1. Invertebrates Chapter 14

2. Simple Invertebrates Invertebrates = Animals without backbones  97% of all animal species  Over 1 million invertebrates have been named  Probably millions more remain undiscovered Section 1

3. No backbones Here!  Characteristics of invertebrates: Body Plans  Bilateral Symmetry = the two halves of its body mirror each other  Radial Symmetry = the body parts are arranged in a circle around a central point.  Asymmetrical = you cannot draw a straight line so that its body is divided into two equal halves.  The simplest invertebrates, the sponges, have no symmetry at all. Section 1

4. No backbones Here! Cont. Getting a Head  Nerves – fibers that carry signals to control the movements of their body. (all animals have these, except sponges)  Ganglia = a structure containing a number of nerve cell bodies, typically linked by synapse, & often forming a swelling on a nerve fiber They occur throughout the body, controlling different body parts  More complex animals have a brain and a head Section 1

5. No backbones Here! Cont. Don’t You Have Any Guts?  Gut = a pouch lined with cells that release powerful enzymes These enzymes break down food into small particles that cells can the absorb.  Coelom = body cavity which allows the gut to move food without interference from the movements of the body Complex animals have this special space. Section 1

6. Sponges  Simplest animals Have no symmetry, no head or nerves, & no gut  Once thought to be plants but they can’t make their own food Section 1

7. Sponges: Cont. Kinds of Sponges  All live in water, most in the ocean  Come in beautiful colors & a variety of shapes  Spicules – skeleton made of needlelike splinters that most sponges have. They protect & support. Made up of different substances. Silicate – Largest class (we used to make glass) Spongin – Bath sponges (a protein that is soft) Calcium Carbonate – another group of sponges Section 1

8. Sponges: Cont. Re-form & Replace  If you brake apart a sponge the separate cells will come back together & re-form the same sponge.  Broken off pieces can form a new sponge  Sponges can also regenerate – can replace body parts Section 1

9. Sponges: Cont. How do Sponges Eat?  Pores – thousands of holes on the outside of the sponge where water is sucked in  Collar cells – cells that filter food particles & microorganisms from water  Osculum – the hole at the top of a sponge where water exits. They don’t have a gut Section 1

10. Cnidarians  All cnidarians have stinging cells  Have a gut, complex tissues & a nervous system  Some can reform The Medusa & the Polyp  Medusa = looks like a mushroom with tentacles streaming down below. (jellyfish) As a medusa’s body, or bell, contracts & relaxes, the medusa swims through the water  Polyp = shaped like vases & usually live attached to a surface. (sea anemone) Section 1

11. Cnidarians: Cont. Kinds of Cnidarians  Three classes: 1. Hydras – live in fresh water, spend their entire life in polyp form 2. Jellyfish – spend most of their life as a medusa 3. Sea anemone & corals – spend all their life in polyp form. Look like brightly colored flowers. Corals live in colonies, which build huge skeletons of calcium carbonate. Each new generation builds on the former generation Section 1

12. Cnidarians: Cont. Catching Lunch  All cnidarians have long tentacles covered with special stinging cells.  These cells carry paralyzing toxins.  They use water pressure to fire a tiny barbed spear called a nematocyst Section 1

13. Cnidarians: Cont. You’ve Got Some Nerve  Nerve net – a simple network of nerve cells The nerve net controls the movement of the body & the tentacles  Medusa has a nerve ring in the center of its nerve net which coordinates the swimming of a jellyfish in the same way that our spinal cord coordinates walking. Its not anything close to a brain though Section 1

14. Flatworms  bilateral symmetry  two large unblinking eyespots – can’t focus but can see the where light is coming from  sensory lobes – earlike bumps that are used for detecting food Section 1

15. Flatworms: Cont. Kinds of Flatworms  Divided into 3 classes Planarians – big-eyed; length of a fingernail; live in water & on land; predators (actively stalk & attack other tiny animals or eat dead creatures); have a gut (food & waste go in & out by the same route) Section 1

16. Flatworms: Cont. The next 2 classes are Flukes & Tapeworms.  Both these classes of worms are parasites  have tiny heads; no eyespots or sensory lobes; have special suckers & hooks for attaching to the host; special skin that resists digestion by the host stomach  Parasite = an organism that feeds on another living creature, usually without killing it.  Host = the victim of a parasite. Parasite may live outside or inside their host Section 1

17. Roundworms  Also called nematodes Are round when viewed in cross section bilateral symmetry most are tiny simple nervous system have a complete gut most are parasites Section 1

18. Mollusk & Annelid Worms These invertebrates are more complex than the invertebrates that we’ve studied so far. They have  a coelom  A circulatory system  A more-complex nervous system than those of the flatworm & roundworm Section 2

19. Mollusks Three classes:  Gastropods: snails & slugs  Bivalves: clams, oysters & other 2-shelled shellfish  Cephalopods: squids & octopuses Most live in the ocean those a few live in fresh water & snails & slugs have adapted to live on land Section 2

20. Mollusks: Cont. How Do You Know a Mollusk When You See One?  Foot – broad & muscular, used to move. In gastropods it secretes mucus that it slides on.  Visceral mass – contains the gills, gut, & other organs. It is located in the coelom.  Mantle – a layer of tissue covers the visceral mass, sides of the foot, & head. It protects those mollusks that don’t have shells.  Shell – In most mollusks, the mantle secretes a shell. It protects the mollusk from predators & keeps land mollusks from drying out. Section 2

21. Mollusks: Cont. How Do Mollusk Eat?  Clams & other bivalves – sit in one place & filter tiny plants, bacteria, & other particles from the water around them.  Snails & slugs – eat with ribbon-like tongues covered with curved teeth called radula.  Octopuses & squids – use tentacles to grab their prey & place it in their powerful jaws Section 2

22. Mollusks: Cont. Have a Heart  Most mollusks have an open circulatory system Open Circulatory System = a simple heart pumps blood though blood vessels into spaces in the animal's body called sinuses  Cephalopods have closed circulatory systems Closed Circulatory System = a heart circulates blood through a network of blood vessels that form a closed loop Section 2

23. Mollusks: Cont. It’s a Brain!  Mollusks have complex ganglia that occur throughout the body (one controls breathing, another controls digestion)  Cephalopods have a more complex nervous system. All their ganglia are connected in a brain. Because of this they are smarter than all other invertebrates. Section 2

24. Annelid Worms These are much more complex then previously discussed worms. They have:  a coelom  a closed circulatory system  nervous system which includes ganglia in each segment & a brain in the head (a nerve cord runs the length of the worm and connects all the ganglia to the brain) Segments = identical, or almost identical, repeating body parts Section 2

25. Annelid Worms: Cont. Kinds of Annelid Worms  Three classes: Earthworm – most common Bristle worms Leeches  Can live in salt or fresh water, or on land.  They can scavenge anything edible, or prey on other organisms as predators or parasites Section 2

26. Annelid Worms: Cont. More than Just Bait – Earthworms  have 100-175 segments, most are identical  eat soil & excrete waste – castings  Castings are better for plants  aerate the soil an make it easier for plants to grow  stiff bristles on the outside of their bodies help them move Section 2

27. Annelid Worms: Cont. Bristle Can Be Beautiful – Bristle worms  Come in many varieties & in brilliant colors  All live in water  Some burrow through soggy sand & mud  eating whatever small creature & particles they meet  Others crawl along the bottom  eating mollusks & other small animals Section 2

28. Annelid Worms: Cont. Blood Suckers & More – Leeches  Most are parasites that suck other animals blood  Some are scavengers that eat dead animals  Others are predators that prey on insects, slugs, & snails  Until the 20 th century leeches were used by doctors to treat patients with “bad blood” Doctors still use them today (to keep swelling down & to keep clots from forming) Section 2

29. Arthropods  More commonly known as insects, spiders, crabs & centipedes.  Largest group of organisms on Earth  Humans have a population of about 6 billion world wide.  Arthropods scientist estimate are around a billion billion Section 3

30. Characteristics of Arthropods  All arthropods have four characteristics in common: Jointed limbs A segmented body with specialized parts An exoskeleton Well-developed nervous system Section 3

31. Characteristics of Arthropods: Cont. Jointed Limbs  Arthro = “joint”  Pod = “foot”  Jointed limbs are arms, legs or other similar body parts that bent at joints  Jointed limbs allow arthropods to move easily Section 3

32. Characteristics of Arthropods: Cont. Segmented & Specialized  Like in annelid worms, arthropods are segmented  In centipedes, nearly every segment is identical (just the head & tail are different)  Most other arthropods have segments that include very specialized parts (wings, antennae, gills, pincers, head, thorax, abdomen, & claws)  The segments fuse together as an embryo & form the specialized parts Section 3

33. Characteristics of Arthropods: Cont. Knights in Shining…Chitin?  Exoskeleton = a hard external skeleton made of protein & a special substance called chitin Works as a frame to support the body When muscles contract they move the exoskeleton which in turn moves the body Protects internal organs & muscles like a suit of armor The chitin keeps them from drying out which allows arthropods to live on land Section 3

34. Characteristics of Arthropods: Cont. They’ve Got Smarts  Have a head & a well developed brain It coordinates info. from many sense organs, including eyes & bristles on the exoskeleton  Bristles – sense movement, vibration, pressure, & chemicals  Most arthropods have compound eyes although some just have eyes that allow them to detect light Compound eye = made up of many identical light-sensitive cells which can see images Section 3

35. Kinds of Arthropods  Arthropods are classified according to the kinds of body parts they have. You can also look at the number of legs, eyes, & antennae that have to tell the difference between them. Antennae = feelers that respond to touch, taste, & smell Section 3

36. Kinds of Arthropods: Cont. Centipedes & Millipedes Both have  a single pair of antennae  Mandibles = jaws  A hard head capsule Easiest way to tell them apart? Count the number of legs per segment  Centipedes have 1 leg  Millipedes have 2 legs Section 3

37. Kinds of Arthropods: Cont. Crustaceans – Shrimps, barnacles, crabs, & lobsters  Nearly all are aquatic & have gills for breathing underwater  They have two compound eyes, usually on the end of stalks (look at picture page 341)  The double antennae set them apart from all other arthropods Section 3

38. Kinds of Arthropods: Cont. Arachnids – spiders scorpions, mites, ticks, & daddy long legs  Have two main body parts  Cephalothorax – consists of both a head & thorax & usually has for pairs of walking legs  Abdomen  No antennae, mandibles or compound eyes  Chelicerae – special mouth parts (see picture on page 341) some look like pincers or fangs  Several have painful bites or stings Section 3

39. Kinds of Arthropods: Cont. Insects – Largest group of arthropods Insects Are Everywhere (Almost)  Live on land, in every fresh water environment, and at the edges of the sea  60% of flowering plants species cannot reproduce without insects  Many insects are pests – fleas, lice, mosquitoes, & flies burrow into flesh, suck blood, carry diseases, or consume up to one-third or crops in this country Section 3

40. Kinds of Arthropods: Cont. Insect Bodies Have three parts:  Head – one pair of antennae, two compound eyes, three pairs of mouthparts, including one pair of mandibles  Thorax – has three segments, each with one pair of legs, in many insects the second & third segments have a pair of wings  Abdomen Section 3

41. Kinds of Arthropods: Cont. Insect Development As insects develop from egg to adult they change form this is called Metamorphosis. Two main types of metamorphosis:  Incomplete – only three stages: egg, nymph, & adult – primitive insect such as grasshoppers & cockroaches have this type of metamorphosis  Complete – four stages: egg, larva, pupa, & adult – butterflies, beetles, flies, wasps, bees, & ants go through this metamorphosis Section 3

42. Echinoderms  All are marine animals – sea stars (starfish), sea urchins, sea lilies, sea cucumbers, brittle stars, & sand dollars.  Can be anywhere from a few millimeters across to one meter in diameter.  Live on the sea floor in all parts of the world’s oceans  Some prey on oysters & other shellfish  Some are scavengers  Others scrape algae of rocky surfaces Section 4

43. Spiny Skinned  Echinoderm – “spiny skinned” (however the skin is not the part with the spines)  Endoskeleton = an internal skeleton similar to the kind that vertebrates have  The hard, bony skeleton is usually covered with spines. They maybe no more then sharp bumps (sea stars) or they may be long and pointed (sea urchins).  All spines are covered by the outer skin of the animal. Section 4

44. Bilateral or Radial?  Adult echinoderms have radial symmetry  Sea stars, sea urchins, sand dollars, and other echinoderms all develop from larvae with bilateral symmetry  In the embryo stage of development echinoderms form a mouth in the same way the embryos of vertebrates do (this is why biologist think that vertebrates are more closely related to echinoderms that to other invertebrates.) Section 4

45. The Nervous System All echinoderms have a simple nervous system similar to that of a jelly fish  Around the mouth is a circle of nerve fibers called the nerve ring.  In sea stars, a radial nerve runs from the nerve ring to the tip of each arm. The radial nerves control the movements of the arm. Its only sense organ is a simple eye at the tip of each arm. The rest of its body is covered with cells sensitive to touch & to chemical signals in the water Section 4

46. Water Vascular System  A system that is unique to the echinoderms is the Water Vascular System  Water Vascular System = this system uses water pumps to help the animal move, eat, breathe, & sense its environment. The workings of the water vascular system: Water enters the system through holes in a flat plate on tope of the seas star, called the sieve plate. The water flows through a tube to the ring canal around the mouth. Section 4

47. Water Vascular System: Cont. From the ring canal, the water flows in the radial canals in the arms. The radial canals connect to dozens of tiny suckers (tube feet). These tube feet are used to move and to capture food. Oxygen enters & wastes leave through the thin walls of the tube feet Each tube foot is connect to a bulb (ampulla). The ampulla regulates fluid pressure so that each tube foot may extend/retract, hang on/let go. The movement of the tube feet & of the arm together move the sea star slowly along the bottom of the sea. Section 4

48. Kinds of Echinoderms Sea stars are the most familiar echinoderm but there are others Brittle Stars & Basket Stars Look like sea stars with long slender arms  They are usually smaller than sea stars Section 4

49. Kinds of Echinoderms: Cont. Sea Urchins & Sand Dollars  Are round & their skeletons form a solid internal shell  Have no arms but they use their tube feet to move in the same way as seas stars do (Some sea urchins walk on their spines)  Sea urchins feed on algae  Sand dollars burrow halfway into soft sand or mud & eat tiny particles of food they find there Section 4

50. Kinds of Echinoderms: Cont. Sea Cucumbers  No arms  Soft leathery body  Long wormlike shape  Move with tube feet Section 4