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Introduction to Animals. General Characteristics. All animals are heterotrophic Different digestive systems Animals are either invertebrates or vertebrates Body variations allow animals to live in a diverse range of habitats
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General Characteristics • All animals are heterotrophic • Different digestive systems • Animals are either invertebrates or vertebrates • Body variations allow animals to live in a diverse range of habitats • Cells are organized into tissue, that is specialized to perform a specific function
Reproduction Hermaphrodites: organism that produces both eggs and sperm in the same body (earthworms) Zygote: when sperm penetrates egg to form a fertilized egg External Fertilization: egg and sperm combine outside the animal’s body (fish) Internal Fertilization: sperm and egg combine inside the animal’s body
Development Endoderm Cells: develop into digestive organs and the lining of digestive tract Ectoderm Cells: Nervous tissue and skin Mesoderm Cells: Muscle tissue, circulatory system, excretory system, and sometimes respiratory system Human Development
Symmetry Symmetry describes the similarity or balance among body structures of organisms • Assymmetrical: Irregular shape and has no symmetry or balance in its body structure • Radial: Can be divided along any plane through a central axis into roughly equal halves • Bilateral: Can be divided into mirror image halves only along one plane through a central axis • Cephaliztion: animals with bilateral symmetry also have an anterior, or head end, and a posterior, or tail end & dorsal (back), ventral (front).
Body Cavities Coelomates: Tissue formed from the mesoderm that lines and encloses the organs in the coelom - Coelom: Huge adaptation in evolution of larger and more specialized body structure. Pseudocoelmates: Fluid-filled cavity that develops between the mesoderm and the endoderm rather than developing entirely within the mesoderm as in coelomates. Acoelomates: Animals that do not have a coelom. Have solid bodies, without a fluid filled body cavity between the gut and the body wall.
Segmentation • Important feature in the evolution of coelomate animals. • Two Advantages of Segmentation: • Segmented animals can survive damage to one section and still live because other sections may be able to carry out the function • Movement is more effective since each segment moves independently