Ecdysozoans

A type of proteosome

2 groups of Ecdysozoans

Limbless and limbed

Limbless

• nematodes

• (another that we aren’t going into)

Limbed

• tardigrades

• velvet worms

• arthropods

Nematode

• unsegmented

• thick multilayered cuticle

• Gas and nutrient exchange occurs through the cuticle and the gut wall

• The pharynx, a muscular anterior organ, moves materials through the gut

• lot are microscopic

• Modes of nutrition

  • Scavengers ​

  • Predators​

  • Parasites

Arthropods

• Has 4 paired jointed appendages

• 4 groups

  • Chelicerates​

  • Myriopods​

  • Crustaceans ​

  • Hexapods

arthropod relatives

Tardigrades, Velvet worms, and Trilobites

Chelicerates

• 2 part body

  • Cephalothorax

  • Abdoman

• Head has two pairs of appendages modified into mouthparts

• Most have 4 pairs of walking legs

• 2 examples

  • Horseshoe crabs

  • arachnids

Horseshoe crab

• Living fossil

• Common in shallow marine waters along eastern North America and Asia.​

• Come into the intertidal zone in large numbers to mate and lay eggs

Arachnids

• Simple life cycle (direct development)

• many are parasites of plants and animals (mites and ticks)

Myriapods

• Head and a long, flexible trunk with many pairs of legs​

• Centipedes—1 pair of legs per segment.​

• Millipedes— 2 pairs of legs per segment

• Mandibulate

Crustaceans

• 3 body regions: head, thorax, abdomen

• Head segments are fused and have 5 pairs of appendages

• Thoracic and abdominal segments usually have 1 pair of appendages each

• carapace - exoskeleton that​ extends over the​ head and thorax​ region

• Specialized appendages

Hexapods

have six legs and include insects

Insects

• 3 body regions

  • Head - one pair of antennae​

  • Thorax - three pairs of legs and two sets of wings in most groups​

  • Abdomen - no appendages

Metamorphosis

substantial physical changes occur between life stages - going from larvae to adult

Incomplete metamorphosis

changes are gradual - ex: grasshoppers

Complete metamorphosis

changes are dramatic - ex: butterflies