24.1 Animal Characteristics

1. 24.1 Animal Characteristics

2. I. General Animal Features • A. Our ancestors are: • 1. Eukaryotic • 2. Multicellular • 3. Heterotrophic –must eat other organisms • 4. No cell walls

3. II. Support • A. Invertebrates – No backbone • 1. Most have EXOSKELETON • A. Hard outer covering • B. Protects soft body tissues • C. As animal grows, must shed exoskeleton • D. Exp: Grasshopper • 2. Endoskeletons • A. Internal skeleton

4. B. Vertebrates- Have a backbone • 1. Endoskeleton that is a backbone • 2. As animal grows, so does backbone

5. III. Reproduction • A. Sexual reproduction- provides genetic variation • 1. Females produce eggs • 2. Males produce sperm • 3. Animals that produce both = hermaphrodites • a. Earthworms • b. Produce egg and sperm at different times so another animal is needed

6. B. Development • 1. Zygote = fertilized egg cell • 2. Blastula = fluid-filled ball of cells • 3. Gastrula = sac with two layers of cells and an opening at one end

7. 3. Gastrula (cont) a. Endoderm = inner layer of gastrula 1. Becomes digestive organs and digestive tract b. Mesoderm = between endoderm and ectoderm 1. becomes muscle tissue, circulatory, excretory, and respiratory c. Ectoderm = outer layer of cell 1. becomes nervous tissue and skin

8. IV. Asexual reproduction • A. Genetically identical to parents • B. Budding • 1. Offspring develops as a growth on parent body • 2. Microscopic • C. Fragmentation • 1. The parent breaks into pieces and each piece can develop into a new animal 2. Earthworm

9. D. Regeneration • 1. A new organism can regrow from lost body part 2. Starfish E. Parthenogenesis 1. Eggs develop without fertilization