Nematodes And Arthrapods Flashcards
What are the key characteristics of nematodes
Round bodies
Elongated structure
Unsegmented
Pseudoceolomates
Multilayered body walk
Covered in a cuticle that must molt for growth
What are the nematode reproductive strategies
Usually have 2 sexes (sometimes hemaphrodites)
Internal fertilisation
Parasitic nematodes often require multiple hosts throughout their life cycle
What are the characteristics of horsehair worms
Very thin
Strictly parasitic
No mouth
Reduced gut
What are the main groups of arthropods
Trilobites (extinct)
Chelicerates (spiders and scorpions)
Myriapods (centipedes and millipedes)
Crustaceans (crabs and barnacles)
Insects
What are the key characteristics of arthropods
Hard exoskeleton
Paired, jointed appendages
Bilateral symmetry
Segmented bodies
How are muscles attached to each segment
Muscles are attached to the inside of the hard exoskeleton and pull against it. When the cuticle is soft after molting, movement is heavily restricted
What are the features of an exoskeleton
Composed of chitin
Very hard, rigid and waterproof
Allowed for movement on land
Provides protection
Prevents drying out (desiccation)
Restricts respiration
What are the main body segments (tagmata) of arthropods
Head
Thorax
Abdomen
What is tagmantisation
The merging of tagmata into a single modified segment. E.g. cephalothorax in spiders
What were the main features of trilobites
First arthropods
Extremely diverse during the Cambrian and Ordovician periods
Went extinct at the end of the Permian
What are the key characteristics of chelicerates
Have chelicera instead of mandibles
2 tagmata, cephalothorax and abdomen
Usually carnivorous
What groups make up the chelicerates
Arachnids
Horseshoe crabs
Psycnogonids (sea spiders)
What groups are the mandibulates composed of
Insects (Hexapods)
Myriapods
Crustaceans
