3. Click on a lesson name to select. Chapter 24 Introduction to Animals Section 1: Animal Characteristics Section 2: Animal Body Plans Section 3: Sponges and Cnidarians

4. 24.1 Animal Characteristics General Animal Features Introduction to Animals Chapter 24  The ancestral animals at the beginning of the evolutionary tree are eukaryotic and multicellular.  They developed adaptations in structure that enabled them to function in numerous habitats.

5. Feeding and Digestion Introduction to Animals  Animals are heterotrophic.  The structure or form of an animal’s mouth parts determines how its mouth functions. 24.1 Animal Characteristics Chapter 24

6. Support Introduction to Animals  Invertebrates  Any animal without a backbone.  95-99% of animal species are invertebrates  The bodies of most are covered by exoskeletons. 24.1 Animal Characteristics Chapter 24

7. Support Introduction to Animals  Exoskeletons  Hard or tough outer coverings that provide a framework of support  Protect soft body tissues  Provide protection from predators 24.1 Animal Characteristics Chapter 24

8. Support Introduction to Animals  Vertebrates  Have an endoskeleton and a backbone 24.1 Animal Characteristics Chapter 24

9. Support Introduction to Animals  Endoskeletons  Protect internal organs  Provide support for the body  Provide an internal brace for muscles to pull against 24.1 Animal Characteristics Chapter 24

10. Movement Introduction to Animals  The evolution of nerve and muscle tissues enables animals to move in ways that are more complex and faster than organisms in other kingdoms. 24.1 Animal Characteristics Chapter 24

11. Reproduction Introduction to Animals  Most animals reproduce sexually, although some can reproduce asexually.  Some animals, such as earthworms, are hermaphrodites, producing eggs and sperm in the same body. 24.1 Animal Characteristics Chapter 24

12. Sexual Reproduction Introduction to Animals  Fertilization occurs when the sperm penetrates the egg to form a fertilized egg cell called the zygote.  Fertilization can be 1) internal or 2) external 24.1 Animal Characteristics Chapter 24

13. Introduction to Animals  Internal fertilization  The sperm and egg combine in the animal’s body.  External fertilization  Occurs when egg and sperm combine outside the body.  Requires an aquatic environment. 24.1 Animal Characteristics Chapter 24

14. Introduction to Animals  Asexual reproduction means that a single parent produces offspring that are genetically identical to itself.  Budding  Fragmentation  Regeneration  Parthenogenesis 24.1 Animal Characteristics Chapter 24

15. Introduction to Animals  Budding-Offspring develop as a growth on the body of the parent 24.1 Animal Characteristics Chapter 24

16. Introduction to Animals  Fragmentation – Parent breaks into pieces and each piece can develop into an adult organism. 24.1 Animal Characteristics Chapter 24

17. Introduction to Animals  Regeneration – A new organism can regenerate or regrow from the lost body part if the part contains enough genetic information. 24.1 Animal Characteristics Chapter 24

18. Introduction to Animals  Parthenogenesis – A female animal produces eggs that can develop without being fertilized. 24.1 Animal Characteristics Chapter 24

19. Early Development Introduction to Animals  The zygote undergoes mitosis and a series of cell divisions to form new cells.  The cells continue to divide, forming a fluid-filled ball of cells called the blastula. 24.1 Animal Characteristics Chapter 24

20. Early Development Introduction to Animals  The blastula continues to undergo cell division as some cells move inward to form a gastrula. 24.1 Animal Characteristics Chapter 24

21. Introduction to Animals 24.1 Animal Characteristics Chapter 24

22. Introduction to Animals Chapter 24

23. Introduction to Animals Tissue Development  Endoderm  inner layer of cells in the gastrula  Forms the digestive organs and digestive tract lining. 24.1 Animal Characteristics Chapter 24

24. Introduction to Animals Tissue Development 24.1 Animal Characteristics Chapter 24  Ectoderm  outer layer of cells in the gastrula  Forms the nervous tissue and skin.

25. Introduction to Animals Tissue Development  Mesoderm  layer of cells between the endoderm and ectoderm  Forms muscle tissue, circulatory, excretory, and respiratory systems 24.1 Animal Characteristics Chapter 24

26. Introduction to Animals 24.1 Animal Characteristics Chapter 24

27. Introduction to Animals Animation Chapter 24  Cell Differentiation in Animal Development Cell Differentiation in Animal Development  Visualizing Protostome and Deuterostome Development Visualizing Protostome and Deuterostome Development  A Sponge A Sponge  A Cnidarian A Cnidarian

28. Introduction to Animals Chapter 24