Kelsey

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Q: 1. Review Questions pg 987.

Why are specialized respiratory structures necessary in a tadpole but not in a flatworm?

Tadpoles need specialized respiratory structures for a variety of reasons. Tadpoles need these specialized structures because in early development they stay in water. This stage of their lives require gills. They stay wet from the surrounding water and obtain their oxygen from the water as well (H2o). In later stages of life the tadpoles will develop into frogs. [|Visit this website to see a brief explaination of the development of a frog.] In this stage of a tadpoles life they can function outside the water. Outside of the water the frogs use a very simple form of lungs which developes from their original gills. In addition to lungs frogs also use there skin for respirational purposes. The flatworm on the other hand does not require specialized respiratory structures, but simply uses its skin. The flatworm is very small with a high surface to volume ratio. They in turn also have a slow metabolic rate and require less oxygen per cell because of it, which makes respiration through their skin the best option to use. So the flatworm exchanges gas (oxygen) through its skin, which is less then 1 mm thick. The first step for the flatworm to do this is to secrete mucus for moisture from the gland cells in the epidermis onto the outside of their skin. The surrounding air's oxygen will dissolve into the mucus. The mucus and oxygen then diffuses into the flatworms skin and in to its blood circulation. It then oxygenates the cells and organs of the body.

B-Wel : Awesome that you used a link to further the information given on the tadpole/frog respiratory development. It's kind of weird to think that we're touching the lungs of worms and frogs when we grab them, they're breathing our chemicals in! When I was little I always thought worms were slimy because they lived in underground water spots. Lol

Amber: Wow I never really thought about how much frogs changed from tadpoles to adults and how their whole respiratory system has to change, and that they have more than one! Amazing how different organisms vary so greatly. Awesome job! :)