Phylum Arthropoda

1. Phylum Arthropoda Chapter 28.1-28.2

2. Chapter 28.1 & 28.2 Vocabulary • Complete Metamorphosis • Incomplete Metamorphosis • Cephalothorax • Thorax • Abdomen • Mandible • Appendage • Antennae • Molting • Pollination • Exoskeleton • Carapace • Spinneret • Chitin • Swimmerettes • Chelicerae • Pedipalps • Mimicry

3. Introduction to Arthropods 28.1

4. What Is An Arthropod? • Three distinguishing features: • 1) Segmented Body • 2) Tough Exoskeleton – made from chitin, protects and supports the body. • 3) Jointed Appendages – structures such as legs and antennae that extend from the body wall • Named for jointed appendages – arthron means “joint” in Greek

5. Form & Function: Feeding • Arthropods include herbivores, carnivores, and omnivores. • Bloodsuckers, filter feeders, detrivores, and parasites • Mouthparts range from pincers or fangs to sickle-shaped jaws that cut through tissues of prey.

6. Form & Function: Respiration • Terrestrial arthropods breathe through a network of branching tracheal tubes. • Spiders breathe through book lungs. • Aquatic arthropods breathe through featherlike gills. • Examples include crabs and lobsters.

7. Form & Function: Circulation • Arthropods have an open circulatory system. • The heart pumps blood through arteries that branch and enter tissues. • Blood enters sinuses and is then pumped through the body.

8. Form & Function: Response • Arthropods have a well-developed nervous system. • Brain – serves as a central switchboard, receives and sends information • Nerves – 2 nerves that encircle esophagus and connects to ventral nerve cord • Ganglia – several ganglia along the nerve cord • Sense organs – compound eyes (2000 lenses) that detect color and motion

9. Form & Function: Response

10. Form & Function: Movement • Arthropods move using well-developed groups of musclesthat are coordinated and controlled by the nervous systems. • Muscles generate force by contracting and then pulling on the exoskeleton.

11. Form & Function: Reproduction • Terrestrial arthropods reproduce by internal fertilization. • Some male species have a reproductive organ that places sperm inside the female. • Other male species may deposit a sperm packet that is picked up by a female. • Aquatic arthropods reproduce by either internal or external fertilization. • Females release eggs and males release sperm into open water.

12. Growth and Development • Arthropods outgrow their exoskeleton and undergo a period of molting. • During this process the arthropod sheds its entire exoskeleton and makes a new, larger one. • Molting is controlled by the arthropod’s endocrine system (chemicals called hormones). • Specialized skin glands digest the inner part of the exoskeleton and other glands secrete a new one. • This process can take several hours and while the new exoskeleton is soft arthropods become vulnerable to predators. • They will generally hide during molting periods.

13. Growth and Development

14. Groups of Arthropods 28.2

16. How are Arthropods Classified? • Arthropods are classified based on the number and structure of their body segments and appendages, mainly their mouthparts. • Three major groups: • 1) Crustaceans (lobsters, crabs, crayfish, barnacles) • 2) Arachnids (spiders, mites, ticks, scorpions) • 3) Insects and their relatives (fly, butterfly, bee) (millipedes, centipedes)

17. Crustaceans • Subphyla: Crustacea • Primarily aquatic. • Includes crabs, shrimps, lobsters, crayfish, and barnacles. • Range in size from small terrestrial pill bugs to enormous spider crabs. • Typically have 2 pairs of antennae, 2 or 3 body sections, and chewing mouthparts called mandibles.

18. Crustaceans

19. Barnacles • Sessile filter feeders wrapped in a hard shell.

20. Chelicerates • Subphyla: Chelicerata • Includes horseshoe crabs, spiders, ticks, and scorpions. • Have mouthparts called chelicerae and 2 body sections. • Nearly all chelicerates have 4 pairs of walking legs. • Lack antennae found on other arthropods. • Mouth contains chelicerae (fangs used to stab and paralyze prey) and pedipalps (to grab prey).

21. Chelicerates • 2 Main Classes: • Merostomata– horseshoe crabs • Arachnida – arachnids (spiders, mites, ticks, and scorpions)

22. Arachnids

23. Arachnids • Most spiders spin a web used to capture prey. • They also spin silk into cocoons for eggs. • Some spiders will chase and catch prey. • Spiders do not have jaws so they must liquefy prey.

24. Uniramians • Subphyla: Uniramia • Includes centipedes, millipedes, and insects. • Contains more species than all other groups of animals alive today. • Uniramians have jaws, 1 pair of antennae, and unbranched appendages. • They have a wide variety of forms and lifestyles. • Centipedes/Millipeds – long, wormlike bodies with many leg bearing segments. • Insects – compact, 3 part bodies, adapted for flight.

25. Centipedes • Class: Chilopoda • Have a few to more than 100 pairs of legs, one pair per segment. • Carnivorous with venomous claws to sting and capture prey. • Prey includes other arthropods, earthworms, toads, snakes, and mice.

26. Millipedes • Class: Diplopoda • Have 2 pairs of legs per segment. • Feed on decaying or dead plant matter. • Not poisonous. • Defend themselves by rolling into a ball or secreting a bad odor.

27. Insects 28.3

28. Insects • Class: Insecta • Insects have a body divided into 3 parts – head, thorax, and abdomen. • 3 pairs of legs are attached to the thorax. • Pair of antennae • 2 pairs of wings • Pair of compound eyes • Some insects have body parts that are clearly separated (ants), others do not (grasshoppers)

30. Response to Stimuli • Insects have many sense organs to detect external stimuli. • Brain – assembles information • Compound eyes – detect color and movement • Chemical receptors – located on mouthparts, antennae, and legs used to detect taste and smell • Sensory hairs – detect slight movements • Ears – hear sounds, located in odd places • Ex) Grasshoppers ears are behind their legs

31. Feeding Adaptations • Insects have 3 pairs of appendages that are used as mouthparts. • Mandibles – saw and grind food (ant) • Tube-like – suck nectar (butterfly) • Sponge-like – lap up food (fly) • Many insects produce saliva containing digestive enzymes to break down food. • Glands on the abdomen of bees secrete wax that is used to build beehives.

33. Movement and Flight • Insects have 3 pairs of legs. • Used for walking, jumping, or capturing and holding prey. • Many insects can fly. • Typically have 2 pairs of wings.

34. Metamorphosis • Metamorphosis – the process of changing shape and form. • Incomplete – egg, nymph, adult • Nymphs look similar to adults although they lack some physical structures. • Complete – egg, larva, pupa, adult • Larva and pupa look different from the adults.

36. Insect Societies • Insects live and work together in groups. • They work instinctively rather than voluntarily. • Ants, bees, termites, and other insects form complex associations called societies. • Societies may consist of more than 7 million individuals. • Individual insects are specialized to perform particular tasks or roles. • Groups of specialized individuals are called castes. • Each species of social insect has its own “language” of visual, touch, sound, and chemical signals to convey information. • Ex) Honeybees communicate with complex movements and with the release of pheromones (chemical messengers that affect behavior or development of insects).

38. Humans & Insects • Many insects are known for their negative effects. • Termites – destroy wood • Mosquitoes – disease • Despite their association with destruction and disease, insects contribute to the richness of human life. • Many insects pollinate crops. • 1/3 of the food we eat depends on plants pollinated by insects. • Insects produce commercially valuable products. • Silk, wax, and honey

39. Insect Orders • Odonata (dragonflies) • Isoptera(termites) • Hemiptera (true bugs) • Homoptera (cicadas, aphids, etc) • Blattodea(cockroaches) • Coleoptera (beetles • Lepidoptera (butterflies & moths) • Diptera(flies) • Hymenoptera (wasps, bees)

40. Fun Facts • Ants and termites alone account for close to 1/3 of the animal biomass in the Amazon basin. • Insects thrive in almost every terrestrial habitat on Earth. • Class insecta contains more species than any other group of animals (between 6 and 10 million).