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JA6. Phyla

Statement

In your assigned readings, you were introduced to the major animal phyla. Choose an animal which represents a particular phylum. Briefly describe its features characteristic of its phylum including morphology, embryology, and physiology. Identify adaptations of your animal compared with other animals. If you chose a more primitive animal, identify adaptations compared with more primitive organisms outside of the animal kingdom.

Solution

The text chooses Giant roundworm (Ascaris lumbricoides) from the phylum Nematoda as its main example.

Nematoda comes from Greek that means thread. There are 25000 species of nematodes, that exists almost everywhere, from the soil to the fresh and salt water. They play an important roles in the ecosystem, as they are decomposers, predators, and parasites. They are also important in the food chain, as they are food for other animals (like crabs and snails) (Manoa, n.d.).

Nematoda Morphology shows a tubular body, complete digestive system (distinct mouth and anus), 3-6 libs and teeth at the front, (Lumen, n.d.).

Nematoda physiology indicates an excretory system that is not well developed as nitrogenous wastes may be lost by diffusion through the entire body or into the pseudocoelom (body cavity), and its nervous system composes of a brain and 4 nerve cords that run along the length of the body and connected to that brain (Rye et al., 2016, p. 771).

Nematoda embryology reproduces through monoecious, dioecious, or parthenogenic strategies. Fertilization is internal and embryonic development starts directly after fertilization. The embryonic development lasts for 14 hours then the embryo is released from the vulva during the gastrulation stage, to live 4 larval stages before becoming an adult (Rye et al., 2016, p. 772).

Ascaris lumbricoides exists inside almost 1 billion human being (CDC, 2023), where it lives in the intestine and passes eggs through the feces of the infected person. To adapt to the environment, Ascaris lumbricoides adapted by having a thick cuticle that protects it from the digestive enzymes of the host, a muscular pharynx that helps it to suck the host’s food, hooks and lips that keep it attached to the host’s intestine, and a high reproductive rate, with females laying thousands of eggs as lots of them do not make it (Rye et al., 2016, p. 772).

The wide distribution of nematodes, their role in the ecosystem, and their parasitic nature, makes them an important group of animals and thus we chose to study them in this text.

References