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Chapter 26-1 Notes Basic Characteristics of Animals I. Kingdom Animalia A. Characteristics of animals a. Multicellular b. Heterotrophic c. Eukaryotic (cells have nucleus) d. No cell walls e. 1.5 million species of animals (35 different phyla) f. 95% of animals are invertebrates (no backbone) B. Animals carry out the following functions: a. Feeding - eating b. Respiration – take in oxygen and give off carbon dioxide c. Circulation – flow of nutrients, oxygen, etc through body d. Excretion – get rid of waste (ex: ammonia) e. Response – respond to environment; some have nerve cells f. Movement – many animals have muscles that provide movement of body and some internal organs g. Reproduction – most reproduce sexually - this maintains genetic diversity; some reproduce asexually – this allows animals to increase their numbers rapidly C. Homestasis - all the body systems work together to create a balance in the organism D. Feedback Inhibition – the result of a process stops or limits that process a. Example: panting in dogs: If dog is hot then they will pant to cool the body; as body temperature lowers, the panting will slow or stop E. Early Development in Animals a. Animals begin as a zygote – fertilized egg that becomes a developing embyro b. Embryo development – 3 main tissue layers: 1. Endoderm – (innermost layer); becomes digestive tract and respiratory system 2. Mesoderm – (middle layer) ; becomes muscles, circulatory system, reproductive and excretory systems 3. Ectoderm – (outermost layer); becomes sense organs, nerves, and outer skin layers F. Body Shape A. Radial Symmetry – body parts extend from a central point B. Bilateral symmetry – body can be divided into 2 equal halves; usually have left and right side, and front and back Body Symmetry Radial Symmetry Bilateral Symmetry Asymmetric Evolutionary Relationships among Major Groups of Animals