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

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.

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

Support Introduction to Animals  Invertebrates  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

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

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 Animal Characteristics Chapter 24

Reproduction Introduction to Animals  Fertilization occurs when the sperm penetrates the egg to form a fertilized egg cell called the zygote.  Internal fertilization  External fertilization 24.1 Animal Characteristics Chapter 24

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

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.  The blastula continues to undergo cell division as some cells move inward to form a gastrula Animal Characteristics Chapter 24

Introduction to Animals 24.1 Animal Characteristics Chapter 24 Cell Differentiation in Animal Development

Introduction to Animals Tissue Development  Endoderm  inner layer of cells in the gastrula  Ectoderm  outer layer of cells in the gastrula  Mesoderm  layer of cells between the endoderm and ectoderm 24.1 Animal Characteristics Chapter 24

Introduction to Animals 24.1 Animal Characteristics Chapter 24

24.2 Animal Body Plans Introduction to Animals Evolution of Animal Body Plans  Anatomical features in animals’ body plans mark the branching points on the evolutionary tree.  Relationships on this tree are inferred by studying similarities in embryological development and shared anatomical features. Chapter 24

Introduction to Animals 24.2 Animal Body Plans Chapter 24

Introduction to Animals Symmetry  Similarity or balance among body structures of organisms  Asymmetry  Radial symmetry  Bilateral symmetry 24.2 Animal Body Plans Chapter 24

Introduction to Animals Cephalization  The tendency to concentrate nervous tissue and sensory organs at the anterior end of the animal 24.2 Animal Body Plans Chapter 24

Introduction to Animals Body Cavities  Coelomates  Have a fluid- filled cavity with tissue formed from mesoderm that lines and encloses the organs in the coelom 24.2 Animal Body Plans Chapter 24

Introduction to Animals Body Cavities  Pseudocoelomates  Have a fluid-filled body cavity that develops between the mesoderm and the endoderm rather than developing entirely within the mesoderm 24.2 Animal Body Plans Chapter 24

Introduction to Animals Body Cavities  Acoelomates  Have solid bodies without a fluid-filled body cavity between the gut and the body wall 24.2 Animal Body Plans Chapter 24

 The mouth develops from the first opening in the gastrula. Introduction to Animals Development in Coelomate Animals  Protostomes  Deuterostomes  The anus develops from the first opening in the gastrula Animal Body Plans Chapter 24 Visualizing Protostomes and Deuterostomes

Introduction to Animals Segmentation  Segmented animals can be “put together” from a succession of similar parts.  Can survive damage to one segment  Movement is more effective 24.2 Animal Body Plans Chapter 24

24.3 Sponges and Cnidarians Introduction to Animals Sponges  Sponges do not develop tissues.  Collar cells with flagella line the inside of the sponge and whip back and forth drawing water into the body of the sponge.  Water and waste materials are expelled from the sponge through the osculum. Chapter 24

Introduction to Animals 24.3 Sponges and Cnidarians Chapter 24 A Sponge

Introduction to Animals Filter Feeder  Food particles cling to the cells.  Digestion of nutrients takes place within each cell Sponges and Cnidarians Chapter 24

Introduction to Animals Archaeocytes  Specialized cells that secrete spicules, which are the support structures of sponges  Spicules are small, needlelike structures made of calcium carbonate, silica, or a tough fibrous protein called spongin 24.3 Sponges and Cnidarians Chapter 24

Introduction to Animals Sponge Diversity  Demospongiae  Calcarea  Hexactinellida 24.3 Sponges and Cnidarians Chapter 24

Introduction to Animals Reproduction  Reproduce asexually  Fragmentation  Budding  Gemmules  Reproduce sexually  Eggs remain within a sponge.  Sperm are released into the water Sponges and Cnidarians Chapter 24

Introduction to Animals Cnidarians  Have one body opening and two layers of cells  Outer layer functions in protecting the internal body  Inner layer functions mainly in digestion 24.3 Sponges and Cnidarians Chapter 24

Introduction to Animals Feeding and Digestion  Tentacles are armed with stinging cells called cnidocytes.  A nematocyst is a capsule that holds a coiled tube containing poison and barbs.  Water inside an undischarged nematocyst is under an osmotic pressure of more than 150 atmospheres Sponges and Cnidarians Chapter 24

Introduction to Animals  As the osmotic pressure increases, the nematocyst discharges forcefully.  A barb is capable of penetrating a crab shell Sponges and Cnidarians Chapter 24 dia.org/wiki/Cni docyte

Introduction to Animals  Cells lining the gastrovascular cavity release digestive enzymes over captured prey.  Undigested materials are ejected though the mouth Sponges and Cnidarians Chapter 24

Introduction to Animals Response to Stimuli  A nerve net conducts impulses to and from all parts of the body.  The impulses cause contractions of musclelike cells in the two cell layers Sponges and Cnidarians Chapter 24

Introduction to Animals Reproduction  Two body forms  Polyp  Medusa 24.3 Sponges and Cnidarians Chapter 24

Introduction to Animals  The two body forms of cnidarians can be observed in the life cycle of jellyfishes Sponges and Cnidarians Chapter 24 A Cnidarian

Introduction to Animals Cnidarian Diversity  Hydroids  Jellyfishes  Sea anemones and corals 24.3 Sponges and Cnidarians Chapter 24 Comparison of Sponges and Cnidarians Part 1Part 1 Part 2Part 2