Since we didn't have a slide of a cross-section of a hydra, we used this picture from an atlas instead. Number 1 identifies the epidermis, where oxygen enters and carbon dioxide exits the hydra via diffusion.
Of course, with most microscopes, you wouldn't be able to see where the oxygen passes (and yes, that is a picture of a budding hydra that we took under a microscope). |
Cnidaria Respiration Cnidarians are an extremely diverse phylum, including organisms such as jellyfish to others like coral. The one common denominator is their stinging cells, called nematocysts, which likely evolved from a common ancestor (1).
Similar to members of the Annelida phylum, cnidarians use the process of diffusion to respirate. Both polyps and medusae have an outer protective layer, or an epidermis (2). We humans have an epidermis as well, but ours functions differently. You see, we don't breathe through our skin. But cnidarians do. Their membranes are semipermeable, and they allow oxygen to travel into the cell via facilitated diffusion. Once inside the cells, the oxygen can be used for cellular respiration to produce ATP, which can be used for other bodily functions. Carbon dioxide is released as waste from the cells and then travels through the epidermis out of the cnidarian.
|
(1) "Introduction to Cnidaria." Introduction to Cnidaria. Hydrozoan Society, n.d. Web. 09 June 2016.
(2) "Cnidaria." Cnidaria. Marine Education Society of Australasia, n.d. Web. 15 June 2016.
(2) "Cnidaria." Cnidaria. Marine Education Society of Australasia, n.d. Web. 15 June 2016.
Evolution |
Cnidarians have mouths, but they are used for ingesting nutrients and excreting digested waste. Since they have to take in a lot of nutrients to survive, and since their bodies are so simple, it is more efficient for them to take in oxygen and release carbon dioxide through diffusion.
|