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Invertebrates

Invertebrates. Invertebrates. The majority of animals on this planet are invertebrates 32 of the 34 phyla of animals are invertebrates Invertebrates lack a true defined backbone. Characteristics of Animals.

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Invertebrates

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  1. Invertebrates

  2. Invertebrates • The majority of animals on this planet are invertebrates • 32 of the 34 phyla of animals are invertebrates • Invertebrates lack a true defined backbone

  3. Characteristics of Animals • Symmetry - is the balanced distribution of duplicate body parts or shapes. The body plans of most multicellular organisms exhibit some form of symmetry, either radial symmetry or bilateral symmetry. A small minority exhibit no symmetry (are asymmetric). • Body Cavity - (coelom) The cavity within the body of all animals higher than the coelenterates and certain primitive worms • Digestion • Reproduction

  4. Phylum Porifera • Sponges – approx 5000 species • Aquatic organisms, usually marine • Usually irregularly shaped – asymmetrical ( no plane of division) • Filter feeders – no true digestive system • Reproduction is asexual (budding) and sexual • Sexual fertilization is external - hermaphrodites • No true body cavity

  5. Phylum Cnidaria • Characterized by bodies that are radial symmetrical • Aquatic organisms – mostly marine • Bodies have a opening that has tentacles around it • Digestion occurs in the opening by secreting digestive juices into the cavity and absorbing the nutrients • Reproduction is both sexual and asexual - hermaphrodites • There is an opening but no body cavity • Sexual fertilization is external

  6. Phylum Platyhelminthes • Flatworms – they have bilateral symmetry and show signs of cephalization (head) • They have body tissues but do not have a true body cavity • Single opening through which food enters and waste exits - digestion is extracelluar • Asexual and sexual reproduction • Fertilization is internal – hermaphrodites

  7. Phylum Nematoda • Roundworms – they have bilateral symmetry • They have three layers of tissue and have a pseudocoelom (tube within a tube) • Does not have a well developed digestive system • One way – two openings • Sexual reproduction – internal fertilization • Hermaphrodites and separate sexes

  8. Phylum Arthropoda • Bilateral symmetry • There is the presence of a true body cavity • Digestion is in a tube with two openings and one direction • Reproduction is sexual – with internal fertilization • Separate sexes with a few hermaphrodites

  9. Scientists have identified over 1 million species • Predict that there are over 10 million species • Extremely diverse, thus, they can be found virtually anywhere

  10. Why are arthropods so successful? • Rigid, jointed external skeleton (exoskeleton) • Water proof protective armour • Site for muscle attachment • Protects against water loss • Specialized nature of body segments • Head • Thorax • Abdomen • Well developed nervous system • Coordinate body movement • Diversity of structures and functions for obtaining nutrition • Utilize plant and animal sources

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