1. Chapter 15 Table of Contents Section 1 Simple Invertebrates
Section 2 Mollusks and Annelid Worms
Section 3 Arthropods
Section 4 Echinoderms

2. Chapter 15
Section 1 Simple Invertebrates
Objectives
Describe the body plans, nervous systems, and guts of invertebrates.
Explain how sponges get food.
Describe three cnidarian characteristics.
Describe the three kinds of flatworms.
Describe the body of a roundworm.

3. Invertebrate Characteristics
Chapter 15
Section 1 Simple Invertebrates
Invertebrate Characteristics
An Invertebrate *
About 96% of all animal species are invertebrates
Invertebrates have three basic body plans, or *

4. Chapter 15
Section 1 Simple Invertebrates

5. Invertebrate Characteristics, continued
Chapter 15
Section 1 Simple Invertebrates
Invertebrate Characteristics, continued
Nerves *.
Nerves allow animals to sense their environment and control their actions.
Some invertebrates have ganglia. A ganglion is a concentrated mass of nerve cells.

6. Invertebrate Characteristics, continued
Chapter 15
Section 1 Simple Invertebrates
Invertebrate Characteristics, continued
Guts Almost all animals digest food in a gut. A gut is a *
Complex organisms have a coelom. A coelom is a *
Other organs can also be found in the coelom, but they are separated from the gut.

7. Chapter 15
Section 1 Simple Invertebrates
Sponges
Sponges are the simplest invertebrates. They are asymmetrical and have no tissues, gut, or nerves.
How Do Sponges Eat? A sponge sweeps water into its body through its pores. Pores are *
Collar cells *
* called the osculum.

8. Chapter 15
Section 1 Simple Invertebrates

9. Chapter 15 Sponges, continued
Section 1 Simple Invertebrates
Sponges, continued
Body Part Abilities Sponges have some unique abilities.
If you forced a sponge’s body through a strainer, the separated cells could come back together and reform the same sponge.
If a part of a sponge is broken off, the missing part can *
Sponges are the only animals that can use regeneration as a form of reproduction.

10. Chapter 15 Sponges, continued
Section 1 Simple Invertebrates
Sponges, continued
Kinds of Sponges All sponges live in water, and most live in the ocean. Sponges come in many different shapes and sizes.
Most sponges have a skeleton made of hard fibers called spicules. Some spicules are *.

11. Chapter 15
Section 1 Simple Invertebrates
Cnidarians
Cnidarians are more complex than sponges. Cnidarians have complex tissues, a gut, and a simple nerve network.
Two Body Forms A cnidarian body can either be in medusa form or polyp form. Medusas swim *
Both the medusa and the polyp forms have radial symmetry.

12. Body Form of Cnidarians
Chapter 15
Section 1 Simple Invertebrates
Body Form of Cnidarians

13. Chapter 15
Section 1 Simple Invertebrates
Cnidarians
Stinging Cells All cnidarians have tentacles covered with stinging cells. Cnidarians use their stinging cells *
Kinds of Cnidarians There are three major classes of cnidarians: *

14. Chapter 15
Section 1 Simple Invertebrates
Flatworms
Flat worms have bilateral symmetry, a clearly defined head and two large eyespots.
The eyespots cannot focus, but the flatworm can use them to sense the direction that light is coming from.
Some flatworms also have sensory lobes that are used for detecting food.

15. Chapter 15 Flatworms, continued
Section 1 Simple Invertebrates
Flatworms, continued
Planarians Planarians live in freshwater lakes and streams or on land in damp places. Most planarians are predators.
Flukes Flukes are parasites. A parasite is *

16. Chapter 15 Flatworms, continued
Section 1 Simple Invertebrates
Flatworms, continued
Tapeworms Tapeworms are similar to flukes. Like flukes, they have a small head with no eyespots or sensory lobes.
Tapeworms do not need a gut because they attach directly to the host’s intestines and absorb nutrients.

17. Chapter 15
Section 1 Simple Invertebrates
Roundworms
Roundworms have bodies that are long, slim, and round, like spaghetti. Like other worms, they have bilateral symmetry.
Roundworms have a simple nervous system. A ring of ganglia forms a simple brain. Parallel nerve cords connect the two ends of their body.
Some round worms eat dead tissue. Many roundworms are parasites.

18. Section 2 Mollusks and Annelid Worms
Chapter 15
Objectives
Explain how mollusks eat, control body functions, and circulate blood.
Describe the four body parts that most mollusks have in common.
Describe the three kinds of annelid worms.

19. Section 2 Mollusks and Annelid Worms
Chapter 15
Mollusks
Snails, slugs, clams oysters, squids, and octopuses are all mollusks.
Most mollusks fit into three classes:
The gastropods include *.
The bivalves include *
The cephalopods include *.

20. Chapter 15 Mollusks, continued
Section 2 Mollusks and Annelid Worms
Chapter 15
Mollusks, continued
Each kind of mollusk has its own way of eating.
Slugs and snails eat with a *
Clams and oysters attach to one place and use gills to filter tiny plants, bacteria, and other particles from the water.
Squids and octopuses grab food with tentacles and place it in their powerful jaws.

21. Chapter 15 Mollusks, continued
Section 2 Mollusks and Annelid Worms
Chapter 15
Mollusks, continued
Ganglia and Brains All mollusks have complex ganglia. They have ganglia to control breathing, movement, and digestion.
Cephalopods, such as octopuses, have large brains that connect all of their ganglia. Cephalopods are thought to be the smartest invertebrates.

22. Chapter 15 Mollusks, continued
Section 2 Mollusks and Annelid Worms
Chapter 15
Mollusks, continued
Pumping Blood Most mollusks have an open circulatory system. In an open circulatory system, *
Squids and octopuses have a closed circulatory system. In a closed circulatory system, a *

23. Chapter 15 Mollusks, continued
Section 2 Mollusks and Annelid Worms
Chapter 15
Mollusks, continued
Mollusk Bodies A snail, a clam, and a squid look quite different from one another, yet they share similar structures.

24. Chapter 15
Section 2 Mollusks and Annelid Worms

25. Section 2 Mollusks and Annelid Worms
Chapter 15
Annelid Worms
Annelid worms are often called segmented worms because their bodies have segments. A segment is*.
Annelid worms have bilateral symmetry, a closed circulatory system and a complex nervous system with a brain.
Annelid worms live in salt water, fresh water, or on land. They eat plant material or animals.

26. Annelid Worms, continued
Section 2 Mollusks and Annelid Worms
Chapter 15
Annelid Worms, continued
Earthworms Earthworms are the most common annelid worms.
Each earthworm has 100 to 175 segments. Most segments are identical, but some have special jobs, such as eating or reproducing.
Earthworms eat soil. Their castings, or waste, improves soil quality.
To move, earthworms use stiff hairs, or bristles, on the sides of their bodies.

27. Annelid Worms, continued
Section 2 Mollusks and Annelid Worms
Chapter 15
Annelid Worms, continued
Marine Worms Marine worms are covered in bristles and come in many colors.
Most marine worms live in the ocean. Marine worms eat mollusks, other small animals, or filter food from the water.
Leeches Some leeches are parasites that suck other animals’ blood. Other leeches eat dead animals or hunt insects, slugs, and snails.
Doctors use leeches to prevent swelling.

28. Chapter 15
Section 3 Arthropods
Objectives
List the four main characteristics of arthropods.
Describe the different body parts of the four kinds of arthropods.
Describe the two types of metamorphosis in insects.

29. Characteristics of Arthropods
Chapter 15
Section 3 Arthropods
Characteristics of Arthropods
Arthropods share four characteristics: a segmented body with specialized parts, jointed limbs, an exoskeleton, and a well-developed nervous system.
Segmented and Specialized Like annelid worms, arthropods are segmented. Many also have specialized parts such as *
Jointed Limbs Jointed limbs are legs or other body parts that bend at the joints and make moving easier.

30. Characteristics of Arthropods, continued
Chapter 15
Section 3 Arthropods
Characteristics of Arthropods, continued
An External Skeleton * is called an exoskeleton. The exoskeleton supports the body, protects internal organs, and prevents water loss.
Sensing Surroundings Arthropods that have compound eyes can see images. A compound eye *

31. Chapter 15 Kinds of Arthropods
Section 3 Arthropods
Kinds of Arthropods
Arthropods are classified by the kinds and numbers of body parts they have.
An antenna is a *

32. Kinds of Arthropods, continued
Chapter 15
Section 3 Arthropods
Kinds of Arthropods, continued
Centipedes and Millipedes Centipedes and millipedes have one pair of antennae, a hard head, and one pair of mandibles. Mandibles *
Centipedes have one pair of legs on each segment and a total of 30 to 354 legs.
Millipedes have two pairs of legs on each segment and as many as 752 legs.

33. Kinds of Arthropods, continued
Chapter 15
Section 3 Arthropods
Kinds of Arthropods, continued
Crustaceans Shrimps, barnacles, crabs, and lobsters are crustaceans.
Crustaceans have gills for breathing, mandibles for eating, two compound eyes on eyestalks, and two pairs of antennae.

34. Kinds of Arthropods, continued
Chapter 15
Section 3 Arthropods
Kinds of Arthropods, continued
Arachnids Spiders, scorpions, mites, and ticks are arachnids.
Arachnids have two main body parts: a cephalothorax and an abdomen.
Most arachnids have four pairs of legs, no antenna, simple eyes, and mouth parts called chelicerae.

35. Body Parts of Arachnids
Chapter 15
Section 3 Arthropods
Body Parts of Arachnids

36. Kinds of Arthropods, continued
Chapter 15
Section 3 Arthropods
Kinds of Arthropods, continued
Insects Insects make up the largest group of arthropods. If you put all the insects in the world together, they would weigh more than all the other animals combined!
Insects have three main body parts, six legs, and two antennae.

37. Chapter 15 The World of Insects
Section 3 Arthropods
The World of Insects
Insect Bodies An insect’s body has three parts: the head, the thorax, and the abdomen.
Metamorphosis is a phase in the life cycle of many animals during which a *
Complete Metamorphosis Most insects go through a complete metamorphosis. Complete metamorphosis has four parts: *

38. Chapter 15
Section 3 Arthropods

39. The World of Insects, continued
Chapter 15
Section 3 Arthropods
The World of Insects, continued
Incomplete Metamorphosis Grasshoppers and cockroaches are some of the insects that go through incomplete metamorphosis.
Incomplete metamorphosis has three main stages: *

40. Incomplete Metamorphosis
Chapter 15
Section 3 Arthropods
Incomplete Metamorphosis

41. Chapter 15
Section 4 Echinoderms
Objectives
Describe the endoskeleton, nervous system, and water vascular system of echinoderms.
Explain how an echinoderm’s body symmetry changes with age.
Describe five classes of echinoderms.

42. Chapter 15 Echinoderms are spiny invertebrates that live in the ocean.
Section 4 Echinoderms
Echinoderms are spiny invertebrates that live in the ocean.
Sea stars, sea urchins, and sand dollars are some familiar members of this group.
Echinoderms eat shellfish, dead plants or animals, or algae that they scrape off rocks.

43. Chapter 15 Spiny Skinned The name echinoderm means *
Section 4 Echinoderms
Spiny Skinned
The name echinoderm means *
The spines are actually on the animals endoskeleton. An endoskeleton in an internal skeleton made of bone or cartilage.

44. Chapter 15 Bilateral or Radial?
Section 4 Echinoderms
Bilateral or Radial?
Adult echinoderms have radial symmetry. Larvae have bilateral symmetry.

45. Chapter 15 The Nervous System
Section 4 Echinoderms
The Nervous System
All echinoderms have a simple nervous system similar to that of a jellyfish. Around the mouth is a circle of nerve fibers called the nerve ring.
Sea stars have a radial nerve that runs from the nerve ring to the tip of each arm.

46. Sea Star Nervous System
Chapter 15
Section 4 Echinoderms
Sea Star Nervous System

47. Chapter 15 Water Vascular System The water vascular system is a *
Section 4 Echinoderms
Water Vascular System
The water vascular system is a *
Echinoderms use their water vascular system to *

48. Chapter 15
Section 4 Echinoderms

49. Chapter 15 Kinds of Echinoderms
Section 4 Echinoderms
Kinds of Echinoderms
There are five major classes of echinoderms. Sea stars are the most familiar class.
Brittle Stars and Basket Stars Brittle stars and basket stars look like sea stars. But these echinoderms have long, slim arms and are often smaller than sea stars. They don’t have suckers on their tube feet.

50. Kinds of Echinoderms, continued
Chapter 15
Section 4 Echinoderms
Kinds of Echinoderms, continued
Sea Urchins and Sand Dollars Sea urchins and sand dollars are round. Their endoskeletons form a solid, shell-like structure.
Sea Lilies and Feather Stars Sea lilies and feather stars have 5 to 200 feathery arms.
Sea Cucumbers Like sea urchins and sand dollars, sea cucumbers have no arms. A sea cucumber has a soft, leathery body.