L8 and 9 Arthropod evolution and diversity Flashcards
What 3 classes of arthropods are there?
Chelicerates
Crustaceans
Myriapods
What 2 subclasses of chelicerates?
Arachnida - scorpions, spiders, mites, ticks. terrestrial
Meristomata - Horseshoe crabs
5 features of chelicerates
No true jaws, chelicerae are hooked structures to cut holes in the host Cephalothorax and abdomen No antennae Simple eyes (horseshoe crabs have compound eyes) Uniramous legs (horseshoe crabs have biramous)
6 features of crustaceans
Mainly marine, 26000 species Cephalothorax and abdomen 2 pairs of antennae Compound eyes Biramous/Polyramous legs Mandibulate
8 features of myriapods
Mainly terrestrial, 13000 species Mandibulate 1 pair antennae Simple eyes Spiracles and trachea Uniramous legs Anamorphic - add body segments at each moult Ametabolous -Juveniles look very similar to adult (no further metamorphosis)
8 common arthropod features
- Exoskeleton of chitin and protein
- Metameric segmentation
- Tagmatisation
- Periodic moulting
- Segmental, jointed appendages
- Haemocoel
- Compound eyes
- Brain and ventral nerve cord
What are 3 primitive close relatives to arthropods?
Tardigrades
Onycophora
Trilobites - abundant 500mya
What similarities and differences do onycophora have to arthropods?
Similar: Cuticle, moulting, (1 pair of antennae)
Different: No tagmatization, jaws, not jointed legs
What similarities and differences do tardigrades have to arthropods?
Similar: cuticle and moulting
Different: No jointed legs
What did Sidnie Manton argue?
evolution of the exo skeleton must have happened very early on, limiting evolutionary possibilities.
All groups must be separate evolutionary lineages.
How is it generally accepted to group arthropods?
Based on birabous/polyramous limb character.
Monophyletic view
Polychaete like common ancestor - Marine, biramous limbs
When did the tracheal system develop?
Upon arthropod move to land
This also brought massive variation in available niches, so much radiation.
What is the superclass that insects are under?
Hexapods
What are the non insect hexapods?
ENTOGNATHA:
Protrura - <2mm, anamorphic and ametabolous
Collembola -ametabolous and not anamorphic
Dipura
All easily dessicate, need damp habitat,
What 2 subclasses of true insects are there?
ECTOGNATHA
Subclass - Apterygota, primitive and wingless
- Pterygota, has wings
Which orders come under apterygota?
Archeognatha - ‘bristletails’ 2 lateral cerci, medial filament, can spring themselves up into the air, abdominal styles.
Zygentoma - ‘silverfish’ silver colour, 2lateral cerci, medial filament.
What 3 series are in Pterygota?
Paleoptera - hemimetabolous, wing buds develop externally
Neoptera - hemimetabolous, external wing buds
Endopterygota - holometabolous, internal wing buds
What orders are within Paleoptera?
- Odonata: anisoptera [dragonflies], Zygoptera [damselflies]
- Ephemeroptera [Mayflies]
What orders are within Neoptera? (10)
Orthoptera [Locusts] Blattodea [Cockroaches] Isoptera [Termites] Dermaptera [earwwigs] Phasmida [Stick insects] Mantodea [mantids] Embioptera [webspinners] Hemiptera [bugs] Thysanoptera [thrips] Pthiraptera [book/bark lice]
What orders are within Endopterygota? (6)
Coleoptera [beetles] Diptera [true flies] Hymenoptera [wasps, ants, bees] Strepsiptera - parasitic, females are neotenic Siphonaptera [fleas] Lepidoptera [butterflies]
Describe holometabolous development
egg - larvae - pupa - adult
All internal organs brokendown, even fat body, reconstructed into adult structures.
Metabolically expensive so must be advantageous
What are 3 types of larval forms?
polypod larvae
oligopod - have thoracic legs, fairly mobile
Apod - no legs, focussed on feeding only
Describe larval to pupa transition
larval cuticle sheds and shrivels, pupal cuticle forms and sclerotizes, beginning to look like adult form. Former cuticles stay on as protection.
