Flatworms and roundworms both can be parasitic or free living. But flatworms have hooks and suckers for adhesion on their host. And roundworms are extremely abundant in soil. Flatworms have a flat body because they lack a fluid-filled body cavity. They also have an incomplete digestive system with a single opening. However, flatworms represent several evolutionary advances in invertebrates. They have the following adaptations: - Flatworms have three embryonic cell layers. They have a mesoderm layer in addition to ectoderm and endoderm layers. The mesoderm layer allows flatworms to... Show more Flatworms and roundworms both can be parasitic or free living. But flatworms have hooks and suckers for adhesion on their host. And roundworms are extremely abundant in soil. Flatworms have a flat body because they lack a fluid-filled body cavity. They also have an incomplete digestive system with a single opening. However, flatworms represent several evolutionary advances in invertebrates. They have the following adaptations: - Flatworms have three embryonic cell layers. They have a mesoderm layer in addition to ectoderm and endoderm layers. The mesoderm layer allows flatworms to develop muscle tissues so they can move easily over solid surfaces. - Flatworms have a concentration of nerve tissue in the head end. This was a major step in the evolution of a brain. It was also needed for bilateral symmetry to evolve. - Flatworms have bilateral symmetry. This gives them a better sense of direction than radial symmetry would. Flatworms reproduce sexually. In most species, the same individuals produce both eggs and sperm. After fertilization occurs, the fertilized eggs pass out of the adult's body and hatch into larvae. There may be several different larval stages. The final larval stage develops into the adult form. Then the life cycle repeats. Some flatworms are free-living organisms. They may live in water or moist soil where they eat invertebrates and decaying organic matter. Other flatworms, such as tapeworms, are parasites that live inside vertebrate hosts. They obtain nutrition directly from their hosts. Usually, more than one type of host is needed to complete the parasite's life cycle. Show less
Flatworms and roundworms both can be parasitic or free living. But flatworms have hooks and suckers for adhesion on their host. And roundworms are extremely abundant in soil.
Flatworms have a flat body because they lack a fluid-filled body cavity. They also have an incomplete digestive system with a single opening. However, flatworms represent several evolutionary advances in invertebrates. They have the following adaptations: - Flatworms have three embryonic cell layers. They have a mesoderm layer in addition to ectoderm and endoderm layers. The mesoderm layer allows flatworms to develop muscle tissues so they can move easily over solid surfaces. - Flatworms have a concentration of nerve tissue in the head end. This was a major step in the evolution of a brain. It was also needed for bilateral symmetry to evolve. - Flatworms have bilateral symmetry. This gives them a better sense of direction than radial symmetry would. Flatworms reproduce sexually. In most species, the same individuals produce both eggs and sperm. After fertilization occurs, the fertilized eggs pass out of the adult's body and hatch into larvae. There may be several different larval stages. The final larval stage develops into the adult form. Then the life cycle repeats. Some flatworms are free-living organisms. They may live in water or moist soil where they eat invertebrates and decaying organic matter. Other flatworms, such as tapeworms, are parasites that live inside vertebrate hosts. They obtain nutrition directly from their hosts. Usually, more than one type of host is needed to complete the parasite's life cycle.
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