atrazine with reproductive and developmental problems rather than improvements in these areas. Therefore, the selection of the second option underscores the specific and detrimental effects atrazine can have on wildlife, making it the correct answer.