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  1. 1. Arthropods
  2. 2. What are ARTHROPODS?• Coelomate• Segmented• Bilateral Symmetry• Exoskeleton – made of protein and chitin• Jointed appendages – any structure (leg or antennae) that grows out of the body
  3. 3. What are Arthropods?• earliest invertebrates to exhibit jointed appendages – Jointed appendages are an advantage because they allow more flexibility for animals with hard, rigid exoskeletons – Joints allow powerful movements and allow appendages to be used in many ways
  4. 4. What are Arthropods? AppendagesJointed Appendages
  5. 5. Exoskeletons Provide Protection• made up of protein and CHITIN• can be a continuous covering over most of body OR made of plates that are held Continuous together by hinges Hinged
  6. 6. Exoskeleton Advantages• Protects, supports internal tissues• Provides place for muscle attachment• Aquatic arthropods have exoskeleton reinforced with calcium carbonate
  7. 7. Exoskeleton Disadvantages• Heavy – the larger the animal, the thicker and heavier the exoskeleton• Exoskeletons don’t grow – animals must molt when they get too large for exoskeleton
  8. 8. Molting• Animal contracts muscles and takes in air or water• Body swells and causes exoskeleton to split open, usually along the back • Most arthropods will molt 4-7 times before becoming an adult.
  9. 9. Before the new exoskeleton hardens...• increased circulation to all parts of the body cause the animal to puff up and new exoskeleton hardens leaving some “growing room”• animal can’t protect itself, can’t move
  10. 10. Question 1 Which of the following organisms would be most likely to have an exoskeleton reinforced with calcium carbonate?B. SpiderC. Beetle Correct!D. CrabE. Dragonfly
  11. 11. Question 2• Exoskeletons are heavy. Why can aquatic arthropods grow so much larger than terrestrial arthropods?The buoyancy of the water helps supportthe weight of the exoskeleton
  12. 12. Question 3• What is one advantage and one disadvantage of flying arthropods having a thinner, lighter weight exoskeleton?Disadvantage: less protectionAdvantage: greater freedom to fly andjump
  13. 13. Question 4• What is one advantage and one disadvantage of having a cephalothorax?Disadvantage: less flexibility, mobilityAdvantage: more protection
  14. 14. Segmentation• 3 segments – abdomen – thorax – head
  15. 15. Segmentation• Sometimes these segments can be fused together – some have head and fused thorax and abdomen – some have abdomen and fused head and thorax (cephalothorax)
  16. 16. Respiration• Efficient respiratory systems to meet large O2 demands• Large O2 demand needed to sustain high metabolism for fast movements• 3 types of respiratory structures – gills (aquatic arthropods) – tracheal tubes (terrestrial arthropods) – book lungs (terrestrial arthropods)
  17. 17. Respiration• Gills – water moves over gills – O2 from water diffuses into gills and into bloodstream – CO2 from body diffuses out through gills into surrounding water
  18. 18. Respiration• Tracheal tubes – branching network of hollow air passages that take air throughout the body Muscle movement brings air in/out through SPIRACLES (openings in abdomen and thorax)
  19. 19. Respiration• Book lungs – spiders and relatives – air filled chambers with leaf-like plates – stacked plates are arranged like pages of a book
  20. 20. Antennae• Acute sensing by antennae – stalk like structure that can detect changes in the environment • movement • sound • chemicals Used for sound and odor communication
  21. 21. Eyes• Compound Eyes – visual structure with many lenses• Simple Eyes – visual structure with one lens for detecting lightone pair of compound eyes and 3-8 simple eyes
  22. 22. Nervous System• Double ventral nerve cord• Anterior brain• Several fused ganglia that control the body section they are located in
  23. 23. Circulatory System• Open circulatory system – blood flows away from the heart in vessels – blood flows out of vessels into tissues – blood returns to the heart through open spaces
  24. 24. Digestive System• Complete digestive system with mouth, intestine, and anus• Mouth has 1 pair of jaws called MANDIBLES – adapted for holding, chewing, sucking, or biting
  25. 25. Reproduction – Sexual and Asexual• Sexual reproduction – separate sexes – internal fertilization for terrestrial species – external fertilization for aquatic species
  26. 26. Reproduction – Sexual and Asexual• Asexual reproduction – PARTHENOGENISIS • a new individual develops from an unfertilized egg • seen with ants, aphids and bees
  27. 27. Arachnids• spiders (largest group), ticks, mites, and scorpions• 2 body regions: cephalothorax and abdomen• 6 pairs of jointed appendages – 12 total appendages!
  28. 28. Arachnids• 1st pair - chelicerae, are near the mouth chelicerae• modified into pincers (hold food) or fangs (inject poison)
  29. 29. Arachnids• 2nd pair – pedipalps, for handling food and sensing pedipalps
  30. 30. Arachnids• Silk, for webs, is secreted by silk glands in the abdomen• as it is secreted, it is spun into thread by SPINNERETTES• spiders are predatory and feed almost exclusively on other animals
  31. 31. Arachnids• Ticks and mites have only 1 body section• Head, thorax and abdomen are completely fused• Ticks feed on blood of other animals
  32. 32. Arachnids• Mites feed on fungi, plants, and animals• small – not usually visible• can transmit diseases Dust mites
  33. 33. Arachnids• Scorpions have many abdominal body segments• Enlarged pincers• Long tail with venomous stinger at the tip
  34. 34. Crustaceans• crabs, lobster, shrimp, crayfish, barnacles• Only arthropods with 2 pairs of antennae• mandibles – move from side to side• 2 compound eyes
  35. 35. Crustaceans• 5 pairs of walking legs• 1st pair are claws for defense claw legs
  36. 36. Crustaceans• Most are aquatic and use gills• pill bugs (roly-polies) live on land, but must have moisture to aid in gas exchange Yes! This is a crustacean!
  37. 37. Centipedes and Millipedes• Centipedes are carnivorous – eat soil arthropods, snails, slugs, and worms• Bites can be painful• Millipedes – eats plants and dead material on damp forest floors• Does not bite, but does spray foul-smelling fluid
  38. 38. Horseshoe Crabs• Class Merostomata• “Living Fossils”- unchanged for 220 million years (Triassic period)• Extensive exoskeleton• Live in deep coastal waters• forage bottoms for algae, annelids and molluscs
  39. 39. Insecta• Flies, grasshoppers, lice, butterflies, beetles• 3 body segments• 6 legs• Very diverse - more insects than all other classes of animals combined
  40. 40. Insecta• mate once in lifetime• internal fertilization• some exhibit parthenogenesis• large number of eggs to increase survival rate
  41. 41. Insecta • insect embryos develop inside Molt eggs, eggsEggs Nymph hatch • some look like Nymph miniature Molt adultsAdult – will molt several times until adult size
  42. 42. Insecta• INCOMPLETE METAMORPHOSIS – 3 stages: egg, nymph, adult• Nymphs can’treproduce• Nymphgraduallybecomes an adult
  43. 43. Insecta• Some undergo COMPLETE Egg METAMORPHOSI Adult S – 4 stages: egg, larva, pupa, adult• Metamorphosis is Larva controlled by Pupa chemical substances in the insect
  44. 44. Insecta• Incomplete metamorphosis:grasshoppers and cockroaches• Complete metamorphosis: ants,beetles, flies, wasps
  45. 45. Origins of Arthropods• Successful because of – varied life styles – high reproductive output – structural adaptations – hard exoskeletons – jointed appendages
  46. 46. Origins of Arthropods• Hard exoskeletons fossilize – a lot is known about evolutionary history• Evolved from ANNELIDS (segmented worms)• Arthropods have more complex segments, more developed nervous systems• circular muscles in annelids do not exist in arthropods
  47. 47. Question 5 Spiders are: Predators!b. predatorsc. scavengersd. decomposerse. parasites
  48. 48. Question 6 Having 2 pairs of antennae distinguish _________ from other arthropods.b. centipedes Crustaceans!c. millipedesd. crustaceanse. horseshoe crabs
  49. 49. Question 7• Why are horseshoe crabs called “living fossils?” They remain unchanged after 220 million years!