1. 23.1 Animal Characteristics Animals

2. 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

3. 23.1 Animal Characteristics Body Structure Dorsal – top Ventral – bottom Anterior – head Posterior - Tail

4. 23.1 Animal Characteristics

5. 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

6. 23.1 Animal Characteristics 23.2 Animal Diversity Radial Symmetry – allows for organism to take in stimuli from all sides

7. 23.1 Animal Characteristics 23.2 Animal Diversity Bilateral Symmetry – adaptation for movement

8. 23.1 Animal Characteristics Cephalization concentration of sensory & brain structures in the anterior region No-cephalization 23.2 Animal Diversity

9. 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

10. 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

11. 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

12. 23.1 Animal Characteristics 23.2 Animal Diversity

13. 23.1 Animal Characteristics Patterns of Development Protostomes – blastopore first develops into a mouth Deuterostomes – blastopore first develops into anus 23.2 Animal Diversity

14. 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

15. 23.1 Animal Characteristics