L.22.1 and L.22.2.pptx animal characteristics

biology

1. L: 22.1

2. * All Animals Are Multicellular Heterotrophs Animals that must eat other organisms to gain the nutrients they need to survive are called heterotrophs.

3. L: 22.2

4. * Bilateral animals are triploblastic , that is, they have three distinct layers of tissue. These layers are the ectoderm, endoderm, and mesoderm. Most radial animals have only two distinct layers of tissue. These layers are an inner endoderm and an outer ectoderm. Radial animals do not have a mesoderm layer, and therefore they lack the complex internal tissues and organs found in triploblastic animals.

5. Developmental patterns: Animals are separated into two major divisions: the protostomes and the deuterostomes. protostome and deuterostome development differs in several ways: * First opening of the digestive cavity: - In protostomes, the mouth is formed first, and the anus second. In deuterostomes, the first opening forms the anus, and the mouth is formed second. * Gut cavity formation: In protostomes, the gut cavity is formed from separations in the mesoderm. In deuterostomes, the gut cavity forms from pouches created by the folds in the gut tube. * Cleavage pattern: In most protostomes, early cell divisions lead to an eight-celled embryo in a twisted arrangement called spiral cleavage . In deuterostomes, cells divide into eight-celled embryos with cells that are lined up one atop the other in an arrangement called radial cleavage .