1. CHAPTER 14 Mollusks, Annelids, Arthropods, and Echinoderms
Mrs. Nell’s 7th Grade Life Science Class

2. MOLLUSKS
Kingdom- Animalia
Phylum- Mollusca

3. Mollusks
Mollusks are the soft-bodied invertebrates in the phylum Mollusca. Mollusks usually have shells (not the slug, though) and bilateral symmetry.

4. The Body of a Mollusk
Mollusks have a soft body covered by a mantle (a thin layer of tissue that makes the shell or protects the body if the mollusk doesn’t have a shell).

5. Mollusk Gills
Mollusks have gills to exchange oxygen and CO2 with the water.
gills

6. Visceral Mass
The body organs are located together in what is called the visceral mass.

7. Mollusk Foot
Mollusks have a muscular foot for movement.

8. Circulatory System
Mollusks have an open circulatory system (blood isn’t contained in vessels- blood bathes the mollusk’s organs).

9. Classifying Mollusks There are three main classes of mollusks:
Gastropods
Bivalves
Cephalopods

10. Gastropods
Gastropods or univalves are the largest class of mollusks. Except for slugs, each has a single shell. Members of the gastropod class are:
Snails
Slugs
Abalones
Whelks
Sea slugs
Conches

11. Nutrition
Gastropods feed on plant material using their radula (a tongue like organ with rows of teeth that works like a file).

12. Bivalves
Bivalves are mollusks with a two-part shell joined by a hinge. Bivalves use siphons to filter feed. Some bivalves are:
Clams
Oysters
Scallops

13. Bivalve Defense
To protect themselves, clams will borrow deep into the sand with their muscular foot. Mussels and oysters will cement themselves to a surface. Scallops will open and close their shell rapidly to move away quickly.

14. Cephalopods
Cephalopods have a large, well-developed head. They have tentacles with strong suckers for capturing prey. They have a well developed nervous system and large eyes. Cephalopods have closed circulatory systems, unlike other mollusks.
Some cephalopods are:
Squid
Octopus
Chambered nautilus

15. Jet Propulsion
Cephalopods move by pushing water out through an opening in their head. This jet of water sends it backward. A squid can move more than 60m/s this way.

16. Squid Internal Anatomy

17. Importance of Mollusks (I)
Mollusks provide food for fish, sea stars, birds, and other organisms.

18. Importance of Mollusks (II)
Some invertebrates, like the hermit crab, use empty mollusk shells as shelter.

19. Importance of Mollusks (III)
Clams, oysters, snails, and scallops are used for food.

20. Importance of Mollusks (IV)
Pearls are produced by many species of mollusks.

21. ANNELIDS
Kingdom- Animalia
Phylum- Annelida

22. Segmented Worms
Segmented worms belong to the Phylum Annelida. Annelid means “little rings” and describes the segments that makeup the body of these worms. Some members of the annelid phylum are…
Earthworm
Leeches
Marine Worms

23. Segmented Worms & Mollusks
Like mollusks, all segmented worms have a body cavity that holds their organs.

24. Setae
On the outside of each segment, annelids have little bristle-like structures called setae that help them move. Segmented worms also use the setae to help them stay in the soil if a bird gets a hold of them!

25. Earthworms
Earthworms eat soil. They use their crop for storage and their gizzard to grind the soil. Digested food moves to the intestine where it is broken down and absorbed by the blood. Undigested soil and waste leave the worm through the anus.

26. The "medicinal leech" feeding on blood from a human arm.
Leeches
Leeches feed on the blood of animals- including humans. They have two suckers that they use to attach to the animal. It will then cut into the flesh and suck out blood. Leeches produce an anesthetic so that the animal doesn’t feel the bite.
For centuries leeches were used for blood letting because of the mistaken belief that bodily disorders and fevers were caused by an excess of blood.
Today leeches are used to keep blood flowing to reattach body parts.
The "medicinal leech" feeding on blood from a human arm.

27. Marine Worms
Marine worms also have segments with setae. Some marine worms trap food in tentacles. Others build tubes to hide in.

28. Annelids & Mollusks- related?
Scientists think segmented worms and mollusks share a common ancestor. They were the first of the animal groups to have bodies with space for the body organs, and they both have a larva stage early in their development.

29. ARTHROPODS
Kingdom- Animalia
Phylum- Arthropoda

30. ARTHROPODS
Arthropods make up the largest phylum of animals in the animal kingdom. Members of the arthropod phylum include…
Insects
Arachnids
Centipedes
Millipedes
Crustaceans

31. Molting Caterpillar

32. The Body of an Arthropod
Arthropoda means “jointed foot” and describes the jointed appendages of arthropods. The appendages on an arthropod include legs antennae, claws, and pinchers.

33. Arthropods and segmented worms- related?
The bodies of arthropods are divided into segments like those of segmented worms so scientists hypothesize they may have a common ancestor.

34. Exoskeletons
All arthropods have an external covering called the exoskeleton that protects the body. It is made of protein and a carbohydrate called chitin. Once the arthropod outgrows its shell it will molt.
Horse shoe crab, cicada shell

35. Insect
Kingdom- Animalia
Phylum- Arthropoda
Class- Insecta

36. Insects
Insects have three body regions: a head, thorax, and an abdomen. The head has a pair of antennae, eyes, and a mouth. The thorax has three pairs of jointed legs and sometimes wings. The abdomen doesn’t have wings or legs attached.

37. The Body of an Insect
Insects have open circulatory systems. For their respiratory system they have openings called spiracles on the abdomen and thorax through which air enters and waste gases are expelled.

38. Metamorphosis
Many species of insects go through a series of changes called metamorphosis. Most insects (butterflies, beetles, ants, bees, moths, flies…) develop through complete metamorphosis. There are four stages of development:
Egg
Larva
Pupa
Adult

39. Incomplete Metamorphosis
Grasshoppers, silverfish, lice, and crickets develop through incomplete metamorphosis. The three stages of development are egg, nymph (a small adult without wings), and adult.

40. Arachnid
Kingdom- Animalia
Phylum- Arthropoda
Class- Arachnida

41. Arachnids
Arachnids are arthropods with only two body regions (the cephalothorax and abdomen). They have four pairs of legs but no antennae. Arachnids have 8 legs and poison glands, stingers, or fangs. Some arachnids are:
Spiders
Scorpions
Mites
Ticks

42. Centipede/Millipede Kingdom- Animalia Phylum- Arthropoda
Class- Chilopoda/Diplopoda

43. Centipedes & Millipedes
Centipedes have one pair of jointed legs per segment. Millipedes have two per segment. Centipedes have a pair of poison claws to inject venom into their prey (they eat snails, slugs, and worms). Millipedes feed on plants.
Centipede bites are painful to humans.

44. Crustacean
Kingdom- Animalia
Phylum- Arthropoda
Class- Crustacea

45. Crustaceans
Crustaceans are arthropods that have one or two antennae and jaws called mandibles for crushing food. They have five pairs of legs. The claws are for catching and holding food. The other four pairs are walking legs. Some members of the class Crustacea are:
Crabs
Crayfish
Lobsters
Shrimp
Barnacles
Pill bugs
Water fleas

46. Blue Crabs
A male crab, or "Jimmy", has a long narrow, inverted "T" shaped abdomen and has blue tipped claws.
A female crab can be easily identified by the shape of her abdomen.
Abdomen of immature female crab
Abdomen of mature female crab

47. “Jimmy”
Some watermen say that a male blue crab looks like it has the Washington Monument on his belly!

48. “Sally”
An immature female, called "she-crab" or "Sally," has an inverted "V" (or triangular) shaped abdomen.

49. “Sook”
An adult female, called a "sook," has an inverted "U" (dome) shaped abdomen. Some watermen say that a sook has the U.S. Capitol Building on her belly! Another easy way to tell a male from a female is that all female crabs "paint their fingernails" (have red tipped claws)- males do not.

50. Pesticides and Insects
Most insects are harmless, but farmers who are concerned about crop yields often use pesticides (chemicals that kill undesirable plants and insects).

51. For Pesticide Use Farmers can produce more food
New ways of applying pesticides may reduce amount needed and ensure it affects only the insect pests

52. Against Pesticide Use
Kill not only intended pest but other organisms as well
Pesticides accumulate in body tissues of organisms
Environmental impact is too great

53. ECHINODERMS
Kingdom- Animalia
Phylum- Echinodermata

54. Echinoderms
Echinoderms are spiny skinned invertebrates that live on the ocean bottom. They include:
Sea stars
Brittle stars
Sea urchins
Sand dollars
Sea cucumbers

55. Water-Vascular System
Sea stars have a water-vascular system (a network of water-filled canals) which attach to thousands of tube feet (‘suction cups’ that help the sea star feed/move).

56. Sea Stars
The sea star turns its stomach inside out and pushes it through its mouth to eat. It then secretes enzymes that digest the animal. When the meal is over, the sea star pulls its stomach back in.

57. The Sea Cucumber
Sea cucumbers have soft-bodies and tentacles around their mouth. When threatened sea cucumbers may expel their internal organs and simply regenerate them in a few weeks!
This sea cucumber is eviscerating a portion of its intestines to thwart an attack.

58. Importance of Echinoderms
Providing information about how body parts regenerate
Feed on dead organisms in the marine environment

59. Echinoderms Similar to Chordates
Of invertebrates- most similar to chordates (mammals, birds, reptiles, amphibians, and fish)
Complex body systems
Embryo develops similar to chordates