Arthropods Flashcards
What are the main features of the phylum Arthropoda?
Body covered by jointed exoskeletons (cuticle)
Cuticle is strong and waterproof - made of chitin
Segmented fused in groups forming regions
Specialised appendages
Well developed brain and sensory organs
Do arthropods have blood?
No as it is not a closed system
Have haemolyin instead
What animals come under the sub-group of arthropods, the chelicerates?
Spiders
Horseshoe crabs
Ticks
What are the main feature of chelicerates?
Have a cephalothorax and abdomen
Cephalothorax lacks antennae
Abdomen usually lacks legs
What are the main features of crustaceans?
Two pairs of antennae
3+ pairs of mouthpart appendages
Thorax has legs for walking
Abdominal segment has swimming appendages
Head and throat are NOT segmented but abdomen is
What are the main features of insects?
3 specialised regions
One pair of antennae
3 pairs of appendages
No legs on the abdomen
Sophisticated sensory organs
Well developed brain
One or two pairs of wings
What does an insect eye comprise of?
Ommatidia
Has poor image resolution but can detect fast movement
Point in multiple directions for a larger field of view
What are the potential origins of insect wings?
Gliding from vegetation to ground
Heat absorption in terrestrial ancestor
Gills in aquatic ancestor
Swimming fins in aquatic ancestor
What features make insect wings possible for flight?
Abundance of muscle tissue
Lightweight joined skeleton
Small body size
Efficient gas and nutrient exchange
Highly developed nervous and sensory system for navigation
How long ago did the echinoderms and chordates separate?
500 million years
What type of cleavage to mammals have?
Rotational
What are the main features of the phylum Echinodermata?
Adults almost always radially symmetrical (have pentanomous symmetry) but larvae are bilateral
Often radiate from a central disc with 5 arms
Endoskeleton is made from calcareous plates
Water vascular system made of canals and tube feet
No brain
Sessile or slow moving
What three systems are in every arm of an animal in the phyla Echinodermata?
Digestive
Reproductive
Water vascular
What are the characteristics of an early animal in the phylum Chordata?
Notochord
Dorsal hollow nerve chord
Pharyngeal slits
Muscular post-anal tail
What are our closes invertebrate relatives?
The cephalochordates
