23.1 Animal Characteristics Animals

23.1 Animal Characteristics Multicellular Heterotrophic Lack cell walls Sexual Reproduction Movement Specialization – adaptation for a cell for a particular function Cells  tissues  organs  organ systems

23.1 Animal Characteristics Body Structure Dorsal – top Ventral – bottom Anterior – head Posterior - Tail

23.1 Animal Characteristics

Body Symmetry Asymmetry – no symmetry Radial – arrangement of body parts around a central axis - top & bottom, no front, back, or right & left sides Bilateral symmetry – 2 similar halves on either side of a central plane 23.2 Animal Diversity

23.1 Animal Characteristics 23.2 Animal Diversity Radial Symmetry – allows for organism to take in stimuli from all sides

23.1 Animal Characteristics 23.2 Animal Diversity Bilateral Symmetry – adaptation for movement

23.1 Animal Characteristics Cephalization concentration of sensory & brain structures in the anterior region No-cephalization 23.2 Animal Diversity

23.1 Animal Characteristics Fertilization Gamete + Gamete = Zygote Sperm membrane fuses with egg membrane –causes an electrical shock that blocks entry by other sperm Sperm nucleus merges with egg nucleus 23.2 Animal Diversity

23.1 Animal Characteristics Cleavage – cell divisions of the zygote immediately following fertilization Rapidly increases # of cells, but cells do not grow in size Increases surface area-to-volume ratio Continues until they form a hollow ball of cells – blastula Central cavity - blastocoel 23.2 Animal Diversity

23.1 Animal Characteristics Gastrulation – blastula collapses inward Blastopore – infolded region - will function as the gut Gastrula – multilayered embryo Deep cavity is formed – archenteron – embryonic stem cells Ectoderm – outer germ (cell) layer Skin, hair, etc. Endoderm – inner germ layer Digestive system Mesoderm – layer between ectoderm & endoderm Muscular and Skeletal systems 23.2 Animal Diversity

23.1 Animal Characteristics 23.2 Animal Diversity

23.1 Animal Characteristics Patterns of Development Protostomes – blastopore first develops into a mouth Deuterostomes – blastopore first develops into anus 23.2 Animal Diversity

23.1 Animal Characteristics Types of Body Cavities Acoelomates – body cavity is absent –Flatworms Pseudocoelomate – mesoderm lines the fluid- filled coelom (body cavity) Coelomates – mesoderm lines the body cavity and surrounds and supports the gut 23.2 Animal Diversity

23.1 Animal Characteristics