Section 1 The Nature of Animals

1. Chapter 32 Introduction to Animals Section 1 The Nature of Animals

2. Chapter 32 Objectives • Identify4 important characteristics of animals. • List2 kinds of tissues found only in animals. • Explainhow the first animals may have evolved from unicellular organisms. • Identifyfour features found only in chordates.

3. Section 1 The Nature of Animals Chapter 32 Characteristics • Animals are multicellular heterotrophic organisms that lack cell walls. • Vertebrates have a backbone. • Invertebrates do not have a backbone. • 95 percent of all animal species alive today

4. Chapter 32 Multicellular Organization • Each cell depends on the presence and functioning of other cells. • specialization among cells • tissue • Organs • Multicellularity and cell specialization have enabled organisms to adapt to many environments.

5. Chapter 32 Evolutionary Relationships in the Animal Kingdom Phylogenetic diagram represents hypothesis for the relationship among members of the animal kingdom based on rRNA analysis.

6. Chapter 32 Evolutionary Relationships in the Animal Kingdom Notice on this diagram the locations of similarities in body tissues, body symmetry and embryonic development.

7. Chapter 32 Characteristics of Animals • Heterotrophic • Sexual Reproduction • gametes fuse and offspring are genetically different • Movement • Most animals move at some point within their life cycle • As a result from the interrelationship of muscle tissue and nervous tissue, or neurons.

8. Chapter 32 Origin and Classification • The first animals may have evolved from colonial protists. • Taxonomists have grouped animals into several phyla by comparing their: • fossils • body symmetry • patterns of embryo development • macromolecules, such as rRNA

9. Chapter 32 Classification Chordates • All chordates have, at some stage in life: • a notochord, flexible rod on the dorsal part of the body • backbone • a dorsal nerve cord, hollow cord • brain and spinal cord • a postanal tail • pharyngeal pouches • outpockets of anterior digestive tract • gills for aquatic animals

10. Chapter 32 Body Structure Patterns of symmetry • Symmetry is a body arrangement in which parts that lie on opposite sides of an axis are identical. • Types of symmetry are: • no Symmetry (asymmetrical) • radial symmetry • bilateral symmetry • cephalization • concentration of sensory structures in the anterior region

11. Chapter 32 Radial and Bilateral Symmetries

12. All animals have true tissues except sponges Chapter 32 Origins of Animal Tissues and Organs; Germ layers

13. Chapter 32 Body Structure and Relatedness The Animal Body: An Evolutionary Journey • Biologists use similarities in body plans and patterns of development to help them classify animals and hypothesize about the evolutionary history of animals.