PHYLUM ARTHROPODA 1 Characteristics of arthropods 34 of

PHYLUM ARTHROPODA `

1. Characteristics of arthropods • 3/4 of all animal species belong to this phylum. • Arthropods are segmented animals. The name means “______”.

• 2. Arthropods have an _______ which provides support and protection.

3. The exoskeleton has three layers. The waxy outer layer is made of proteins and ______. This makes it water repellent and helps keep them from drying out.

4. The middle layer is composed of protein and _____ and sometimes calcium carbonate. It also provides support and protection.

5. The inner layer also contains protein and chitin but is flexible at the joints allowing movement. _____ are attached to the inner layer to help them move.

6. Most have a high degree of cephalization with sensory structures and complex mouths. Many have segmented antennae, compound ____ (eyes composed of many light detectors, each with its own lens).

7. All arthropods have an ______ circulatory systems. • Because the skeleton is on the outside it must be shed in order for the arthropod to grow. This process is called molting.

8. An arthropod molts many times in its life becoming ______ with each molting. In between molts the tissues swell until they put a lot of pressure on the exoskeleton.

9. A hormone is then released that induces molting. In response to the hormone certain cells secrete enzymes that digest the flexible inner layer of the _____.

10. At the same time the epidermis begins to make a new exoskeleton using a lot of the digested material. Eventually the outer layer of the old exoskeleton loosens, breaks along specific lines, and is ________.

11. The new exoskeleton, which is flexible at first stretches to fit the enlarged animal. It takes a few days for the new exoskeleton to harden. The animal is very vulnerable at this time and usually ______.

12. Arthropods are divided into _____ subphyla on the basis of differences in their mouth parts and other appendages as well as how they develop.

The 4 subphyla are –Trilobita –Crustace –Chelicerata –Uniramia

13. The trilobites are all _____. They had similar paired appendages on each of the body segments.

14. Crustacea includes shrimp, lobsters, crabs, crayfish, barnacles, isopods, copepods, and water fleas. They have branched antennae and a pair of chewing mouthparts called ____.

15. Chelicerata includes spiders, ticks, scorpions, mites, sea spiders, and horseshoe crabs. • They have ____ antennae. • They have pincer-like mouthparts called chelicera.

16. Unirania includes centipedes and millipedes and insects. They have antennae but their appendages are unbranched. They are the only group that is believed to have evolved on land.

17. Contains about 40, 000 species. • Crustaceans are the only arthropods that have ___ pairs of appendages on their head that act as feelers.

• 18. Each segment has usually has a pair of branched appendages. Some have over 60 segments but they usually have 16 – 20 which are fused into several _____. A tagmata is several segments that have fused to perform a specific function.

• 19. The exoskeletons of many aquatic crustaceans have a lot of calcium carbonate which makes them very hard. • The crustacean larva is called a _________ larva. Six appendages, one eye.

• 20. Most crustaceans are very small. Copepods are only about 1 millimeter in length but may be the most abundant species on earth.

• 21. Copepods make up most of the plankton in the ocean where they are an important part of the ocean food chain.

• 22. Barnacles are ____ crustacean that attach themselves to rocks, ships, piers, whales, etc.

• 23. Sow bugs and pill bugs are terrestrial members of a group of crustaceans called _____. They have to live in moist environments to keep from drying out. They usually live under rocks and in leaf litter.

24. The Crayfish Structurally they are very similar to lobsters. Both are called _____ (ten feet). Shrimps and crabs are also decapods.

• 25. The body is divided into 2 major sections. The cephalothorax and the abdomen. • The cephalothorax consists of 2 tagmata, the head which has 5 segments and the thorax which has 8.

• 26. They have a large covering called a _____ that covers most of the body. The abdomen is divided into 7 segments. The last one is called the _____ and looks like a paddle. It helps them swim backwards quickly.

• 27. They have antennules that serve as feelers which respond to touch and taste. • They chew their food with the mandibles and manipulate it with two pairs of maxillae and three pairs of maxillipeds.

• 28. The most anterior appendages on the thorax are the ______. They are used for defense and to capture food. • The swimmerets are appendages attached to the 5 abdominal segments. They are used in reproduction.

• 29. Food passes through the esophagus to the stomach where teeth made of chitin and calcium carbonate grind the food into a paste. The paste is mixed with enzymes secreted by the digestive gland.

• 30. It then enters the intestine and digestive gland for digestion and absorption. What does not get digested is removed through the anus. • Crayfish use ____ for respiration.

• 31. They have an _____ circulatory system with a heart. • Because they live in fresh water they are constantly receiving water into the body. This excess water is removed by organs called ______ glands.

• 32. The fluid collected by the green glands is removed from the body through a pore at the base of the antennae. • The crayfish ____ consists of a pair of ganglia above the esophagus that gets signals from the eyes, antennules, and antennae.

• 33. Crayfish sense vibrations and chemicals in the water with thousands of sensory hairs that are distributed over the body. • The compound eyes are set on 2 short moveable stalks. Each eye has more than 2, 000 light sensitive units with their own lenses.

SUBPHYLA CHELICERATA & MYRIAPODA 34. All the members of these subphyla are terrestrial. The major group in Chelicerata is the class Arachnida.

• 35. Class Arachnida have a body divided into a cephalothorax and an abdomen. The cephalothorax in arachnids usually has 1 pair of chelicerae, 1 pair of _____ (used for holding food and chewing. ), and 4 pairs of walking legs.

• 37. Spiders can range from ½ mm to 9 cm. • The chelicerae are modified as _____ and are used to inject venom into prey. The venom is produced by poison glands and flows through ducts in the chelicera to the tips of the fangs.

• 38. Most spiders have _____ simple eyes. Each eye has a single lens. • On the tip of the abdomen of many spiders are 3 pairs of spinnerets. Each spinneret is made of hundreds of microscopic tubes that connect the silk glands to the abdomen.

• 39. A protein-containing fluid produced in the silk gland hardens into threads as it is pulled from the spinnerets. The silk is used to make webs, build nests, and protect eggs.

• Sheet web

• Sheet web

Dome web

Funnel web

• Orb spider web

• 40. In some spiders respiration happens in ____ , paired sacs in the abdomen with many parallel folds that resemble the pages of a book. The folds increase the surface area where gas exchange occurs.

• 41. In other spiders there are systems of tubes called _____ that carry air directly to the tissues from openings in the exoskeleton called spiracles. • Some spiders have both tracheae and book lungs!

• 42. The main excretory system of spiders are organs called Malpighian tubules. They are hollow projections of the digestive tract that collect body fluids and wastes and carry them to the intestine.

• 43. After most of the water is reabsorbed the waste leaves the body in a nearly solid form as feces. • Some spiders also have ____ glands which remove wastes and discharge them through openings at the base of the legs.

• Wolf spider

• Wolf spider

• Banded garden spider

• Brown widow

• Spined micrathena

Jumping spider

• Funnel web weaver

• Nursery web spider

• Brown recluse

• Lynx spider

• Black widow

• 43. Scorpions differ from spiders in two ways. Scorpions have large, pincerlike pedipalps that they hold in a forward position. They also have a large stinger on the last segment of the body which is usually curled over the body.

• 44. They are usually hiding during the day and come out at night to hunt insects and spiders. They seize the prey with the pedipalps and inject venom into it.

• 45. Only one species in North America are fatal to humans, Centruroides exilicauda.

• 46. Ticks and mites are the most abundant and most specialized arachnids. They differ from spiders and scorpions in that they have a completely __ cephalothorax and abdomen with no sign of separation.

• 47. Most mites are less than 1 mm in length, some small enough to live on a dust particle. Some are free living while others are parasitic. • Spider mites parasitize fruit trees and crops by sucking the fluid from the leaves.

• 48. The larva of the harvest mite attaches to the skin of vertebrates where they feed on the dissolving flesh and blood (they are also called chiggers).

• 50. Ticks can cause diseases such as Rock Mountain spotted fever and Lyme disease.

• 51. The subphylum Uniramia include the myriapods (many foot). • They are all terrestrial with highly segmented bodies. • They have ___ pair of unbranched antennae.

• 52. They do not have a waxy exoskeleton so they must live in damp environments. • Class Diplodopa are the millipedes. They have ___ pairs of legs on each body segment except the last two.

• 53. The legs are short and are used to burrow through soil. • They have rounded bodies. • They have short antennae and two groups of simple eyes. • They eat plants or decaying plant matter in the soil.

• 54. When threatened they curl up and can secrete a toxic fluid that contains ___.

• 55. Class Chilipoda are the centipedes. In the tropics they may reach a foot in length. Around here they are usually only an inch. • They have a flattened body with longer legs than millipedes.

• 56. The segments have only one pair of legs. The appendages on the first segment are modified into a pair of poison claws. • They have ___ antennae and two clusters of simple eyes located on the head.

• 57. Centipedes are fast movers and catch and eat earthworms, insects, and even mice. • They kill the prey with ___ and use the mandibles to tear it apart. Most are not harmful to humans.