Arthropods and Their Relatives

1. Arthropods and Their Relatives • Characteristics • Exoskeleton (external covering made of CHITIN) • Molts or sheds exoskeleton to grow • Jointed appendages - Groups very often named in relation to number or type of feet. • Tend to undergo metamorphosis or pass through a number of distinct growth stages during their lives • Tendency toward High degree of cephalization, especially in Class Insecta

2. Arthropods • Relative abundance. • 3/4 of all known species of animals are arthropods. • More known species of arthropods than known species of plants and animals combined. Great diversity in form and habitat.

3. Major Groups of Arthropods • Subphylum Trilobita - all forms extinct (believed) perhaps some of earliest arthropods • Subphylum Chelicerata - First pair of appendages form chelicera or pincher-like structures used for feeding. 4 pair of walking legs, no antennae. The Arachnida is the only important parasitic group.

6. Major Groups of Arthropods • Subphylum Crustacea - mostly aquatic, most have gills, two pair of antennae. Biramous appendages, meaning limbs have more than one branch. Also have mandibles. Some are parasitic but we will not cover them. • Subphylum Uriramia – single branch or uriramous appendages, mandibles, one pair of antennae

8. Major Groups of Arthropods • Diplopoda - Millipedes - two pair of legs per body segment • Chilopoda - Centipedes - one pair of legs per body segment • Insecta - 3 pair of legs on adults, many with wings, most important group

11. Metamorphosis • Simple or gradual • three changes • egg • nymph • 3-5 instars • adult • adults and nymphs • eat same food

12. Metamorphosis • Complex or complete • four changes • egg • larva • pupa • adult • larvae and adults • eat different food • larvae are destructive

13. Fundamental External structure • Insects • 3 body regions • head • thorax • abdomen • 3 pair legs attached to thorax • 1 pair antennae • wings usually present in adult state.

16. Hind Wing Fore Wing Antennae Simple Eye Compound Eye Jumping Leg Mouth Cerci Palps Spiracles Walking Legs Ovipositor Abdomen Thorax Head

18. Circulatory System • Closed circulatory system • Well developed heart pumps blood • Heart is long and narrow • Arteries branch into blood vessels and return blood to the heart via veins – cool, just like us!

19. Excretion • Recall the Nephridia in Annelids • The Malphigian Tubules in Arthropods collect nitrogenous wastes in the tubules from blood • Wastes are concentrated (like a kidney does.) Why concentrated? • Excreted out anus

20. Book Gills – folded Gills increase SA for RespirationHorseshoe Crab

21. Respiratory System • Gills or lungs, as you’ll see on the next slide  • Organism is too large to rely on surface area. That is, the internal volume is too great to be supplied with oxygen from a minimal SA.

22. Book Lungs are Characteristic of Arachnids

23. Sensory Adaptations • Well developed nervous system • Compound eyes with many lenses give Mosaic Vision or multi-images

24. Ultravision – Seeing in the UV Spectrum

25. The Compound Eye Each crystalline eye generates an image. All images together generate a mosaic effect

26. Simple Eye (Ocelli) • Do not form the picture • Just gather light • Tell whether it’s light or dark

27. Exoskeleton of Chitin and Muscles attach on Inside

28. How do You Grow Larger if you Skeleton is on the Outside? Molt, or shed the outer covering

29. External structure of Subphylum Chelicerata, Class Arachnae • Chelicerates have specialized mouthparts called chelicerae – think of the hooked grabbers! • Arachnids (spiders and mites) • 2 body regions • Cephalothorax • abdomen • usually 4 pair legs • no wings • no antennae

30. Chelicera = Fangs, for example, on a Spider

31. Chelicerates Include the Horseshoe Crab

32. Body of Arachnids

33. Other Members of Phylum Arachnida (4 Pairs of Walking Legs) • Spiders • Ticks and Mites • Scorpions

34. Nature Says Don’t Bug Me with the Colour Red!

35. How Nature Says Do Not Touch