In animal populations, DDT causes _____.

• A. decreased cellular respiration in plants
• B. enhanced nitrogen fixation
• C. increased rates of photosynthesis
• D. bioaccumulation and thinning of eggshells in birds

Answer: (D)

Verified step by step guidance

1. Understand the context of the problem: DDT (dichlorodiphenyltrichloroethane) is a synthetic pesticide that was widely used in agriculture but is now banned in many countries due to its harmful environmental effects.
2. Recognize the concept of bioaccumulation: DDT is a persistent organic pollutant that accumulates in the fatty tissues of organisms as it moves up the food chain. This process is called bioaccumulation.
3. Connect bioaccumulation to its effects on birds: High concentrations of DDT in birds, particularly predatory birds, interfere with calcium metabolism, leading to the production of thin and fragile eggshells.
4. Understand the ecological impact: Thinning of eggshells reduces the survival rate of bird embryos, leading to population declines in affected species. This was notably observed in species like the bald eagle and peregrine falcon.
5. Eliminate the incorrect options: The other choices (decreased cellular respiration in plants, enhanced nitrogen fixation, and increased rates of photosynthesis) are unrelated to the effects of DDT. The correct answer is bioaccumulation and thinning of eggshells in birds.