Question

deformed frogs caused by parasites and fertilizer
study links farm runoff to worms that make frogs grow extra limbs
in the effort to understand puzzling and disturbing events that make frogs grow extra limbs, there have been ongoing scientific research. one pinning the deformities on parasitic trematode worms that infect the normal development of limbs, and also pinning the abnormalities on chemical - containing fertilizers and pesticides.
recent work has the potential to bring together these two hypotheses. it shows fertilizer from farm runoff can explode growth in the populations of trematode worms, and the rise of frog malformation and deformity rates in kind. farm runoff has already been blamed on the growing dead zones in coastal waters, such as the well - sized area of depleted oxygen choking the gulf of mexico at the mouth of the mississippi.
there, excess nitrogen from fertilizer is concentrated from americas farm heartland, and dumped into the open waters of the gulf where it feeds algae growth that sucks oxygen from the water. in a similar ripple of events, scientists at the university of colorado say they were able to cause excess deformities by adding fertilizer to ponds, which boosted algae, which boosted the population of snails that feed on algae.
the primary host of the trematode worm that causes frog deformities is the small snail (the snail is only a stopping - off point for the worm as it develops into an adult), so if you have more snails, you have more worms - and consequently, more frog deformities. according to the scientists, quoted in the rocky mountain news, the findings could have implications for a wide range of diseases - from cholera and malaria to west nile virus and diseases affecting coral reefs.
its also an example of conservation medicine - a growing field that links environmental conditions to the emergence of disease, including wildlife diseases that can jump the species barrier and affect humans like west nile virus and avian influenza.

1. what is happening to the frogs?
2. what biotic factor causes deformities in frogs?
3. what abiotic factor causes deformities in frogs?

Explanation:

1. The text states that frogs are growing extra limbs and experiencing deformities.
2. Parasitic trematode worms are a primary factor causing frog deformities as they interrupt the normal development of limbs.
3. Excess nitrogen from fertilizer is an aquatic factor. It boosts algae growth, which in turn boosts snail populations (the primary host of the trematode worms), leading to more worm - related deformities in frogs.

Answer:

1. Frogs are growing extra limbs and experiencing deformities.
2. Parasitic trematode worms.
3. Excess nitrogen from fertilizer.