Introduction to AnimalsSection 2 CH 26:Introduction to Animals Sec 1 and Sec 2

Introduction to AnimalsSection 2 General Features of Animals Animals are multicellular, heterotrophic organisms with cells that lack cell walls. Humans depend on other animals for food, companionship, and to pollinate crops. Most animals move to get food. But filter eaters, such as sponges and corals, catch particles of food that drift by in the water.

Introduction to AnimalsSection 2 Kinds of Animals Animals are often grouped as invertebrates or vertebrates. Vertebrates make up only a subgroup of one phylum— Chordata. Most animals are invertebrates.

Introduction to AnimalsSection 2 Kinds of Animals, continued Vertebrates Vertebrates have a cranium and an internal skeleton composed of bone or cartilage. Vertebrates are chordates that have a backbone. The backbone supports and protects a dorsal nerve cord and provides a site for muscle attachment. Pg 625

Introduction to AnimalsSection 2 CH26 Sec 2: Animal Body Systems

Introduction to AnimalsSection 2 Key Ideas Why is an animal's skeleton important? What are the functions of the digestive and excretory systems? What is the function of the nervous system? Why are the respiratory and circulatory systems important? What are two reproductive strategies of animals?

Introduction to AnimalsSection 2 Support An animal's skeleton provides a framework that supports the animal's body and is vital to an animal's movement. Many soft-bodied invertebrates, such as jellyfish, have a hydrostatic skeleton, which is a water-filled cavity that is under pressure. An exoskeleton is a rigid external skeleton that encases the body of an animal. Insects, clams, and crabs have exoskeletons.

Introduction to AnimalsSection 2 Support, continued An endoskeleton is an internal skeleton made of bone and cartilage. Humans and other vertebrates have endoskeletons.

Introduction to AnimalsSection 2 Digestive and Excretory Systems The digestive system is responsible for extracting energy and nutrients from an animal's food. The excretory system removes waste products from the animal's body.

Introduction to AnimalsSection 2 Digestive and Excretory Systems, continued Digestive System A gastrovascular cavity is a digestive cavity with only one cavity. There are no specialized digestive cells. The hydra has a gastrovascular cavity.

Introduction to AnimalsSection 2 Digestive and Excretory Systems, continued Digestive System, continued In a digestive tract, food moves from one opening, the mouth, to a second, the anus. Digestive tracts allow for specialization and more efficient digestion.

Introduction to AnimalsSection 2 Digestive and Excretory Systems, continued Excretory System Excretion is the removal of wastes produced by cellular metabolism. Simple aquatic invertebrates and some fishes excrete ammonia through their skin or gills. Terrestrial animals need to minimize water loss. Some convert ammonia to less toxic chemicals before passing them out of the body.

Introduction to AnimalsSection 2 Nervous System The nervous system carries information about the environment through the body and coordinates responses and behaviors. Not all animals have a complex nervous system, and some do not have a brain to coordinate the nervous system.

Introduction to AnimalsSection 2 Nervous System, continued Simple Nervous Systems All animals except sponges have nerve cells. In the simplest arrangement of nerves, called a nerve net, nerve cells do not coordinate actions efficiently. Jellyfish and hydras have a nerve net.

Introduction to AnimalsSection 2 Hydra Nervous System

Introduction to AnimalsSection 2 Nervous System, continued Simple Nervous Systems, continued Many animals have clusters of nerve cells called ganglia that can coordinate responses. Flatworms have large more-complex ganglia, similar to a brain.

Introduction to AnimalsSection 2 Flatworm Nervous System

Introduction to AnimalsSection 2 Nervous System, continued Complex Nervous Systems More-complex invertebrates have a true brain with sensory structures, such as eyes, associated with it. Vertebrates have a relatively large brain, and may species have special sensory systems that make these animals even better at catching food and avoiding predators than other animals are.

Introduction to AnimalsSection 2 Grasshopper Nervous System

Introduction to AnimalsSection 2 Respiratory and Circulatory Systems The respiratory system is responsible for exchanging oxygen and carbon dioxide between the body and the environment. The circulatory system transports gases, nutrients, and other substances within the body.

Introduction to AnimalsSection 2 Respiratory and Circulatory Systems, continued Respiratory System Most animals have specialized respiratory systems. Aquatic animals respire by using thin projections of tissue called gills. A variety of respiratory organs, including lungs, have evolved in terrestrial animals.

Introduction to AnimalsSection 2 Respiratory and Circulatory Systems, continued Circulatory System In an open circulatory system, a heart pumps fluid containing oxygen and nutrients through vessels into the body cavity. The fluid provides oxygen and nutrients as it washes across the tissues. In a closed circulatory system, the blood is pumped through the body within vessels and is never in direct contact with the body's tissues.

Introduction to AnimalsSection 2 Open and Closed Circulatory Systems

Introduction to AnimalsSection 2 Reproduction Asexual reproduction occurs when an individual produces exact copies of itself and does not mix its genes with those of another. Sea stars and some salamanders and fishes reproduce asexually.

Introduction to AnimalsSection 2 Reproduction, continued In sexual reproduction, a new individual is formed by the union of a male and female gamete. Some species can reproduce either asexually or sexually. Coral colonies grow larger though asexual reproduction, but new colonies are formed through sexual reproduction.