Transcript Insects and Their Relatives
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
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.
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.
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
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
Metamorphosis
• Simple or gradual – three changes • egg • nymph – 3-5 instars • adult – adults and nymphs • eat same food
Metamorphosis
• Complex or complete – four changes • egg • larva • pupa • adult – larvae and adults • eat different food – larvae are destructive
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.
Hind Wing Fore Wing Simple Eye Compound Eye Antennae Jumping Leg Cerci Ovipositor
Abdomen
Spiracles Walking Legs
Thorax Head
Mouth Palps
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!
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
Book Gills – folded Gills increase SA for Respiration Horseshoe Crab
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.
Book Lungs are Characteristic of Arachnids
Sensory Adaptations
• Well developed nervous system • Compound eyes with many lenses give Mosaic Vision or multi-images
Ultravision – Seeing in the UV Spectrum
The Compound Eye Each crystalline eye generates an image. All images together generate a mosaic effect
Simple Eye (Ocelli) • Do not form the picture • Just gather light • Tell whether it’s light or dark
Exoskeleton of Chitin and Muscles attach on Inside
How do You Grow Larger if you Skeleton is on the Outside?
Molt, or shed the outer covering
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
Chelicera = Fangs, for example, on a Spider
Chelicerates Include the Horseshoe Crab
Body of Arachnids The Spider Body A spider's body is divided into two parts:
Cephalothorax
Fused head & thorax. The legs are located on the cephalothorax
Abdomen
- Similar to that of insects..
Other Members of Phylum Arachnida (4 Pairs of Walking Legs) 1. Spiders 2. Ticks and Mites 3. Scorpions
Nature Says Don’t Bug Me with the Colour Red!